BETIMOL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for BETIMOL (BETIMOL).
Nonselective beta-adrenergic receptor antagonist; reduces intraocular pressure by decreasing aqueous humor production.
| Metabolism | Primarily metabolized by CYP2D6; also undergoes glucuronidation. |
| Excretion | Primarily renal (unchanged drug and metabolites). Approximately 60-80% of a dose is excreted renally as unchanged timolol, with the remainder as inactive metabolites. Biliary/fecal excretion accounts for less than 20%. |
| Half-life | 2.5 to 5 hours (average 4 hours) in patients with normal renal function; may be prolonged in renal impairment (up to 8-10 hours). |
| Protein binding | 10-20% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | 1.7 L/kg (indicating extensive tissue distribution). |
| Bioavailability | Ophthalmic: variable (significant systemic absorption via nasolacrimal duct; plasma concentrations detectable but low); Oral: approximately 75-90%. |
| Onset of Action | Ophthalmic: 15-30 minutes; Oral: 1-2 hours. |
| Duration of Action | Ophthalmic: 6-12 hours (clinically significant IOP reduction for 24 hours with twice-daily dosing); Oral: 12-24 hours for antiarrhythmic effects. |
1 drop of 0.25% or 0.5% solution in the affected eye(s) twice daily. If inadequate response, increase to 0.5% solution twice daily.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No dose adjustment required for topical ophthalmic use; systemic absorption is minimal. |
| Liver impairment | No dose adjustment required for topical ophthalmic use; systemic absorption is minimal. |
| Pediatric use | Safety and efficacy not established in children; use only if benefit outweighs risk. |
| Geriatric use | No specific dose adjustment; monitor for systemic effects (e.g., bradycardia, hypotension) due to possible increased sensitivity. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for BETIMOL (BETIMOL).
| Breastfeeding | Limited excretion into breast milk; M/P ratio unknown. Use with caution in neonates due to potential beta-blockade (bradycardia, hypoglycemia). Monitor infant for signs of beta-blockade. |
| Teratogenic Risk | First trimester: Avoid; beta-blockers may cause fetal bradycardia and growth restriction. Second/third trimester: Risk of intrauterine growth restriction (IUGR), neonatal bradycardia, and hypoglycemia. Use only if benefit outweighs risk; discontinue 48-72 hours before delivery to reduce neonatal adverse effects. |
■ FDA Black Box Warning
None
| Serious Effects |
["Bronchial asthma","History of bronchial asthma or severe COPD","Sinus bradycardia","Greater than first-degree atrioventricular block","Cardiogenic shock","Overt cardiac failure","Hypersensitivity to betaxolol or any component of the formulation"]
| Precautions | ["May exacerbate respiratory diseases such as asthma or COPD","May cause bradycardia or heart block in patients with pre-existing cardiac conditions","May mask signs of hypoglycemia in diabetic patients","May worsen peripheral vascular disease","Abrupt withdrawal may exacerbate angina or precipitate myocardial infarction in patients with coronary artery disease"] |
| Food/Dietary | No specific food interactions. Absorption unaffected by food. Avoid excessive alcohol consumption as it may lower blood pressure. |
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| Fetal Monitoring |
| Maternal: Heart rate, blood pressure, signs of heart failure. Fetal: Heart rate monitoring, growth ultrasounds to detect IUGR, and assessment of neonatal bradycardia or hypoglycemia after delivery. |
| Fertility Effects | No known direct effect on fertility. However, underlying conditions treated (e.g., glaucoma, hypertension) or systemic effects of beta-blockade may indirectly affect reproductive function. |
| Clinical Pearls | BETIMOL (timolol ophthalmic solution) is a non-selective beta-blocker used to reduce intraocular pressure (IOP) in open-angle glaucoma. Monitor for systemic beta-blockade effects, especially in patients with asthma, COPD, bradycardia, or heart failure. Use with caution in patients with diabetes as it may mask hypoglycemic symptoms. Consider nasolacrimal occlusion or eyelid closure for 1-2 minutes after instillation to minimize systemic absorption. Avoid concurrent use of oral beta-blockers due to additive systemic effects. |
| Patient Advice | Apply one drop in the affected eye(s) twice daily, unless otherwise directed. · Wash hands before and after administration. · Tilt head back, pull down lower eyelid, and squeeze bottle gently to instill drop. · Close eye and press finger against the inner corner of the eye (nasolacrimal duct) for 1-2 minutes after each drop to reduce systemic absorption. · Wait at least 5 minutes between different eye medications. · Do not touch the dropper tip to any surface to prevent contamination. · Remove contact lenses before administration and wait 15 minutes before reinserting. · May cause blurred vision; do not drive or operate machinery until vision clears. · Report any difficulty breathing, slow heartbeat, dizziness, or fainting to your doctor immediately. · Do not stop using this medication abruptly without consulting your doctor. |