Drug Interactions between Questran and Xanax

GENERALLY AVOID: The pharmacologic activity of oral midazolam, triazolam, and alprazolam may be increased if taken after drinking grapefruit juice. The proposed mechanism is CYP450 3A4 enzyme inhibition. In addition, acute alcohol ingestion may potentiate CNS depression and other CNS effects of many benzodiazepines. Tolerance may develop with chronic ethanol use. The mechanism may be decreased clearance of the benzodiazepines because of CYP450 hepatic enzyme inhibition. Also, it has been suggested that the cognitive deficits induced by benzodiazepines may be increased in patients who chronically consume large amounts of alcohol.

MANAGEMENT: The manufacturer recommends that grapefruit juice should not be taken with oral midazolam. Patients taking triazolam or alprazolam should be monitored for excessive sedation. Alternatively, the patient could consume orange juice which does not interact with these drugs. Patients should be advised to avoid alcohol during benzodiazepine therapy.

ADJUST DOSING INTERVAL: Bile acid sequestrants and the phosphate binder, sevelamer, can decrease the absorption of fat-soluble vitamins A, D, E, and K. By binding bile acids, these agents may interfere with normal fat digestion and absorption, thereby preventing the absorption of fat-soluble vitamins. When 8 grams of cholestyramine was administered simultaneously with a normal meal containing 250,000 units of vitamin A acetate in four healthy young adult subjects, plasma vitamin A levels were significantly reduced during a 9-hour postprandial period compared to the values obtained with the control meal. Coadministration with 4 grams of cholestyramine had no significant effect. In a crossover study involving healthy subjects, coadministration of sevelamer with calcitriol resulted in a significant reduction in bioavailability for calcitriol (calcitriol with sevelamer vs calcitriol alone: AUC 137 pg*h/mL vs 318 pg*h/mL and Cmax 40.1 pg/mL vs 49.7 pg/mL, respectively). Chronic use of bile acid sequestrants has been rarely associated with an increased bleeding tendency due to hypoprothrombinemia resulting from vitamin K deficiency. Isolated cases of Vitamin A (including one case of night blindness) and D deficiencies have also been reported with chronic cholestyramine therapy.

MANAGEMENT: When bile acid sequestrants are given for prolonged periods, some manufacturers recommend that concomitant supplementation with water-miscible or parenteral forms of fat-soluble vitamins be considered. If oral vitamin supplements are used with cholestyramine or colestipol, advise patients to take them at least 1 hour before or 4 to 6 hours after the bile acid sequestrant to minimize the potential impact on their absorption. No recommendations are available for sevelamer, but it may be advisable to follow the same precautions.