Selective α (Alpha) - and nonselective β (Beta)-adrenergic blocking agent.
Competitively blocks adrenergic stimulation of β-receptors within the myocardium (β1-receptors) and within bronchial and vascular smooth muscle (β2-receptors) and α1-receptors within vascular smooth muscle.
Following slow, direct IV injection, hypotensive effect is apparent within 2–5 minutes and usually maximal within 5–15 minutes.
Following slow, direct IV injection, the hypotensive effect generally persists for about 2–4 hours, although a longer duration of effect (i.e., up to 24 hours) has been reported in some patients.
Severe Hypertension and Hypertensive Crisis
- Adjust dosage according to the severity of hypertension and the patient’s supine BP response and tolerance.
- Initial goal of IV therapy is to reduce mean arterial BP by no more than 25% within minutes to 1 hour, followed by further reductionif stable toward 160/100 to 110 mm Hg within the next 2–6 hours, avoiding excessive declines in pressure that could precipitate renal, cerebral, or coronary insufficiency. If this BP is well tolerated and the patient is clinically stable, further gradual reductions toward normal can be implemented in the next 24–48 hours.
- Patients with aortic dissection should have systolic pressure reduced to <100 mm Hg if tolerated.
- Obstructive airway disease (e.g., bronchial asthma)
- Overt cardiac failure.
- Heart block greater than first degree.
- Cardiogenic shock.
- Severe bradycardia.
- Other conditions associated with severe and prolonged hypotension.
- Known hypersensitivity to labetalol or any ingredient in the formulation.
Rarely: jaundice, hepatitis, severe hepatocellular injury.
Possible precipitation of CHF. Use contraindicated in patients with overt CHF. May use cautiously in patients with well-compensated heart failure (e.g., those controlled with cardiac glycosides and/or diuretics). Use with caution in patients with inadequate cardiac function.
- Symptomatic orthostatic hypotension
- Dizziness or light headedness
- Nausea or dyspepsia
- Initially, 20–80 mg by slow, direct IV injection.
- Higher initial doses (e.g., 1–2 mg/kg) have been administered but the 20-mg dose is recommended to minimize adverse effects and the risks associated with too rapid reduction in BP.
- May give additional doses, usually 40–80 mg (range: 20–80 mg),at 10-minute intervals until the desired supine BP is achieved or up to a total cumulative dose of 300 mg
- Alternatively, initial rate of 0.5–2 mg/minute by continuous IV infusion; adjust rate according to the BP response.
- The usual effective, cumulative dose is 50–200 mg; up to 300 mg may be required.
- Progressive, incremental IV infusion regimen (i.e., infusing 20, 40, 80, and 160 mg/hour for 1 hour at each dose level, or until the desired BP is achieved) has been used, and may result in more gradual BP reduction, minimizing adverse effects compared with repeated IV injections of the drug. Controlled comparisons of various IV administration methods are not available.
- Maximum cumulative dose of 300 mg