COMBIGAN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for COMBIGAN (COMBIGAN).
Combigan is a fixed combination of brimonidine tartrate, an alpha-2 adrenergic receptor agonist, and timolol maleate, a non-selective beta-adrenergic receptor antagonist. Brimonidine reduces aqueous humor production and increases uveoscleral outflow, while timolol reduces aqueous humor production by blocking beta-2 receptors in the ciliary epithelium.
| Metabolism | Brimonidine is extensively metabolized in the liver and other ocular tissues by aldehyde dehydrogenase and cytochrome P450 enzymes; timolol is partially metabolized in the liver by CYP2D6, with significant first-pass metabolism after systemic absorption. |
| Excretion | Brimonidine: primarily renal (74% as unchanged drug and metabolites), with minor fecal elimination (22%). Timolol: renal (20% as unchanged drug, remainder as metabolites) and some biliary/fecal. |
| Half-life | Brimonidine: terminal half-life approximately 2.1 hours. Timolol: terminal half-life about 4.0 hours; clinically, systemic effects may persist for 12-24 hours due to ophthalmic dosing. |
| Protein binding | Brimonidine: approximately 25-30% bound to plasma proteins. Timolol: approximately 60% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | Brimonidine: Vd about 1.0 L/kg, indicating wide tissue distribution. Timolol: Vd about 1.5-2.0 L/kg, suggesting extensive extravascular distribution. |
| Bioavailability | Ophthalmic (eye drops): systemic bioavailability is low due to dilution and nasolacrimal drainage; approximate 10-20% absorption for both drugs. |
| Onset of Action | Ophthalmic: brimonidine onset 1-2 hours (IOP reduction), timolol onset 30 minutes; maximal effect at 2-3 hours. |
| Duration of Action | Brimonidine: duration 8-12 hours; timolol: duration 12-24 hours. Both given twice daily for sustained IOP control. |
One drop in the affected eye(s) twice daily, approximately 12 hours apart.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No specific dose adjustment recommended for GFR >30 mL/min; use with caution in severe renal impairment (GFR <30 mL/min) due to potential systemic absorption of brimonidine. |
| Liver impairment | Contraindicated in patients with Child-Pugh Class C (severe hepatic impairment); use with caution in Child-Pugh Class A or B, with monitoring for systemic effects. |
| Pediatric use | Contraindicated in neonates and infants <2 years of age due to risk of CNS depression; safety and efficacy in children ≥2 years have not been established, use not recommended. |
| Geriatric use | No specific dose adjustment; monitor for increased systemic effects (e.g., hypotension, bradycardia) due to age-related decreased renal function and polypharmacy. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for COMBIGAN (COMBIGAN).
| Breastfeeding | No data on human milk excretion; timolol is excreted in breast milk. M/P ratio unknown. Caution advised; monitor infant for bradycardia or hypotension. |
| Teratogenic Risk | Insufficient human data; animal studies show fetal harm at maternally toxic doses. Avoid in first trimester unless benefit outweighs risk. Use only if clearly needed in second and third trimesters. |
| Fetal Monitoring |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["Hypersensitivity to brimonidine, timolol, or any component of the formulation.","Neonates and infants (age <2 years) due to risk of central nervous system depression.","Reactive airway disease including bronchial asthma or history of asthma.","Severe COPD.","Sinus bradycardia, sick sinus syndrome, second- or third-degree atrioventricular block without a functioning pacemaker.","Cardiogenic shock or uncontrolled heart failure."]
| Precautions | ["Sulfite allergy: Contains sodium metabisulfite, may cause allergic reactions in susceptible patients.","Systemic beta-blockade: Caution in patients with asthma, COPD, sinus bradycardia, heart block, or uncontrolled heart failure.","Alpha-agonist effects: May cause hypotension, syncope, or drowsiness; use caution in patients with cardiovascular disease, depression, or cerebral insufficiency.","Ocular effects: Risk of corneal edema, conjunctival hyperemia, and allergic reactions.","Potential for additive effects with other beta-blockers or alpha-agonists."] |
| Food/Dietary |
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| Monitor intraocular pressure, maternal heart rate and blood pressure; fetal ultrasound if used in pregnancy. |
| Fertility Effects | No specific human data; animal studies show no impairment of fertility at clinically relevant doses. |
| No specific food interactions. Avoid alcohol as it may increase drowsiness associated with brimonidine. No dietary restrictions required. |
| Clinical Pearls | COMBIGAN is a fixed-dose combination of brimonidine (alpha-2 agonist) and timolol (beta-blocker) for reducing intraocular pressure (IOP) in glaucoma or ocular hypertension. Use with caution in patients with asthma, COPD, sinus bradycardia, heart block, or heart failure due to timolol's systemic beta-blockade. Brimonidine can cause allergic conjunctivitis or follicular conjunctivitis in up to 9% of patients; monitor for ocular itching, redness, and swelling. The hypotensive effect may decrease over time; check IOP regularly. Avoid use in patients taking oral beta-blockers or calcium channel blockers due to additive cardiovascular effects. Do not use in neonates or infants due to risk of CNS depression from brimonidine. |
| Patient Advice | Instill one drop in the affected eye(s) twice daily, about 12 hours apart. · After instilling the drop, close your eye and press on the inner corner for 1-2 minutes to reduce systemic absorption. · Do not touch the dropper tip to your eye or any surface to avoid contamination. · Remove contact lenses before use and wait at least 15 minutes before reinserting. · Avoid driving or operating machinery if you experience blurred vision or drowsiness. · Report any eye pain, redness, swelling, or changes in vision to your doctor. · If you have asthma, heart problems, or low blood pressure, inform your doctor before use. · Do not use this medication if you are pregnant or breastfeeding unless directed by your doctor. · Store at room temperature away from light and moisture. |