A single dose of azathioprine does not affect the pharmacokinetics of prednisolone following oral prednisone.

Clinical and pharmacokinetic observations suggest that azathioprine may diminish the plasma level of prednisolone. To study the extent of this possible interaction, and to define the underlying mechanism, total and unbound prednisolone and total prednisolone concentrations were assessed in 11 subjects following an oral dose of prednisone once with and once without concomitant oral administration of azathioprine. Azathioprine did not affect the area under the plasma concentration-time curve of total and unbound prednisolone; furthermore, the interconversion of prednisone into prednisolone was not influenced by azathioprine.