tetrabenazine

1. Introduction

2. Pharmacology

3. Clinical employment

4. Drug interaction and side

effects

5. Conclusions

6. Expert opinion

Drug Evaluation

TetrabenazineAlfonso Fasano† & Anna Rita BentivoglioUniversit�a Cattolica del Sacro Cuore, Istituto di Neurologia, Largo Agostino Gemelli,

8-00168 Roma, Italy

Background: Tetrabenazine (TBZ) depletes presynaptic dopamine in the CNS.

It has been found to be beneficial in hyperkinetic movement disorders

without carrying the extrapyramidal side effects that are characteristic of

neuroleptics. Objective: To summarize current knowledge on the use of TBZ

and draw conclusions about its efficacy and safety. Methods: PubMed liter-

ature searches using the term ‘tetrabenazine’ were carried out for the period

prior to May 2009. Additional relevant studies referenced by these publica-

tions were included. Conclusions: Both short- and long-term studies have

consistently yielded favorable results for the use of TBZ in the treatment of

hyperkinetic movement in terms of efficacy and safety. TBZ is most effective in

reducing chorea (including Huntington’s disease associated chorea), tic asso-

ciated with Tourette’s syndrome and tardive dyskinesias. Furthermore, TBZ

might also have potential for use in other hyperkinetic disorders (e.g.,

myoclonus and dystonia), for which future clinical trials are needed.

Keywords: chorea, dyskinesias, dystonia, Huntington’s disease, tardive dyskinesias, tetrabenazine,

therapy, tic, Tourette’s syndrome

Expert Opin. Pharmacother. (2009) 10(17):2883-2896

1. Introduction

Tetrabenazine (TBZ) is a monoamine-depleting agent mainly acting on dopami-nergic terminals within the CNS (Box 1). It was first introduced in the 1960s as anantipsychotic [1]. Subsequently, it was found to be beneficial in hyperkineticmovement disorders, with a better tolerability in terms of extrapyramidal sideeffects, when compared to neuroleptics [2].

To date, several reports have suggested that TBZ ameliorates hyperkineticmovement disorders, in particular Huntington’s disease (HD) associated chorea.However, the number of controlled studies is scarce, possibly because the drug is notregistered in most countries: to date, there have been only a few randomized, double-blind, placebo-controlled trials demonstrating the efficacy of TBZ in amelioratingchoreic dyskinesias in HD.

The aim of this paper is to review the current evidences supporting the efficacyand safety of TBZ in the treatment of several movement disorders characterizedby hyperkinesias.

1.1 Review criteriaAll the papers listed in the PubMed (http://www.ncbi.nlm.nih.gov/pubmed) sortedby the term ‘tetrabenazine’ were carried out for the period prior to May 2009.Additional relevant studies referenced by these publications were included.

2. Pharmacology

TBZ is a benzoquinolizine derivative with the chemical name 2-oxo-3-isobutyl-9,10-dimethoxy-1,2,3,4,6,7 hexahydrobenzo[a]quinolizine (Figure 1).

The pharmacodynamics and pharmacokinetics of TBZ in humans have not beenwell characterized. After intravenous administration of the radiolabeled compound,

10.1517/14656560903386292 © 2009 Informa UK Ltd ISSN 1465-6566 2883All rights reserved: reproduction in whole or in part not permitted

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54% is excreted in urine after 48 h; TBZ is excreted in humanbreast milk [3] and crosses the placenta [4]. However, no case ofteratogenicity has been reported so far. TBZ displays variableinter-individual half-life and a relatively low bioavailability:0.049 ± 0.032 [4].TBZ is rapidly metabolized by reduction of the 2-keto

group by first pass metabolism into two compounds, a- andb-dihydrotetrabenazine (DTBZ). The ratio of a-DTBZ:b-DTBZ is ~ 3:1, while it can potentially vary > 20-foldbetween individuals. The clinical significance of the a:b ratiohas not been determined. In contrast to TBZ, DTBZ displayshigh bioavailability. DTBZ is less protein-bound (44 – 59%)compared with TBZ (83 – 88%) [4]. Plasma levels of DTBZare higher than TBZ and the half-lifes are longer: mean half-life of a-DTBZ is between 2 and 6 h whereas that of the bform is between 2 and 4 h [4,5]. TBZ and DTBZ follow linearkinetics in the commonly used doses [3].

2.1 Mechanism of actionThe precise mechanism underlying the effects of TBZ is notclear. However, it is thought to be related to depletion ofmonoamines from CNS nerve terminals due to the ability ofTBZ to inhibit the human vesicular monoamine transporter 2(VMAT2) (Figure 2) [6]. This transporter is responsible for thetranslocation of monoamines from the cytoplasm into thesynaptic vescicles for storage and subsequent release. VMAT2is a large protein, with 12 transmembrane helices, expressedmostly in the brain. In contrast, VMAT1 is expressed in theperiphery [7]. TBZ binds with high affinity to VMAT2 but notto VMAT1 [8].

Therefore, TBZ reversibly inhibits VMAT2 with a Ki valueof about 100 nM, resulting in reduced uptake of monoaminessuch as dopamine into the synaptic vesicles and depletion ofmonoamine stores [9-11] by potentiating monoamine degra-dation in the cytoplasm. Human VMAT2 is also inhibited bythe major circulating metabolite a-DTBZ while b-DTBZ isalmost inert [4].

Monoamine neurotransmitters depleted via VMAT2 inhi-bition by TBZ include serotonin, dopamine and norepine-phine [10,11]; however, dopamine is preferentially depleted [7].In an autopsy study of 18 patients with HD, those who hadreceived TBZ displayed an overall depletion of monoaminesin the caudate, amygdala, hippocampus and temporal lobewhen compared with patients not exposed to TBZ. Dopaminedepletion was most pronounced in the caudate nucleus [12].

In vitro studies have shown that TBZ blocks dopamine D2

receptors, as suggested by its ability to inhibit [3H]spiperone

N

O

CH3O

CH3O

CH2CH(CH3)2

Figure 1. Chemical structure of tetrabenazine.

Box 1. Drug summary.

