US Brand Names
Guanfacine (GWAHN-fa-seen) belongs to the general class of medicines called antihypertensives. It is used to treat high blood pressure (hypertension).
High blood pressure adds to the workload of the heart and arteries. If it continues for a long time, the heart and arteries may not function properly. This can damage the blood vessels of the brain, heart, and kidneys, resulting in a stroke, heart failure, or kidney failure. High blood pressure may also increase the risk of heart attacks. These problems may be less likely to occur if blood pressure is controlled.
Guanfacine works by controlling nerve impulses along certain nerve pathways. As a result, it relaxes blood vessels so that blood passes through them more easily. This helps to lower blood pressure.
Guanfacine is available only with your doctor's prescription, in the following dosage form:
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For guanfacine, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to guanfacine. Also tell your health care professional if you are allergic to any other substance, such as foods, preservatives, or dyes.
Guanfacine has not been studied in pregnant women. However, guanfacine has not been shown to cause birth defects or other problems in rats or rabbits given many times the human dose. In rats and rabbits given extremely high doses (up to 200 times the human dose), there was an increase in deaths of the animal fetus.
It is not known whether guanfacine passes into breast milk. However, this medicine has not been reported to cause problems in nursing babies.
Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of guanfacine in children with use in other age groups.
Dizziness, drowsiness, or faintness may be more likely to occur in the elderly, who are more sensitive to the effects of guanfacine.
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your health care professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.
Other medical problems
The presence of other medical problems may affect the use of guanfacine. Make sure you tell your doctor if you have any other medical problems, especially:
• Heart disease or
• Heart attack or stroke (recent)-Lowering blood pressure may make problems resulting from these conditions worse
• Liver disease-Effects may be increased because of slower removal of guanfacine from the body
• Mental depression-Guanfacine may cause mental depression
In addition to the use of the medicine your doctor has prescribed, treatment for your high blood pressure may include weight control and care in the types of foods you eat, especially foods high in sodium. Your doctor will tell you which of these are most important for you. You should check with your doctor before changing your diet.
Many patients who have high blood pressure will not notice any signs of the problem. In fact, many may feel normal. It is very important that you take your medicine exactly as directed and that you keep your appointments with your doctor even if you feel well.
Remember that this medicine will not cure your high blood pressure but it does help control it. Therefore, you must continue to use it as directed if you expect to lower your blood pressure and keep it down. You may have to take high blood pressure medicine for the rest of your life . If high blood pressure is not treated, it can cause serious problems such as heart failure, blood vessel disease, stroke, or kidney disease.
Take your daily dose of guanfacine at bedtime. (If you are taking more than one dose a day, take your last dose at bedtime.) Taking it this way will help lessen daytime drowsiness.
The dose of guanfacine will be different for different patients. Follow your doctor's orders or the directions on the label . The following information includes only the average doses of guanfacine. If your dose is different, do not change it unless your doctor tells you to do so.
The number of tablets that you take depends on the strength of the medicine.
• For oral dosage form (tablets):
o For high blood pressure:
§ Adults-At first, 1 milligram (mg) once a day at bedtime. Then, your doctor may gradually increase your dose up to 3 mg a day, if needed.
§ Children-Dose must be determined by your doctor.
If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses. If you miss taking guanfacine for two or more days in a row, check with your doctor . If your body suddenly goes without this medicine, some unwanted effects may occur. If you have any questions about this, check with your doctor.
To store this medicine:
• Keep out of the reach of children.
• Store away from heat and direct light.
• Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
• Do not keep outdated medicine or medicine no longer needed. Be sure any discarded medicine is out of the reach of children.
It is important that your doctor check your progress at regular visits to make sure this medicine is working properly.
Check with your doctor before you stop taking guanfacine. Your doctor may want you to reduce gradually the amount you are taking before stopping completely.
Make sure that you have enough guanfacine on hand to last through weekends, holidays, and vacations. You should not miss any doses. You may want to ask your doctor for another written prescription for guanfacine to carry in your wallet or purse. You can then have it filled if you run out when you are away from home.
Before having any kind of surgery (including dental surgery) or emergency treatment, tell the medical doctor or dentist in charge that you are using this medicine.
Do not take other medicines unless they have been discussed with your doctor . This especially includes over-the-counter (nonprescription) medicines for appetite control, asthma, colds, cough, hay fever, or sinus problems, since they may tend to increase your blood pressure.
Guanfacine will add to the effects of alcohol and other CNS depressants (medicines that slow down the nervous system, possibly causing drowsiness). Some examples of CNS depressants are antihistamines or medicine for hay fever, other allergies, or colds; sedatives, tranquilizers, or sleeping medicine; prescription pain medicine or narcotics; barbiturates; medicine for seizures; muscle relaxants; or anesthetics, including some dental anesthetics. Check with your doctor before taking any of the above while you are using this medicine .
Guanfacine may cause some people to become dizzy, drowsy, or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy or are not alert .
Guanfacine may cause dryness of the mouth, nose, and throat. For temporary relief of mouth dryness, use sugarless candy or gum, melt bits of ice in your mouth, or use a saliva substitute. However, if dry mouth continues for more than 2 weeks, check with your physician or dentist. Continuing dryness of the mouth may increase the chance of dental disease, including tooth decay, gum disease, and fungus infections.
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor as soon as possible if any of the following side effects occur:
Confusion; mental depression.
Signs and symptoms of overdose
Difficulty in breathing; dizziness (extreme) or faintness; slow heartbeat; unusual tiredness or weakness (severe).
Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:
Constipation; dizziness; drowsiness; dryness of mouth.
Decreased sexual ability; dry, itching, or burning eyes; headache; nausea or vomiting; trouble in sleeping; unusual tiredness or weakness.
After you have been using this medicine for a while, unwanted effects may occur if you stop taking it too suddenly. After you stop taking this medicine, check with your doctor if any of the following side effects occur:
Anxiety or tenseness; chest pain; fast or irregular heartbeat; headache; increased salivation; nausea or vomiting; nervousness or restlessness; shaking or trembling of hands and fingers; stomach cramps; sweating; trouble in sleeping.
Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.
August 19, 1998