Guanadrel

In the U.S.

• Hylorel

Available Dosage Forms:

• Tablet

Therapeutic Class: Antihypertensive

Pharmacologic Class: Adrenergic Blocker

Guanadrel 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.

It is important that your doctor check your progress at regular visits to make sure that guanadrel 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.

Applies to guanadrel: oral tablet

Along with its needed effects, guanadrel may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Get emergency help immediately if any of the following symptoms of overdose occur while taking guanadrel:

• Blurred vision
• dizziness or faintness (severe)

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

• Swelling of feet or lower legs

• Chest pain
• shortness of breath

Some side effects of guanadrel may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

• 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)

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

Applies to guanadrel: oral tablet

Nervous system

The most common problems associated with guanadrel affect the nervous system. Up to 60% of patients have experienced drowsiness, fatigue, or headaches, 25% of patients experienced paresthesias or visual disturbances, and 2% experienced sleep disorders during therapy[Ref]

Cardiovascular

Cardiovascular side effects can result from excessive sympathetic blockade or a relative increase in parasympathetic tone. Orthostatic hypotension occurs in 8% to 50% of patients, some of whom experience syncope.

Unopposed or excessive parasympathetic tone can cause excessive bradycardia in rare cases. This may cause serious problems in patients with underlying sinus node dysfunction.

Peripheral edema has been reported in up to 30% of patients.

Other cardiovascular problems include chest pain in 28%, dyspnea at rest in 18%, dyspnea on exertion in 46%, and palpitations in 30% of patients. Underlying diseases may account for the relatively high incidence of some of these side effects.[Ref]

The risk of orthostatic hypotension, sometimes followed by syncope, is greatest within the first 10 minutes after dosing or early in the morning, and in hypovolemia. It is accentuated by alcohol, hot weather, or exercise--all of which are associated with peripheral vasodilation. The manufacturer recommends that guanadrel be gradually withdrawn over at least two weeks prior to administration of general anesthetics to avoid cardiovascular collapse during induction.[Ref]

Gastrointestinal

Gastrointestinal side effects are also related to increased parasympathetic tone. Diarrhea has been reported in 5% to 30% of patients, some of whom discontinue therapy because of it. Constipation has been reported in up to 21% of patients. Dry mouth or parotid tenderness have been associated with the use of this drug in approximately 2% of patients.[Ref]

Genitourinary

There is evidence that peripherally-acting antiadrenergic drugs may interfere with ejaculation by inhibiting contraction of the seminal vesicle, ampula and ductus deferens.[Ref]

Sexual impotence is a relatively common genitourinary complaint, occurring in 5% to 18% of male patients. Smaller studies, where specific questions were asked, revealed an incidence of impotence as high as 60% of male patients who were receiving a similar drug, guanethidine. Impotence appears to be reversible upon discontinuation of therapy or reduction in dosage. Urinary frequency or urgency has occurred in 30% to 50% of patients.[Ref]

Musculoskeletal

Musculoskeletal cramping has occurred in approximately 20% to 40% of patients.[Ref]

Some side effects of guanadrel may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.