Accutane constipation can occur during treatment because isotretinoin may reduce moisture in mucosal tissues, including those of the digestive tract. This can slow stool movement, make bowel movements harder to pass, and lead to symptoms such as bloating, straining, or rectal irritation.
In a prospective study of 210 patients, 17.1% reported constipation, while smaller numbers reported anal bleeding or fissures, which shows that bowel changes are a recognized side effect in some patients.