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Antihistamines
Chapter 69
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Outcomes
Identify concepts related to medication classificationsand application to manage allergic reactions,conditions of the upper respiratory system, acid
indigestion and gastric reflux. Choose nursing interventions related to the applied
pharmacokinetics and pharmacodyanmics specific tothese medications
Implement the nursing process in the administrationof medication classes covered herein
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Background
Histamines (Predominantly H1)
Endogenous
Vessel effects
Bronchi effects
Stomach effects
Secretes Mucus
Greatest interest Allergic reactions (mild / anaphylaxis)
PUD (Peptic Ulcer Disease)
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Histamine Release
Allergic response
Requires IgE antibodies
Prior exposure to allergen
Non-allergic direct stimulation of cells
Some drugs, chemicals, radiocontrast media,plasma expanders - require no prior exposure
Cell injury (histamines can cause)
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Physio / Pharm Effects
H1 Stimulation Vasodilation (If this, then?) BP drops, nose gets stuffy,
edema, puffy eyes, etc.
Vessel wall cells contract (If this, then?)
Bronchoconstriction (If this, then?) Trouble breathing
Itching & pain
Mucus secretion
CNS effect cognition / memory / sleep
H2 Stimulation Secretion of gastric acid (If this, then?)
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Allergies & Pharmacology
Mild Allergy Hay fever, urticaria, mild transfusion rx.
Sxms caused by? histamines
TX?
Severe Anaphylactic shock (bronchocontriction,
hypotension, & edema of glottis) Sxms caused by? leukotrienes
TX? (ch 17) Epi
Other Uses Common cold runny nose
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Antihistamines: 1st Generation
H1 Antagonists (classic antihistamines)
No single prototype
dyphenhydramine [Benadryl]
Highly sedating
MOA
Blockers (1st Gen)
Selectively bind to histaminic receptors
Can also bind to nonhistaminic receptor(muscarinic)
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Therapeutic Effects (TE) Vessels (If blocks histamine, then ?)
Capillaries (If blocks, then ?)
Sensory nerves (If, then) itching relief Mucous membranes (If, then)
CNS
Therapeutic doses (If, then) - sedation Overdose stimulation, seizures esp. in young
Other: relieve N & V, motion sickness
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Clinical uses Mild allergies, seasonal rhinitis, acute
urticaria, allergic conjunctivitis, mild
transfusion reactions Some block muscarinic & H1 receptor sites
useful for motion sickness promethazine [Phenergan] and dimenhydrinate
[Dramamine] Insomnia (diphenhydramine [Benadryl])
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Adverse Effects
CNS
Sedation = to excess ETOH (If this, then?)
Dizziness, lack of coordination, confusion
Paradoxical: insomnia, excitation, tremors,convulsions
GI N, V, Diarrhea / constipation, loss of appetite
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Anticholinergic effects Dry mouth, throat, nasal passages, thickened secretions,
(cautions?) urinary hesitancy, constipation, palpitations
Cardiac Dysrhythmias w some 2nd
Gen. Torsades de pointes, V-fib terfenadine [Seldane] & astemizole [Hismanal]
Contraindications third trimester
Precautions: asthma, children/elderly, urinaryretention, HTN, OA glaucoma, prostatichypertrophy
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D D
ETOH, barbs/benzos/ opioids, antidepressants
Toxicity
Sxms similar to atropine poisoning (anticholinergic),hyperpyrexia (super fever, can kill children)
Can lead to death in children via excitation,hallucinations, convulsion, coma, CV collapse, death.
Tx: remove and support may use charcoal followedwith cathartics
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Antihistamines: 2nd Generation
Prototypes - Fexofenadine [Allegra] -EXPENSIVE
MOA / TE antagonists of histamine to
relieve sxms of allergic rhinitis andurticarias ADME - Do not readily cross B-B barrier
therefore non-sedating w minimized
anticholinergic SEs Precautions ETOH, drowsiness, liver,
kidneys
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Drugs for Treating Allergic
Rhinitis, Coughs, Colds
Ch 75
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Allergic Rhinitis
Review of sxms
Commonly associated disorders
Seasonal vs. Perennial
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Antihistamines
First line - oral
Prophylaxis first
No use against cold Adverse effects
1st gen - sedation, anticholinergic
2nd
gen - rare
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Intranasal Glucocorticoids
Prototype: fluticasone (Flonase)
Action / Use Predominantly local anti-inflammatory
First line - Most effective against all sxms Adverse Effects
Drying, burning, or itching (when applied topically)
Rare - sore throat, epistaxis and HA
Rare - systemic adrenal suppression / slowedgrowth in children
Dose: Adults 2 sprays of 50 mcg. once daily
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Intranasal Cromolyn
Prototype: cromolyn (NasalCrom)
Action / Use
Suppresses release of histamine
Best suited for prophylaxis
May not see results for week or more
Adverse effects
Negligible
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Sympathomimetics (fight or flight)(Decongestants)
Prototype: phenylephrine (Neo-Synephrine) Action / Uses - Reduce nasal congestion via ?
