This is a clinical trial to characterize drug interactions between silimarine and the protease inhibitor darunavir/ritonavir.

The silimarine is the main component of milk thistle (Sylibum marianum), a medicinal herb which, due to its attributed hepatoprotective properties, is widely used by HIV infected patients

15 patients on stable antiretroviral therapy including darunavir/ritonavir 600/100 mg twice a day during four weeks will be enrolled. After their inclusion in the study, patients will receive treatment with silimarine (150 mg every 8 hours) from day 1 until two weeks later (day 14). On days 0 and 14, blood samples will be drawn immediately before and 1, 2, 4, 6, 8, 10 and 12 hours after the administration of darunavir/ritonavir, and darunavir and ritonavir concentrations in plasma will be determined by high performance liquid chromatography using a validated method.

Inclusion Criteria:

• Patients receiving antiretroviral therapy containing darunavir / ritonavir at the approved dose of 600/100 mg twice daily for at least 4 weeks
• HIV viral load in plasma <50 copies / mL
• Absence of acute infections and / or tumors in the three months prior to inclusion.
• Subject able to follow the treatment period, without suspicion of poor adherence in previous antiretroviral treatments.

Exclusion Criteria:

• Any clinical or historical observation that could interfere with the pharmacokinetics of medications, such as gastrointestinal illness or surgery (except for herniotomy and appendectomy), changes in the composition of plasma proteins, some indication of hepatic or renal dysfunction.
• Active alcohol consumption (> 50 g / day) or illicit drugs (except cannabis).