Comparing renal transplant patients' adherence to free cyclosporine and free tacrolimus immunosuppressant therapy

Background: The purpose of this study is to determine if there is a difference in renal transplant patients' (RTPs) adherence to cyclosporine compared to tacrolimus when medications are supplied free to the RTPs. Methods: Adult primary RTPs were included in the study if they received a renal transplant at the Medical College of Georgia (MCG) from June 1998 through August 2001 and received their first post-transplant year of follow-up care at MCG and free cyclosporine or free tacrolimus from the MCG outpatient pharmacy. Adherence was estimated by comparing each RTPs' tacrolimus or cyclosporine pharmacy refill records to the prescribed regimen for 12 months after transplant. Patients' cyclosporine and tacrolimus serum concentrations were used to validate adherence. Kaplan-Meier analysis was used to estimate the fraction of RTPs remaining adherent and to compare the mean time RTPs were adherent in each group (cyclosporine vs. tacrolimus). Results: Thirty-three RTPs were included in the study, 25 (76%) received cyclosporine and eight received tacrolimus. The mean time to the first non-adherent month was 8 months post-transplant. At 12-months post-transplant, approximately 42% of the patients remained adherent. A greater percentage of the patients who received tacrolimus remained adherent compared with those who were taking cyclosporine (63% vs. 33%, p < 0.05). Approximately 75% of non-adherent patients were found to have subtarget drug concentrations, and only 24% of adherent patients had subtarget levels (p < 0.01). Conclusions: When provided free, patients are more adherent to tacrolimus than cyclosporine. Regardless of treatment, intensive efforts to increase adherence should be implemented.