Several drug classes reviewed, found unlikely to trigger microscopic colitis
Microscopic colitis rates were not elevated in patients taking NSAIDs, proton-pump inhibitors, statins, angiotensin-converting enzyme inhibitors, or angiotensin-receptor blockers.
A study found no evidence of a causal relationship between most previously suspected pharmacologic triggers and risk for microscopic colitis.
Swedish researchers conducted an emulation of six target trials among all the country's residents who were ages 65 years or older between 2006 and 2017 and met eligibility criteria. The primary outcome was biopsy-verified microscopic colitis, and they looked for associations with six drug classes: NSAIDs, proton-pump inhibitors (PPIs), statins, angiotensin-converting enzyme (ACE) inhibitors, angiotensin-receptor blockers (ARBs), and selective serotonin reuptake inhibitors (SSRIs).
For the target trials of NSAIDs, statins, and PPIs, the researchers compared initiation of the study medication at baseline versus no initiation of the medication at baseline or throughout the follow-up. For the target trials of ACE inhibitors and ARBs, they compared initiation of a calcium-channel blocker (CCB). For the target trial of SSRIs, they compared initiation of an SSRI at baseline versus initiation of mirtazapine at baseline. Results were published July 22 in Annals of Internal Medicine.
The 12- and 24-month cumulative incidences of microscopic colitis were less than 0.5% with all the studied drugs. Estimated 12-month risk differences were close to null with ACE versus CCB initiation, ARB versus CCB initiation, NSAID initiation versus noninitiation, PPI initiation versus noninitiation, and statin initiation versus noninitiation. One small risk difference was 0.04% (95% CI, 0.03% to 0.05%) for SSRIs versus mirtazapine over 12 months. Several medications were also associated with increased likelihood of a colonoscopy with a normal colorectal mucosa biopsy result.
Previously reported associations may be due to surveillance bias from cross-sectional or case-controlled trials, researchers noted.
“Although SSRIs were associated with a modest increase in risk for MC [microscopic colitis], initiation of most of these medications … was not associated with increased risk for MC,” the authors wrote. The increased likelihood of a colonoscopy with normal results with several of the drugs might help explain the association of SSRIs with microscopic colitis as unmeasured confounding, with medication initiation being a proxy for increased contact with the health care system, they explained.