Topical - rapid and intense Oral - prolonged, moderate, systemic effects
Also used in sinusitis and colds
Adverse effects Rebound congestion CNS stimulation
Cardiovascular Hemorrhagic stroke w phenylporpanolamine Abuse (pseudoephedrine and ephedrine)
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Sympathamometics (contd)
Nasal sprays
2 3 sprays every 4 hours needed not toexceed 5 consecutive days (to reduce
dependence)
What cocaine is
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Anticholinergics
Prototype: ipratropium bromide (Atrovent)
Action / Use
Blocks cholinergic receptors and inhibitssecretions to relieve rhinorrea in allergicrhinitis and asthma
No systemic effects
SEs: drying, irritation Dry mouth, throat, etc.
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Leukotriene Antagonist
Prototype: montelukast (Singulair)
Action / Uses;
Blocks binding of leukotrienes to receptorsthereby relieving nasal congestion
Leukotrienes normally vasodilate and increasevascular permeability, causing congestion
Adverse Effects: None significant Table 75-1 in book
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Treatment of Coughs
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Antitussives
Antitussives (cough suppressants)
Actions / use: elevate cough threshold incommon cold and URTI
Opioid (codeine and hydrocodone) best (stopscough in the brain)
Dosage: codeine 10 to 20 mg up to 6 times daily
Nonopioid (dextromethorphan) - best
Opioid derivative w/o euphoria or dependence
Can lead to mind-body dissociation equal to PCP
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Expectorants
Prototype - guaifenesin (Mucinex) MOA / Use increases flow of respiratory tract
secretions
Dont use for COPD or something else readthe friggin book
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Mucolytics
Prototype acetylcysteine (Mucomyst)
Can also use hypertonic saline
MOA / Use directly thins secretions
ADME
Inhalation delivery
Adverse effects Can trigger bronchospasm
Antidote for tylenol!
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Colds
Drug regimen
Symptomatic
Combination products
Decongestants
Antitussives
Analgesics
Antihistamines - anticholinergic to suppress mucus Caffeine
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Treatment of Severe Allergy
Chapter 17
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Adrenergic Agonist
Prototype - epinephrine
MOA/Use
Direct receptor binding ( 1&2, 1&2) mimicing the
sympathetic nervous system Also known as sympathomimetic & catecholamine (think of
these to mean stimulation)
ADME
Broken down quickly in stomach & significant 1st passeffect (cant take it PO)
Cant cross blood-brain
Discolors (pink/brownish) as it degrades (If, then?)
(Throw it away!)
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TEs (Therapeutic Effects) Vasoconstriction (most common use)
Hemostasis Augments local anesthetic via vascontriction Elevates blood pressure
Restores beating heart Bronchodilates
TOC for anaphylactic shock Mydriasis (rare use)
Adverse effects: HTN, necrosis, bradycardia w HTN, tachycardia,
tremor, chest pain, elevated blood sugar
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Table 17-3
D D MAOIs
TCAs
General anesthestics (myocardial effects)
Precautions
IV admin can cause potentially fatal effect
check concentrations! Insure patent and healthy IV site (you dont
want epi going into the tissuesThe range can be from 1:100,000 to 1:1,000 make sure to read the
label!!!!
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EpiPen
Anaphylactic deaths
PCN, venoms & foods
Device: EpiPen & EpiPen Jr.
Storage & Replacement Room temp dark do NOT refrigerate
Injection
Duration 10-20 mins SEs
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Selected Drugs for
Peptic Ulcer Disease (PUD)Chapter 76
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Histamine2-Receptor Antagonists
Prototype: cimetadine (Tagamet) First choice for gastric / duodenal ulcers
Action / Uses:
Promote healing through acid reduction
GERD, Aspiration Pneumonitis (aspiration of acid in the lungs) inobese & gyne prior to anesthesia
Adverse effects Low incidence of gynecomastia (breasts devlpmnt in men),
reduced libido, impotence, CNS depression / excitement,pneumonia
D D Inhibits hepatic drug metabolism therefore?
Major Drugs of concern warfarin, phenytoin, theophylline,lidocaine
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Famotidine (Pepsid)
For Heartburn, acid indigestion, sourstomach
Cut dose in renal compromise/failure
No antiandrogenic effects
No effect on hepatic metabolism of otherdrugs
Doesnt cause a lot of the things that Tagamet
does
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Proton Pump Inhibitors
Prototype - omeprazole (Prilosec)
Action / Uses suppress secretion of gastric acid Irreversible - days - up to weeks after cessation
Superior to H2RAs
Adverse effects HA, diarrhea, N & V
Long term may increase risk of CA
ADME give 30 min before meal once daily
D
D, D
F Reduced absorption of atazanavir, ketocanazole anditracanazole NOT recommended concurrently with atazanavir
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Antacids
Prototypes - magnesium hydroxide / aluminumhydroxide
Action / Uses alkaline agents that neutralizeacid & decrease destruction of gut wall And prophylactically to prevent aspiration pneumonia
ADME Take regularly to promote healing
In PUD: 1 and 3 hr after each meal & at bedtime Goal is gastric pH greater than 5
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Adverse effects
Constipation (aluminum base) / Diarrhea(magnesium base)
Sodium loading
High levels in renal failure clients
DD may interfere with absorption of
other drugs