HTR4 and Chronic constipation: In Europe, the Summary of Product Characteristics (SmPC) for prucalopride states: “prucalopride (a selective, high affinity 5-hydroxytryptamine receptor 4 [5-HT4] agonist) is indicated for symptomatic treatment of chronic constipation in women in whom laxatives fail to provide adequate relief” (SmPC Prucalopride).