Which of the following drug is contraindicated in glaucoma: September 2009
Correct Answer: Atropine
Description: Ans. C: Atropine Most categories of drugs that list glaucoma as a contraindication or adverse effect are concerned with inducing acute angle-closure glaucoma. These medications will incite an attack only in those individuals with occludable angles (ie, very narrow anterior chamber angles). The classes of medications that have the potential to induce angle closure are: - Topical anticholinergic (Atropine) or sympathomimetic dilating drops - Tricyclic antidepressants - Monoamine oxidase inhibitors Antihistamines - Antiparkinsonian drugs - Antipsychotic medications - Antispasmolytic agents. Sulfa containing medications may induce angle-closure glaucoma by a different angle-closure mechanism, involving anterior rotation of the ciliary body. Typically, the angle closure is bilateral and occurs within the first several doses of the sulfonamide-containing medication. Patients with narrow or wide open angles are potentially susceptible to this rare and idiosyncratic reaction. * Drug-induced elevation of IOP is more common by an open-angle mechanism: -- Coicosteroids are a class of drugs that may produce IOP elevation by this mechanism Atropine: Topical atropine is used as a cycloplegic, to temporarily paralyze the accommodation reflex, and as a mydriatic, to dilate the pupils. Atropine degrades slowly, typically wearing off in 7 to 14 days, so it is generally used as a therapeutic mydriatic, whereas tropicamide (a shoer-acting cholinergic antagonist) or phenylephrine (an alpha-adrenergic agonist) is preferred as an aid to ophthalmic examination. Atropine induces mydriasis by blocking contraction of the circular pupillary sphincter muscle, which is normally stimulated by acetylcholine release, thereby allowing the radial pupillar dilator muscle to contract and dilate the pupil. Atropine induces cycloplegia by paralyzing the ciliary muscles, whose action inhibits accommodation to allow accurate refraction in children, helps to relieve pain associated with iridocyclitis, and treats ciliary block (malignant) glaucoma. Atropine is contraindicated in patients pre-disposed to narrow angle glaucoma. Adverse reactions to atropine include ventricular fibrillation, supraventricular or ventricular tachycardia, dizziness, nausea, blurred vision, loss of balance, dilated pupils, photophobia, dry mouth and potentially extreme confusion, dissociative hallucinations and excitation especially amongst the elderly. These latter effects are because atropine is able to cross the blood-brain barrier. A common mnemonic used to describe the physiologic manifestations of atropine overdose is: "hot as a hare, blind as a bat, dry as a bone, red as a beet, and mad as a hatter". These associations reflect the specific changes of warm, dry skin from decreased sweating, blurry vision, decreased sweating/ lacrimation, vasodilation, and central nervous system effects on muscarinic receptors, type 4 and 5. This set of symptoms is known as anticholinergic toxidrome, and may also be caused by other drugs with anticholinergic effects, such as diphenhydramine, phenothiazine antipsychotics and benztropine. The antidote to atropine is physostigmine or pilocarpine.
Category:
Pharmacology
Get More
Subject Mock Tests
Practice with over 200,000 questions from various medical subjects and improve your knowledge.
Attempt a mock test nowMock Exam
Take an exam with 100 random questions selected from all subjects to test your knowledge.
Coming SoonGet More
Subject Mock Tests
Try practicing mock tests with over 200,000 questions from various medical subjects.
Attempt a mock test now