Drug name Tetrabenazine

Phase Launched

Indication Huntington’s diseaseTardive dyskinesiaTics in Tourette�s syndrome

Pharmacology description Dopamine depletor

Route of administration Alimentary, po

Chemical structure

N

O

CH3O

CH3O

CH2CH(CH3)2

Pivotal trial(s) In an open-label study in 75 patients who successfully completed treatment in a 13 week double-blind, placebo-controlled Phase III trial, 45 patients completed the 80 week study withsignificantly reduced symptoms of chorea associated with HD as measured by the TotalMaximum Chorea Score (TMCS)In a randomized, parallel-group, double-blind, pivotal Phase III trial (study ‘004) in 84 HDpatients, 12.5 mg once-daily titrated to 100 mg/day over 7 weeks and followed by 5 weeksmaintenance therapy gave a 5.0 point reduction in the unified HD rating scale, cf 1.5 points withplacebo

Tetrabenazine

2884 Expert Opin. Pharmacother. (2009) 10(17)

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binding to striatal membranes with a Ki of ~ 2.1 � 10-6

M [13,14]. TBZ has also been found to block the pharmacologicaction of the dopamine agonist apomorphine [15], providingfurther evidence of dopamine receptor blocking activity.However, the affinity for D2 is 1000-fold lower than itsaffinity for VMAT2 [13,14], and this accounts for the lowincidence of extrapyramidal side effects at the doses commonlyused. On the other hand, it is unlikely that the weakD2 receptor antagonism might be responsible for TBZ clinicaleffects, although it may possibly be involved in acute dystonicreactions rarely reported with TBZ [16]. The presynapticdepletion and weak postsynaptic dopamine receptor inhibi-tion may be responsible for increased dopamine turnover assuggested by the increased levels of the major dopamine

DA

DA transporter

Cocaine

DA autoreceptors

Tetrabenazinereserpine

Tyr

VMAT2

Ca++

Amphetamine(amantadine)

DA receptors

Synapticvesicles

DOPA

DA

DA agonists:

Antagonism

Agonism

Typical neurolepticsAripiprazoleOlanzapineRisperidone(Tetrabenazine)

Aripiprazole

ApomorphinePramipexoleRopinirolePergolideCabergolineRotigotineBromocriptine

Figure 2. The dopaminergic synapse and its pharmacology.DA: Dopamine; DOPA: Ddihydroxy-phenylalanine; Tyr: tyrosine.

Table 1. Pharmacologic differences between TBZ and

reserpine.

Pharmacologic

properties

TBZ Reserpine

Receptor VMAT2 VMAT1 and VMAT2

Binding site Intravescicular Cytoplasmatic

Type of inhibition Reversible Irreversible

Peripheral monoaminedepletion (hypotension,pain, diarrhea)

No Yes (VMAT 1)

Duration of action Hours Days

TBZ: Tetrabenazine; VMAT: Vescicular monoamine transporter.

Fasano & Bentivoglio

Expert Opin. Pharmacother. (2009) 10(17) 2885

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metabolite, homovanillic acid, in the cerebrospinal fluid ofpatients with HD taking TBZ [17].TBZ is similar to reserpine (Table 1), but in contrast to

reserpine, TBZ lacks an indolic group [9]. Both drugs actcentrally on VMAT2, but reserpine also inhibits VMAT1leading to peripheral monoamine depletion, which may explainthe higher incidence of hypotension and gastrointestinal sideeffects, such as epigastric pain and diarrhea. TBZ has a muchshorter half-life than reserpine (hours versus days), with morerapid onset of action. In addition, reserpine binds irreversiblyboth VMATs [18]. These last features are advantageous in theclinical setting as efficacy can be assessed more rapidly (within7 days) with TBZ and side effects abate rather quickly afterdiscontinuation of the drug. In conclusion, VMAT binding(and monoamine depletion) by TBZ is reversible, lasts hoursand is not modified by chronic treatment [19].

2.2 Preclinical investigations in animal modelsManyof the aforementionedproperties ofTBZcome fromearlyanimal studies [3,10,11,14,20]. Recently, the persistent elevation ofstriatal dopamine levels has been found to contribute to theglutamate induced neurodegeneration in a transgenic HDmouse model [21]. The same study has provided evidencesthat TBZ has a partial neuroprotective effect in vivo (duringa beam walking assay and on rotarod) and in vitro (the striatalneuronal counts) [21].On the other hand, another study revealedthat the repetitive administration of TBZ for 7 days in healthyrats produced histological changes in the neurons of the sub-stantia nigra pars compacta [22]. The therapeutic potentialbeyond the well-established symptomatic benefit of TBZ hasto be carefully investigated in future trials.

3. Clinical employment

TBZ has been used in a variety of movement disorders.However, in many countries its use is off-label and this shouldbe kept in mind by clinicians (Table 2).

3.1 Huntington’s diseaseHD is a progressive degenerative disorder inherited as anautosomal dominant trait causing chorea and neuropsychiatricdisturbance [23]. Chorea is characterized by brief and irregularcontractions, not repetitive or rhythmic, appearing to flowfrom one muscle to the next; in addition, in later stages, severefunctional disability develops due to occurrence of severemotor impairment, dementia and dysphagia [23].

In spite of several attempts and trials, no neuroprotectivedrug is yet available for HD [24]. Therefore, the only treat-ments proven to be effective in the management of HD aresymptomatic [24]. In early stages of HD, degeneration ofstriatal GABAergic neurons causes hyperactivity of dopami-nergic systems. Postsynaptic D2-receptor blockers (such ashaloperidol, pimozide, tiapride, risperidone, olanzapine) havebeen largely used for treating chorea and psychosis in HDpatients (Table 3) [17,25-30]. Neuroleptics reduce chorea butmay induce side effects on motor performance (inducing orworsening Parkinsonism and akathisia) and affectivity (abulia,depression) and exacerbate cognitive impairment and worsenmood and apathy. HD patients seem to be more vulnerablethan other patients to Parkinsonism because hyperkinetic andhypokinetic movement disorders coexist, as a consequence ofthe involvement of direct and indirect pathways in the basalganglia–thalamus–cortical motor circuit [31].

