The assay allows precise quantification of IMPDH activity, hypoxanthine, guanine, and adenine in lymphocytes. Some individuals may possess a counteracting purine response to the MPA-mediated inhibition of IMPDH. Reduction of the guanine/hypoxanthine ratio may be related to prolonged inhibition of IMPDH and seems as an intriguing pharmacodynamic biomarker for MPA.

Total and free MPA are equally good predictors of the immunosuppressive effect exerted by MPA as defined by IMPDH activity. IMPDH activity measurements represent a promising approach to TDM in patients treated with MPA.

Infusion of albumin during surgery resulted in maintained albumin values and almost maintained binding parameters for the study drugs, although some statistically significant changes were found. The use of starch solutions, however, led to in a reduction in albumin values and a significant reduction in binding parameters.

A transfusion of albumin results in an increase in the free fraction of naproxen. The transient increase in free-fraction naproxen decreased together with the detectable levels of the stabilizers N-acetyl-DL-tryptophan and caprylate. N-acetyl-DL-tryptophan and caprylate have a short half-life in serum.