LABETALOL HYDROCHLORIDE IN DEXTROSE
Clinical safety rating: safe
Other drugs that lower heart rate or blood pressure can have additive effects Can cause liver injury and bronchospasm in susceptible patients.
Competitive antagonist at beta-1 adrenergic receptors (cardiac) and selective alpha-1 adrenergic receptors (vascular smooth muscle). Reduces heart rate, myocardial contractility, and peripheral vascular resistance.
| Metabolism | Primarily hepatic via glucuronidation; minor pathways include conjugation. Not significantly metabolized by CYP450 enzymes. |
| Excretion | Renal: 40-60% as unchanged drug and metabolites; biliary/fecal: ~50% as metabolites; <5% unchanged in feces. |
| Half-life | Terminal elimination half-life: 5-8 hours (adults); 8-12 hours (elderly); 2-4 hours (children). Clinical context: half-life may be prolonged in hepatic or renal impairment. |
| Protein binding | ~93-96% bound, primarily to albumin (alpha-1-acid glycoprotein binding also reported). |
| Volume of Distribution | Vd: 3-9 L/kg (total body); 0.5-1.0 L/kg (central compartment). Clinical meaning: extensive distribution into tissues, including placenta and breast milk. |
| Bioavailability | Oral: 30-40% (range 25-50%) due to extensive first-pass metabolism; intravenous: 100%. |
| Onset of Action | Intravenous: 2-5 minutes for blood pressure reduction; oral: 20-60 minutes (first dose), 2-4 hours (steady state). |
| Duration of Action | Intravenous: 2-4 hours (dose-dependent, up to 6 hours at high doses); oral: 8-12 hours (twice daily dosing). Clinical notes: longer duration in elderly or hepatic impairment. |
Adult: Initial 0.5-2 mg/min IV infusion, titrate to response; typical maintenance 2-8 mg/min. Max cumulative dose 300 mg.
| Dosage form | SOLUTION |
| Renal impairment | No specific dose adjustment for GFR; use with caution in severe renal impairment due to potential metabolite accumulation. No data for specific GFR thresholds. |
| Liver impairment | Child-Pugh A: No adjustment. Child-Pugh B: Reduce dose by 50%. Child-Pugh C: Contraindicated due to extensive hepatic metabolism. |
| Pediatric use | 0.25 mg/kg IV over 2 min; may repeat after 10 min if needed. Max cumulative dose 1.5 mg/kg or 40 mg. Not recommended for neonates. |
| Geriatric use | Start at lower doses (e.g., 0.5 mg/min IV) due to increased bioavailability and reduced clearance. Titrate slowly. Monitor for hypotension and bradycardia. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Other drugs that lower heart rate or blood pressure can have additive effects Can cause liver injury and bronchospasm in susceptible patients.
| FDA category | Human |
| Breastfeeding | Labetalol is excreted in breast milk with a milk-to-plasma ratio of approximately 0.8-1.2 (M/P ratio ~1.6 reported). Infant plasma levels are low (<10% maternal), and no adverse effects have been reported. The American Academy of Pediatrics considers it compatible with breastfeeding, but monitor infant for bradycardia. |
| Teratogenic Risk |
■ FDA Black Box Warning
None.
| Common Effects | Bradycardia |
| Serious Effects |
["Bronchial asthma","Overt cardiac failure","Cardiogenic shock","Severe bradycardia (heart rate < 45 bpm)","Second- or third-degree heart block (unless pacemaker present)","Hypersensitivity to labetalol or any component of the formulation","Sinus node dysfunction"]
| Precautions | ["Avoid abrupt discontinuation (may precipitate angina or myocardial infarction in patients with coronary artery disease)","May exacerbate heart failure; use with caution","May mask signs of hypoglycemia and hyperthyroidism","Use caution in patients with peripheral vascular disease (can precipitate arterial insufficiency)","May cause bronchospasm in patients with asthma or COPD","Hepatic injury (rare); monitor liver function","May cause orthostatic hypotension, especially if administered intravenously","Use in pregnancy: only if benefit outweighs risk (crosses placenta)","Labetalol may interfere with laboratory tests for catecholamines"] |
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| Pregnancy Category C. First trimester: Limited human data, animal studies show no teratogenicity but increased embryotoxicity at high doses. Second and third trimesters: May cause fetal bradycardia, hypotension, hypoglycemia, and growth restriction; risk of β-blocker-related adverse effects. Monitor for neonatal effects if used near term. |
| Fetal Monitoring | Monitor maternal blood pressure, heart rate, and symptoms of hypotension. In neonates, monitor for hypoglycemia, bradycardia, and respiratory depression. Perform fetal ultrasound and growth assessments throughout pregnancy. Consider fetal heart rate monitoring during labor. |
| Fertility Effects | No specific human studies on fertility. Animal studies with high doses have shown reduced implantation and fetal weight, but no effect on male or female fertility at clinical doses. |
| Food/Dietary | No significant food interactions with intravenous labetalol. However, advise avoiding excessive alcohol consumption as it may potentiate hypotensive effects. |
| Clinical Pearls | Labetalol in dextrose is a combined alpha-1 and beta-adrenergic blocker used intravenously for hypertensive emergencies. It does not cause reflex tachycardia due to its alpha-blocking activity. Monitor for bradycardia, hypotension, and bronchospasm. Contraindicated in asthma, heart block, and decompensated heart failure. Titrate dose carefully; onset of action is within 2-5 minutes with peak effect at 5-15 minutes. Avoid abrupt discontinuation to prevent rebound hypertension. |
| Patient Advice | This medication is given intravenously in the hospital to rapidly lower blood pressure. · You may experience dizziness, lightheadedness, or fatigue; avoid sudden position changes. · Report any difficulty breathing, slow heartbeat, or swelling of the extremities. · Do not stop taking other blood pressure medications unless instructed by your doctor. · Inform your healthcare provider if you have asthma, diabetes, or a history of heart problems. |