Irritable Bowel Syndrome and Mirtazapine

Ms. A was a 35-year-old divorced woman with a history of recurrent depression, panic disorder, and posttraumatic stress disorder (PTSD) who was referred for what her gastroenterologist had diagnosed as irritable bowel syndrome. She reported a 7-month history of severe abdominal cramping, bloating, and constipation. These symptoms were accompanied by a 20-lb weight loss. The results of an extensive medical evaluation were negative. Her gastroenterologist had treated her with diazepam, 5 mg t.i.d., and cisapride, 10 mg q.i.d., with minimal improvement. The symptoms of irritable bowel syndrome had been present episodically throughout her life but had been virtually unremitting for the past 7 months. In the 6 months before her referral, Ms. A had a total of 10 visits with her primary care physician or a specialist. She also had missed at least 15 days from work and had planned most of her days around access to a restroom.

When Ms. A was seen by a psychiatrist, her diagnosis of irritable bowel syndrome was confirmed by the use of ICD-9 criteria. Ms. A also met the criteria for major depression, panic disorder, and PTSD. She began treatment with mirtazapine, 7.5 mg q.i.d., which was increased in 7.5-mg increments every 2 weeks up to a daily dose of 30 mg. At 12 weeks she was significantly improved. Ms. A stated that her bowel movements were normal, and she had a marked decrease in all gastrointestinal symptoms. In addition, she had gained 20 lb, thereby attaining her target weight of 120 lb. She had missed no days from work in 2 months and had not seen a physician other than myself in that period. She reported that this was the first medication that had helped her.