Drug information of Guanabenz


Drug group:

An alpha-2 selective adrenergic agonist used as an antihypertensive agent.

Mechanism of effect

Guanabenz's antihypertensive effect is thought to be due to central alpha-adrenergic stimulation, which results in a decreased sympathetic outflow to the heart, kidneys, and peripheral vasculature in addition to a decreased systolic and diastolic blood pressure and a slight slowing of pulse rate.


Chronic administration of guanabenz also causes a decrease in peripheral vascular resistance.


Bioavailability: 75%

Onset: initial effect: 60 min; max effect: 2-4 hr

Peak plasma time: 2-5 hr

Duration: 10-12 hr

Protein binding: 90%

Vd: 7.4-13.4 L/kg

Metabolism: Liver

Metabolites: para-hydroxy guanabenz; 2,6-dichlorobenzaldehyde azine (inactive)

Half-Life: 6 hr

Dialyzable: HD: No, PD: No

Excretion: Feces 16%, urine <1%

Drug indications





Initial dose: 4 mg PO q12hr intially; may increase dose by 4-8 mg/day at 1-2 week intervals

Maintenance dose range is typically 4-16 mg PO q12hr

Not to exceed 32 mg PO q12hr


Safety and effectiveness not established

Drug contraindications



Tizanidine , teriflunomide


Avoid abrupt withdrawal (rebound hypertension)

CVD, recent MI, sedation, severe coronary insufficiency liver disease, renal impairment

Avoid during breast-feeding

Points of recommendation

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 guanabenz 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.

If you miss a dose of guanabenz, 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 two or more doses in a row, check with your doctor. If your body suddenly goes without guanabenz, some unpleasant effects may occur.

Pregnancy level

Group c - Not adequate studies in pregnant women

Related drugs

Methyldopa , Clonidine , Guanfacine

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