phentolamine ophthalmic (Rx)

>10%

Instillation site discomfort including pain, stinging, and burning (16%)

Conjunctival hyperemia (12%)

1-10%

Dysgeusia (6%)

Contraindications

None

Cautions

Not recommended when active ocular inflammation (eg, iritis) is present because adhesions (synechiae) may form between iris and lens

Avoid touching vial tip to eye or to any other surface to avoid eye injury or contamination

Advise contact lens wearers to remove their lenses before instilling phentolamine and wait 10 minutes after dosing before reinserting contact lenses

Pregnancy

There are no available data with administration in pregnant females to inform a drug-associated risk

Animal data

• When phentolamine was administered orally to pregnant mice and rats during organogenesis skeletal immaturity and decreased growth was observed in offspring at doses at least 24x the recommended clinical dose
• Additionally, a lower rate of implantation was seen in pregnant rats treated with phentolamine administered at least 60xthe recommended clinical dose
• No malformations or embryofetal deaths were observed in offspring of pregnant mice, rats, and rabbits administered phentolamine during organogenesis at doses of at least 24x, 60x, and 20x, respectively, the recommended clinical dose

Lactation

There is no information regarding the presence of phentolamine in human milk, effects on breastfed infants, or effects on milk production during lactation to inform risk to an infant

Pregnancy Categories

A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

NA: Information not available.

Mechanism of Action

Nonselective alpha-1 and alpha-2 adrenergic antagonist

Reversibly binds to alpha-1 adrenergic receptors on the iris dilator muscle, thereby reducing pupil diameter

Phentolamine directly antagonizes mydriatic effect of an alpha-1 adrenergic agonist, and indirectly reverses mydriasis induced by muscarinic antagonist effects on the iris sphincter muscle

Absorption

Onset of action: 30 min

Maximal effects: 60-90 min

Duration of effect: 24 hr

Peak plasma time: 15 min - 1 hr

Peak plasma concentration: 0.45 ng/mL

Ophthalmic Administration

Use 1 single-patient-use vial to dose each dilated eye; discard single-patient-use vial immediately after use

Storage

Refrigerate at 2-8ºC (36-46ºF), not to exceed expiration date printed on carton and pouch

Protect from freezing

After opening foil pouch, store at 25ºC (68-77ºF) and use within 14 days; not to exceed expiration date printed on vial

Discard single-patient-use vial once opened immediately after use