homatropine hydrobromide
Homatropine ◆, Isopto Homatropine

Available forms
Available by prescription only
Ophthalmic solution: 2%, 5%

Indications and dosages
 Cycloplegic refraction. Adults: Instill 1 to 2 drops of 2% or 1 drop of 5% solution in eye; repeat in 5 to 10 minutes, p.r.n.
Children: Instill 1 drop of 2% solution in the eye; repeat at 10-minute intervals, p.r.n.
 Uveitis. Adults: Instill 1 to 2 drops of 2% or 5% solution in eye up to q 3 or 4 hours.
Children: Instill 1 drop of 2% solution b.i.d. or t.i.d.

Pharmacodynamics
Cycloplegic and mydriatic actions: Anticholinergic action prevents the sphincter muscle of the iris and the muscle of the ciliary body from responding to cholinergic stimulation, resulting in unopposed adrenergic influence and producing pupillary dilation (mydriasis) and paralysis of accommodation (cycloplegia).

Pharmacokinetics
Absorption: Unknown.
Distribution: Unknown.
Metabolism: Unknown.
Excretion: Recovery from cycloplegic and mydriatic effects usually occurs within 1 to 3 days.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug or other belladonna alkaloids such as atropine, and in those with glaucoma or those who have adhesions between the iris and lens.
  Use cautiously in elderly patients and in those with increased ocular pressure.

Interactions
Drug-drug. Carbachol, cholinesterase inhibitors, pilocarpine: Interferes with antiglaucoma effects of these drugs. Avoid use together.

Adverse reactions
CNS: confusion, somnolence, headache.
CV: tachycardia.
EENT: eye irritation, blurred vision, photophobia, increased intraocular pressure, transient stinging and burning, conjunctivitis, vascular congestion, edema.
GI: dry mouth.
Skin: dryness, rash.

Effects on lab test results
None reported.

Overdose and treatment
Signs and symptoms of overdose include flushed dry skin, dry mouth, blurred vision, ataxia, dysarthria, hallucinations, tachycardia, and decreased bowel sounds.
 Treat accidental ingestion with emesis or activated charcoal. Use physostigmine to antagonize anticholinergic activity of homatropine in severe toxicity; propranolol may be used to treat symptomatic tachyarrhythmias unresponsive to physostigmine.

Special considerations
• Drug may produce symptoms of atropine sulfate poisoning, such as severe mouth dryness and tachycardia.
• Monitor patient for adverse reactions and to ascertain therapeutic result.
Pediatric patients
• Use drug cautiously in young children and infants. There’s an increased chance of sensitivity in children with Down syndrome, spastic paralysis, or brain damage. Feeding intolerance may result.
Geriatric patients
• Use drug cautiously in elderly patients because of the risk of undiagnosed glaucoma and increased sensitivity to drug effects.

Patient education
• Provide patient with information on correct method of administration.
• Inform patient that vision will be temporarily blurred after instillation, and to avoid driving or operating machinery.
• Inform patient that drug may produce drowsiness.
• Patient may be photophobic and may benefit from wearing dark glasses to minimize discomfort.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use