3 4 cholinergic pharmacology younus h johan 2016

Important drugs used in glaucoma

Dr. Younus H Johan Dr. Younus H Johan Department of pharmacology & toxicology College of pharmacy University of al-anbar2016

VISUAL FIELD LOSS

OPTIC NERVE

DAMAGE

GLAUCOMA

INCREASE

IOP

Normal

Open-angle glaucoma

Drainage

Cholinergics

Production

Cholinergics

Closed-angle glaucoma

Mydriatics (contra.)

Adhesion glaucoma

DarknessMydriatics

Drugs or class Nature of action and important remarks

Cholinergic agentsMuscarinic agonists (pilocarpine)Anticholinesterases [physostigmine,

Improved drainage of aqueous humour (contracting the longitudinal muscle of the ciliary body leading to opening the trabecular meshwork around Schlemm’s canal (drainage channels), immediate drop s [physostigmine,

DFP (isoflurophate)]

channels), immediate drop (IOP). •acute glaucoma •chronic open-angle glaucoma.

M.AK.Lafi : Essentials of Medical Pharmacology 2009


-blockersTimololBetaxololCartelolMetipranolol

Decrease production of AH -to reduced IOP. No effect on focusing for near vision or pupil size;(used in Metipranolol (used in chronic open-angle glaucoma, narrow and acute glaucoma.


Drugs or class

Nature of action and important remarks

α-agonistsNon-selectiveAdrenaline

α2-selectivePraclonidine

Enhances AH outflow (drainage, -receptors) by increasing PG production that enhance uveoscleral drainage

decreases production of AH by vasoconstriction of the ciliary body blood Praclonidine

Brimonidinevasoconstriction of the ciliary body blood vessels leading to reduced IOP. Topical 2% adrenaline solution used in chronic open-angle glaucoma.

C/I •closed-angle •acute glaucomas



Prostaglandins(PGF2α derivatives:latanoprost, unoprostone)

Increase outflow by acting at the FP receptor -stimulates collagenase and metalloproteinase to degrade the extracellular matrix between ciliary muscle bundles, which in turn leads to the reduction of hydraulic resistance to uveoscleral flowSESE•irreversible brown pigmentation of the iris and eyelashes,

•Eyelash : lengthening, thickening•drying of the eyes, and conjunctivitis.



Diuretics

Carbonic anhydrase inhibitorsAcetazolamide

Decreases production of AH by blocking carbonic anhydrase in the ciliary body leading to reduced IOP. •chronic glaucoma •acute closed-angle glaucoma.•acute closed-angle glaucoma.

Osmotic agentsMannitol

Reduces IOP in acute closed-angle glaucoma.


Summary of selected mydriatic and cycloplegicsmydriatic and cycloplegics

Mydriasismiosis Mydriasismiosis

Drug Duration Use

Tropicamide 3-6 hr Fundus examination

Homatropine 1-3 days Cycloplegic for refraction* in children

Atropine 7-10 days For refraction as above; also iridocyclitis**(+ phenylephrine)

They may precipitate acute glaucoma in the elderly and predisposed patients


Thank YouThank You

Anticholinergic drugs

Dr. Younus H Johan Department of pharmacology & toxicology College of pharmacy University of al-anbar

Effects• Decreased secretion• Mydriasis • Cycloplegia (decreased accommodation )• Hyperthermia• Tachycardia

Antichloinergic prototype:

Atropine

• Sedation• Urinary retention and constipation• Behavioural excitation and

hallucinations

Selected therapeutic uses and important remarks*

Antimuscarinicagents

• to produce mydriasis & cycloplegia prior to refraction (7 days)

• spastic disorders of GI and lower urinary tracts• organophosphate poisoning

Atropine( click )

• organophosphate poisoning• premedication prior to surgery, to suppress

respiratory secretion in children




• to produce mydriasis & cycloplegia prior to refraction (7 days)

• spastic disorders of GI and lower urinary tracts• organophosphate poisoning• premedication prior to surgery, to suppress

respiratory secretion in children

Atropine( click )

• Cycloplegic for refraction in children (24 hr)Homatropine

• Fundus examination (3 hr)Tropicamide




• In obstetrics with morphine to produce amnesia and sedation

Scopolamine(hyoscine) and sedation

• Motion sickness(hyoscine)

• Asthma (inhalation)Ipratropium




• With chlordiazepoxide (Librax®) in GI disorders like • peptic ulcer, • nervous dyspepsia,• irritable bowel syndrome, • spastic colitis, • mild ulcerative colitis

Clidinium

With trifluoperazine (Stelabid®) in • peptic ulcer, • visceral spasm

Isopropamide

• Peptic ulcer (inhibits acid secretion), Pirenzepine • Peptic ulcer (inhibits acid secretion), • poorly enters the CNS, thus, no or little CNS side-effects

Pirenzepine

• Peptic ulcer, • irritable bowel syndrome, & • urinary disorders of storage (urinary frequency,

incontinence, nocturnal enuresis

Propantheline

• Urinary disorders of storage (as above)Emepronium(Cetiprin®)




• Peptic ulcer (inhibits acid secretion), • poorly enters the CNS, thus, no or little CNS side-effects

Pirenzepine

• Peptic ulcer, • irritable bowel syndrome, &

Propantheline• irritable bowel syndrome, & • urinary disorders of storage (urinary frequency,

incontinence, nocturnal enuresis

• Urinary disorders of storage (as above)Emepronium(Cetiprin®)


CNS AgentsBenzotropine

(Centrally acting antimuscarinic antagonists)• Drug induced dystonias• Parkinson’s disease

BenzotropineProcyclidineBenzhexol-HClOrphenadrine

Adverse-effects commonly observed with cholinergic antagonists:

blurred vision, mydriasis, tachycardia, constipation, urinary retention, and confusion.


Moderately severe to severe hypertensionGanglionic blockersMecamylamineMecamylamine

Short-term treatment of hypertension (emergency lowering of blood pressure, when other agents cannot be used)

Trimethaphan


See appropriate section in the chapter on CNS pharmacology (later on)

Neuromuscular blockersNondepolarising(competitive agents)(competitive agents)Depolarising agents


3 4 cholinergic pharmacology younus h johan 2016

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