PHENYLKETONURICS: QUESTRAN LIGHT CONTAINS 28.1 mg PHENYLALANINE PER 6.4 GRAM DOSE.
Chronic use of QUESTRAN may be associated with increased bleeding tendency due to hypoprothrombinemia associated with Vitamin K deficiency. This will usually respond promptly to parenteral Vitamin K1 and recurrences can be prevented by oral administration of Vitamin K1. Reduction of serum or red cell folate has been reported over long term administration of QUESTRAN. Supplementation with folic acid should be considered in these cases.
There is a possibility that prolonged use of QUESTRAN, since it is a chloride form of anion exchange resin, may produce hyperchloremic acidosis. This would especially be true in younger and smaller patients where the relative dosage may be higher. Caution should also be exercised in patients with renal insufficiency or volume depletion, and in patients receiving concomitant spironolactone.
QUESTRAN may produce or worsen pre-existing constipation. The dosage should be increased gradually in patients to minimize the risk of developing fecal impaction. In patients with pre-existing constipation, the starting dose should be 1 packet or 1 scoop once daily for 5–7 days, increasing to twice daily with monitoring of constipation and of serum lipoproteins, at least twice, 4–6 weeks apart. Increased fluid intake and fiber intake should be encouraged to alleviate constipation and a stool softener may occasionally be indicated. If the initial dose is well tolerated, the dose may be increased as needed by one dose/day (at monthly intervals) with periodic monitoring of serum lipoproteins. If constipation worsens or the desired therapeutic response is not achieved at one to six doses/day, combination therapy or alternate therapy should be considered. Particular effort should be made to avoid constipation in patients with symptomatic coronary artery disease. Constipation associated with QUESTRAN may aggravate hemorrhoids.
Information for Patients
Inform your physician if you are pregnant or plan to become pregnant or are breastfeeding. Drink plenty of fluids and mix each 9-gram dose of QUESTRAN POWDER in at least 2 to 6 ounces of fluid. Mix each 6.4 gram dose of QUESTRAN LIGHT in at least 4 to 6 ounces of fluid before taking. Sipping or holding the resin suspension in the mouth for prolonged periods may lead to changes in the surface of the teeth resulting in discoloration, erosion of enamel or decay; good oral hygiene should be maintained.
Serum cholesterol levels should be determined frequently during the first few months of therapy and periodically thereafter. Serum triglyceride levels should be measured periodically to detect whether significant changes have occurred.
The LRC-CPPT showed a dose-related increase in serum triglycerides of 10.7%–17.1% in the cholestyramine-treated group, compared with an increase of 7.9%–11.7% in the placebo group. Based on the mean values and adjusting for the placebo group, the cholestyramine-treated group showed an increase of 5% over pre-entry levels the first year of the study and an increase of 4.3% the seventh year.
QUESTRAN (Cholestyramine for Oral Suspension, USP) may delay or reduce the absorption of concomitant oral medication such as phenylbutazone, warfarin, thiazide diuretics (acidic), or propranolol (basic), as well as tetracycline, penicillin G, phenobarbital, thyroid and thyroxine preparations, estrogens and progestins, and digitalis. Interference with the absorption of oral phosphate supplements has been observed with another positively-charged bile acid sequestrant. QUESTRAN may interfere with the pharmacokinetics of drugs that undergo enterohepatic circulation. The discontinuance of QUESTRAN could pose a hazard to health if a potentially toxic drug such as digitalis has been titrated to a maintenance level while the patient was taking QUESTRAN.
Because cholestyramine binds bile acids, QUESTRAN may interfere with normal fat digestion and absorption and thus may prevent absorption of fat-soluble vitamins such as A, D, E and K. When QUESTRAN is given for long periods of time, concomitant supplementation with water-miscible (or parenteral) forms of fat-soluble vitamins should be considered.
SINCE QUESTRAN MAY BIND OTHER DRUGS GIVEN CONCURRENTLY, IT IS RECOMMENDED THAT PATIENTS TAKE OTHER DRUGS AT LEAST ONE HOUR BEFORE OR 4 TO 6 HOURS AFTER QUESTRAN (OR AT AS GREAT AN INTERVAL AS POSSIBLE) TO AVOID IMPEDING THEIR ABSORPTION.
Carcinogenesis, Mutagenesis, Impairment of Fertility
In studies conducted in rats in which cholestyramine resin was used as a tool to investigate the role of various intestinal factors, such as fat, bile salts and microbial flora, in the development of intestinal tumors induced by potent carcinogens, the incidence of such tumors was observed to be greater in cholestyramine resin-treated rats than in control rats.
The relevance of this laboratory observation from studies in rats to the clinical use of QUESTRAN is not known. In the LRC-CPPT study referred to above, the total incidence of fatal and nonfatal neoplasms was similar in both treatment groups. When the many different categories of tumors are examined, various alimentary system cancers were somewhat more prevalent in the cholestyramine group. The small numbers and the multiple categories prevent conclusions from being drawn. However, in view of the fact that cholestyramine resin is confined to the GI tract and not absorbed, and in light of the animal experiments referred to above, a six-year post-trial follow-up of the LRC-CPPT5 patient population has been completed (a total of 13.4 years of in-trial plus post-trial follow-up) and revealed no significant difference in the incidence of cause-specific mortality or cancer morbidity between cholestyramine and placebo treated patients.
Pregnancy Category C
There are no adequate and well controlled studies in pregnant women. The use of QUESTRAN in pregnancy or lactation or by women of childbearing age requires that the potential benefits of drug therapy be weighed against the possible hazards to the mother and child. QUESTRAN is not absorbed systemically, however, it is known to interfere with absorption of fat-soluble vitamins; accordingly, regular prenatal supplementation may not be adequate (see PRECAUTIONS: Drug Interactions).
Caution should be exercised when QUESTRAN is administered to a nursing mother. The possible lack of proper vitamin absorption described in the “Pregnancy” section may have an effect on nursing infants.
Although an optimal dosage schedule has not been established, standard texts (6,7) list a usual pediatric dose of 240 mg/kg/day of anhydrous cholestyramine resin in two to three divided doses, normally not to exceed 8 gm/day with dose titration based on response and tolerance.
In calculating pediatric dosages, 44.4 mg of anhydrous cholestyramine resin are contained in 100 mg of QUESTRAN POWDER and 62.7 mg of anhydrous cholestyramine resin are contained in 100 mg of QUESTRAN LIGHT.
The effects of long-term administration, as well as its effect in maintaining lowered cholesterol levels in pediatric patients, are unknown. (Also see ADVERSE REACTIONS.)