TBZ has been used for the treatment of chorea associatedwith HD in Australia since 1971. In 1979, Kingstonsummarized the experience of 40 Australian patients withchorea and other movement disorders treated with TBZ [32].Since then, numerous open clinical trials on relatively smallnumbers of subjects have proven the clinical benefits inpatients with chorea, most affected by HD. One open-labellong-term (18 months) study found a moderate improvementin 10 patients with HD [33].

A single-blind crossover study with TBZ versus placebo ineight patients with HD found that 75% experienced a markedto moderate improvement of chorea [34]. The degree of

Table 2. Official indications for TBZ according to country where it is marketed.

Country Registered Indications

UK 1971 and 2000 Huntington’s chorea, hemiballismus and senile chorea (1971). Tardive dyskinesia (2000)

Ireland 1971 Same as UK, but not tardive dyskinesia

Australia 1979 Control of chorea, hemiballismus, tardive dyskinesias and dystonic syndromes

Denmark 1980 Hyperkinesias

New Zealand 1982 Same as UK

Canada 1995 Huntington’s chorea, hemiballismus, senile chorea, tic, Tourette’s syndrome and tardive dyskinesia

Portugal 2004 Same as UK

France 2005 Huntington’s chorea and hemiballismus

Israel 2006 Movement disorders disabling or socially embarrassing

Germany 2007 Huntington’s chorea and moderate to severe tardive dyskinesia

Italy 2007 Huntington’s chorea and moderate to severe tardive dyskinesia

US 2008 Huntington’s chorea

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improvement continued for the 3-week duration of the study.An open-label follow-up of the same subjects found that mostof them continued to display moderate reduction of chorea6 – 18 months later [6]. In 2002, Ondo et al. in a single-blindstudy on 19 HD patients observed that TBZ was effective andwell tolerated [35]. The patients, evaluated 5.9 ± 3.3 monthsafter starting TBZ at a mean final dose of 62.5 ± 37.4 mg/day,subjectively rated themselves as markedly improved (7), mod-erately improved (7), mildly improved (3) and unchanged(1) [35]. Chorea improved significantly based also on the resultsof blinded raters using a modified Abnormal InvoluntaryMovement Scale (AIMS). Subjective patients’ ratings ofimprovement were in nice agreement with the objectivechanges on the AIMS [35].

Only a few double-blind, placebo-controlled studies havebeen conducted (Table 4). After the first double-blind study in1974 [17], the Huntington Study Group (HSG) recently com-pleted a Phase III study assessing the safety, efficacy and dosetolerability of TBZ for ameliorating chorea in patients with HD

(TETRA-HD) in a short-term interval [36]. Eighty-four patientswere randomized to placebo (n = 30) or TBZ (n = 54) withincreasing doses of 12.5 mg/week. The dose was titratedupwards until satisfactory control of chorea was achieved, untilintolerable side effects occurred or until a dose of 100 mg/daywas reached. The duration of treatment was 12 weeks, includ-ing a 7-week dose titration period and a 5-week maintenanceperiod. After 12 weeks, all treatment was discontinued andpatients returned 1 week later for the final study visit.

The primary efficacy outcome was the change from thebaseline in the chorea score of theUnifiedHuntington’sDiseaseRating Scale (UHDRS). On this scale, chorea is rated from 0 to4 (with 0 representing no chorea) for seven different parts of thebody, and the total score ranges from0 to 28.Overall, treatmentwith TBZ resulted in a reduction of 5 units in chorea severitycompared with a reduction of 1.5 units for treatment with aplacebo. About 50% of TBZ-treated patients had a 6-point orgreater improvement compared with 7% of placebo-treatedpatients.TBZwas also superior to the placebowith regard to the

Table 3. Randomized clinical trials using neuroleptics in the management of chorea associated with HD.

Ref. Medication Control agent Study

design

N* Effect Length

of study

Dose Assessment tools

[17] Thiopropazate Placebo, tetrabenazine Crossover 9 Positive 2 wk 30 mg/day Subjective + video

[25] Haloperidol Placebo, lithium Crossover 6 None 3 wk 5 mg/day Subjective

[26] Clozapine Placebo Crossover 3 Poor 4 wk Variable(max 500 mg/day)

Subjective

[27] Tiapride Placebo Crossover 22 None 2 wk 300 mg/day Subjective + video

[28] Sulpiride Placebo Crossover 11 Poor 4 wk 1200 mg/day CSS

[29] Tiapride Placebo Crossover 23 Positive 3 wk 3 g/day Subjective

[30] Clozapine Placebo Crossover 26 Poor 31 day Variable(max 150 mg/day)

AIMS, UHDRS

*Number of patients in the active arm who completed the study.

AIMS: Abnormal involuntary movement scale; CSS: Chorea severity score; HD: Huntington’s disease; UHDRS: Unified Huntington’s disease rating scale; video: Blinded

video rating; wk: Weeks.

Table 4. Randomized clinical trials using TBZ in the management of chorea associated with HD.

Ref. Control agent Study design N* Effect Length of study Dose Assessment tools

[17] Placebo,thiopropazate

Crossover 9 Positive 2 wk 200 mg/day Subjective + video

[55] Placebo Crossover 1 Positive 10 wk 200 mg/day Subjective + video

[36] Placebo Crossover 49 Positive 7 wk Variable (max100 mg/day)

UHDRS, CGI

[37] Partial orno withdrawal

Parallel 12 Worseningafter washout

5 days Partial or completewithdrawal

UHDRS, TFC

[75] AP Crossover 6 Positive (comparableto AP)

12 wk 95.83 ± 33.2 mg/day UDHRS, EES, HDS

*Number of patients in the active arm who completed the study.

AIMS: Abnormal involuntary movement scale; AP: Aripiprazole; CGI: Clinical global impression; EES: Epworth sleepiness scale; HD: Huntington’s disease;

HDS: Hamilton depression scale; TBZ: Tetrabenazine; TFC: Total functional capacity scale; UHDRS: Unified Huntington’s disease rating scale; video: Blinded video

rating; wk: Weeks.



