Which drug is considered a direct cholinergic agonist used for urinary retention?

The correct answer is Bethanechol, which is a direct cholinergic agonist specifically used to treat urinary retention. This medication works by stimulating the muscarinic receptors in the bladder, leading to increased bladder contraction, which facilitates urinary voiding. It is particularly effective in cases where the retention is due to atony or decreased muscle tone of the bladder.

In contrast, Roflumilast is primarily a phosphodiesterase-4 inhibitor used to manage chronic obstructive pulmonary disease, and does not directly influence bladder function. Pilocarpine is also a cholinergic drug, but it is mainly used to treat dry mouth and glaucoma, rather than urinary retention. Atropine, on the other hand, is an anticholinergic agent that inhibits the action of acetylcholine and would oppose the effects required to alleviate urinary retention. Therefore, Bethanechol stands out as the most appropriate choice for its specific action on urinary retention.