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Active ingredient: Guanethidine - Brands, Medical Use, Clinical Data

Brands, Medical Use, Clinical Data

Drug Category

  • Adrenergic Agents
  • Antihypertensive Agents
  • Sympatholytics

Dosage Forms

  • Tablet

Brands / Synonyms

Apo-Guanethidine; Guanethidine Monosulfate; Guanethidine Sulphae; Ismelin; Ismelin

Indications

For the treatment of moderate and severe hypertension, either alone or as an adjunct, and for the treatment of renal hypertension.

Pharmacology

High blood pressure can cause the heart and arteries to 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. Guanethidine works by decreasing the heart rate and relaxing the blood vessels so that blood can flow more easily through the body, thereby reducing these risks. It is a postganglionic sympathetic nerve terminal blocker that prevents the release of norepinephrine from nerve terminals.

Mechanism of Action

Guanethidine acts at the sympathetic neuroeffector junction by inhibiting or interfering with the release and/or distribution of norepinephrine, rather than acting at the effector cell by inhibiting the association of norepinephrine with its receptors. In contrast to ganglionic blocking agents, Guanethidine suppresses equally the responses mediated by alpha-and beta-adrenergic receptors but does not produce parasympathetic blockade. Since sympathetic blockade results in modest decreases in peripheral resistance and cardiac output, Guanethidine lowers blood pressure in the supine position. It further reduces blood pressure by decreasing the degree of vasoconstriction that normally results from reflex sympathetic nervous activity upon assumption of the upright posture, thus reducing venous return and cardiac output more.

Absorption

3-30% of oral dose (poor and highly variable)

Toxicity

Side effects include drowsiness, dizziness, tiredness or confusion. LD50=1000 mg/kg (mouse, oral)

Biotrnasformation / Drug Metabolism

Guanethidine is converted by the liver to three metabolites, which are excreted in the urine. The metabolites are pharmacologically less active than the parent compound.

Contraindications

Known or suspected pheochromocytoma; hypersensitivity; frank congestive heart failure not due to hypertension; use of monoamine oxidase (MAO) inhibitors.

Drug Interactions

http://www.rxlist.com/cgi/generic3/guanethidine_od.htm

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