In the U.S.—

• Antihypertensive

Guanadrel (GWAHN-a-drel) belongs to the general class of medicines called antihypertensives. It is used to treat high blood pressure (hypertension).

High blood pressure adds to the work load 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.

Guanadrel works by controlling nerve impulses along certain nerve pathways. As a result, it relaxes the blood vessels so that blood passes through them more easily. This helps to lower blood pressure.

Guanadrel is available only with your doctor's prescription, in the following dosage form:

Oral
• Tablets (U.S.)

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 guanadrel, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to guanadrel. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy—Guanadrel has not been studied in pregnant women. However, guanadrel has not been shown to cause birth defects or other problems in animal studies.

Breast-feeding—It is not known whether guanadrel passes into breast milk. However, it has not been reported to cause problems in nursing babies.

Children—Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of guanadrel in children with use in other age groups.

Older adults—Dizziness or faintness may be more likely to occur in the elderly, who are usually more sensitive to the effects of guanadrel.

Other medicines—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. When you are taking guanadrel, it is especially important that your health care professional know if you are taking any of the following:

• Chlorprothixene (e.g., Taractan) or
• Loxapine (e.g., Loxitane) or
• Thiothixene (e.g., Navane) or
• Tricyclic antidepressants (amitriptyline [e.g., Elavil], amoxapine [e.g., Asendin], clomipramine [e.g., Anafranil], desipramine [e.g., Pertofrane], doxepin [e.g., Sinequan], imipramine [e.g., Tofranil], nortriptyline [e.g., Aventyl], protriptyline [e.g., Vivactil], trimipramine [e.g., Surmontil]) or
• Trimeprazine (e.g., Temaril)—May decrease the effects of guanadrel on blood pressure

• Monoamine oxidase (MAO) inhibitor activity (isocarboxazid [e.g., Marplan], phenelzine [e.g., Nardil], procarbazine [e.g., Matulane], selegiline [e.g., Eldepryl], tranylcypromine [e.g., Parnate])—Taking guanadrel while you are taking or within 1 week of taking MAO inhibitors may cause a severe increase in blood pressure

• Asthma (history of) or
• Diarrhea or
• Pheochromocytoma or
• Stomach ulcer (history of)—Guanadrel may worsen these conditions

• Fever—Effects of guanadrel may be increased

• Heart attack or stroke (recent) or
• Heart or blood vessel disease—Lowering blood pressure may make problems resulting from these conditions worse

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 guanadrel will not cure your high blood pressure but it does help control it. Therefore, you must continue to take 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.

To help you remember to take your medicine, try to get into the habit of taking it at the same time each day.

Dosing—

The dose of guanadrel 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 guanadrel. 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):
  • For high blood pressure:
    • Adults—At first, 5 milligrams (mg) two times a day. Then, your doctor may increase your dose to 20 to 75 mg a day, divided into two to four doses.
    • Children—Use and dose must be determined by your doctor.

Missed dose—

If you miss a dose of guanadrel, 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.

Storage—

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 that 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 that this medicine is working properly.

Dizziness, lightheadedness, or fainting may occur, especially when you get up from a lying or sitting position. This may be more likely to occur in the morning. Getting up slowly may help. If you feel dizzy, sit or lie down. When you get up from lying down, sit on the edge of the bed with your feet dangling for 1 or 2 minutes. Then stand up slowly. If the problem continues or gets worse, check with your doctor.

The dizziness, lightheadedness, or fainting is also more likely to occur if you drink alcohol, stand for long periods of time, exercise, or if the weather is hot. While you are taking guanadrel, be careful to limit the amount of alcohol you drink. Also, use extra care during exercise or hot weather or if you must stand for long periods of time.

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.

Before having any kind of surgery (including dental surgery) or emergency treatment, tell the medical doctor or dentist in charge that you are taking guanadrel.

Tell your doctor if you get a fever since that may change the amount of medicine you have to take.

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 immediately if either of the following side effects occurs since they may be symptoms of an overdose:

• Rare
  • Blurred vision;  dizziness or faintness (severe) 
  
  

Check with your doctor as soon as possible if any of the following side effects occur:

• More common
  • Swelling of feet or lower legs 
  
  

• Less common or rare
  • Chest pain;  shortness of breath 
  
  

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:

• More common
  • Difficulty in ejaculating;  dizziness, lightheadedness, or fainting, especially when getting up from a lying or sitting position;  drowsiness;  unusual tiredness or weakness;  weight gain or loss (excessive)  
  
  

• Less common or rare
  • Diarrhea or increase in bowel movements;  dryness of mouth;  headache;  muscle pain or tremors;  nighttime urination 
  
  

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.