Bile acid sequestrants

Bile acid sequestrants

i. Cholestyramine resin

Mode of action: It is a styrene copolymer with divinyl benzene and quaternary ammonium functional group. The resin is insoluble in water, remains unchanged in the intestinal tract, unaffected by digestive enzymes, and is not absorbed. These are basic ion exchange resins, which binds with bile acids, interferes in the enterohepatic circulation, and leads to the excretion of cholesterol in faeces. This also indirectly leads to the enhanced hepatic metabolism of cholesterol to bile acids, so more LDL receptors are exposed on liver cells and the plasma intermediate density and very low-density lipoprotein clearance is more.

Properties and uses: It is a white or almost white fine powder, and is hygroscopic, insoluble in water, in methylene chloride and in ethanol, used as lipid-regulating drug.

Assay: It is assayed by adopting liquid chromatography technique.

Storage: It should be stored in well-closed airtight containers and protected from light.

Dosage forms: Colestyramine oral powder B.P.

ii. Colestipol

Properties and uses: It exists as yellow to orange beads, hygroscopic in nature. It swells, but does not dissolve in water and dilute aqueous solutions of acids and alkali, insoluble in ethanol and in dichloromethane. It is an insoluble copolymer of diethylene triamine and epichlorhydrin, containing secondary and tertiary amine functionalities. It is potent in reducing cholesterol levels. It is effective in the treatment of type II hyperlipoproteinaemias.

Storage: Colestipol hydrochloride should be stored in airtight containers.

Dosage forms: Colestipol granules B.P.