Brand Name(s):

  • Wytensin®¶

WHY is this medicine prescribed?

Guanabenz is used to treat high blood pressure. It works by decreasing your heart rate and relaxing the blood vessels so that blood can flow more easily through the body.

This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

HOW should this medicine be used?

Guanabenz comes as a tablet to take by mouth. It usually is taken twice a day at evenly spaced intervals. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take guanabenz exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Guanabenz controls high blood pressure but does not cure it. Continue to take guanabenz even if you feel well. Do not stop taking guanabenz without talking to your doctor.

Abruptly stopping guanabenz may increase blood pressure and cause unwanted side effects.

What SPECIAL PRECAUTIONS should I follow?

Before taking guanabenz,

  • tell your doctor and pharmacist if you are allergic to guanabenz or any other drugs.
  • tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially other medications for high blood pressure, amitriptyline (Elavil), clomipramine (Anafranil), desipramine (Norpramin), doxepin (Adepin, Sinequan), imipramine (Tofranil), nortriptyline (Aventyl, Pamelor), protriptyline (Vivactil), sleeping pills, trimipramine (Surmontil), and vitamins.
  • tell your doctor if you have or have ever had coronary artery disease, kidney or liver disease, or a heart attack.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking guanabenz, call your doctor.
  • if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking guanabenz.
  • you should know that this drug may make you drowsy or dizzy. Do not drive a car or operate machinery until you know how this drug affects you.
  • ask your doctor about the safe use of alcohol while you are using guanabenz. Alcohol can make the side effects from guanabenz worse.

What SPECIAL DIETARY instructions should I follow?

Your doctor may prescribe a low-salt or low-sodium diet. Follow these directions carefully.

What should I do IF I FORGET to take a dose?

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

What SIDE EFFECTS can this medicine cause?

Guanabenz may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • dry mouth
  • drowsiness
  • dizziness
  • weakness
  • headache
  • decreased sexual ability
  • upset stomach

If you experience any of the following symptoms, call your doctor immediately:

  • fainting
  • increased or decreased heartbeat
  • irregular heartbeat
  • swollen ankles or feet

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online [at Web Site] or by phone [1-800-332-1088].

What should I know about STORAGE and DISPOSAL of this medication?

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store at room temperature and away from excess heat and moisture (not in the bathroom). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.

What should I do in case of OVERDOSE?

In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.

What OTHER INFORMATION should I know?

Keep all appointments with your doctor and the laboratory. Your blood pressure should be checked regularly to determine your response to guanabenz.

Your doctor may ask you to check your pulse (heart rate) daily and will tell you how rapid it should be. Ask your doctor or pharmacist to teach you how to take your pulse. If your pulse is slower or faster than it should be, call your doctor before taking the drug that day.

To avoid dizziness or faintness, get up slowly from a sitting or lying position. If you feel dizzy or faint at any time, you should lie or sit down.

To relieve dry mouth caused by guanabenz, chew gum or suck sugarless hard candy.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

¶This branded product is no longer on the market. Generic alternatives may be available.

AHFS® Consumer Medication Information. © Copyright, The American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

Last Reviewed: September 1, 2010.