Paremyd®

GoodRx

Hydroxyamphetamine 1% / Tropicamide 0.25% · ophthalmic solution

Mydriatics/Cycloplegics

Approved uses

Mydriasis for diagnostic procedures

One to two drops in the conjunctival sac.

Dilation starts within 15 minutes, peaks by 60 minutes, and most patients recover fully in 6 to 8 hours.

Dilation for binocular indirect ophthalmoscopy

One drop in each eye; the label allows one to two drops in the conjunctival sac.

Dark brown irides dilate more slowly, though one drop dilates adequately at any iris pigmentation.

OFF-LABELNot in the FDA label for this product

Horner syndrome, localising the lesion (single-agent hydroxyamphetamine, not this combination)

The test uses hydroxyamphetamine 1% ALONE. That product is no longer marketed in the United States: hydroxyamphetamine is listed only as a bulk ingredient, and Paremyd adds tropicamide 0.25%, which dilates on its own and so confounds the reading.

n=54 · single agent only

Hydroxyamphetamine releases noradrenaline from an intact third-order neuron, so it separates where cocaine cannot. In 54 patients with Horner syndrome, those with postganglionic damage dilated LESS on the affected side, while almost all with preganglionic lesions dilated MORE. A companion study of 26 normal subjects established the baseline that makes the reading interpretable: a mean 1.96 mm of dilation, and near-symmetric between an individual's two eyes at a mean interocular difference of -0.087 mm, so between-subject variation is much larger than within-subject. Read this row for the pharmacology and the history: the single-agent product it depends on is not available, which is why localisation is now usually left to imaging.

Cremer SA, Thompson HS, Digre KB, Kardon RH. Hydroxyamphetamine mydriasis in Horner's syndrome. Am J Ophthalmol. 1990;110(1):71-6

Contraindications

Angle-closure glaucoma, or narrow angles in whom pupil dilation may precipitate an attack.
Hypersensitivity to any component.

Available Forms

Ophthalmic solution, 15 mL bottle, hydroxyamphetamine hydrobromide 1% / tropicamide 0.25%

Mechanism of Action

Combines hydroxyamphetamine, an indirect sympathomimetic that releases endogenous norepinephrine from intact adrenergic nerve terminals with minimal cycloplegic action, and tropicamide 0.25%, a parasympatholytic blocking the iris sphincter and ciliary muscle; the two act at different effector sites, so the mydriatic effect is additive while full cycloplegia does not occur at this anticholinergic concentration. Onset within 15 minutes, maximum effect at 60 minutes, dilation and partial cycloplegia lasting 3 hours, complete recovery in 6 to 8 hours or up to 24 hours in some patients.

Warnings & Precautions

Angle-closure precipitation: Estimate the depth of the anterior chamber angle before instillation.
Intraocular pressure elevation: There is evidence that mydriatics may produce a transient rise in patients with open-angle glaucoma; monitor the elderly and others in whom glaucoma or raised pressure may follow administration.
Cardiovascular and endocrine comorbidity: Monitor patients with hypertension, hyperthyroidism, diabetes, or cardiac disease such as arrhythmias or chronic ischemic heart disease after instillation.
CNS disturbances: Rare, and may be particularly dangerous in infants, children, or the aged.
Route restriction: Topical ophthalmic use only, not for injection.

Common Side Effects

Ocular: Transient stinging, blurred vision, photophobia with or without corneal staining; increased intraocular pressure reported following mydriatics.
Systemic: Dry mouth, tachycardia, headache, allergic reactions, nausea, vomiting, pallor, muscle rigidity, CNS disturbances.
Serious cardiovascular events: Rare reports shortly after instillation, including death due to myocardial infarction, ventricular fibrillation, and significant hypotensive episodes.
Anticholinergic class effects: Psychotic reactions, behavioral disturbances, and vasomotor or cardiorespiratory collapse.

Pregnancy & Lactation

Pregnancy: Category C; no animal reproduction studies have been conducted and fetal harm is unknown; give only if clearly needed.

Lactation: Excretion in human milk is unknown; exercise caution in a nursing woman.

Pediatric Use

Safety and effectiveness not established; rare CNS disturbances may be dangerous in infants and children.