Drug Interactions
                        =================

þ Terfenadine (Seldane) and Ketoconazole/Erythromycin etc.
 - terfenadine is almost 100% metabolized in first pass through liver to an
   active metabolite.
 - ketoconazole, erythromycin, and other inhibitors of Cytochrome P450 (CYP)
   3A4 enzyme in the liver allow large levels of unmetabolized terfenadine which
   cause the problem.

þ Cisapride (Propulsid)
 - prolongs QT similar to Procainamide, Quinidine, Seldane, Hismanal;
 - and similar to those drugs, ketoconazole or erythromycin may prolong the QT
   to the point of causing Toursades de Pointes.

þ Bactrim and Coumadin
 - Bactrim tends to prolong PT in those on Coumadin
   [Mercy Pharmacy and Therapeutics Update, Jan/Feb 1998]