Carbamazepine-induced constipation

We report three patients who developed constipation as an adverse effect of carbamazepine (CBZ) therapy. Constipation occurred within a few days of CBZ introduction, resolved after CBZ discontinuation, and was not dose-responsive. It was refractory to the concomitant use of oral laxatives in two cases, necessitating CBZ discontinuation. In a third patient, constipation was controlled by a fiber agent, allowing continuation of CBZ therapy. Potential mechanisms for this idiosyncratic, poorly reported adverse event are discussed.