Drug Groups

withdrawn

Description

Mibefradil was withdrawn from the market in 1998 because of potentially harmful interactions with other drugs.

Indication

For the treatment of angina and high blood pressure.

Pharmacology

Mibefradil belongs to a group of medicines called calcium channel blocking agents, or, more commonly, calcium channel blockers. Calcium channel blocking agents affect the movement of calcium into the cells of the heart and blood vessels. As a result, they relax blood vessels and increase the supply of blood and oxygen to the heart while reducing its workload. Mibefradil is a benzimidazoyl-substituted tetraline that selectively binds and inhibits T-type calcium channels.

Affected Organisms

Biotransformation

The two metabolic pathways that mibefradil undergoes are esterase-catalyzed hydrolysis of the ester side chain (producing an alcohol metabolite) and cytochrome P450 3A4-catalyzed oxidation (that becomes less important during chronic dosing). The pharmacologic effect of the metabolite is approximately 10% of that of the parent mibefradil.

Absorption

Bioavailability after a single dose is 70%. After multiple dosing, the proportion of mibefradil undergoing first-pass metabolism is reduced, resulting in a steady state bioavailability of approximately 90%. Food does not affect the rate or extent of absorption of mibefradil.

Half Life

17 to 25 hours at steady state.

Protein Binding

≥ 99%, primarily to alpha 1-acid glycoprotein.

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