ALPHAGAN P
Clinical safety rating
cautionComprehensive clinical and safety monograph for ALPHAGAN P (ALPHAGAN P).
Alpha-2 adrenergic agonist; decreases intraocular pressure by reducing aqueous humor production and increasing uveoscleral outflow.
| Metabolism | Minimal systemic metabolism; undergoes extensive ocular metabolism. Systemic metabolism primarily hepatic via aldehyde oxidase and cytochrome P450 enzymes. |
| Excretion | Renal: approximately 70% unchanged; fecal: <10% as metabolites. |
| Half-life | Terminal elimination half-life: approximately 2 hours (range 1.5-3 hours) in aqueous humor after topical administration; systemic half-life: ~3 hours. |
| Protein binding | Approximately 30% bound to plasma proteins (mainly albumin). |
| Volume of Distribution | Vd: ~0.8 L/kg, indicating moderate tissue distribution; the drug distributes into aqueous humor and ocular tissues. |
| Bioavailability | Topical ophthalmic: systemic bioavailability is approximately 80% due to absorption through nasal mucosa and gastrointestinal tract after drainage; oral bioavailability is high but not clinically used. |
| Onset of Action | Topical ophthalmic: reduction of intraocular pressure begins within 1-2 hours; peak effect at 2-4 hours. |
| Duration of Action | Topical ophthalmic: IOP-lowering effect persists for 8-12 hours, supporting twice-daily dosing. |
| Molecular Weight | 292.14 |
One drop of 0.1% or 0.15% ophthalmic solution in the affected eye(s) three times daily, approximately 8 hours apart.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No specific dose adjustment recommended; use with caution in severe renal impairment (eGFR <30 mL/min/1.73 m²) due to potential systemic accumulation. |
| Liver impairment | Contraindicated in patients with severe hepatic disease (Child-Pugh class C). For mild to moderate impairment (Child-Pugh A or B), consider using the lowest concentration (0.1%) and monitor for adverse effects. |
| Pediatric use | Not recommended for use in children under 2 years of age. For children ≥2 years, same as adult dosing (one drop of 0.1% solution three times daily). |
| Geriatric use | No specific dose adjustment required, but monitor for systemic effects (e.g., hypotension, bradycardia) due to potential age-related reduced clearance. |
| 1st trimester | Limited human data; animal studies show no teratogenic risk at clinically relevant doses. Use only if benefit outweighs risk. |
| 2nd trimester | Limited human data; no known risk of fetal harm. Use cautiously. |
| 3rd trimester | Potential risk of neonatal hypotension and bradycardia due to alpha-2 agonism. Avoid near term. |
Clinical note
Comprehensive clinical and safety monograph for ALPHAGAN P (ALPHAGAN P).
| Placental transfer | Brimonidine crosses the placenta in animals; human data limited. |
| Breastfeeding | Brimonidine is excreted in breast milk in low concentrations. Use caution, especially in neonates due to potential hypotension and bradycardia. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Brimonidine (ALPHAGAN P) is category B. Animal studies show no fetal harm at doses up to 2.5 mg/kg/day. No adequate human studies in first trimester. Potential for reduced placental perfusion due to alpha-2 agonism; avoid in late pregnancy (risk of uterine contractions). |
| Fetal Monitoring | Assess maternal blood pressure and heart rate for hypotension/bradycardia. Monitor fetal heart rate and uterine activity if used near term. |
| Fertility Effects | No adverse effects on fertility reported in animal studies. Human data limited; unlikely to cause significant reproductive toxicity at ophthalmic doses. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to brimonidine or any component of the formulationConcomitant use with monoamine oxidase inhibitors (MAOIs)
| Precautions | May cause fatigue/drowsiness and dizziness, impairing ability to drive or operate machinery, Use with caution in patients with severe cardiovascular disease or depression, May cause allergic reactions, including ocular pruritus and hyperemia, May reduce heart rate and blood pressure, Caution in patients with renal impairment |
| Food/Dietary | No specific food interactions. Avoid alcohol as it may exacerbate drowsiness or dizziness. |
| Clinical Pearls | Alphagan P (brimonidine tartrate) is a selective alpha-2 adrenergic agonist used to lower intraocular pressure (IOP) in open-angle glaucoma or ocular hypertension. It reduces aqueous humor production and increases uveoscleral outflow. Onset of action is within 1-2 hours. It is available as 0.1% and 0.15% solutions, with 0.1% having fewer side effects. Avoid use with MAOIs and in patients with severe hepatic impairment. Monitor for systemic hypotension and bradycardia, especially in elderly. Rebound ocular hypertension may occur upon discontinuation. |
| Patient Advice | Instill one drop in the affected eye(s) three times daily, about 8 hours apart. · Wash hands before and after use. Avoid touching the dropper tip to any surface. · If using more than one ophthalmic drug, wait at least 5 minutes between applications. · Remove contact lenses before instillation and wait at least 15 minutes before reinserting. · Do not drive or operate machinery until you know how this medication affects you, as it may cause drowsiness or blurred vision. · Report persistent eye pain, redness, or vision changes to your healthcare provider. · Store at room temperature, away from heat and light. Do not freeze. · Dispose of any unused solution 28 days after first opening. |
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