Which drug is primarily classified as a cholinergic agonist?

Pilocarpine is primarily classified as a cholinergic agonist because it directly stimulates muscarinic receptors, which are a subtype of cholinergic receptors that respond to the neurotransmitter acetylcholine. Cholinergic agonists enhance the effects of acetylcholine in the body, leading to responses such as increased salivation, sweating, and muscle contraction. Pilocarpine, in particular, is used therapeutically to treat conditions like glaucoma by increasing the outflow of aqueous humor in the eye and also in situations where stimulation of salivary glands is needed, such as in patients with dry mouth due to Sjögren's syndrome.

Other drugs listed in the options do not primarily function as cholinergic agonists. For instance, atropine is an anticholinergic agent that blocks the action of acetylcholine, which contradicts the classification of agonists. Succinylcholine is a neuromuscular blocker that acts as a depolarizing agent at the neuromuscular junction, while oxybutynin is an anticholinergic medication used to manage overactive bladder by inhibiting acetylcholine’s action on muscarinic receptors. Thus, the distinct action of pilocarpine as a direct chol