Levodopa/dopa decarboxylase inhibitor associated microscopic colitis: An under-recognized drug reaction

Microscopic colitis is a form of inflammatory bowel disease characterized by profuse non-bloody watery diarrhea. Macroscopic abnormality is not present on colonoscopy, and it requires biopsy for diagnosis. Few cases have been attributed to levodopa/dopa-decarboxylase inhibitor therapy. A retrospective cohort study of 21 patients on levodopa/benserazide and one patient on levodopa-carbidopa intestinal gel with clinically suspected or biopsy proven microscopic colitis. All 21 patients on oral levodopa/benserazide had resolution of diarrhea with cessation of the medication. Four patients discontinued levodopa permanently. Two were rechallenged with levodopa/benserazide without symptom recurrence. One patient on oral levodopa/carbidopa developed diarrhea only with intermittent dispersible levodopa/benserazide. 14 were switched to levodopa/carbidopa with resolution of diarrhea in 9 but symptom recurrence in 5. One patient on oral levodopa/benserazide developed profuse diarrhea when switched to levodopa-carbidopa intestinal gel. Of 7/22 patients who had colonoscopy and biopsy, 5 had histopathological proven microscopic colitis. levodopa/dopa-decarboxylase inhibitor induced microscopic colitis may be more common than previously suspected, with the potential to affect treatment compliance and therapeutic options. •Microscopic colitis should be suspected in any PD patient with unexplained acute, subacute, or chronic, non-bloody or watery diarrhea on levodopa/dopa decarboxylase therapy.•Following the exclusion of other etiologies and if clinically significant, a trial of substitution with an alternative levodopa/dopa decarboxylase therapy should be considered as the initial treatment strategy, being mindful of the potential impact on parkinsonian symptoms. A carefully supervised trial of withdrawal may be required as a last resort.•If diarrhea persists, colonoscopy and random colonic biopsy should be performed even if the endoscopic appearance is normal.