Drug information of Guanadrel


Drug group:

Guanadrel belongs to the general class of medicines called antihypertensives. It is used to treat high blood pressure

Mechanism of effect

Guanadrel is an adrenergic neuron inhibitor that slowly displaces norepinephrine from its storage in nerve endings. It blocks the release of norepinephrine in response to the sympathetic nerve stimulation, leading to reduced arteriolar vasoconstriction, especially the reflex increase in sympathetic tone that occurs with a change in position.


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.


Absorption:Rapidly and readily absorbed from the gastrointestinal tract.

Protein binding:Low, approximately 20%

Metabolism:Primarily hepatic

Half life:10 hours

Drug indications

High Blood Pressure



Initial dose: 10 mg/day orally in 1 to 2 divided doses.
Maintenance dose: 20 to 75 mg/day orally in 2 to 4 divided doses

Drug contraindications

Hypersensitivity to this drug


Side effects

Diarrhea , Headache , weight decrease , chest pain , dry mouth , Blurred vision , vertigo , asthenia , myalgia , Tremor , Weight increase , difficulty urinating

Difficulty in ejaculating

dizziness, lightheadedness, or fainting, especially when getting up from a lying or sitting position


unusual tiredness or weakness

weight gain or loss (excessive)

Swelling of feet or lower legs

     Diarrhea or increase in bowel movements

dryness of mouth


muscle pain or tremors

nighttime urination

Chest pain

shortness of breath

Blurred vision

dizziness or faintness

Clorgyline , Lazabemide


-The presence of other medical problems may affect the use of guanadrel. Make sure you tell your doctor if you have any other medical problems, especially:

  • 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

-Dizziness, lightheadedness, or fainting may occur

-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

-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.

Points of recommendation

Tell your doctor if you have ever had any unusual or allergic reaction to guanadrel or any other medicines

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

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.


Pregnancy level



Animal studies have revealed no evidence of harm to the fetus, however, there are no adequate studies in pregnant women OR animal studies have shown an adverse effect, but adequate studies in pregnant women have failed to demonstrate a risk to the fetus.

Breast feeding warning

There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding

Related drugs

Guanethidine , Doxazosin , Alfuzosin

Drug forms


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