Pharmacist-Led Follow-Up After Off-Label Cholestyramine Use for Suspected Bile Acid Diarrhea in a Patient With a Prior Cholecystectomy: A Case Report.

Bile acid diarrhea (BAD) is a condition in which excessive bile acids reach the colon, promoting water and electrolyte secretion and potentially causing diarrhea, and is known as one possible mechanism of post-cholecystectomy diarrhea. This case involved a 59-year-old man who had undergone cholecystectomy approximately 18 years earlier and had persistent loose stools and increased stool frequency. BAD was suspected by the treating physician, although it was not definitively confirmed by specific diagnostic testing. The patient was prescribed Questran powder 44.4% at 18 g/day. However, in Japan, the approved indications for Questran powder 44.4% include hypercholesterolemia, and its use for suspected BAD is off-label. The pharmacist was not involved in the diagnosis or treatment selection but reviewed domestic and overseas drug information as support for appropriate use after off-label prescribing. Based on the United Kingdom Summary of Product Characteristics, the pharmacist explained the administration method, the need to separate from concomitant medications, and the need for early follow-up. Before treatment, the patient-reported Bristol Stool Form Scale (BSFS) score was 5-6, and stool frequency was five to six times per day. On day 5, after treatment initiation, pharmacist follow-up showed improvement to a BSFS score of 4-5 and stool frequency of approximately two to three times per day. However, the patient reported difficulty taking the suspension because of its texture. Although the prescription instructed Questran powder 44.4% 18 g/day in two divided doses, the patient maintained the prescribed total daily amount of 18 g/day but took it in three divided administrations. The pharmacist provided the treating physician with information on symptom changes, administration difficulties, and discrepancies between the prescribed regimen and actual medication use via a tracing report. This single uncontrolled observation cannot establish the efficacy of cholestyramine or confirm BAD. Rather, this case illustrates the potential value of pharmacist-led follow-up after off-label prescribing, including early monitoring, identification of medication-use problems, and communication with the treating physician.