Coadministration of medroxyprogesterone (150 mg, intramuscular depot injection) with lopinavir/ritonavir (400/100 mg, twice daily) was studied in 24 HIV positive women and compared to historical values from 14 HIV positive women receiving medroxyprogesterone without antiretroviral therapy. Medroxyprogesterone AUC, Cmin and Cmax increased by ~70%, ~20% and ~89%, respectively. Despite the increase in medroxyprogesterone exposure, medroxyprogesterone was well-tolerated. Lopinavir AUC, Cmin and Cmax increased ~6%, ~11% and ~3%, respectively, whereas ritonavir AUC, Cmin and Cmax decreased by ~3%, ~1% and ~2%, respectively. Based on progesterone concentrations, ovulation did not occur during coadministration. The authors conclude that coadministration of medroxyprogesterone and lopinavir/ritonavir is safe.