cholestyramine
Questran, Questran Light

Available forms
Available by prescription only
Powder: 378-g cans, 9-g single-dose packets (Questran), 5-g single dose packets (Questran Light). Each scoop of powder or single-dose packet contains 4 g of cholestyramine resin.

Indications and dosages
 Primary hyperlipidemia and hypercholesterolemia unresponsive to dietary measures alone, reduction of risks of atherosclerotic coronary artery disease and MI, pruritus from partial biliary obstruction, cardiac glycoside toxicity ◇. Adults: 4 g P.O. before meals and h.s. not to exceed 32 g daily. Can be given in one to six divided doses.
Children older than age 6: 80 mg/kg or 2.35 g/m² P.O. t.i.d.

Pharmacodynamics
Antilipemic action: Bile is normally excreted into the intestine to facilitate absorption of fat and other lipid materials. Cholestyramine binds with bile acid, forming an insoluble compound that’s excreted in feces. With less bile available in the digestive system, less fat and lipid materials in food are absorbed, more cholesterol is used by the liver to replace its supply of bile acids, and the serum cholesterol level decreases. In partial biliary obstruction, excess bile acids accumulate in dermal tissue, resulting in pruritus; by reducing levels of dermal bile acids, cholestyramine combats pruritus.
  Drug can also act as an antidiarrheal in postoperative diarrhea caused by bile acids in the colon.

Pharmacokinetics
Absorption: Not absorbed. Cholesterol levels may start decreasing 24 to 48 hours after therapy starts and may continue falling for up to 12 months. In some patients, the initial decrease is followed by a return to baseline levels (or higher) as therapy continues. Relief of cholestasis-related pruritus occurs 1 to 3 weeks after therapy starts. Diarrhea related to bile acids may stop in 24 hours.
Distribution: None.
Metabolism: None.
Excretion: Insoluble cholestyramine with bile acid complex is excreted in feces.

Contraindications and precautions
Contraindicated in patients hypersensitive to bile-acid sequestering resins and in those with complete biliary obstruction. Use cautiously in patients with coronary artery disease or a predisposition to constipation.

Interactions
Drug-drug. Acetaminophen, cardiac glycosides, corticosteroids, thiazide diuretics, thyroid preparations: May reduce absorption of these drugs. Give other drugs 1 hour before or 4 to 6 hours after cholestyramine. To prevent high-dose toxicity, readjust dosages of these drugs when cholestyramine is withdrawn.
Warfarin: May decrease anticoagulant effects. Avoid use together. Monitor PT and INR carefully.

Adverse reactions
CNS: headache, anxiety, vertigo, dizziness, insomnia, fatigue, syncope.
EENT: tinnitus.
GI: constipation,fecal impaction, hemorrhoids, abdominal discomfort, flatulence, nausea, vomiting, steatorrhea, GI bleeding, diarrhea, anorexia.
GU: hematuria, dysuria.
Hematologic: anemia, bleeding tendencies.
Metabolic: hyperchloremic acidosis with long-term use or very high doses.
Musculoskeletal: backache, muscle and joint pain, osteoporosis.
Skin: rash; irritation of skin, tongue, and perianal area, ecchymoses.
Other: vitamin A, D, E, and K deficiencies from decreased absorption.

Effects on lab test results
• May increase alkaline phosphatase level. May increase or decrease serum chloride, phosphorus, potassium, calcium, and sodium levels.
• May decrease hemoglobin and hematocrit.

Overdose and treatment
Drug overdose hasn’t been reported. Chief risk is intestinal obstruction.
 Treatment depends on location and degree of obstruction and on intestinal motility.

Special considerations
• To mix, sprinkle powder on surface of preferred beverage or wet food, let stand a few minutes and stir to obtain uniform suspension; avoid excess foaming by using large glass and mixing slowly. Use at least 90 ml of water or other fluid, soup, milk, or pulpy fruit; rinse container and have patient drink this liquid to be sure he ingests entire dose.
• Drug has been used to treat cardiac glycoside overdose because it binds these agents and prevents enterohepatic recycling. When used as an adjunct to hyperlipidemia, monitor levels of cardiac glycosides and other drugs to ensure appropriate dosage during and after therapy with cholestyramine.
• Questran Light contains aspartame and provides 1.6 calories per packet or scoop.
• Cholecystography using iopanoic acid will yield abnormal results because iopanoic acid is also bound by cholestyramine.
• Monitor serum cholesterol level frequently during first few months of therapy and periodically thereafter.
• Monitor bowel function. Treat constipation promptly by decreasing dosage, adding a stool softener, or stopping drug.
• Observe patient for signs of vitamin A, D, or K deficiency.
Pregnant patients
• Although drug wouldn’t be expected to harm fetus, its known interference with absorption of fat-soluble vitamins may cause fetal harm. Use dietary management.
Breast-feeding patients
• Safety in breast-feeding women hasn’t been established.
Pediatric patients
• Children may be at greater risk of hyperchloremic acidosis during cholestyramine therapy. Safe dosage hasn’t been established for children younger than age 6.
Geriatric patients
• Patients older than age 60 are more likely to experience adverse GI effects as well as adverse nutritional effects.

Patient education
• Urge patient to comply with continued blood testing and special diet; although therapy isn’t curative, it helps control serum cholesterol level.
• Urge patient to control weight and to stop smoking as part of attempt to increase awareness of othcUrge patient to control weight and to stop smoking as part of attempt to increase awareness of other cardiac risk factors.
• Tell patient not to take the powder in dry form; teach him to mix drug with fluids or pulpy fruits.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use