labetalol high blood pressure medicine
Labetalol is a drug that is used as a high blood pressure medicine. It is related to carvedilol (Coreg). Nerves that are part of the adrenergic nervous system travel to most arteries where they release an adrenergic chemical norepinephrine. The norepinephrine attaches to receptors on the muscles of the arteries and causes the muscles to contract, narrowing the arteries, and increasing the blood pressure. Labetalol blocks receptors of the adrenergic nervous system. When labetalol attaches to and blocks the receptors, the arterial muscles relax, and the arteries expand, resulting in a fall in blood pressure.
Labetalol is used alone or in combination with other drugs as a high blood pressure medicine.
Labetalol can mask early warning symptoms of hypoglycemia (low blood sugar) such as tremors and increased heart rate. These symptoms are caused by activation of the adrenergic nervous system which labetalol blocks. Therefore, diabetics taking medicine that lower blood sugar such as insulin or oral anti-diabetic medicine may need to increase the frequency with which they monitor their blood sugar in order to prevent hypoglycemia.
Labetalol taken with calcium channel blockers such as diltiazem (Cardizem) or verapamil (Calan) may trigger an irregular heart rhythm or an increase in high blood pressure.
Labetalol taken with tricyclic antidepressants such as amitriptyline (Elavil), imipramine (Tofranil), or nortriptyline (Pamelor) may lead to an increase in the tremor that is a side effect of the antidepressants.
If taken with adrenergic stimulating drugs used for treating asthma, for example, albuterol (Proventil, Ventolin) or pirbuterol (Maxair), the adrenergic blocking effects of labetalol may counteract the effects of the stimulating drugs and reduce their effectiveness for treating asthmatic attacks. More of the adrenergic drug may be needed.
Glutethimide (Doriden) may decrease the effectiveness of labetalol by increasing its elimination. When both drugs are used concomitantly, more labetalol or less glutethimide may be needed. Cimetidine (Tagamet) may increase the effectiveness of labetalol by blocking its elimination and increasing its levels in the blood. Therefore, less labetalol may be needed when cimetidine and labetalol are used together.
It has not been determined if it is safe to use labetalol during pregnancy.
Labetalol high blood pressure medicine may be given two or three times daily. The starting oral dose is 100 mg twice daily and the dose can be increased by 100 mg twice daily every 2-3 days based on the response of the blood pressure. Usual maintenance doses are 200-400 mg twice daily. Patients with severe high blood pressure may require 1.2 to 2.4 g daily.
The initial intravenous dose of labetalol is 20 mg injected over 2 minutes. Additional injections of 40 or 80 mg may be administered every 10 minutes as needed up to a total dose of 300 mg. Maximum effect is usually seen within 5 minutes after intravenous administration. Labetalol also may be administered by intravenous infusion.
BRAND NAMES: Normodyne, Trandate
Labetalol high blood pressure medicine has been found in human breast milk. Therefore, it should be used cautiously in nursing mothers because of the risk that the infant may develop a slow heart rate.