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Drugs reference index «Guanfacine hydrochloride»

Guanfacine hydrochloride

Why is Guanfacine hydrochloride prescribed?

Guanfacine is given to help control high blood pressure. This medication reduces nerve impulses to the heart and arteries; this slows the heartbeat, relaxes the blood vessels, and thus reduces blood pressure. Guanfacine may be given alone or in combination with other high blood pressure medications, especially thiazide diuretics, such as Diuril, Esidrix, or Naturetin.

Most important fact about Guanfacine hydrochloride

You must take guanfacine regularly for it to be effective. Since blood pressure declines gradually, it may be several weeks before you get the full benefit of guanfacine; and you must continue taking it even if you are feeling well. Guanfacine does not cure high blood pressure; it merely keeps it under control.

How should you take Guanfacine hydrochloride?

Take guanfacine exactly as prescribed by your doctor--usually 1 dose per day. Guanfacine should be taken at bedtime, since it will probably cause drowsiness.

After 3 or 4 weeks, if your blood pressure is still too high, your doctor may raise the dosage of guanfacine. In some cases, you may take 2 evenly spaced doses per day rather than a single dose at bedtime.

--If you miss a dose...

Take the forgotten dose as soon as you remember. This will help to keep the proper amount of medicine in your body. However, if it is almost time for the next dose, skip the one you missed and go back to your regular schedule. Never try to "catch up" by doubling the dose. If you miss taking guanfacine for 2 or more days in a row, check with your doctor.

--Storage instructions...

Store guanfacine at room temperature. Use the container it came in.

Guanfacine hydrochloride side effects

Side effects cannot be anticipated. If any develop or change in intensity, inform your doctor as soon as possible. Only your doctor can determine whether it is safe for you to continue taking guanfacine. This medication will probably make you drowsy, especially when you first begin to take it.

  • Side effects may include:Constipation, dizziness, dry mouth, fatigue, headache, impotence, sleepiness, weakness

Some of these side effects may lessen or disappear as your body gets used to guanfacine.

Why should Guanfacine hydrochloride not be prescribed?

Do not take guanfacine if you are sensitive to it or have ever had an allergic reaction to it.

Guanfacine is not recommended for controlling the severe high blood pressure that accompanies toxemia of pregnancy (a disorder of pregnant women characterized by a rise in blood pressure, swelling, and leakage of protein into urine).

Special warnings about Guanfacine hydrochloride

While taking guanfacine, you should be monitored very closely by your doctor if you have any of the following medical conditions:Chronic kidney or liver failureHeart diseaseHistory of strokeRecent heart attack

Since guanfacine causes drowsiness and may also make you dizzy, do not drive, climb, or perform hazardous tasks until you find out exactly how Guanfacine hydrochloride affects you.

While taking guanfacine, use alcoholic beverages with care; you may feel intoxicated after drinking only a small amount of alcohol.

If you have kidney damage and also take the antiseizure drug phenytoin (Dilantin), your body may process and eliminate guanfacine rather quickly; in that case, you may need fairly frequent doses of guanfacine to lower your blood pressure adequately.

If you have been taking guanfacine for a while, do not stop taking it without consulting your doctor. Discontinuing abruptly may result in nervousness, rapid pulse, anxiety, heartbeat irregularities, and so-called rebound high blood pressure (higher than before you started taking guanfacine). If you do have rebound high blood pressure, it will probably develop 2 to 4 days after your last dose of guanfacine. Rebound high blood pressure, if it occurs, will usually diminish and then disappear over a period of 2 to 4 days.

Possible food and drug interactions when taking Guanfacine hydrochloride

If guanfacine is taken with certain other drugs, the effects of either could be increased, decreased, or altered. It is especially important to check with your doctor before combining guanfacine with the following:Barbiturates such as Amytal, Seconal, Tuinal, and othersBenzodiazepines such as Tranxene, Valium, Xanax, and othersPhenothiazines such as Mellaril, Stelazine, Thorazine, and othersPhenytoin (Dilantin)

Special information if you are pregnant or breastfeeding

If you are pregnant or plan to become pregnant, notify your doctor immediately. Guanfacine should be taken during pregnancy only if clearly needed. It is not known whether guanfacine appears in breast milk. Check with your doctor if you plan to breastfeed.

Recommended dosage for Guanfacine hydrochloride


The usual recommended dose of guanfacine is 1 milligram daily, taken at bedtime. If necessary, after 3 to 4 weeks your doctor may increase the daily dosage to 2 milligrams.


The safety and effectiveness of guanfacine have not been established in children under 12 years of age.


Any medication taken in excess can have serious consequences. If you suspect an overdose of guanfacine, seek medical attention immediately.

  • Symptoms of guanfacine overdose may include:Drowsiness, lethargy, slowed heartbeat, very low blood pressure
  • Guanfacine Prescribing Information (FDA)
  • Guanfacine Professional Patient Advice (Wolters Kluwer)
  • guanfacine Advanced Consumer (Micromedex) - Includes Dosage Information
  • Guanfacine MedFacts Consumer Leaflet (Wolters Kluwer)
  • Intuniv Prescribing Information (FDA)
  • Intuniv Extended-Release Tablets MedFacts Consumer Leaflet (Wolters Kluwer)
  • Intuniv Consumer Overview

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