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secondary efficacy outcome of the Clinical Global Impressionscale [36]. A post hoc analysis of chorea response by dosage in thisstudy indicates that subjects treatedwith 50mg/day or less had agreater improvement in chorea at week 12 than those receivinghigher doses. Differences in susceptibility to TBZ due tohepatic processing, avidity of VMAT-2 or other unknownfactors may account for this finding.In another randomized, double-blind study, 30 HD sub-

jects with a clinical response to TBZ were randomized intothree groups: 12 subjects stopped TBZ on day 1 (group 1:withdrawal), 12 on day 3 (group 2: partial withdrawal) and6 subjects continued on TBZ (group 3: non-withdrawal) [37].Subjects were withdrawn in a double-blind fashion byreplacing TBZ with identical placebo tablets. The primaryoutcome measure was the difference between the day 1 andday 3 UHDRS chorea scores. Adjusted mean chorea scores forsubjects withdrawn on day 1 increased by 5.3 units, whilethose remaining on TBZ increased by 3 units (p = 0.08). Theprimary outcome measure did not reach the statistical signif-icance; however, a post hoc analysis showed a positive lineartrend for re-emergent chorea (p = 0.05).

3.1.1 Long-term studies in HDTBZ has been used at the Baylor College of Medicine(Houston, USA) since 1979. The authors presented theirexperience in the largest published series of the long-termeffects of TBZ. Four hundred patients with different move-ment disorders, treated until 1995, were assessed retrospec-tively using a composite global response scale that included theassessment from the patient, caregiver and the rater’s neuro-logic examination. The global response rating of 1 (markedimprovement) was recorded in 82.8% of 29 patients with HD(average duration of TBZ treatment: 28.9 months). Theauthors concluded that the drug was effective and safe forthe treatment of hyperkinetic movement disorders [38].The same group published another analysis of the data

retrieved from 98 patients in the interval 1997 – 2004: > 80%of patients experienced a complete or marked amelioration ofchorea [39]. Approximately two-thirds of patients remained ontreatment, a quarter withdrew from treatment due to travel/financial difficulties (38.1%), while 33.3% stated adverseevent intolerability; the remainder were lost to follow-up.The doses used by these researchers were higher in thebeginning of their experience (109.5 ± 53.8 mg) [38] thanin their subsequent publication where they stated that ‘in mostcases, patients were treated with 50 to 75 mg’ [39]. This mayaccount for the higher incidence of side effects in the formerpublication [38].We have recently published the results of a retrospective

analysis of patients with HD followed up at the MovementDisorder clinic of the Gemelli Hospital in Rome. The studyreports the largest number of HD patients followed up for avery long-term period: sixty-eight HD patients (mean diseaseduration of 55.8 ± 34.7 months) [40]. The mean UHDRSmotor score at the time of the first visit was 39.4/120 ± 14.5

(range: 14 – 68). The mean dystonia subscore was 3.5/20 ±2.9 (range: 0 – 10); the mean chorea subscore was 10.4/28 ±4.1 (range: 3 – 18). At the moment of data collection, 46(68%) patients were still under treatment. The mean dose atfirst follow-up, after 9.7 ± 7.8 months, was 35.3 ± 14.7 mgwhereas it was 57.5 ± 14.7 mg at the latest follow-up visit,34.4 ± 25.2 months after the first visit.

When compared to the baseline visit, at the first follow-upchorea was significantly improved by 21% (p = 0.00005),whereas the dystonia subscore was reduced but the differencewith the baseline scores failed to reach statistical significance.Of 68 patients treated, 5 (7%) did not gain any improvementof chorea and withdrew TBZ. As expected, at the latest follow-up visit, HD had worsened, as revealed by a significant increaseof the mean UHDRS motor score (+32%; p = 0.005); themean score of dystonia section was increased by 37%; and themean score of the chorea section was reduced by 9% (com-pared to 21% of the first follow-up visit), notwithstanding amean dose increase of 63% (p < 0.01) [40]. These data aredifficult to interpret, as the natural history of HD in mostpatients includes a progressive reduction of chorea, whiledystonia and Parkinsonism worsen.

We analyzed the predictors of TBZ efficacy on chorea: dose,gender, age at the moment of treatment and therapy durationwere unrelated to the improvement, whereas an older age atonset predicted a good outcome, possibly due to chorea beingmore pronounced than dystonia in late onset HD [41].

3.2 Tardive dyskinesiasTardive dyskinesias (TD) are a group of movement disordersinduced by the dopamine receptors antagonism, that is, typicalneuroleptics [42]. In contrast to acute dystonic reactions, whichare often dramatic, with an abrupt onset and resolution afterdiscontinuation of the causing agent [43], TD are characterizedby delayed onset (months or years). Several tardive phenotypeshave been described, including stereotypy, akathisia, dystonia,myoclonus and tremor frequently presenting in association inthe same patient (tardive syndrome). Clinicians frequently usethe term TD referring to oro-facial-lingual movements [43]. Thebest approach to TD is prevention; because up to 43% ofpatients exposed to chronic antipsychotic medications haveevidence of TD [44], these should be used only when strictlynecessary and for the shortest time.

TBZ is probably the most effective drug for the treatmentof TD. Kazamatsuri et al. reported the effectiveness of TBZ forTD in 24 patients using a single-blinded design [45] andinspired a new trial randomizing 13 patients to receive eitherhaloperidol or TBZ [46]. Haloperidol was more efficacious inthe early part of the study, although the clinical benefit wanedat the end of the 16th week. Several studies have providedevidence that TBZ is highly effective, at relatively low doses,within 1 week of treatment (Table 5). In a retrospective chartanalysis of 100 consecutive patients with TD treated with TBZat the Baylor College of Medicine, the efficacy of TBZ wasassessed using a 0 – 4 rating scale, (0 = unchanged; 4 =marked

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improvement): the average improvement of all patients onTBZ was rated 3.3 ± 1.0 [43]. TBZ was more efficacious inreducing stereotypies and/or akathisia than dystonia.

The retrospective review of patients treated at the BaylorCollege of Medicine between 1980 and 1995 reported on94 patients with tardive stereotypy and 82 with tardivedystonia [38]. Most patients improved markedly in bothgroups; 89.2 and 80.5%, respectively. The positive responsewas maintained for the duration of follow-up, averaging28.9 ± 3 1.1 months. The same end points were assessedin patients treated from 1997 to 2004. Of 149 patients treatedwith TBZ for TD, 83.5% reported a marked to moderateimprovement after a short duration treatment [39]. In anotherstudy at the Baylor College of Medicine, 20 patients with TDwere videotaped before and after TBZ using an open-labeltrial design [47]. Blind raters noted a 54.2% improvementon the modified AIMS. Patients’ self-reporting of AIMSimproved by 60.4% [47].

