Constipation triggered the malignant syndrome in Parkinson's disease.

A 69-year-old, chronically constipated patient with Parkinson's disease developed fecal impaction and the malignant syndrome simultaneously, even while the patient was taking anti-parkinsonian drugs as prescribed. Administration of intravenous levodopa and oral Dai-kenchu-tou, an herbal medicine with serotonergic 5-HT3 receptor agonistic property successfully ameliorated his clinical symptoms. Constipation may trigger worsening of Parkinson's disease and occurrence of the malignant syndrome by affecting levodopa absorption. Further, improved bowel motility may prevent worsening of Parkinson's disease and occurrence of the malignant syndrome.