Which eye drop has a red cap and lasts about 24 hours?

Which eye drop has a red cap and lasts about 24 hours?

• A. Cyclopentolate
• B. Phenylephrine
• C. Tropicamide
• D. Homatropine

Answer: (A)

The key idea is matching duration of action with the drug’s use. Cyclopentolate is a cycloplegic that dilates the pupil and temporarily relaxes the eye’s focusing muscles for about a day. That longer duration distinguishes it from the other common mydriatics: tropicamide and phenylephrine produce dilation for only a few hours, while homatropine can last longer but is more variable. The red cap is a branding cue used with cyclopentolate in many packaging schemes, helping clinicians quickly identify it. So the eye drop with a red cap that lasts about 24 hours is cyclopentolate.

The key idea is matching duration of action with the drug’s use. Cyclopentolate is a cycloplegic that dilates the pupil and temporarily relaxes the eye’s focusing muscles for about a day. That longer duration distinguishes it from the other common mydriatics: tropicamide and phenylephrine produce dilation for only a few hours, while homatropine can last longer but is more variable. The red cap is a branding cue used with cyclopentolate in many packaging schemes, helping clinicians quickly identify it. So the eye drop with a red cap that lasts about 24 hours is cyclopentolate.