Diarrhea Problems – Case Study

A 76-year-old male has a past medical history of hypertension, diarrhea, mild cognitive impairment, diabetes, osteoarthritis, and gout. He has had a concern that has been ongoing for about 3 months with the symptoms recently escalating over the last 1-2 weeks. “Diarrhea problems” is what the patient is reporting. His primary provider recently did a “bunch of tests” and didn’t come up with any idea what is going on. He was prescribed cholestyramine daily to help with the symptoms and has just started taking this medication.

He reports to you his other medications which include:

Losartan (podcast) 25 mg daily
Hydrochlorothiazide (podcast) 12.5 mg daily
Donepezil 10 mg at bedtime
Ibuprofen 200-400 mg PRN for osteoarthritis
Allopurinol 200 mg daily
Colchicine 0.6 mg PRN gout flares
Vitamin E 400 units daily
Tums PRN for an upset stomach
Metformin 500 mg BID
Sitagliptin 25 mg daily

Cholestyramine is a medication that is indicated for hypercholesterolemia but in all actuality is rarely used for this indication. I more frequently see this medication used for diarrhea that the attending provider cannot attribute to any other condition (i.e. infection, adverse effect, etc.). Whenever I see this medication utilized, I’m sure to take a deep dive into the current medication list to ensure that medication isn’t the culprit of diarrhea problems.

Based on the side effect profile of these medications, we have numerous medications that may be contributing to diarrhea. The medication with the highest incidence of diarrhea from my perspective is likely colchicine. I would want to ask this patient if he has had any recent gout flares and/or if he has been taking this medication. NSAIDs or corticosteroids would be alternatives for gout flares if this is the cause (great board exam question!).

I would classify metformin as a relatively common cause of drug-induced diarrhea. This would be my 1B choice as the potential cause of diarrhea problems. Worsening renal function, increasing dosages, and being newly started would be a few things that would make me think metformin could be the culprit of the problems.

The last medication that would most likely cause diarrhea would be donepezil. Recall that the way donepezil works is the opposite of anticholinergic drugs. Anticholinergics can cause constipation and worsen memory whereas acetylcholinesterase inhibitors like donepezil can potentially help with cognitive impairment but may contribute to diarrhea.

Whenever you see an order for cholestyramine for diarrhea, be sure you take the time and go through the medication list. You don’t want to miss an opportunity to help a patient and stop the prescribing cascade.

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