3.2.1 Tardive tremor‘Tardive tremor’ is a rare condition aggravated by and persistedafter neuroleptic withdrawal. It is an involuntary oscillatorymovement, with a frequency range of 3 – 5 Hz, prominentduring maintenance of a posture, but also present at rest andduring a goal-directed movement [48]. TBZ can induce wors-ening of tremor in the context of Parkinsonism; however, it hasbeen successfully used in a few cases of tardive tremor [48,49].

3.3 Tic and Tourette’s syndromeTourette’s syndrome (TS) is a neurologic disease characterizedby motor and phonic tics, frequently accompanied by a varietyof behavioral and psychiatric problems [50]. A tic is a sudden,repetitive, nonrhythmic, stereotyped motor movement or vocal-ization involving discrete muscle groups. Tics are thought to becaused by a central dopaminergic hyperactivity; accordingly,neuroleptics can improve them, as first observed in the 1960s.In the setting of mild symptoms, treatment may be unnecessary.Antinoradrenergic drugs (such as clonidine or guanfacine) orneuroleptics (typical or atypical) are used to decrease the sever-ity and frequency of tics as well as anti-convulsants (topiramate,levetiracetam), baclofen and botulinum toxin injections [50].Haloperidol and pimozide have been approved in mostcountries for the treatment of tics in patients with TS.

Since the first report of efficacy of TBZ on TS published in1974 [51], numerous clinical studies have confirmed theusefulness of TBZ as an alternative to conventional neuro-leptics (Table 6), thereby, circumventing the risk of TD. Theclinical efficacy of TBZ for the treatment of tics has beenextensively demonstrated, but to date no large double-blind,placebo-controlled, studies are available.

In one open-label study, TBZ induced a marked and long-lasting improvement in four of nine medically refractory TSpatients, and a mild improvement in three [52]. These datahave been confirmed in other retrospective studies [33,53,54].

Kenney et al. reviewed the medical records of 92 patientstreated for tics with TBZ between 1997 and 2004 [39]. The

Table 5. Efficacy of TBZ in studies of patients with TD.

Ref. Study design N Patients moderately or highly improved

[45] Single-blinded versus placebo 24 58%

[32] Open 6 67%

[34] Open 10 60%

[55] Double-blind crossover versus placebo 4 100%

[80] Open 23 NA

[38] Retrospective 94 (Tardive stereotypy)82 (Tardive dystonia)

89.2% (Tardive stereotypy)80.5% (Tardive dystonia)

[47] Single-blinded 20 54.2% (Blind raters)*60.4% (Patients’ self-reporting)*

[54] Retrospective 17 59%

[39] Retrospective 149 83.5%

*Percentage represents the magnitude of improvement.

TBZ: Tetrabenazine; TD: Tardive dyskinesias.

Table 6. Efficacy of TBZ in studies of patients with TS.

Ref. Study design N Patients moderately

or highly improved

[51] Open 5 40%

[81] Open 9 67%

[55] Double-blind crossover 1 100%

[52] Open 9 78%







TBZ: Tetrabenazine; TS: Tourette’s syndrome.



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majority of patients (76.7%) experienced either a marked or amoderate reduction in tics. Furthermore, efficacy of responsedid not vary over time (77.8%).

3.4 Other movement disordersA large body of literature reports on the favorable results ofTBZ to treat a variety of hyperkinetic movement disorders.However, it is well recognized that chorea (regardless ofetiology [54,55]) and TD respond better than other movementdisorders. Accordingly, in a large long-term study, the major-ity of patients with either TD (60.4%) or chorea (63.3%)remained on TBZ treatment whereas a smaller proportion ofpatients with dystonia (43.9%), tics (48.9%) and myoclonus(52.6%) continued treatment with TBZ [39].

3.4.1 DystoniaDystonia is a neurologic disorder that interferes with voluntarymotor control, causing development of bizarre postures andtwisting movements. In 1974, Marsden et al. stated that TBZcould play a therapeutical role in dystonia [56]. Later on, theyproposed a combined therapy with TBZ and pimozide inconjunction with anticholinegics for medically refractory cases(the ‘Marsden’s cocktail’) [57].In the following years, several studies have reported the

effect of TBZ on dystonia. In a blinded videotape assessmentversus placebo, TBZ improved three of eight patients withdystonic disorders [34]. In a double-blind crossover trial, TBZ

improved four of six patients with Meige’s syndrome (acombination of two forms of facial dystonia, blepharospasmand oromandibular dystonia), and five of six patients withother dystonias [55].

In a follow-up study on 217 patients treated with TBZ forabout 18 months, the mean effect – in a scale of 0 – 5, lowervalues indicating improvement, 5 worsening – was rated as2.8 in 19 with generalized dystonia, 2.8 in 57 with Meige’ssyndrome and 3.4 in 25 with other focal dystonias [33].

A better outcome in patients with facial dystonia has beenobserved in another study on 118 patients; the same study alsoreported a good improvement in two cases of trunk dysto-nia [54]. Another long-term series reported that 67.2% ofpatients with dystonia had a good response and that therate was virtually identical at the last visit (69.5%) [39]. Finally,TBZ seems to be a good first-line therapy in the managementof status dystonicus (the acute and severe worsening ofdystonia) because it has been successfully used in 10/37episodes collected in a recent review [58].

In spite of these encouraging results, currently TBZ is notamong the first-choice treatments for dystonia. In a retrospec-tive series of the 68 patients with a wide spectrum of dystonicsyndromes, 25 patients had improvement with botulinumtoxin injections, 16 with anticholinergics, benzodiazepinesand/or baclofen, and only 2 with TBZ [59]. Figure 3 showsan algorithm for the treatment of dystonias: TBZ may play arole as second option in focal and segmental forms while itcould be used as the first-line strategy in generalized dystonia.

3.4.2 MyoclonusSpinal myoclonus is a focal involuntary muscular contractionsoften associated with lesions of the spinal cord. After the firstreport on four patients successfully treated with TBZ [60],other series of larger numbers of patients confirmed theefficacy of TBZ [38,61], even in the long term [39].

