Time of day of taking immunosuppressive agents after renal transplantation: a possible influence on graft survival.

Large-amplitude circadian rhythms in immune responses and the known variations in the effects of glucocorticoids with the time of day of administration suggest that immunosuppressive regimens may need to take this variable into account. In two similar groups of patients with renal transplants functioning satisfactorily after three months subsequent graft failure developed in 66% of those taking all immunosuppressives in the evening, compared with only 22% of those taking immunosuppressives twice daily (p < 0.05). A survey of other transplant units showed that one unit with outstanding results--graft survival at three years 82%--had a unique policy of morning-only administration of immunosuppressives. Doctors need to consider more carefully the time of drug administration when prescribing, as it may be possible to obtain better results with less toxicity.