| Pharmacotherapeutic group: Drugs acting on serotonin receptors, ATC code: A03AE04. Mechanism of action Prucalopride is a dihydrobenzofurancarboxamide with gastrointestinal prokinetic activities. Prucalopride is a selective, high affinity serotonin (5-HT4) receptor agonist, which is likely to explain its prokinetic effects. In vitro, only at concentrations exceeding its 5-HT4 receptor affinity by at least 150-fold, affinity for other receptors was detected. In rats prucalopride in vivo at doses above 5 mg/kg (at and above 30-70 times the clinical exposure) induced hyperprolactinaemia caused by an antagonistic action at the D2 receptor. In dogs, prucalopride alters colonic motility patterns via serotonin 5-HT4 receptor stimulation: it stimulates proximal colonic motility, enhances gastroduodenal motility and accelerates delayed gastric emptying. Furthermore, giant migrating contractions are induced by prucalopride. These are equivalent to the colonic mass movements in humans, and provide the main propulsive force to defecation. In dogs, the effects observed in the gastrointestinal tract are sensitive to blockade with selective 5-HT4 receptor antagonists illustrating that the observed effects are exerted via selective action on 5-HT4 receptors. Clinical experience The efficacy of prucalopride was established in three multicentre, randomised, double-blind, 12-week placebo-controlled studies in subjects with chronic constipation (n=1,279 on prucalopride, 1,124 females, 155 males). The prucalopride doses studied in each of these three studies included 2 mg and 4 mg once daily. The primary efficacy endpoint was the proportion (%) of subjects that reached normalisation of bowel movements defined as an average of three or more spontaneous, complete bowel movements (SCBM) per week over the 12-week treatment period. For the population targeted in this label, the results are the following: The proportion of female patients in whom laxatives fail to provide adequate relief (target population) treated with the recommended dose of 2 mg prucalopride (n=458) that reached an average of 3 SCBM per week was 31.0% (week 4) and 24.7% (week 12), versus 8.6% (week 4) and 9.2% (week 12) on placebo. A clinically meaningful improvement of 1 SCBM per week, the most important secondary efficacy endpoint, was achieved in 51.0% (week 4) and 44.2% (week 12) treated with 2 mg prucalopride versus 21.7% (week 4) and 22.6% (week 12) of placebo patients. Also for the target population prucalopride proved significantly superior (p<0.001) to placebo at the primary endpoint. In all three studies, treatment with prucalopride also resulted in significant improvements in a validated and disease specific set of symptom measures (PAC SYM), including abdominal, stool and rectal symptoms, determined at week 4 and week 12. A significant benefit on a number of Quality of Life measures, such as degree of satisfaction with treatment and with bowel habits, physical and psychosocial discomfort and worries and concerns, was also observed at both the 4 and 12 week assessment time points. Prucalopride has been shown not to cause rebound phenomena, nor to induce dependency.A thorough QT study was performed to evaluate the effects of prucalopride on the QT interval at therapeutic (2 mg) and supratherapeutic doses (10 mg) and compared with the effects of placebo and a positive control. This study did not show significant differences between prucalopride and placebo at either dose, based on mean QT measurements and outlier analysis. This confirmed the results of two placebo controlled QT studies. In double blind clinical studies, the incidence of QT-related adverse events and ventricular arrhythmias was low and comparable to placebo.Data from open label studies up to 2.6 years offer some evidence for longer-term safety and efficacy; however, no placebo controlled efficacy data for treatments longer than 12 weeks duration are available. | |