3.5 TBZ in the pediatric populationThe published experience with TBZ in the pediatric literatureis limited. In a small series of five patients between 22 monthsand 10 years, the efficacy of TBZ for chorea related todifferent etiologies was assessed [62]. No significant side effectswere noted and four of the five patients responded well totreatment with marked improvement of movements.A retrospective chart analysis of 76 hyperkinetic patients underthe age of 18 revealed significant improvement in myoclonus(100%), chorea (89%), tics (72%) and dystonia (50%) [63].Overall, TBZ is better tolerated in younger patients andappears to be efficacious. Higher doses may be required inthe pediatric population.

4. Drug interaction and side effects

Many experiences on the safety of TBZ have been collected inliterature because most studies have been designed to increase

Focal Segmental Generalized

Oral therapy(levodopa, anticholinergic

> TBZ > neuroleptics >etc*)

Botulinum neurotoxin

Oral therapy(anticholinergic > TBZ >

neuroleptics > etc*)

Surgery(deep brain stimulation,

lesional)

Surgery(deep brain stimulation,

lesional)Intrathecal baclofen‡

> >

Figure 3. Algorithm for the treatment of dystonias (modifiedfrom [83]). TBZ may play a role as the second option in focal andsegmental forms while it could be used as the first-line strategy ingeneralized dystonia. Botulinum neurotoxin injection may be usefulin generalized forms to improve selective dystonic districts.*Several drugs have occasionally been used with inconsistent results (e.g., oral

bacloflen, antiepileptics, benzodiazepines, tizanidine).‡Intrathecal baclofen is mostly indicated for secondary dystonias with spastic

component.

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the dose until intolerable side effects were noted. Up to 50%of patients may initially report at least one side effect but – dueto the short half-life of TBZ – they are easily reversed with areduction of dosage and a slow titration [34,39,40].

TBZ-induced monoamine depletion (dopamine, serotoninand noradrenalin) accounts for all the commonly observed sideeffects: sedation, Parkinsonism, depression, insomnia andakathisia, all of which are reversible [63]. In the controlled trialrecently performed in patients with HD [36], 70% of placeboand 91% of TBZ participants experienced at least one sideeffect. Four withdrawals occurred in the TBZ group due toserious adverse events whereas there were no severe side effectsin the placebo group. There were no significant differencesbetween TBZ and placebo with regard to other specific sideeffects except for drowsiness and insomnia, which was reportedin > 25% of TBZ cases and in none in the placebo group [36].

It is important to note that no case of TD has beendescribed after TBZ use despite up to 21 years of exposurein some cases [39]. Other extrapyramidal side effects can occur,but less frequently than with typical neuroleptics. Olderpatients are more likely to develop Parkinsonism probablydue to an underlying age-related dopamine deficiency thatbecomes clinically manifest with the use of TBZ. On the otherhand, younger subjects tolerate TBZ better despite being moreprone to develop insomnia and depression. An importantcaveat should be made for depression because TBZ increasesthe risk of severe depression and suicidality in subjects with aprevious history of depression [64]: two cases of suicide havebeen described soon after the introduction of TBZ in HDpatients [36,65].

Generally, TBZ is a safe drug and the withdrawals due toside effects are uncommon: 2.9% in our experience [40], 7.4%in the study by the HSG [36] and 17% in another long-termstudy [39]. As an example of short-term tolerability, a case

report has described an overdose in a 27-year-old womanwithout any significant sequelae, except for sedation, aftertaking ~ 1 g of TBZ [66]. However, a few publicationsmentioned fatalities occurring in patients taking TBZ: hyper-thermia [67], neuroleptic malignant syndrome [68-71], acutedystonic reaction [16] and severe dysphagia [38,72].

4.1 Long-term experiencesBecause many trials last only some weeks, it is not possible todraw inferences about TBZ-related adverse effects from pro-longed exposure. Therefore, longitudinal studies of TBZ treat-ment have been performed to assess the long-term risks. Thesafety of long-termTBZ therapy has been recently confirmedbyKenney et al.,whoperformedaretrospective chart reviewon448patients treated for a mean of 2.3 ± 3.4 years [39]. In ourexperience, the drug is generally well tolerated and side effectsare easily managed by reducing the dose or adding antidepres-sants or anti-Parkinsoniandrugs (amantadine and/or dopamineagonists) [40]. Figure 4 shows the percentages of side effectsdisplayedbypatients takingTBZ in the long-term studies [38-40]:in our experience, TBZ was even more tolerated, probablybecause we used smaller doses (57.5 ± 14.7 mg at the latestfollow-up) than others [38-40].

4.2 Drug interactionsTBZ blocks the action of reserpine; the concomitant use ofboth drugs should be avoided. Levodopa should be admin-istered with caution. TBZ and DTBZ inhibit the cytochromeCYP2D6: clinicians should be aware of the possible interac-tions despite being only rarely clinically relevant. CYP2D6 hasseveral substrates, among them all tricyclic antidepressants.Therefore, it has been reported that the concomitant treat-ment with tricyclic antidepressants may limit or reverse theeffects of TBZ.

40

35

30

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Jankovic & Beach, 1997Kenney et al., 2007Fasano et al., 2008

Figure 4. Percentages of side effects displayed by patients taking TBZ in the long-term studies [38-40].



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5. Conclusions

The medical literature reveals a long-lasting experience withTBZ dating back to the 1950s. TBZ has an elegant and uniquemechanism of action: it is a dopamine depletor mainly actingin the CNS. Both short- and long-term studies have consis-tently yielded favorable results for the use of TBZ in thetreatment of hyperkinetic movement disorders and haveconfirmed its safety. Despite being well tolerated in mostcases, it might induce potentially serious side effects of whichphysicians should be aware. TBZ is highly effective especiallyin the management of chorea (including HD), with a grade ofrecommendation B (according to the evidence based medicinecriteria) [63]. A recent Cochrane review on the therapeuticinterventions for symptomatic treatment in HD has con-cluded that TBZ is the anti-choreic drug with the best qualitydata available and the only one showing a clear efficacy forthe control of chorea. The remaining pharmacologicalinterventions revealed no clear effectiveness [73].The results of several studies and clinical experience suggest

an important role also in TS and TD; however, the level ofevidence for these indications remains undetermined [63].Furthermore, TBZ might also have potential for use in otherhyperkinetic disorders (e.g., dystonia), for which it is currentlyunder investigation. In 1974, McLellan et al. stated that TBZ‘is the drug of first choice for the suppression of chorea’ [17];based on subsequent studies and personal experience, theirconclusion is still justified today.

