Interaction of chloramphenicol and the calcineurin inhibitors in renal transplant recipients.

Several case reports have described a pharmacokinetic interaction between chloramphenicol and the calcineurin inhibitors (CNIs). Based on these reports, we set out to characterize the effects of chloramphenicol on cyclosporine and tacrolimus trough concentrations in renal transplant recipients. We retrospectively evaluated daily trough CNI concentrations and compared them with baseline CNI concentrations prior to chloramphenicol. Six adult renal or pancreas/kidney transplant recipients received 11 courses of chloramphenicol. Of these, three received cyclosporine (6 episodes) and three received tacrolimus (5 episodes). The mean dose and duration of chloramphenicol was not significantly different between groups. Chloramphenicol coadministration increased mean cyclosporine troughs maximally by 41.3% on day 4, though overall differences were not significant using analysis of variance (anova). Tacrolimus trough levels increased to 99% above baseline on day 2, 151% on day 3, 161% on day 4, 191% on day 5, and to 207% on day 6 and reached statistical significance by anova (P = 0.001). These results confirm case reports and suggest that careful trough monitoring should be implemented if chloramphenicol is to be used with the CNIs.