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Possible Interaction between Propulsid® (Cisapride) and Flagyl® (Metronidazole)
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From the National Community Pharmacists Association:
"First linked to drug metabolism in the 1970s, the cytochrome P450 enzymes have become one of
the hottest topics in the world of pharmacy. The term "cytochrome P450" refers to a group of
enzymes that are responsible for, among other things, the metabolism of many of the drugs in use
today. As knowledge about these enzymes grew, their involvement in drug interactions attracted
significant attention. This was highlighted by the interaction of terfenadine (Seldane) with
erythromycin and ketoconazole (Nizoral) that resulted in potentially fatal cardiac arrhythmias.
Since then, several new examples of drug interactions involving cytochrome P450 enzymes have
received attention. For example, the withdrawal of mibefradil (Posicor) from the U.S. market
was, in part, due to its potential to inhibit some of the cytochrome P450 enzymes. Another
example is the recently strengthened warnings in the labeling of cisapride (Propulsid), which
stemmed from the potential of that agent to cause potentially fatal cardiac arrhythmias when
combined with certain cytochrome P450 enzyme inhibitors" like Metronidazole (Flagyl) see Table 3.
From the American Academy of Family Physiscians:
"Cisapride. Serious ventricular arrhythmias have been reported in patients taking cisapride (Propulsid)
and drugs that inhibit CYP3A, the isoform responsible for metabolism of cisapride. Ketoconazole,
fluconazole, itraconazole, metronidazole, erythromycin and clarithromycin have been associated with
cisapride-induced torsade de pointes. Concurrent use of cisapride with fluoxetine, sertraline,
fluvoxamine and nefazodone might be problematic because of CYP3A inhibition."
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