6. Expert opinion

6.1 How to use TBZTBZ has been used most commonly at a daily dose rangingfrom 25 to 200 mg, although a commonly used therapeuticdose is 50 – 75 mg/day. In the published studies and in clinicalpractice, TBZ is slowly titrated from ~ 25 mg/day in two orthree divided doses up to a maximum of 50 mg three times aday (t.i.d.), on the basis of weekly increments of 12.5 – 25 mg.Albeit there are no studies specifically addressing this issue, werecommend introducing TBZ at very small doses (6.25 mgtwice a day or t.i.d.) especially in selected cases, for example,older patients or those at risk of depression. Given the shorthalf-life, dosing t.i.d. is necessary although sometimes theclinical benefit is achievable with a single or double intake aday. TBZ should be tapered until a satisfactory control ofdyskinesias is achieved or when a troublesome side effectoccurs. In conclusion, TBZ doses should be individualizedand adjusted periodically, as patients may require dosereduction with advancing disease (see below).The dose-dependent nature of side effects is an important

point to keep in mind as most side effects improve with dosageadjustment. Consequently, clinical studies using highdoses [38,39] more frequently reported side effects than others(Figure 4) [40]. Such dose-dependent effects are probably notlinear when considering the therapeutic efficacy [36,40].

6.2 Proposed therapeutic algorithm for Huntington’sdisease–choreaThe treatment of HD-associated movement disorders is indi-cated when they have a significant impact on daily function.However, reducing chorea would help patients also if it causessocial embarrassment or limits some specific daily activities.For a long time, haloperidol has been considered the first-linetherapy, although no adequately controlled clinical trials wereperformed confirming its effectiveness. Still, many neurolo-gists consider typical neuroleptics the first-choice drug in themanagement of chorea despite considerable risk of psychic andmotor adverse events. These side effects mimic the symptomsassociated with natural progression of the disease and so caremust, therefore, be taken to distinguish them from each other.We believe that the use of typical neuroleptics should be time-limited and carefully monitored, being strictly necessary onlyfor severe psychosis, resistant to atypical neuroleptics such asclozapine or quetiapine.

According to evidence based criteria, TBZ should beconsidered as the first-choice therapy for controlling choreicdyskinesias and only when not tolerated or inefficacious orunavailable, treatment options should include the atypicalantipsychotics. Among them, quetiapine and clozapine havethe best safety profile (unlikely to cause extrapyramidalsymptoms) but are less effective in controlling chorea thanrisperidone or olanzapine which have a higher D2-affinity, butmay worsen the underlying Parkinsonism. Olanzapine, in theauthors’ experience, is better tolerated than risperidone; more-over, it induces weight gain, which can be of help in patientswith weight loss [74]. Aripiprazole (AP) is a D2 receptor partialagonist used in the treatment of psychosis but, in our expe-rience, it is often effective in the management of tics andchorea. Recently, in a single-blinded trial, AP and TBZ havebeen compared: both were equally able to improve chorea butTBZ treatment induced drowsiness more frequently thanAP [75]. However, it has to be kept in mind that especiallyin the long-term use either olanzapine or AP may worsenParkinsonism and even cause TD [76,77].

Benzodiazepines can be efficacious in selected cases, that is,when chorea is worsened by concomitant anxiety. Sometimes,other therapeutic strategies are used alone or in combinationwith TBZ to improve motor functioning or reduce the risk forside effects. The majority of our patients are concomitantlytaking the NMDA antagonist amantadine or a small dose ofdopaminergic drugs for the management of Parkinsonism.TBZ could be safely administered in conjunction with neu-roleptics if psychiatric symptoms or chorea require additionalmanagement. Antidepressant drugs may reduce the impact ofTBZ on mood.

Finally, deep brain stimulation of the posteroventral globuspallidus internus may offer a treatment option for patientswith dyskinetic phenotype and minimal cognitive impair-ment, but its role in the management of HD remains inves-tigational [78]. A trial conducted by the Euro-HD network iscurrently ongoing.

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6.2.1 Effect on psychiatric symptomsTBZ was first introduced in the 1960s as an antipsychotic [1].We retrospectively evaluated the effect on psychiatricsymptoms in our cohort of 68 patients (unpublished data).After the first TBZ prescription, 14% of patients did notreport any effect, 76% a mild to moderate amelioration andthe remaining 10% a great improvement. Interestingly, theeffect seems to be related to dose (b: 0.35; Spearman rankorder correlation, p < 0.05).

6.3 Future directionsSeveral questions remain open and need to be addressed inwell-designed studies: i) The functional benefit of suppressingchorea has not been definitively demonstrated; due to thepotential for rare serious adverse effects, a symptomatictherapy with TBZ must be carefully weighed against thereal improvement of daily functioning; ii) TBZ should beconsidered the first-line strategy in controlling choreic dyski-nesias but its superiority versus atypical neuroleptics has neverbeen established; iii) Do concomitant treatments with anti-depressant/antiglutamatergic drugs really reduce the risk forside effects? iv) Because the acute effect of TBZ on chorea inHD patients has been recently investigated (the maximumeffect achieved was 163 ± 59 min after the administration ofthe drug) [79], is it possible to predict the chronic effect of

the drug settling a test challenge? and v) The impact of TBZon dystonia is sometimes disappointing and studies per-formed so far have shown a good effect on facial dyskinesias,symptoms more easily treated with botulinum neurotoxininjections. Future trials should explore the efficacy of TBZin more severe types of dystonia (e.g., complex torticollis):it could be conceivable that phasic dystonic movementsmight be more responsive to TBZ due to a pathophysiologymechanism closer to that of chorea. The same considerationsshould be made for other movement disorders (e.g., myoc-lonus) because the publication bias could erroneously favoran apparent effectiveness in conditions not investigated byregistered trials.

