PK Study of Rifampicin Interactions With DMPA and Efavirenz in TB

Globally, women comprise 52% of all people living with human immunodeficiency virus (HIV). Decisions about contraception in a population of women infected with both tuberculosis (TB) and HIV are of paramount importance. In the setting of the treatment of active TB, preventing pregnancy becomes even more important because it allows women to attain a level of health that will support healthy future pregnancies. Treatment options for TB may be limited in pregnancy because of concerns about teratogenicity. Millions of women around the world use depot medroxyprogesterone acetate (DMPA, trade name Depo-Provera) for prevention of pregnancy. DMPA is an intermediate-acting progesterone-only injectable contraceptive with a high efficacy rate. Unfortunately, DMPA's safety and effectiveness among women co-infected with TB and HIV is unknown since the interactions of TB treatment, combination ART (cART), and DMPA have not been well studied. The results of this study are likely to be applicable to women receiving RIF-containing TB treatment who are not being treated concurrently with EFV as well, given that addition of EFV to RIF is unlikely to increase induction of metabolizing enzymes significantly beyond the induction achieved with RIF alone.

The study population included premenopausal women, 18 to 46 years of age, who were co-infected with HIV and TB. To be eligible to enroll in the study, participants must have been on EFV 600 mg once daily plus two or more nucleoside reverse transcriptase inhibitors (NRTIs) for at least 28 days prior to study entry with no plans to change therapy for the 12 weeks of the study. Women must have been on the continuation phase of active TB treatment (with a minimum of 12 weeks remaining) taking RIF 8-12 mg/kg orally and INH 4-6 mg/kg orally on a 5-day or more per week schedule (or as directed by national guidelines for TB treatment). At study entry/week 0, DMPA 150 mg was administered intramuscularly as a single dose.

Study duration was 12 weeks. Visits occurred at weeks 0, 2, 4, 6, 8, 10, and 12. The key evaluations included physical examination, clinical assessments, hematology, chemistry, HIV RNA, pregnancy testing, plasma progesterone levels, and plasma DMPA concentration levels.

The sample size was 46 participants, of which 42 had to be evaluable. Participants who missed two successive visits prior to week 8 and those who did not complete the week 10 and week 12 clinic visits with available DMPA concentrations and progesterone levels were not evaluable and replaced in the sample size. The final number of participants enrolled was 62 participants, with only 42 evaluable.

Inclusion criteria

• HIV-1 infection.
• Current tuberculosis infection, confirmed or probable diagnosis.
• Currently stable on EFV-based cART for at least 28 days with no intention to change the regimen during the 12-week study period.
• Currently receiving RIF and Isoniazid (INH)-based TB therapy on at least 5 days per week schedule after completion of the intensive phase of TB treatment (minimum of 8 weeks of TB treatment) and expected to be on TB treatment for a minimum of 12 weeks after enrollment. [Does not exclude the use of ethambutol on study.]
• Premenopausal female with presumed normal ovarian function based on normal menstrual history and absence of previous ovarian dysfunction diagnosis.
• Last menstrual period (LMP) ≤35 days prior to study entry.
• Negative serum or urine-HCG pregnancy test within 30 days prior to study entry and negative pregnancy test at entry at any network-approved laboratory that operates in accordance with Good Clinical Practices and participates in appropriate external quality assurance programs.
• All participants must agree not to participate in a conception process (e.g., active attempt to become pregnant or in vitro fertilization) for the duration of the study. Women of reproductive potential, who are participating in sexual activity that could lead to pregnancy, must agree to use an additional reliable method of contraception while in the study. Acceptable forms of contraceptives include:

• Condoms (male or female) with or without a spermicidal agent
• Diaphragm or cervical cap with spermicide
• Non-hormonal IUD
• Bilateral tubal ligation
• Male partner vasectomy
• Laboratory values within 30 days prior to study entry:

• Absolute neutrophil count ≥500 cells/mm^3
• Platelet count ≥50,000 platelets/mm^3
• Hemoglobin ≥8.0 g/dL
• Aspartate transaminase (AST) and alanine aminotransferase (ALT) <5 x upper limit of normal (ULN)
• Creatinine ≤1.5 x ULN
• Total bilirubin ≤2.0 x ULN
• Ability and willingness to provide written informed consent.

Exclusion criteria

• Receipt of DMPA or any other injectable contraceptive within 180 days prior to study entry.
• Receipt of other hormonal contraceptives within 30 days prior to study entry.
• Use of any drugs other than RIF and EFV known to: 1) induce CYP3A4 system within 30 days and to 2) inhibit the CYP3A4 system with one week prior to study entry. [Because ethambutol does not induce or inhibit the CYP3A4 system, its use is consistent with the language in the protocol.]
• ≤40 kg in weight.
• Bilateral oophorectomy.
• Less than 30 days postpartum at study entry.
• Hypersensitivity to DMPA, medroxyprogesterone acetate (MPA), or any of the other ingredients in DMPA.
• Any previous breast cancer diagnosis.
• Serious illness requiring systemic treatment and/or hospitalization within 21 days prior to study entry.
• Karnofsky performance score <70 within 14 days prior to study entry.
• Use of any immunosuppressant medication including systemic corticosteroids within 30 days prior to study entry.
• Active drug or alcohol use or dependence that, in the opinion of the site investigator, would interfere with adherence to study requirements.
• History of deep venous thrombosis or pulmonary emboli.