NORMODYNE
Clinical safety rating
cautionComprehensive clinical and safety monograph for NORMODYNE (NORMODYNE).
Competitive antagonist at beta-1 adrenergic receptors with additional alpha-1 adrenergic receptor blocking activity, resulting in vasodilation and decreased heart rate, contractility, and cardiac output.
| Metabolism | Primarily hepatic via glucuronidation and sulfation; first-pass effect; CYP2D6 minor role. |
| Excretion | Renal: 55-65% as unchanged drug and metabolites; Fecal: ~20% via bile; Hepatic metabolism: ~25% |
| Half-life | 8-12 hours; extended in hepatic impairment (up to 20 hours) and renal impairment (up to 15 hours) |
| Protein binding | Labetalol: ~50% bound to albumin |
| Volume of Distribution | 11 L/kg (extensive tissue distribution, including placenta and breast milk) |
| Bioavailability | Oral: 25-40% due to extensive first-pass metabolism; IV: 100% |
| Onset of Action | Oral: 30-60 minutes; IV: 5-10 minutes |
| Duration of Action | Oral: 8-12 hours; IV: 4-6 hours; duration may be prolonged in elderly or hepatic impairment |
| Molecular Weight | 364.9 |
Oral: Initial 100 mg twice daily, increase by 100 mg/day every 2 weeks; maintenance 200-400 mg twice daily. Max 1200 mg/day. IV: 20 mg (1 mL) over 2 minutes, repeat if needed at 10 min intervals up to total 300 mg.
| Dosage form | INJECTABLE |
| Renal impairment | GFR > 50 mL/min: No adjustment. GFR 10-50 mL/min: Reduce dose by 50% or prolong interval. GFR < 10 mL/min: Use with caution; consider 50% dose reduction. |
| Liver impairment | Child-Pugh A: No adjustment. Child-Pugh B: Use with caution; reduce dose by 50%. Child-Pugh C: Contraindicated. |
| Pediatric use | Oral: 0.25-1 mg/kg/dose twice daily; increase gradually. Max 2 mg/kg/day (up to 120 mg/day). IV: 0.1-0.2 mg/kg over 2 minutes; may repeat every 10 min up to 1 mg/kg total. |
| Geriatric use | Start at lowest dose (100 mg twice daily oral); titrate slowly. Monitor orthostatic hypotension and bradycardia. IV use with caution; reduce initial dose to 10 mg. |
| 1st trimester | Avoid use in first trimester unless essential; associated with fetal bradycardia and hypotension. |
| 2nd trimester | Use only if potential benefit outweighs risk; monitor fetal heart rate and growth. |
| 3rd trimester | Avoid due to risk of neonatal bradycardia, hypotension, and hypoglycemia. |
Clinical note
Comprehensive clinical and safety monograph for NORMODYNE (NORMODYNE).
| Placental transfer | Crosses placenta readily; achieves fetal serum concentrations approximately 50-80% of maternal levels. |
| Breastfeeding | Labetalol is excreted into breast milk in low concentrations. Monitor breastfed infant for bradycardia, hypotension, and signs of beta-blockade. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | First trimester: Limited human data; animal studies show no teratogenicity at clinically relevant doses. Second and third trimesters: Use may cause fetal hypotension, bradycardia, and growth restriction; risk of neonatal hypotension, bradycardia, and hypoglycemia if used near term. Avoid in preeclampsia due to risk of fetal distress. |
| Fetal Monitoring | Monitor maternal blood pressure and heart rate; fetal heart rate and growth; neonatal monitoring for hypotension, bradycardia, and hypoglycemia after delivery. |
| Fertility Effects | No known adverse effects on fertility in animal or human studies. |
■ FDA Black Box Warning
Exacerbation of angina pectoris and myocardial infarction may occur following abrupt discontinuation of beta-blocker therapy.
| Serious Effects |
Bronchial asthmaOvert cardiac failureCardiogenic shockSevere bradycardiaSecond- or third-degree heart blockHypersensitivity to labetalol
| Precautions | Congestive heart failure, Bronchospasm in patients with asthma/COPD, Hepatic injury, Hypotension/syncope, Masking of hypoglycemia in diabetics, Thyrotoxicosis symptoms masked, Abrupt discontinuation leading to rebound hypertension/angina |
| Food/Dietary | Take with food to enhance absorption. Avoid excessive alcohol intake as it may increase hypotensive effects. Grapefruit juice may increase drug levels; limit consumption. |
| Clinical Pearls | Normodyne (labetalol) is a non-selective beta-blocker with alpha-1 blocking activity. It causes less reflex tachycardia than pure vasodilators. Bioavailability increases with food. Dosing should be titrated. Abrupt withdrawal may exacerbate angina or hypertension. Use cautiously in asthma, COPD, and heart failure. |
| Patient Advice | Take exactly as prescribed; do not stop suddenly as this may cause a rapid rise in blood pressure. · May cause dizziness or lightheadedness; avoid driving or operating machinery until you know how you react. · Do not take over-the-counter cold or allergy medications without consulting your doctor. · Inform your doctor if you experience slow heartbeat, shortness of breath, or swelling of extremities. · If you have diabetes, monitor blood sugar closely as labetalol may mask signs of hypoglycemia. |
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