BLOCADREN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for BLOCADREN (BLOCADREN).
Non-selective beta-adrenergic receptor antagonist; blocks beta-1 and beta-2 receptors, reducing heart rate, myocardial contractility, and blood pressure.
| Metabolism | Primarily hepatic via CYP2D6; also undergoes glucuronidation. |
| Excretion | Primarily renal (80-95% unchanged), minor hepatic metabolism to inactive metabolites, minimal fecal excretion (<5%) |
| Half-life | Terminal elimination half-life: 12-15 hours; prolonged in renal impairment (up to 24 hours) and elderly; dose adjustment required in CrCl <35 mL/min |
| Protein binding | Approximately 12-15% bound to plasma proteins (mainly albumin) |
| Volume of Distribution | 1.5-2.5 L/kg; distributes widely into body tissues, including central nervous system |
| Bioavailability | Oral bioavailability: 70-90% due to extensive absorption and low first-pass metabolism (10-15% hepatic extraction); IV bioavailability: 100% |
| Onset of Action | Oral: 1-2 hours for reduction in heart rate and blood pressure; IV: 2-5 minutes for acute effects on heart rate |
| Duration of Action | Oral: 12 hours for antihypertensive and antianginal effects; IV: 2-4 hours for hemodynamic effects; clinical duration correlates with half-life |
| Molecular Weight | 316.42 |
Hypertension: initial 10 mg PO twice daily, increase gradually to 20-40 mg/day; maximum 60 mg/day. Post-MI: 10 mg PO twice daily starting 1-4 weeks post-infarction.
| Dosage form | TABLET |
| Renal impairment | CrCl <10 mL/min: reduce dose by 50% or extend interval to every 48 hours. CrCl 10-50 mL/min: use with caution, consider dose reduction. |
| Liver impairment | Child-Pugh Class A: no adjustment. Child-Pugh Class B: reduce dose by 50%. Child-Pugh Class C: contraindicated. |
| Pediatric use | Hypertension: initial 0.5-1 mg/kg/day PO divided q12h; maximum 2 mg/kg/day. Not recommended in patients <6 years. |
| Geriatric use | Initiate at 5 mg PO twice daily; titrate slowly due to increased sensitivity and decreased renal function. Monitor heart rate and blood pressure closely. |
| 1st trimester | Use only if potential benefit justifies risk. May cause fetal bradycardia, growth restriction, and hypoglycemia. Avoid as much as possible. |
| 2nd trimester | Avoid use if possible. Monitor fetal growth and heart rate if used. |
| 3rd trimester | Avoid use due to risk of neonatal bradycardia, hypotension, hypoglycemia, and respiratory depression. Discontinue at least 72 hours before delivery if possible. |
Clinical note
Comprehensive clinical and safety monograph for BLOCADREN (BLOCADREN).
| Placental transfer | Timolol crosses the placenta. Reported transfer ratio (cord blood/maternal blood) is approximately 0.8–1.0, indicating significant transfer. |
| Breastfeeding | Timolol is excreted into breast milk in low amounts. Monitor infant for bradycardia, hypotension, and hypoglycemia. Consider alternative therapies, especially when nursing preterm or low-birth-weight infants. |
■ FDA Black Box Warning
No FDA boxed warning.
| Serious Effects |
Sinus bradycardiaSecond- or third-degree atrioventricular blockCardiogenic shockOvert cardiac failureHypersensitivity to timolol or any componentBronchial asthma or severe chronic obstructive pulmonary disease
| Precautions | Abrupt withdrawal may exacerbate angina or cause myocardial infarction, May mask signs of hyperthyroidism or hypoglycemia, Use caution in patients with bronchospastic disease, May cause bradycardia or heart block, May worsen peripheral vascular disease |
| Food/Dietary | No significant food interactions. However, avoid excessive alcohol intake as it may enhance hypotensive effects. Maintain low-sodium diet in hypertensive patients to optimize blood pressure control. |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Timolol (Blocadren) is a nonselective beta-blocker. Pregnancy category C. First trimester: Limited data suggest possible risk of fetal bradycardia, growth restriction, and hypoglycemia; avoid if possible. Second/third trimester: Chronic use may cause fetal bradycardia, low birth weight, and neonatal beta-blockade (bradycardia, hypotension, hypoglycemia). Discontinue 2–3 days before delivery if possible. |
| Fetal Monitoring | Monitor maternal blood pressure, heart rate, and signs of heart failure. Fetal surveillance: ultrasound growth scans (every 4–6 weeks) for growth restriction, fetal heart rate monitoring for bradycardia. Neonatal: observe for bradycardia, hypotension, hypoglycemia, and respiratory depression for 48–72 hours postpartum. |
| Fertility Effects | Beta-blockers may impair male and female fertility due to effects on sperm motility and libido (sympathetic blockade). Timolol can also cause erectile dysfunction in males. Reversible upon discontinuation. |
| Clinical Pearls | BLOCADREN (timolol) is a non-selective beta-blocker without intrinsic sympathomimetic activity. It is used orally for hypertension and post-MI prophylaxis, and ophthalmically for open-angle glaucoma. Oral timolol should be avoided in patients with asthma, COPD, or bradycardia due to risk of bronchospasm and heart block. When switching from another beta-blocker, dose adjustments may be needed. In glaucoma, systemic absorption from eye drops can produce systemic beta-blockade effects; monitor pulse and blood pressure, especially in elderly. Timolol may mask symptoms of hypoglycemia and thyrotoxicosis. Do not discontinue abruptly due to risk of myocardial ischemia. |
| Patient Advice | Do not stop taking this medication suddenly, as it may increase your risk of heart attack. Follow your doctor's instructions for gradual dose reduction. · If you have diabetes, monitor blood glucose closely as timolol can mask signs of low blood sugar such as rapid heartbeat. · Avoid activities requiring alertness until you know how timolol affects you; it may cause dizziness or fatigue. · Inform all healthcare providers that you are taking timolol before undergoing surgery or procedures. · If using eye drops, apply pressure to the tear duct after each drop to reduce systemic absorption and side effects. |