BRIMONIDINE TARTRATE AND TIMOLOL MALEATE
Clinical safety rating: safe
Other drugs that lower heart rate or blood pressure can have additive effects Can cause bronchospasm in patients with asthma.
Brimonidine tartrate is a selective alpha-2 adrenergic receptor agonist that reduces aqueous humor production and increases uveoscleral outflow. Timolol maleate is a non-selective beta-adrenergic receptor antagonist that decreases aqueous humor production by blocking beta-2 receptors in the ciliary epithelium.
| Metabolism | Brimonidine: Extensive hepatic metabolism via aldehyde oxidase, N-dealkylation, and glucuronidation. Timolol: Hepatic metabolism via CYP2D6, also undergoes glucuronidation. |
| Excretion | Brimonidine: ~74% renal (unchanged and metabolites), ~22% fecal. Timolol: ~20% renal (unchanged), ~80% hepatic metabolism with biliary and fecal elimination. |
| Half-life | Brimonidine: ~2.9 hours (terminal) after ophthalmic administration. Timolol: ~4 hours (terminal); clinically, systemic exposure is low due to topical route. |
| Protein binding | Brimonidine: ~30% (plasma proteins). Timolol: ~60% (plasma proteins). |
| Volume of Distribution | Brimonidine: ~2.1 L/kg (high, indicating extensive tissue distribution). Timolol: ~1.3–2.0 L/kg (moderate distribution). |
| Bioavailability | Ophthalmic: Systemic bioavailability is low; brimonidine ~12%, timolol ~80% absorbed nasolacrimally but hepatic first-pass reduces systemic exposure. |
| Onset of Action | Ophthalmic: Brimonidine onset at 1–4 hours for maximum IOP reduction; Timolol onset within 1 hour, peak at 2–4 hours. |
| Duration of Action | Brimonidine: 8–12 hours (reduced IOP). Timolol: 12–24 hours (sufficient for twice-daily dosing). Clinical note: Combination product used BID. |
One drop in the affected eye(s) twice daily (approximately 12 hours apart).
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. Not recommended for severe renal impairment (CrCl < 30 mL/min) due to lack of data. |
| Liver impairment | Use with caution in patients with hepatic impairment. No specific dose adjustment guidelines; monitor for systemic effects especially in Child-Pugh class B and C. |
| Pediatric use | Not recommended for use in children <2 years of age. Safety and efficacy in pediatric patients aged 2-16 years have not been established. |
| Geriatric use | No specific dose adjustment required. Caution due to potential increased systemic absorption and comorbidities; monitor blood pressure and heart rate. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Other drugs that lower heart rate or blood pressure can have additive effects Can cause bronchospasm in patients with asthma.
| FDA category | Animal |
| Breastfeeding | Timolol is excreted into breast milk; brimonidine is likely excreted. No M/P ratio available. Potential for beta-blockade in infant (bradycardia, hypotension). Use with caution; consider alternative therapy. |
| Teratogenic Risk | Pregnancy Category C. No adequate and well-controlled studies in pregnant women. Animal studies with brimonidine showed increased fetal resorptions and reduced fetal body weight at maternally toxic doses. Timolol has been associated with intrauterine growth restriction and bradycardia in neonates after maternal use of oral beta-blockers. Risk to fetus in first trimester cannot be excluded; second and third trimester exposure may cause fetal bradycardia and hypoglycemia. |
■ FDA Black Box Warning
None
| Common Effects | hypertension |
| Serious Effects |
["Hypersensitivity to brimonidine, timolol, or any component","Bronchial asthma or history of asthma","Severe chronic obstructive pulmonary disease","Sinus bradycardia","Second- or third-degree atrioventricular block","Cardiogenic shock","Overt cardiac failure","Neonates and infants (less than 2 years of age)"]
| Precautions | ["Potential for ocular hypotony or low intraocular pressure","May cause allergic reactions (e.g., follicular conjunctivitis, conjunctival hyperemia)","Systemic absorption may cause cardiovascular and respiratory effects, especially in patients with pre-existing conditions","Use caution in patients with hepatic or renal impairment","May cause blurred vision or somnolence, affecting ability to drive or operate machinery"] |
| Food/Dietary |
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| Fetal Monitoring | Monitor maternal blood pressure and heart rate. Fetal heart rate monitoring during labor if used near term. Neonatal monitoring for bradycardia, hypoglycemia, and respiratory depression. |
| Fertility Effects | No human data available. Animal studies with timolol showed no effect on fertility; brimonidine studies limited. Potential for reduced fertility due to systemic effects of beta-blockade. |
| No clinically significant food interactions. Avoid excessive alcohol intake as it may enhance hypotensive effects. |
| Clinical Pearls | Assess cardiovascular and respiratory status before initiating; avoid in patients with sinus bradycardia, heart block, or reactive airway disease. Monitor intraocular pressure (IOP) reduction within 1-2 hours; peak effect at 2-6 hours. Warn about potential hypotension and syncope, especially in the elderly. Use caution with concurrent oral beta-blockers and alpha-agonists. Discontinue if ocular reactions like keratitis or iritis occur. |
| Patient Advice | Use once daily in the morning; skip if dose is missed and resume next day—do not double dose. · May cause temporary blurred vision, altered taste (unusual or metallic), or droopy eyelids; report persistent or severe symptoms. · Wait at least 5 minutes between different eye drops to prevent washout. · Avoid driving or hazardous activities until vision clears after instillation. · Contact lens wearers: remove lenses before instillation, wait 15 minutes before reinserting. · Report weight gain, shortness of breath, slow heart rate, or fainting immediately. · Store at room temperature, away from heat and light; keep bottle tightly closed. |