Guanadrel (By mouth)


Guanadrel (GWAHN-a-drel)

Treats high blood pressure.

Brand Name(s)

When This Medicine Should Not Be Used

How to Use This Medicine


  • Take this medicine exactly as your doctor ordered. Even if you feel fine your blood pressure can still be high.

If a dose is missed:

  • Take the missed dose as soon as you remember.
  • Skip the missed dose if it is almost time for your next regular dose.
  • You should not use two doses at the same time.

How to Store and Dispose of This Medicine

  • Store at room temperature, away from heat, moisture, and direct light.
  • Keep all medicine out of the reach of children.

Drugs and Foods to Avoid

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Make sure your doctor knows if you are taking Temaril®, Navane®, Taractan®, Loxitane® or antidepressants such as Elavil®, Tofranil®, or Sinequan®.
  • Make sure your doctor knows if you have taken an MAO inhibitor such as Nardil®, Parnate®, or Marplan® within the past 1 to 2 weeks.
  • Avoid drinking alcohol while taking this medicine.

Warnings While Using This Medicine

  • Check with your doctor before taking guanadrel if you have asthma, heart failure or other heart disease, diarrhea, stomach ulcers, or stroke.
  • Talk with your doctor before taking this medicine if you are pregnant or breastfeeding.
  • Tell your doctor or dentist that you are taking guanadrel before having any kind of surgery.
  • Guanadrel can make some people dizzy or drowsy, be careful if you drive a car or operate machinery.
  • To avoid dizziness while taking this medicine, stand up slowly from a sitting or lying position.
  • Dizziness, lightheadedness, or faintness may occur more often in the morning and can be made worse by hot weather, fever, exercise, drinking alcohol, or standing for a long time.

Possible Side Effects While Using This Medicine

Call your doctor right away if you notice any of these side effects:

  • Fever or severe diarrhea
  • Blurred vision
  • Fainting or severe dizziness
  • Shortness of breath
  • Chest pain
  • Skin rash, severe itching or hives

If you notice these less serious side effects, talk with your doctor:

  • Dizziness, weakness, tiredness, or drowsiness
  • Diarrhea or constipation
  • Stomach pain, gas, or nausea
  • Headache
  • Trouble sleeping
  • Loss of desire for sex

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Version Info

  • Last reviewed on 10/4/2017

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