Coadministration has not been studied. Prednisone is converted to the active metabolite prednisolone by 11-B-hydroxydehydrogenase. Prednisolone is then metabolized by CYP3A4. Coadministration could potentially increase prednisolone concentrations thus increasing the risk of steroid related toxicity. Following administration of prednisone (20 mg single dose) to HIV+ subjects receiving either lopinavir/ritonavir or efavirenz or no antiretrovirals (n=10 per group), prednisolone AUC was significantly lower (40% decrease) in the presence of efavirenz versus lopinavir/ritonavir, and was higher in the subjects taking lopinavir/ritonavir than in subjects on no antiretrovirals (30% increase), but this was not significant. A similar increase may occur with darunavir/ritonavir. Careful monitoring for adverse effects is recommended.