The effect of short-term dipyrone administration on cyclosporin pharmacokinetics

Background: A large number of drugs have been shown to affect the metabolis m of cyclosporin A (CSA) and, since cyclosporin is characterized by a narro w therapeutic range, the consequences of such drug interactions may often b e of clinical importance. Objective: To evaluate the effect of short-term a dministration of dipyrone on steady state CSA pharmacokinetics. Methods: Six kidney- and two heart-transplanted patients on chronic CSA the rapy participated in this study, which consisted of two 4-day study periods separated by 3-week washout periods. The patients received, in addition to their usual drugs, dipyrone 500 mg or placebo t.i.d., as identical-looking tablets, and the order of administration was randomized. CSA concentration s were measured in whole blood by means of radio-immunoassay (CYCLO-Trac SP ) daily during the study periods and periodically over 24 h on the fourth s tudy day. Results: CSA concentrations over time were reduced after dipyrone (ANOVA, P < 0.01), but statistical significance was noted only at 2, 4, 5 and 10 h a fter drug intake (P < 0.05). Peak CSA concentration was not altered by dipy rone, but the time required to reach maximal concentration was longer with dipyrone treatment than with the placebo (3.8 +/- 2.6 h vs 2.1 +/- 0.6 h, P < 0.05). No consistent changes were noted for CSA trough level, eliminatio n half-life and area under the concentration-time curve from 0 h to 12 h. S eparate analysis of the kidney transplanted patients yielded similar result s. Conclusions: Short-term administration of dipyrone is associated with a mil d decrease in CSA blood concentration, which is most prominent in the first few hours after drug intake. In practice, no dose adjustment of CSA seems to be indicated during a short course of dipyrone treatment.