Final answer:
The drug to avoid in acute angle-closure glaucoma is atropine, as it would prevent the necessary action of pupil constriction needed to alleviate the condition. Pilocarpine would be beneficial in this case due to its action as a muscarinic agonist.
Step-by-step explanation:
The drug to avoid in acute angle-closure glaucoma is c) Atropine. Atropine is an anticholinergic medication, which means it blocks the action of acetylcholine, a neurotransmitter that can constrict the pupil. In the case of acute angle-closure glaucoma, pupil constriction is needed to open the angle and improve aqueous humor outflow, thereby reducing intraocular pressure. Atropine would prevent this necessary action and could worsen the condition.
Pilocarpine, on the other hand, is a muscarinic agonist that is useful in treating glaucoma because it contracts the ciliary muscle and creates openings at the base of the cornea for aqueous humor drainage. Timolol, a beta-blocker, and diphenhydramine, an antihistamine with anticholinergic properties, are not as contraindicated as atropine in this scenario. Therefore, pilocarpine would be a choice in managing this condition, not a drug to avoid.