ABSTRACT
Cyclosporine is a potent immunosuppressive drug with a well-established effect on organ transplantation. Because cyclosporine A (CsA) is subject to extensive hepatic metabolism, the possibility of pharmacokinetic drug interactions can be anticipated if drugs which enhance or inhibit its metabolism are co-administered. In addition, there is the possibility of pharmacodynamic interaction if other drugs given with CsA are nephrotoxic, since they may enhance the toxicity of CsA. CsA is a potent immunosuppressive drug that is metabolized extensively in the liver by the cytochrome P-450 enzyme system. Drugs that may enhance or inhibit this system could interact with CsA when they are co-administered. Some drugs act to enhance (as rifampin) or inhibit (as diltiazem) microsomal enzyme activity, modifying CsA clearance. In some other cases (phenytoin) there is a reduction of the CsA intestinal absorption. Some drugs (erythromycin) could perhaps interact by a double mechanism, inhibiting microsomal activity and increasing intestinal CsA absorption (6).
