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Alpha-1 Adrenergic Agonist — Mydriatic Pregnancy: Use with caution — systemic absorption from 10%; 2.5% considered lower risk

Phenylephrine Eye Drops 2.5% / 10%

Brand names: Minims Phenylephrine

Adult dose

Dose: 1 drop of 2.5% solution (routine mydriasis); 1 drop of 10% (resistant mydriasis or fundoscopy in dark irides)
Route: Topical (ophthalmic)
Frequency: Single application; onset in 15–30 minutes; duration 3–5 hours
Max: 1–2 drops; repeat after 1 hour if inadequate dilation
10% solution: systemic absorption can cause significant cardiovascular effects — hypertension, reflex bradycardia, arrhythmias; use LOWEST effective concentration. Compress nasolacrimal punctum for 1–2 minutes after instillation to reduce systemic absorption. Avoid 10% in children, elderly, and cardiovascular disease.

Paediatric dose

Route: Topical
Frequency: Single application
Max: 2.5% formulation only in children — 10% CONTRAINDICATED in children
10% phenylephrine CONTRAINDICATED in children and neonates — systemic absorption causes severe hypertension and cardiac arrhythmias; 2.5% maximum

Dose adjustments

Renal

Use with caution — systemic absorption from 10% concentration in renal impairment

Hepatic

Use with caution with 10% in severe hepatic impairment

Clinical pearls

  • 10% vs 2.5%: the 10% solution achieves more profound and faster mydriasis but carries significant cardiovascular risk from systemic absorption — associated with fatal arrhythmias and stroke, predominantly in elderly patients and children; UK guidance recommends 2.5% as standard
  • Nasolacrimal compression: pressing the inner canthus for 1–2 minutes after instillation blocks nasolacrimal drainage and reduces systemic absorption by up to 70% — critical practice, especially when using 10%
  • Angle-closure glaucoma precipitant: any mydriatic (phenylephrine, tropicamide, atropine) can precipitate acute angle-closure glaucoma in anatomically predisposed eyes (shallow anterior chamber, narrow angles); ophthalmoscopy is contraindicated without angle assessment in suspected narrow-angle glaucoma
  • Combined with tropicamide: phenylephrine 2.5% + tropicamide 1% is the standard UK combination for fundus examination — phenylephrine provides pupil dilation, tropicamide provides cycloplegia and faster recovery
  • Floppy iris syndrome (IFIS) risk: alpha-1 blockers (tamsulosin, doxazosin) cause intraoperative floppy iris syndrome during cataract surgery — phenylephrine does NOT prevent IFIS; surgeon must be informed of any alpha-blocker history

Contraindications

  • 10% solution: cardiovascular disease, hypertension, severe arteriosclerosis
  • 10% solution: children under 12 years and elderly
  • Angle-closure glaucoma risk (phenylephrine dilates pupil — can precipitate angle closure in predisposed eyes)
  • Concurrent MAOI therapy — hypertensive crisis risk

Side effects

  • Systemic hypertension — particularly with 10% formulation
  • Reflex bradycardia
  • Ventricular arrhythmias (10% in susceptible patients)
  • Local: burning, stinging, pallor of conjunctiva
  • Photophobia (mydriasis)

Interactions

  • MAOIs — contraindicated; severe hypertensive crisis
  • Tricyclic antidepressants — enhanced cardiovascular pressor response
  • Beta-blockers — reflex bradycardia may be exaggerated; bradycardia-hypertension syndrome

Monitoring

  • Blood pressure and pulse when 10% used in susceptible patients
  • Duration of mydriasis — warn patient about photophobia and not driving for 4–6 hours

Reference: BNFc; BNF 90; RCOphth Mydriatic Guidelines; MHRA Phenylephrine 10% Safety; SPC Minims Phenylephrine. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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