Certified Paraoptometric (CPO) Practice Exam 2026 – All-in-One Study Guide to Ensure Exam Success!

Phenylephrine, a sympathomimetic medication often used as a vasoconstrictor in ocular procedures, typically lasts about 3 to 5 hours when administered topically in the form of eye drops. This duration can vary based on the individual’s metabolism and specific circumstances of use, but on average, the effects of phenylephrine will be noticed within this timeframe.

While the other options may reflect durations associated with other medications or variations in individual response, the established duration of action for phenylephrine in an ophthalmic setting is best represented by the choice of 3 to 5 hours. This timeframe is important for practitioners to consider when planning for follow-up care or additional treatments.