The use of clarithromycin in kidney transplant patients is avoided as its relatively contraindicated in view of its interaction with cyclosporine.Cytochrome P450 3A4 also known as CYP3A4 is an enzyme that metabolizes various drugs and foreign entities including toxins in the body. Cytochrome P450 enzymes system comprise of many enzymes but the two most important ones, in relation to drug-drug interactions, are CYP3A4 and CYP2D6.

                                                                                

This helps in their overall excretion. Clarithromycin can cause several drug interactions because it is an inhibitor of the cytochrome P450 (CYP) 3A4 enzyme system. This clarithromycin cyclosporine interaction results in much higher levels of cyclosporine than required in kidney transplant patients.