glaucoma tozammal

8/14/2019 Glaucoma Tozammal

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Skeletal muscle relxants

Nicotinic (Muscle) receptor blockers Skeletal muscle relaxants.

Nicotinic (Nerve) receptor blockers Ganglion blockers


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Skeletal muscle relaxants

Skeletal muscle relaxants blockperipherally at the

neuromuscular junction (Nicotinic

receptor of Ach Muscle). Types of Skeletal muscle relaxants:

Competitive (Non-depolarizing)

Non-competitive (Depolarizing)Directly acting Muscle relaxants

Miscellaneous : Aminoglycosides


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Skeletal muscle relaxantsPharmacokinetics :

Most peripheral NM blockers are quaternarycompounds not absorbed orally.

Administered intravenously.

Do not cross blood brain barrier or placenta SCh is metabolized by Pseudocholinesterase.

Atracurium is inactivated in plasma by spontaneousnon-enzymatic degradation (Hoffman

elimination).


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Neuromuscular blockers

Non - depolarizing ( competitive )Long acting : Pancuronium,

Pipecuronium,Intermediate : Vecuronium, Rocuronium,Atracurium

Short acting : Mivacurium

Depolarizing blockers : (Non-competitive)Succinylcholine (Suxamethonium)


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Neuromuscular blocking agents :

Non-depolarizing agents (Competitiveblockers).

Mechanism of action :These have anaffinity for the Nicotinic (NM) receptorsat the muscle end plates but have no

intrinsic activity. The antagonism is surmountable by

increasing the conc. of Ach.


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Skeletalmusclerelaxants

Duration mins

Pancuronium 40-80

Pipecuronium 50-100

Vecuronium 20-40

Atracurium 20-40

Rocuronium 20-40

Succinylcholine

3-6


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Depolarizing block ( Non-competitive ) :

Succinylcholine have affinity and submaximal intrinsic activity at NM receptors.

They open Na channels whichcause initial twitching and fasciculations.

It do not dissociate rapidly from thereceptors resulting in prolonged

depolarization and inactivation of the Na +channels


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Depolarizing block (Non-competitive) :Succinylcholine

It causes muscle pain.

It causes hyperkalemia.

Malignant Hyperthermia.


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CompetitiveNon-depolarizing

Non-CompetitiveDepolarizing

Paralysis Flaccid Fasciculations--- Flaccid

Neostigmine Antagonizes Exaggerate /no effect.

Examples Pancuronium Succinylcholine


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USES OF NEUROMUSCULAARBLOCKERS :

Adjuvant in general anesthesia

Intubation and endoscopies

Brief procedure reduction of #.


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Directly acting muscle relaxants :

Dantrolene :Depolarization triggered release of

calcium from the sarcoplasmiccontraction is blocked / reduced.

Dantrolene is used orally/ i.v to reducesspasticity in hemiplegia and cerebral

palsy. It is the drug of choice malignant

hyperthermia


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Central skeletal musclerelaxants

These produce selective action in thecerebrospinal axis acts as skeletal musclerelaxants

Theses depress the spinal and supraspinalpolysynaptic reflexes involved in theregulation of muscle tone.

Polysynaptic reflex in the RAS involved inthe wakefulness also depressed sedativeaction.


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Central skeletal musclerelaxants

Examples of centrally acting skeletalmuscle relaxants :

Chlorzoxazone, Methocarbamol

Diazepam

Baclofen


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Ganglion blockers

Ganglion blockersare competitiveantagonist at NN receptors inautonomic ganglia.

Net effect of the blocker is to reducethe predominant tone.

Effects are predictable and depend

on the relative dominance in terms ofPANS and SANS.


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Ganglion blockers

Effectororgans

Dominantsystem

Effects of ganglionicblockade

Arterioles/veins

SANS Vasodilatation, hypotension

Sweat glands SANS Anhydrosis

Genitals PANS/SANS Impotence

Heart PANS TachycardiaIris PANS Mydriasis

Ciliary PANS Cycloplegia

Bladder PANS Urinary retention

Salivary PANS Xerostomia


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Ganglion blockers

Ganglionic blocking agents :

Mecamylamine, Trimethaphan.

It is used in severe hypertension.


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Ganglion blocking agents

Ganglion blocking agents block theautonomic reflexes, including changes inheart rate elicited by increase / decrease

in blood pressure. Hexamethonium will block the reflex

bradycardia that occurs whenphenylephrine causes vasoconstriction, it

will not block a bradycardia that resultsfrom direct activation of muscarinicreceptors in heart.


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Glaucoma


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Glaucoma

Glaucoma is increased intraocular pressure.

Intraocular pressure is determined by thebalance between fluid input & drainage out of

the globe----- aqueous humor produced by ciliaryepitheliumand drained at the filtrationangleof the anterior chamber.

Objective of glaucoma therapy: ---increase outflow& ordecreaseproduction of aqueous humor.


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Glaucoma

Major route of aqueous humordrainage is ~ 90% throughtrabecular route ~

10% passes through within the ciliarymuscle into episceral vessels(uveosceral flow)


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D f l


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Drugs for glaucoma

Beta blockers

Alpha agonist

CA inhibitor

Pilocarpine PG analog


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Glaucoma

Muscarinic cholinomimetics : Direct-acting : Pilocarpine, Carbachol

Indirect-acting : Physostigmine

----> contraction of ciliary muscle open

the trabecular spaces so that aqueoushumor drains more easily.----> iris pulled from angle of anteriorchamber widening the filtration angle and

opening the trabecular network----> increased outflow of aqueous humor----> decreased intraocular pressure.


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Glaucoma

Beta adrenoceptor blockers :Timolol, Betaxolol

----> decreased production ofaqueous humor by ciliary epithelium.

No change in pupil size, Noheadache, No fluctuations in IOT arethe advantages of the beta blockers.


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Glaucoma

Carbonic anhydrase inhibitors : Dorzolamide

It blocks the formation of aqueous humor byblocking the carbonic anhydrase enzyme

required for the synthesis of it.Alpha Adrenoceptor agonists :

Apraclonidine----> alpha 2 agonist acts by reducing the

formation of aqueous humor.


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Glaucoma

Prostaglandins :

Latanaprost

It increases the aqueous drainage through

the alternate pathways uveoscleral route. May eventually cause permanent darkening

of the iris to brown (heterochromia),eyelashesreddening of the eyes.

glaucoma tozammal

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