A six-hour extrapolated sampling strategy for monitoring mycophenolic acid in renal transplant patients in the Indian subcontinent.

BACKGROUND Therapeutic drug monitoring for mycophenolic acid (MPA) is increasingly being advocated. The present therapeutic range relates to the 12-hour area under the serum concentration time profile (AUC).However, this is a cumbersome, tedious, cost restricting procedure. Is it possible to reduce this sampling period? AIM To compare the AUC from a reduced sampling strategy with the full 12-hour profile for MPA. SETTINGS AND DESIGN Clinical Pharmacology Unit of a tertiary care hospital in South India. Retrospective, paired data. MATERIALS AND METHODS Thirty-four 12-hour profiles from post-renal transplant patients on Cellcept were evaluated. Profiles were grouped according to steroid and immunosuppressant co-medication and the time after transplant. MPA was estimated by high performance liquid chromatography with UV detection. From the 12-hour profiles the AUC up to only six hours was calculated by the trapezoidal rule and a correction factor applied. These two AUCs were then compared. STATISTICAL ANALYSIS Linear regression, intra-class correlations (ICC) and a two-tailed paired t-test were applied to the data. RESULTS Comparing the 12-hour AUC with the paired 6-hour extrapolated AUC, the ICC and linear regression(r2) were very good for all three groups. No statistical difference was found by a two-tailed paired t-test. No bias was seen with a Bland Altman plot or by calculation. CONCLUSION For patients on Cellcept with prednisolone +/- cyclosporine the 6-hour corrected is an accurate measure of the full 12-hour AUC.