Homatropin

Homatropine is a tropane alkaloid and competitive antimuscarinic agent related to atropine. It is used primarily in ophthalmology to produce mydriasis (pupil dilation) and cycloplegia (paralysis of accommodation) for eye examinations and procedures. Historically it has also been used as a gastrointestinal antispasmodic, though this use is now uncommon.

In ophthalmic practice, homatropine hydrobromide is given as eye drops, commonly 2% or 5% solutions. Onset of dilatation occurs in about 30–60 minutes and the effect lasts roughly 24–72 hours, with cycloplegia of similar duration. Systemic absorption can produce anticholinergic effects, especially in children and older adults.

Indications include facilitating retinal examination and other procedures by dilation and accommodation suppression; it may relieve ciliary spasm in certain inflammatory eye conditions. Systemic use for GI symptoms is rare today.

Contraindications include hypersensitivity to homatropine or other antimuscarinics and narrow-angle glaucoma. Caution is advised in cardiac disease, elderly patients, those with urinary retention or cognitive impairment, and in patients taking other anticholinergic drugs.

Adverse effects range from ocular irritation and photophobia to blurred vision; systemic exposure may cause dry mouth, tachycardia, urinary retention, constipation, or confusion, particularly in young children or the elderly. Drug interactions occur with other antimuscarinics and agents with anticholinergic activity.