The purpose of this clinical trial is to characterize drug interactions between one medicinal herb: Echinacea purpurea and the protease inhibitor etravirine.

Because of its CYP3A4 inducer activity in the liver but its inhibitor effect at the intestinal site, concomitant administration of Equinacea purpurea (a medicinal herb frequently used by HIV-infected patients) and etravirine (an HIV reverse transcriptase inhibitor) might result in clinically relevant pharmacokinetic drug interactions.

15 HIV-infected patients on stable antiretroviral therapy including etravirine at the dosage of 200 mg twice daily during at least 4 weeks will be enrolled. After their inclusion in the study, patients will receive Echinacea purpurea root (500 mg every 8 hours) in addition to their antiretroviral treatment, 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 an etravirine dose, and etravirine concentrations in plasma will be determined by high performance liquid chromatography using a validated method.

Inclusion criteria:

1. Patients infected with HIV-1 (at least one documented positive Western-Blot).
2. Age 18 years or more.
3. Patients receiving antiretroviral therapy including etravirine at the approved dose of 200 mg twice daily for at least 4 weeks
4. HIV viral load in plasma <50 copies / mL
5. Absence of acute infections and / or tumors in the three months prior to inclusion.
6. Subject able to follow the treatment period, without suspicion of poor adherence in previous antiretroviral treatments.
7. Voluntary written informed consent.

Exclusion criteria:

1. 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.
2. Antiretroviral regimen including drugs ritonavir or atazanavir (CYP3A4 inhibitors)
3. Concomitant treatment with drugs inductors of CYP3A4 (rifampicin, fenitoin, carbamazepin, ...)
4. Active alcohol consumption (> 50 g / day) or illicit drugs (except cannabis).
5. Pregnancy or lactation