From the Guidelines
Intravenous labetalol starts to lower blood pressure within 5-10 minutes after administration, as stated in the 2019 European Heart Journal study 1. The onset of action of labetalol IV is relatively quick, making it a suitable option for managing hypertensive emergencies.
- The duration of action of labetalol IV is around 3-6 hours, allowing for sustained blood pressure control 1.
- The recommended dose of labetalol IV is 0.25–0.5 mg/kg i.v. bolus, followed by a continuous infusion of 2–4 mg/min until the goal blood pressure is reached 1.
- It is essential to monitor patients closely during labetalol administration, as it can cause adverse effects such as bronchoconstriction and fetal bradycardia, particularly in patients with a history of asthma or heart block 1.
- The dual mechanism of action of labetalol, which blocks both alpha and beta adrenergic receptors, makes it an effective option for managing hypertensive emergencies, but it should be used cautiously in patients with certain comorbidities, such as heart failure or bradycardia 1.
From the FDA Drug Label
In a clinical pharmacologic study in severe hypertensives, an initial 0. 25 mg/kg injection of labetalol HCl, administered to patients in the supine position, decreased blood pressure by an average of 11/7 mmHg. Additional injections of 0.5 mg/kg at 15-minute intervals up to a total cumulative dose of 1.75 mg/kg of labetalol HCl caused further dose-related decreases in blood pressure. The maximal effect of each dose level occurred within 5 minutes.
The maximal effect of labetalol IV on lowering blood pressure occurs within 5 minutes of administration.
- The initial dose of 0.25 mg/kg can decrease blood pressure by an average of 11/7 mmHg.
- Additional doses can cause further decreases in blood pressure, with the maximal effect of each dose level occurring within 5 minutes 2.
From the Research
Labetalol IV Administration for Lowering Blood Pressure
- Labetalol is a combined alpha- and beta-adrenoceptor blocking agent used to treat hypertension, and its intravenous administration has been studied for its effectiveness in lowering blood pressure rapidly 3, 4, 5.
- The antihypertensive effects of intravenous labetalol were evaluated in 59 patients with hypertensive crises or severe hypertension, and the results showed a rapid reduction in blood pressure, with a mean decrease of 55/33 mmHg after the last dose of labetalol 4.
- A study published in 1976 found that a single intravenous dose of 50 mg labetalol decreased mean arterial pressure by 24 mmHg in patients with mild to moderately severe hypertension, with the peak response occurring approximately 4 minutes after administration 5.
- Another study found that intravenous labetalol was effective in reducing blood pressure in patients with severe hypertension, with a reduction in mean arterial pressure of 19 mmHg after a further 50-mg dose administered 30 minutes after the initial injection 5.
- The safety and efficacy of intravenous labetalol for the treatment of asymptomatic hypertension in hospitalized patients have been evaluated, and the results suggest that it is a safe and effective treatment option, although more research is needed to fully understand its effects 6.
Time to Onset of Action
- The peak response to intravenous labetalol occurs approximately 4 minutes after administration, with further reductions in blood pressure achieved with additional doses 4, 5.
- The duration of action of intravenous labetalol is approximately 6 hours, although this may vary depending on the individual patient and the dose administered 3.
Dosing and Administration
- The initial dose of intravenous labetalol is typically 20 mg, followed by repeated incremental doses of 20 to 80 mg given at 10-minute intervals to achieve the desired reduction in blood pressure 4.
- The dose required to achieve the therapeutic effect may be less in patients who have been pretreated with beta-adrenergic blockers, although the duration of action may be shorter in these patients 4.