Guanfacine Hydrochloride

Brand Name - Tenex

  • Type of Drug: Antihypertensive.
  • Prescribed for: High blood pressure, heroin withdrawal, migraine headaches, nausea, and vomiting.

General Information

Guanfacine works by stimulating a particular portion of the nervous system that dilates (widens) blood vessels. Because the studies of Guanfacine were conducted only in people taking a thiazide-type diuretic, the drug is recommended for use only in combination with one of those drugs. Guanfacine’s effect is long-acting; it can be taken only once a day (usually at bedtime, to benefit from the drug’s side effect of producing sleepiness).

Cautions and Warnings

Do not use Guanfacine if you are allergic to it. Guanfacine should be used with caution if you have severe coronary insufficiency, a recent history of heart attack, blood vessel disease of the brain, or kidney or liver failure. People with kidney disease should have their Guanfacine dosage adjusted by their doctor because the drug passes out of the body primarily through the kidneys.

Guanfacine causes sedation, especially when it is first taken. This sedation is greater with larger doses and is intensified by other nervous-system depressants, including phenothiazine antipsychotic medicines, benzodiazepine sedatives and sleeping pills, and barbiturate sedatives and sleeping pills.

Abruptly stopping Guanfacine may result in a rebound reaction consisting of anxiety, nervousness, and occasional increases in bipod pressure. When rebound reactions occur, they happen 2 to 4 days after the medicine is stopped. This is consistent with the fact that it takes longer for Guanfacine to leave the body than Clonidine or other similar drugs.

Possible Side Effects

Guanfacine may cause sedation, especially when treatment is first started. The frequency with which drowsiness occurs tends to increase with increased drug dosage and to become less severe as you continue to take the drug.

  • Most common: drowsiness.
  • Less common: heart palpitations, chest pain, slow heartbeat, abdominal pain, diarrhea, upset stomach, difficulty swallowing, nausea, memory loss, confusion, depression, loss of sex drive, runny nose, taste changes, ringing or buzzing in the ears, conjunctivitis (“pink-eye”), eye irritation, blurring and other visual disturbances, leg cramps, unusually slow movements, breathing difficulty, itching, rash, skin redness, sweating, testicle disorders, poor urinary control, feelings of ill health, and tingling in the hands or feet.
  • Other: dry mouth, weakness, dizziness, headache, constipation, and sleeplessness.

Drug Interactions

• Alcohol or any other nervous-system depressant will increase the sedative effects of Guanfacine.
• Indomethacin, Ibuprofen, and other nonsteroidal anti-inflammatory pain relievers (NSAIDs) may decrease Guanfacine’s effectiveness. Stimulants, ‘ including those used in nonprescription decongestants and diet pills, can antagonize Guanfacine’s effect.
• Estrogen drugs may cause fluid retention, which increases blood pressure.
• Any medication that lowers blood pressure will increase the blood-pressure-lowering effect of Guanfacine.

Food Interactions

Guanfacine may be taken with food if it upsets your stomach.

Usual Dose

Adult and Adolescent (age 12 and older): 1 to 3 mg per day, taken at bedtime. Doses above 3 mg per day are rarely used because side effects increase, whereas effectiveness does not.
Child (less than age 12): not recommended.


Symptoms are likely to be drowsiness, slow heartbeat, low blood pressure, and weakness. Overdose victims should be taken to a hospital emergency-room. ALWAYS bring the medicine bottle with you.

Special Information

High blood pressure is usually a symptomless condition. Be sure to continue taking your medicine even if you feel perfectly healthy. If the medicine causes problems, do not stop taking it unless your doctor so advises. Abruptly stopping Guanfacine treatment can result in a rebound increase in blood pressure after 2 to 4 days.

Call your doctor if you develop any of the following: breathing difficulty; slow heartbeat; extreme dizziness; dry mouth that lasts more than 2 weeks and is not relieved by gum, candy, or saliva substitutes; dry, itchy, or burning eyes; sex-drive loss; headache; nausea or vomiting; sleeping difficulty; unusual tiredness or weakness during the daytime; or other persistent or intolerable side effects.

People taking Guanfacine must be careful when performing tasks requiring concentration and coordination because it may make them tired, dizzy, or light-headed.

Visit your doctor regularly to check on your progress, and be sure to follow your doctor’s directions for diet, salt restriction, and other lifestyle approaches to control your blood pressure.

Pay extra attention to dental hygiene while taking Guanfacine. The dry mouth caused by the drug can make it easier for you to develop cavities and gum disease.

This medicine is generally taken at bedtime. If you forget to take a dose, you may take it the following morning, but it can make you tired during the day. If you don’t remember until it is almost time for your next dose, skip the one you forgot and continue with your regular schedule. Do not take a double dose. Call your doctor if you miss 2 or more consecutive doses.

Special Populations

Animal studies indicate that high doses of Guanfacine may be toxic to a developing fetus. This drug is not recommended to treat high blood pressure during pregnancy. Consult your doctor.
Guanfacine passes into animal breast milk, but it is not known if this happens in humans. Nursing mothers who must take Guanfacine should exercise caution.

Older adults may be more sensitive to the sedative and blood-pressure-lowering effects of Guanfacine because of usual age-related losses of kidney function. This factor should be taken into account by your doctor when determining your daily dosage of Guanfacine.