Bile Acid Binding Resins

BILE ACID BINDING RESINS

·              These drugs are the safest agents available for lowering plasma lipoproteins. Both cholestyramine and colestipol hydrochloride are anion-exchange resins and are not absorbed for the most part, acting by promoting bile acid excretion. Inhibition of the return of bile acids to the liver results in an increase in conversion of cholesterol to bile acids. Triglyceride synthesis is enhanced which promotes very low density lipoprotein (VLDL) removal, contributing to the low density lipoprotein (LDL), lowering effect.

·      Colestipol is indicated as adjunctive therapy for the reduc-tion of elevated serum total and LDL-C in patients with primary hypercholesterolaemia (elevated LDL-C) who do not respond adequately to diet.

Adverse and Toxic (Clinical) Features

·      Anorexia, bloating, abdominal discomfort, vomiting, flatu-lence, perianal pruritis, and constipation. Rarely there may be faecal impaction.

·      Transient and modest elevations of aspartate amino-transferase (AST, SGOT), alanine aminotransferase (ALT, SGPT) and alkaline phosphatase have been observed with colestipol.

·      Mild increases in serum calcium and decreases in serum phosphorus and 25-hydroxy-vitamin D levels have been reported in children on long-term therapy.

·      Headache, chest pain, angina, tachycardia, and shortness of breath have been reported infrequently during therapeutic use.

·      Since colestipol hydrochloride is a chloride form of an anion exchange resin, there is a possibility that prolonged use may lead to the development of hyperchloraemic acidosis.

·      Since colestipol hydrochloride is an anion exchange resin, it may have a strong affinity for anions other than the bile acids. It is recommended by the manufacturer that patients should take other drugs one hour before or 4 hours after colestipol to prevent absorption problems of concomitant therapy. Colestipol can interfere with normal fat absorp-tion and prevent the absorption of some fat soluble vita-mins such as vitamin K.

Treatment

·      These agents are largely not absorbed in the gastrointes-tinal tract. Attempts at gastrointestinal decontamination are generally not warranted.

·      In minimal to moderate ingestions, increased fluid intake, fibre, and a stool softener should be instituted.

·      If obstruction is ruled out, a polyethylene glycol electrolyte oral solution (PEG-ES) may be used to expedite the evacu-ation of these resins (2 litres initially followed by 1.5 to 2 litres per hour).