Suspected Pharmacologic Triggers Do Not Appear to Cause Microscopic Colitis

MONDAY, July 7, 2025 (HealthDay News) — There does not appear to be a causal relationship between most previously suspected pharmacologic triggers and the risk for microscopic colitis (MC), according to a study published online July 1 in the Annals of Internal Medicine.

Hamed Khalili, M.D., M.P.H., from Massachusetts General Hospital in Boston, and colleagues examined the potential causal effects of previously implicated medications on the risk for MC in an emulation of six target trials involving residents in Sweden aged 65 years or older between 2006 and 2017. Inverse probability weighting was used to estimate 12- and 24-month cumulative incidences and absolute risk differences for MC.

The researchers found that under all treatment strategies, the 12- and 24-month cumulative incidences of MC were less than 0.5 percent. For angiotensin-converting enzyme versus calcium-channel blocker (CCB) initiation, angiotensin-receptor blocker versus CCB initiation, nonsteroidal anti-inflammatory drug initiation versus noninitiation, proton pump inhibitor initiation versus noninitiation, and statin initiation versus noninitiation, the estimated 12-month risk differences were close to null. For selective serotonin receptor inhibitors versus mirtazapine, the estimated 12-month risk difference was 0.04 percent. For 24-month differences, the results were similar. An increased risk for receiving a colonoscopy with a normal colorectal mucosa biopsy result was seen in association with several medications.

“Our study demonstrated that, contrary to the previous belief, it”s unlikely that medications are the primary triggers for microscopic colitis,” Khalili said in a statement. “Clinicians should carefully balance the intended benefits of these medications against the very low likelihood that they cause microscopic colitis.”

Abstract/Full Text (subscription or payment may be required)