Phenylephrine with tropicamide

How it works

Phenylephrine is an alpha-adrenergic agonist that stimulates the iris dilator muscle, while tropicamide is an antimuscarinic that paralyses the sphincter pupillae and ciliary muscle, so together they produce rapid, effective mydriasis and some cycloplegia.

Prescribing in practice

• The combination can precipitate acute angle-closure glaucoma in eyes with shallow anterior chambers, and phenylephrine can cause systemic cardiovascular effects, so use with caution in cardiovascular disease and in susceptible eyes.
• Higher-strength phenylephrine carries greater systemic absorption risk and is generally avoided in infants, the elderly and those with significant hypertension or heart disease.
• Warn patients that vision, particularly near focusing, will be blurred and that they should not drive until it recovers.

Monitoring

No laboratory monitoring is needed, but observe susceptible patients for systemic cardiovascular effects and for symptoms of acute angle closure after dilation.

Counselling the patient

• Your vision will be blurred and your eyes light-sensitive for some hours, so arrange not to drive and bring sunglasses.
• Seek urgent help if you develop a painful red eye with haloes around lights or nausea after dilation.
• Punctal occlusion (pressing the inner corner of the eye) can reduce systemic absorption if advised.

Evidence & guidelines

Combined phenylephrine and tropicamide is standard practice for diagnostic and pre-operative mydriasis, with class cautions on angle closure and systemic sympathomimetic effects set out in the SPC.