Labetalol
Mechanism :
Labetalol combines both selective, competitive, alpha1-adrenergic blocking and nonselective, competitive, beta-adrenergic blocking activity in a single substance.
Indication :
- Hypertension (off-label)
- Hypertensive crisis
Contraindications :
Labetalol is contraindicated in cardiogenic shock, sinus bradycardia and greater than first degree block, bronchial asthma, congestive heart failure unless the failure is secondary to a tachyarrhythmia treatable with Labetalol.
Dosing :
Hypertensive crisis:
0.4-1 mg/kg/hour by continuous intravenous infusion; Max: 3 mg/kg/hour.
Hypertension:
1-3 mg/kg/day given orally in two divided doses OR 0.3-1 mg/kg intermittently as an intravenous injection; Max: 1.2 g/day.
Adverse Effect :
Bradycardia, intermittent claudication, Raynaud’s phenomena, postural hypotension, precipitation of heart block, thrombocytopenia, hypoglycemia, confusion, hallucinations, dizziness, paraesthesia, mood changes, nightmares and tingling sensation of scalp. Respiratory effects are bronchospasm.
Interaction :
Calcium Channel Blockers: Additive effect.
Prostaglandin Synthase inhibiting drugs: Decrease the hypotensive effects of beta blockers.
Catecholamine-depleting drugs such as reserpine: Hypotension, marked bradycardia, vertigo, syncopal attacks, or orthostatic hypotension.
Haloperidol: Hypotension and cardiac arrest.
Theophylline: Clearance is reduced.
Cimetidine: Increasing blood levels.
Chlorpromazine: Increased plasma levels of both drugs.
Phenytoin, Phenobarbitone and Rifampin: Accelerate labetalol clearance.
Ethanol: Slows the rate of absorption of labetalol.
Aluminium Hydroxide Gel: Greatly reduces intestinal absorption of labetalol.
Renal Dose :
Dose in Renal Impairment GFR (mL/min)
| 20-50 | Dose as in normal renal function |
| 10-20 | Dose as in normal renal function |
| <10 | Dose as in normal renal function |
Dose in Patients undergoing Renal Replacement Therapies
| CAPD | Not dialysed. Dose as in normal renal function |
| HD | Not dialysed. Dose as in normal renal function |
| HDF/High flux | Unknown dialysability. Dose as in normal renal function |
| CAV/VVHD | Probably not dialysed. Dose as in normal renal function |
Hepatic Dose :
Hepatic impairment: Reduce dose by 50%