labetalol, Normodyne, Trandate

  • Pharmacy Author:
    Omudhome Ogbru, PharmD

    Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.

  • Medical and Pharmacy Editor: Jay W. Marks, MD
    Jay W. Marks, MD

    Jay W. Marks, MD

    Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

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What is labetalol, and how does it work (mechanism of action)?

Labetalol is a drug that is used for treating high blood pressure. And is related to carvedilol (Coreg). Nerves from the adrenergic nervous system travel from the spinal cord to arteries where they release norepinephrine. Norepinephrine attaches to adrenergic receptors on arteries and causes the arteries to contract, narrowing the arteries, and increasing blood pressure. Labetalol blocks receptors of the adrenergic nervous system. When labetalol attaches to and blocks the receptors, arteries expand, resulting in a fall in blood pressure. The FDA approved labetalol in August 1984.

What brand names are available for labetalol?

None. Normodyne and Trandate are discontinued.

Is labetalol available as a generic drug?

Yes

Do I need a prescription for labetalol?

Yes

What are the side effects of labetalol?

The most common side effects of labetalol are:

Postural hypotension (a rapid decrease in blood pressure when going from the lying or seated position to the standing position that may cause light-headedness or fainting) occurs rarely. Patients should be observed for this possible side effect within two to four hours of the first labetalol dose and after any changes in dose.

Other important side effects include:

  • sexual dysfunction,
  • abnormal heart rhythm,
  • slow heart rate,
  • liver failure, and
  • allergic reactions.

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What is the dosage for labetalol?

The recommended starting oral dose of labetalol 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 severely high blood pressure may require 1.2 to 2.4 g daily.

Side effects may be less if labetalol is given in three daily doses rather than two. Stopping or changing the dose of the drug should be directed by a physician because serious side effects may occur. 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. Labetalol also may be administered by intravenous infusion at 1-2 mg/minute.

Which drugs or supplements interact with labetalol?

Labetalol can mask early warning symptoms of hypoglycemia (low blood sugar) such as tremors and increased heart rate which are the result of activation of the adrenergic nervous system. Therefore, people with diabetes taking medications that lower blood sugar such as insulin or oral antidiabetic medications may need to increase the frequency with which they monitor their blood sugar in order to prevent hypoglycemia.

Combining labetalol with tricyclic antidepressants such as amitriptyline (Elavil, Endep), imipramine (Tofranil), or nortriptyline (Pamelor) may lead to an increase in tremor which is a side effect of tricyclic antidepressants.

If combined 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 together, 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.

Halothane anesthesia may contribute to the blood pressure lowering effects of labetalol.

Is labetalol safe to take if I'm pregnant or breastfeeding?

There are no adequate studies of labetalol during pregnancy.

Labetalol is excreted 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.

What else should I know about labetalol?

How should I keep labetalol stored?

Tablets should be stored between 20 C - 30 C (36 F - 86 F).

Medically reviewed by Eni Williams; PharmD, Ph.D. REFERENCE:

FDA Prescribing Information

Quick GuideHow to Lower Blood Pressure: Exercise Tips

How to Lower Blood Pressure: Exercise Tips

Summary

Labetalol (Normodyne, Trandate) is a medication prescribed for the treatment of high blood pressure. Side effects, drug interactions, and pregnancy safety should be reviewed prior to taking this drug.

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See more info: labetalol on RxList
Reviewed on 5/11/2017
References
Medically reviewed by Eni Williams; PharmD, Ph.D. REFERENCE:

FDA Prescribing Information

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