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 |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for BLOCADREN (BLOCADREN).
| Breastfeeding | Timolol is excreted into breast milk (M/P ratio approximately 1.0). Concentrations are low (0.2–1.0% of maternal weight-adjusted dose). Consider infant monitoring for bradycardia and hypotension; may use with caution, especially with low birth weight infants. |
| 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. |
■ FDA Black Box Warning
No FDA boxed warning.
| Serious Effects |
["Bronchial asthma","Sinus bradycardia","Heart block greater than first degree","Cardiogenic shock","Decompensated heart failure","Hypersensitivity to any component"]
| 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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| 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. |