10 Fluticasone propionate (interaction with ritonavir): in a clinical study where ritonavir 100 mg capsules twice daily were co − administered with 50 μ g intranasal fluticasone propionate (4 times daily) for seven days in healthy subjects, the fluticasone propionate plasma levels increased significantly, whereas the intrinsic cortisol levels decreased by approximately 86% (90% confidence interval 82 − 89%).