Declaration of interest

A Fasano and AR Bentivoglio are members of the Euro-HDnetwork. This project was supported in part by FondazioneIRCCS Istituto Carlo Besta, grant PS – NEURO 56/05/11‘Biomarcatori periferici di Neurodegenerazione finalizzati alladiagnostica presintomatica e al follow-up terapeutico: Unnetwork nazionale per la Malattia di Huntington, la Malattiadi Alzheimer, e la Sclerosi Multipla’.

AR Bentivoglio has received speaker’s fees from Chiesi,which distributes tetrabenazine in Italy.

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(28.5%), depression (15.0%), insomnia

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Clin Neuropharmacol 2008;31:313-18. The authors analyzed 68 HD patients

who had been treated with TBZ for a

mean period of 34.4 ± 25.2 months

(3 – 104 months). At the first follow-up,

after 9.7 ± 7.8 months, UHDRS score of

chorea was reduced by 21%. During the

follow-up, the clinical benefit persisted,

but the magnitude was reduced despite a

progressive increase of the doses (up to

60%). Motor improvement was not

influenced by sex, or doses or duration

of therapy; age at onset was the only

predictor of a good outcome. Five (7%)

patients did not gain any improvement

and TBZ was discontinued. There

were two withdrawals because of side

effects; 34 patients reported at least one

side effect.

41. Mahant N, McCusker EA, Byth K, et al.

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44. Halliday J, Farrington S, Macdonald S,

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46. Kazamatsuri H, Chien CP, Cole JO.

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dyskinesia with haloperidol and

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1973;130:479-83. After having reported the effectiveness of

TBZ for TD for the first time, the authors

conducted a trial randomizing 13 patients

to receive either haloperidol or TBZ.

Haloperidol was more efficacious in the

early part of the study, although the

clinical benefit waned at the end of the

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47. Ondo WG, Hanna PA, Jankovic J.

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1999;156:1279-81. The authors studied the effect of TBZ in

20 patients with TD. Randomized

videotapes were scored with the motor

subset of the modified AIMS by raters

blind to pre or post-treatment status. One

patient did not tolerate TBZ owing to

sedation. The remaining 19 were rated

after a mean of 20.3 weeks at a mean TBZ

dose of 57.9 mg/day. There were

significant improvements in mean scores

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the AIMS motor subset evaluated by the

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48. Stacy M, Jankovic J. Tardive tremor.

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50. Leckman JF. Tourette’s syndrome. Lancet

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52. Jankovic J, Glaze DG, Frost JD Jr. Effect

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de la Tourette’s syndrome. Neurology

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patients with TS. Marked and sustained

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mild or transient improvement occurred

in three patients and two patients had

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53. Jankovic J, Rohaidy H. Motor, behavioral

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54. Paleacu D, Giladi N, Moore O, et al.

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a retrospective chart review over

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and assessed using the CGI. The mean

CGIC score was +1 (mild improvement).

The group of patients who had the best

clinical effect (+3 on the CGIC)

represented 18.6% of all patients. They

had HD, other types of chorea, facial

dystonia/dyskinesia, TD, trunk dystonia,

TS and tardive akathisia.

55. Jankovic J. Treatment of hyperkinetic

movement disorders with tetrabenazine: a

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56. Marsden CD, Harrison MJ. Idiopathic

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Brain 1974;97:793-810

57. Marsden CD,Marion MH, Quinn N. The

treatment of severe dystonia in children

and adults. J Neurol Neurosurg Psychiatry

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58. Mariotti P, Fasano A, Contarino MF, et al.

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59. Scott BL. Evaluation and treatment of

dystonia. South Med J 2000;93:746-51

60. Hoehn MM, Cherington M. Spinal

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61. Jankovic J, Pardo R. Segmental

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62. Chatterjee A, Frucht SJ. Tetrabenazine in

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Mov Disord 2003;18:703-6. TBZ experience in pediatric patients is

limited. This is a report on five

children with severe chorea who were

treated with TBZ. TBZ effectively

controlled chorea in four patients, and

despite the need for relatively high doses,

it was well tolerated.

63. Kenney C, Jankovic J. Tetrabenazine in the

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74. Bonelli RM, Wenning GK.

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75. Brusa L, Orlacchio A, Moschella V, et al.

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76. Rauchverger B, Isakov V, Jabarin M.

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successfully treated by tetrabenazine.

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77. Zaidi SH, Faruqui RA. Aripiprazole is

associated with early onset of Tardive

Dyskinesia like presentation in a patient

with ABI and psychosis. Brain Inj

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78. Fasano A, Mazzone P, Piano C, et al.

GPi-DBS in Huntington’s disease: results

on motor function and cognition in a

72-year-old case. Mov Disord

2008;23:1289-92

79. Kenney C, Hunter C, Davidson A, et al.

Short-term effects of tetrabenazine on

chorea associated with Huntington’s

disease. Mov Disord 2007;22:10-13. The authors assessed the short-term

clinical effects of TBZ on choreic

movements in HD patients. To this end,

the usual morning dose of TBZ was

administered and patients were followed

with serial UHDRS motor examinations

approximately every 2 h until choreic

movements subsided and then returned.

TBZ decreased the UHDRS chorea score

on an average 42.4 ± 17.8%. The mean

duration of effect was 5.4 ± 1.3 h.

80. Watson MW, Skelton D, Jamali F.

Treatment of tardive dyskinesia:

preliminary report on use of tetrabenazine.

Can J Psychiatry 1988;33:11-13

81. Shapiro AK, Shapiro AS, Bruun R.

Gilles de la Tourette Syndrome. NY:

Raven Press; 1978

82. Kenney C, Hunter C, Mejia N, et al.

Tetrabenazine in the treatment of Tourette

syndrome. J Pediatric Neurol 2007;5:9-13

83. Jankovic J. Dystonia: medical therapy and

botulinum toxin. Adv Neurol

2004;94:275-86

AffiliationAlfonso Fasano† MD &

Anna Rita Bentivoglio MD PhD†Author for correspondence

Universita Cattolica del Sacro Cuore,

Istituto di Neurologia,

Largo Agostino Gemelli,

8-00168 Roma, Italy

Tel: +39 06 3015 5633; Fax: +39 06 3015 5633;

E-mail: [email protected]

Tetrabenazine


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