Warnings for cisapride
Cisapride will be withdrawn from the American market in July. The drug is being withdrawn because of concern about serious adverse effects. By the start of 2000, the Food and Drug Administration had reports of 341 cases of arrhythmia and 80 deaths. Many of these adverse reactions were the result of cisapride interacting with other drugs.
The metabolism of cisapride mainly involves cytochrome P450 3A4. If this metabolism is inhibited by other drugs (see box), plasma concentrations of cisapride increase. This prolongs the QT interval on the ECG and can provoke arrhythmias. These arrhythmias include torsades de pointes and ventricular fibrillation.
Cisapride is contraindicated in patients who already have a prolonged QT interval. This abnormality can be congenital, but may be present in patients with:
- heart disease
- diabetes mellitus
- electrolyte abnormalities.
In the USA, cisapride was approved for the treatment of night-time heartburn due to gastro-oesophageal reflux disease. In Australia, the approved indication for reflux oesophagitis limits treatment with cisapride to six months or less.
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Cisapride is contraindicated in combination with:
- macrolide antibiotics (e.g. erythromycin, clarithromycin)
- azole antifungals (e.g. fluconazole, itraconazole, ketaconazole, miconazole)
- HIV protease inhibitors (e.g. indinavir, ritonavir)
- nefazodone
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