Which drug's metabolism is affected by the use of echothiopate drops for chronic glaucoma and is contraindicated?

Echothiopate is an organophosphate used in the treatment of chronic glaucoma, and it works by inhibiting the enzyme acetylcholinesterase. This inhibition leads to an accumulation of acetylcholine in the body, which can significantly affect the neuromuscular junction and muscle function.

Succinylcholine, a depolarizing neuromuscular blocker used primarily for muscle relaxation during surgery, is particularly impacted by acetylcholinesterase inhibitors like echothiopate. The metabolism of succinylcholine relies on its breakdown by the enzyme acetylcholinesterase. When this enzyme is inhibited, succinylcholine remains active for a longer period, leading to prolonged neuromuscular blockade and potential respiratory paralysis.

In contrast, the other options, such as fentanyl, propofol, and oxycodone, do not share the same mechanism of action or metabolic pathway involving acetylcholine and therefore are not contraindicated in patients receiving echothiopate. This understanding of the interaction between succinylcholine and echothiopate underscores the importance of careful drug selection in patients undergoing treatment for chronic glaucoma.