Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started
My Medicine

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Verelan PM


Selected Alpha-1 Blockers/Verapamil

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Moderate. These medicines may cause some risk when taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

The cause of the interaction is not known. When these two medicines are taken together, the effects of both medicines to lower your blood pressure may increase.

What might happen:

The effects of these medicines to lower blood pressure may be greater than with either drug alone. This may be an advantage. However, additional problems due to excess effects may occur.

What you should do about this interaction:

If you experience weakness or dizziness when you sit up or stand up, contact your doctor.Your healthcare professionals (e.g. doctor or pharmacist) may already be aware of this drug interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.


1.Pasanisi F, Elliott HL, Meredith PA, McSharry DR, Reid JL. Combined alpha adrenoceptor antagonism and calcium channel blockade in normal subjects. Clin Pharmacol Ther 1984 Dec;36(6):716-23.

2.Meredith PA, Elliott HL, Pasanisi F, Reid JL. Prazosin and verapamil: a pharmacokinetic and pharmacodynamic interaction. Br J Clin Pharmacol 1985 Sep;21(1):85P.

3.Elliott HL, Meredith PA, Campbell L, Reid JL. The combination of prazosin and verapamil in the treatment of essential hypertension. Clin Pharmacol Ther 1988 May;43(5):554-60.

4.Meredith PA, Elliott HL. An additive or synergistic drug interaction: application of concentration-effect modeling. Clin Pharmacol Ther 1992 Jun;51(6):708-14.

5.Hytrin (terazosin hydrochloride) US prescribing information. Abbott Laboratories July, 2009.

Selected from data included with permission and copyrighted by First Databank, Inc. This copyrighted material has been downloaded from a licensed data provider and is not for distribution, expect as may be authorized by the applicable terms of use.

CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgment of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.

More about Drugs and Medications


Subscribe to free WebMD newsletters.

  • WebMD Daily

    WebMD Daily

    Subscribe to the WebMD Daily, and you'll get today's top health news and trending topics, and the latest and best information from WebMD.

  • Men's Health

    Men's Health

    Subscribe to the Men's Health newsletter for the latest on disease prevention, fitness, sex, nutrition, and more from WebMD.

  • Women's Health

    Women's Health

    Subscribe to the Women's Health newsletter for the latest on disease prevention, fitness, sex, diet, anti-aging, and more from WebMD.

By clicking Submit, I agree to the WebMD Terms & Conditions & Privacy Policy and understand that I may opt out of WebMD subscriptions at any time.

URAC: Accredited Health Web Site TRUSTe online privacy certification HONcode Seal AdChoices