Drug Groups

approved

Description

Highly crosslinked and insoluble basic anion exchange resin used as anticholesteremic. It may also may reduce triglyceride levels. [PubChem]

Indication

For use, as adjunctive therapy to diet, for the reduction of elevated serum total and LDL-C in patients with primary hypercholesterolemia (elevated LDL-C) who do not respond adequately to diet.

Pharmacology

Cholesterol is the major, and probably the sole precursor of bile acids. During normal digestion, bile acids are secreted via the bile from the liver and gall bladder into the intestines. Bile acids emulsify the fat and lipid materials present in food, thus facilitating absorption. A major portion of the bile acids secreted is reabsorbed from the intestines and returned via the portal circulation to the liver, thus completing the enterohepatic cycle. Only very small amounts of bile acids are found in normal serum. Colestipol hydrochloride binds bile acids in the intestine forming a complex that is excreted in the feces. This nonsystemic action results in a partial removal of the bile acids from the enterohepatic circulation, preventing their reabsorption. Since colestipol hydrochloride is an anion exchange resin, the chloride anions of the resin can be replaced by other anions, usually those with a greater affinity for the resin than the chloride ion.

Toxicity

Oral LD₅₀ in rats is > 1000 mg/kg. Symptoms of overdose may include eye irritation, constipation, abdominal cramps, nausea, vomiting, diarrhea, and hypersensitivity. However, as colestipol is not absorbed, the risk of systemic toxicity is low.

Affected Organisms

Biotransformation

Not applicable (not hydrolyzed by digestive enzymes and not absorbed).

Absorption

Not absorbed from the gastrointestinal tract.

Protein Binding

Not applicable (not hydrolyzed by digestive enzymes and not absorbed).

Elimination

Colestipol hydrochloride binds bile acids in the intestine forming a complex that is excreted in the feces. In humans, less than 0.17% of a single 14C-labeled colestipol hydrochloride dose is excreted in the urine when given following 60 days of chronic dosing of 20 grams of colestipol hydrochloride per day. The increased fecal loss of bile acids due to colestipol hydrochloride administration leads to an increased oxidation of cholesterol to bile acids.

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