Wytensin Side Effects

Generic Name: guanabenz

Note: This page contains side effects data for the generic drug guanabenz. It is possible that some of the dosage forms included below may not apply to the brand name Wytensin.

It is possible that some side effects of Wytensin may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

For the Consumer

Applies to guanabenz: oral tablet

As well as its needed effects, guanabenz (the active ingredient contained in Wytensin) may cause unwanted side effects that require medical attention.

If any of the following side effects occur while taking guanabenz, check with your doctor or nurse as soon as possible:

Signs and symptoms of overdose
  • Dizziness (severe)
  • irritability
  • nervousness
  • pinpoint pupils
  • slow heartbeat
  • unusual tiredness or weakness

Some guanabenz side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

More common
  • Dizziness
  • drowsiness
  • dryness of mouth
  • weakness
Less common or rare
  • Decreased sexual ability
  • headache
  • nausea

After you stop taking this drug, it is possible that you may still experience side effects that need medical attention. If you notice any of the following side effects check with your doctor immediately:

  • Anxiety or tenseness
  • chest pain
  • fast or irregular heartbeat
  • headache
  • increased salivation
  • increase in sweating
  • nausea or vomiting
  • nervousness or restlessness
  • shaking or trembling of hands or fingers
  • stomach cramps
  • trouble in sleeping

For Healthcare Professionals

Applies to guanabenz: compounding powder, oral tablet


In comparative studies the overall incidence of side effects associated with guanabenz (the active ingredient contained in Wytensin) was as high or higher than that seen with methyldopa or clonidine, but particularly troublesome effects, such as sodium retention, mental depression or sexual dysfunction, which have been associated with these drugs, have not been associated with guanabenz.

Nervous system

The most common side effects involve the nervous system. Drowsiness is a complaint in up to 35% of patients, and, with dry mouth, is the main reason some patients discontinue therapy. Weakness or dizziness each occur in 6% and headache in 2% in patients.


Gastrointestinal side effects include dry mouth in up to 37%, constipation in 2%, and nausea in 1% of patients.


Postural hypotension may not have been observed, at least during initial therapy with guanabenz (the active ingredient contained in Wytensin) due to peripheral vascular resistance and cardiac output remaining unchanged.

Although usually asymptomatic, guanabenz can decrease heart rate. Other cardiovascular side effects are rare. Unlike some other alpha-2-adrenoreceptor agonists, guanabenz is only rarely associated with orthostatic hypotension. Rebound hypertension can be a significant problem that may be accompanied by nervousness, palpitations, diaphoresis, anxiety, insomnia, malaise, and abdominal cramps. It has been observed anywhere from 16 to 72 hours after discontinuation of therapy.


Nasal congestion has been reported in less than 3% of patients.


Dermatologic rashes have been reported in less than 3% of patients.


Ocular side effects are limited to rare cases of blurry vision.


There are no serious endocrinologic side effects associated with guanabenz (the active ingredient contained in Wytensin) The drug does not appear to adversely affect the lipid profile. Some data indicate significant decreases in total and LDL cholesterol levels during guanabenz therapy.


There are no known clinically significant renal side effects from guanabenz (the active ingredient contained in Wytensin) Acutely (within the first day of therapy), guanabenz may cause a mild water diuresis. Unlike some alpha-2-adrenoreceptor agonists, guanabenz is not associated with sodium and water retention.

Some data have shown significant increases in glomerular filtration rate, natriuresis, and free water clearance associated with the use of guanabenz during the first few hours of therapy. Use of guanabenz for one week or more, however, has not been associated with significant changes in renal function parameters.

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