Discuss the indications of cholestyramine?
Bile acid malabsorption- This can be caused by ileal disease or resection, idiopathic or bacterial overgrowth (deconjugation of bile acids). Bile acid malabsorption can be documented by SeHCAT test.
Under normal conditions, bile acids are actively absorbed in the distal ileum. The reabsorbed bile acids enter the portal bloodstream and are taken up rapidly by hepatocytes, reconjugated and resecreted into bile (the `enterohepatic circulation’). Failure of the active transport of bile acids in the terminal ileum results in bile acid malabsorption. These unabsorbed bile acids affect colonocytes and impair water and salt absorption. In colon bile salts are also dehydroxylated to deoxy bile salts, which induce colonic water secretion. This causes secretory diarrhoea. At the same time, the liver is unable to increase the rate of bile salt production to a sufficient degree to compensate for the loss and fat digestion may be compromised, leading to steatorrhoea and malabsorption of fat-soluble vitamins.
Cholestyramine can be used for idiopathic bile acid malabsorption.
Cholestyramine may help with bile salt diarrhoea secondary to ileal resection. However, it will increase fat malabsorption by further reducing the bile salt pool and hence should not be used in patients with > 100 cm of ileal resection. Cholestyramine helps if < 100cms of ileum resected. (i.e. ileal resection of more than 100cms causes steatorrhoea. <100cm resection can cause diarrhoea without necessarily leading to steatorrhea)
Treatment of pruritus in Primary biliary cirrhosis- cholestyramine is the initial treatment for pruritus in PBC.  The cause of pruritus in PBC is unknown. However, it is believed that the pruritogenic substances are made in the liver, excreted in bile, and as a result of cholestasis accumulate in tissues. Cholestyramine promotes excretion of these pruritogenic substances and improves pruritus.

Treatment of primary hypercholesterolemia- Cholestyramine binds with bile acids in the intestine, causing an increase in hepatic synthesis of bile acids from cholesterol. This depletion of hepatic cholesterol increases hepatic LDL receptor activity, which removes LDL cholesterol from the plasma.

Discuss the dose and administration of cholestyramine?
Available as 4 gm sachets
Dose- 1-2 sachets (maximum 24 gm in day)
Mix powder with water or other fluid prior to administration. It is not systemically absorbed.
Take other medications 1 hour before or 4-6 hours after cholestyramine (to avoid decreased absorption)
Discuss the side effects?
It is well tolerated but may cause nausea, vomiting, belching, bloating, diarrhoea, headache, abdominal pain.
It may interfere with absorption of fat soluble vitamins. This may lead to an increased bleeding tendency by causing hypoprothrombinaemia.

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