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Alpha-1 Adrenergic Agonist — Mydriatic

Phenylephrine Eye Drops 2.5% / 10%

Brand names: Minims Phenylephrine

Phenylephrine eye drops are a topical sympathomimetic mydriatic used to dilate the pupil for ophthalmic examination and procedures and, at lower concentrations, to relieve minor ocular redness.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It is a selective alpha-1 adrenoceptor agonist that stimulates contraction of the iris dilator muscle, producing mydriasis, and constricts conjunctival blood vessels.

Prescribing in practice

  • The higher-strength preparation can cause systemic cardiovascular effects, including a rise in blood pressure, so it should be used with caution in patients with cardiovascular disease, hypertension or hyperthyroidism, and avoided where high systemic absorption is a concern.
  • It may precipitate acute angle-closure glaucoma in predisposed eyes with narrow anterior chamber angles.
  • Unlike antimuscarinic mydriatics it does not cause cycloplegia, so accommodation is preserved.

Monitoring

When the higher-strength drops are used, blood pressure and cardiovascular status should be considered, and the eye observed for the intended dilation and any pressure rise.

Counselling the patient

  • Your vision may be blurred and your eyes sensitive to light for a period after dilation, so arrange not to drive until this settles.
  • Wear sunglasses to ease light sensitivity while the pupils are dilated.
  • Tell your clinician about any heart conditions or high blood pressure before the drops are used.

Evidence & guidelines

Topical phenylephrine is a long-established mydriatic for ophthalmic examination, with its effects and cardiovascular cautions described in ophthalmology references and the SPC.

Reference: RCOphth Mydriatic Guidelines; MHRA Phenylephrine 10% Safety; SPC Minims Phenylephrine; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

Pathways