Report from the NASPGN Therapeutics Subcommittee. Cisapride and the attack of the P-450s

Usage of the claim database of national health insurance programme for analysis of cisapride-erythromycin co-medication in Taiwan

PURPOSE

This study aimed to use the National Health Insurance Research Database, Taiwan for risk analysis of concomitant use of cisapride and erythromycin.

METHODS

The sample consisted of subjects identified in the Outpatient Sampling Database (OSD) and Longitudinal Health Insurance Database 2000 (LHID 2000), derived from the original claim data of the National Health Insurance Research Database, Taiwan.

RESULTS

According to the LHID 2000, a total of 464 individuals experienced 685 episodes of cisapride-erythromycin co-medication prescribed by 295 physicians, revealing a prevalence of 4.5% concomitant use, with higher prevalence in clinics (9.2%) than in other medical institutes (3.7-5.4%). Among the co-medication episodes, 81.9% and 61.2% were prescribed from the same health institutes and by the same physicians, respectively. No medical record of cardiac arrhythmias was found among these patients in 2001 and 2002, probably due to the fact that 78.9% of the 464 individuals were under age 16, 84.0% had short exposure duration (1-4 days) and 98.0% of the episodes were prescribed with a cisapride dose of less than 0.8 mg/kg/day.

CONCLUSIONS

Findings from this study suggest that there exists an urgent need for accreditation in terms of pharmacovigilance of clinical sites and their practicing physicians for the prevention of irrational concomitant prescription in Taiwan. Our findings also indicate that it is necessary to investigate other possible conditions of potentially dangerous co-medication in Taiwan and other developing countries.

Identification of the cytochrome P450 enzymes involved in the metabolism of cisapride: in vitro studies of potential co-medication interactions

Cisapride is a prokinetic drug that is widely used to facilitate gastrointestinal tract motility. Structurally, cisapride is a substituted piperidinyl benzamide that interacts with 5-hydroxytryptamine-4 receptors and which is largely without central depressant or antidopaminergic side-effects. The aims of this study were to investigate the metabolism of cisapride in human liver microsomes and to determine which cytochrome P-450 (CYP) isoenzyme(s) are involved in cisapride biotransformation. Additionally, the effects of various drugs on the metabolism of cisapride were investigated. The major in vitro metabolite of cisapride was formed by oxidative N-dealkylation at the piperidine nitrogen, leading to the production of norcisapride. By using competitive inhibition data, correlation studies and heterologous expression systems, it was demonstrated that CYP3A4 was the major CYP involved. CYP2A6 also contributed to the metabolism of cisapride, albeit to a much lesser extent. The mean apparent K(m) against cisapride was 8.6+/-3.5 microM (n = 3). The peak plasma levels of cisapride under normal clinical practice are approximately 0.17 microM; therefore it is unlikely that cisapride would inhibit the metabolism of co-administered drugs. In this in vitro study the inhibitory effects of 44 drugs were tested for any effect on cisapride biotransformation. In conclusion, 34 of the drugs are unlikely to have a clinically relevant interaction; however, the antidepressant nefazodone, the macrolide antibiotic troleandomycin, the HIV-1 protease inhibitors ritonavir and indinavir and the calcium channel blocker mibefradil inhibited the metabolism of cisapride and these interactions are likely to be of clinical relevance. Furthermore, the antimycotics ketoconazole, miconazole, hydroxy-itraconazole, itraconazole and fluconazole, when administered orally or intravenously, would inhibit cisapride metabolism.

Upper gastrointestinal tract bleeding in critically ill pediatric patients

Similar to adults, children under physiologic stress can develop an imbalance in defensive (mucosal layer, motility) and aggressive (gastric acid, bile salts, enzymes) factors responsible for maintaining a healthy gastrointestinal tract. Hypoxia in the gastrointestinal tract likely disrupts the defensive factors, thereby permitting damage by aggressive factors to upper gastrointestinal epithelium that may progress to stress ulceration and acute upper gastrointestinal tract bleeding (UGIB). The basic pathophysiology may be similar in children and adults; however, differences in the time to developing ulceration, ulcer location, and number of ulcers have been reported. Functional development of the gastrointestinal tract is influenced by disease, gestational and postnatal age, and exposure to and type of enteral feedings, thereby confounding the development and prophylaxis of UGIB in neonates and infants. In addition, pharmacotherapy decisions are often complicated by drug administration issues and adverse effects.

QT interval in children and infants receiving cisapride

OBJECTIVES

Life-threatening arrhythmias and prolonged QT interval have been reported in adults and children using cisapride, a medication structurally similar to procainamide. Premature infants have reduced activity of cytochrome p-450, the system responsible for metabolism of cisapride, which could lead to QT prolongation. Therefore, we prospectively studied premature infants and children receiving cisapride to analyze the effect of prolonged cisapride therapy on QT interval.

DESIGN

Premature infants in a neonatal intensive care unit and children seen at a pediatric gastroenterology clinic in a tertiary care hospital had electrocardiography-analyzed and -corrected QT interval measured before cisapride (0.8/mg/kg per day) therapy, and again after 1 month of therapy. If baseline electrocardiography was not performed initially, it was obtained after cessation of therapy.

RESULTS

A total of 30 children participated in the study. Mean corrected QT interval was similar at baseline and at 1 month after therapy. Significant QT prolongation was not found, and no adverse effects were recorded.

CONCLUSIONS

Corrected QT interval during prolonged cisapride therapy at 0.8 mg/kg per day appears to be similar for premature infants and children. An inherent trend toward QT prolongation was not detected in either group. In the absence of other risk factors that alter cisapride metabolism or predispose to arrhythmia, cisapride may be safe for use in premature infants as well as in children. Additional studies are needed to confirm these data.