• Ratio of cord blood concentration to maternal blood concentration [ Time Frame: throughout study ] [ Designated as safety issue: No ]
• ratio of 6-beta-hydroxycortisol to cortisol [ Time Frame: throughout study ] [ Designated as safety issue: No ]
• ratio of unbound/total drug concentrations for atazanavir, fosamprenavir, efavirenz, nelfinavir, and tipranavir [ Time Frame: throughout study ] [ Designated as safety issue: No ]

• Ratio of cord blood concentration to maternal blood concentration
• ratio of 6-beta-hydroxycortisol to cortisol
• ratio of unbound/total drug concentrations for atazanavir, fosamprenavir, efavirenz, nelfinavir, and tipranavir

The purpose of this study is to determine what doses of anti-HIV medications are appropriate for pregnant women.

Anti-HIV medication taken during pregnancy may control a woman's viral load and reduce the chance that the baby will become infected with HIV. Pregnant women may require different doses of anti-HIV drugs than women who are not pregnant. This study will use pharmacokinetic (PK) sampling to determine what doses of anti-HIV medications are best for HIV infected pregnant women and their infants.

Pregnant women experience unique physiological changes that may result in clinically significant alterations in drug PKs. Unfortunately, there have been few clinical trials to study the PK of antiretroviral (ARV) medications in pregnant women. The development of appropriate dosing regimens for the HIV infected pregnant woman is critical to the health of both mother and fetus. Overdosing may lead to maternal adverse events and increased risk of fetal toxicity, while underdosing may lead to inadequate virologic control, increased risk of developing drug resistance mutations, and a higher rate of perinatal HIV transmission. This study will develop and evaluate dosing regimens that are most effective in preventing perinatal HIV transmission and in maintaining the health of both mother and fetus.

Participants will be enrolled in this study starting from their twentieth week of pregnancy and for 12 weeks after delivery. Participants will not receive ARV medications through this study. Medical history, a physical exam, and blood and urine collection will occur during all study visits.

Intensive PK sampling will be performed at study visits during the second and third trimester of pregnancy and between 2 and 3 weeks and 6 and 12 weeks postpartum. The timing of antepartum and postpartum PK samplings will vary by drug. Blood collection from the mother and the detached umbilical cord will occur during delivery. Additional study visits may occur depending on the ARV drug regimen prescribed.

• Best BM, Mirochnick M, Capparelli EV, Stek A, Burchett SK, Holland DT, Read JS, Smith E, Hu C, Spector SA, Connor JD; the PACTG P1026s Study Team. Impact of pregnancy on abacavir pharmacokinetics. AIDS. 2006 Feb 28;20(4):553-560.
• Stek AM, Mirochnick M, Capparelli E, Best BM, Hu C, Burchett SK, Elgie C, Holland DT, Smith E, Tuomala R, Cotter A, Read JS; for the PACTG 1026s study team. Reduced lopinavir exposure during pregnancy. AIDS. 2006 Oct 3;20(15):1931-1939.
• Loutfy MR, Walmsley SL. Treatment of HIV infection in pregnant women: antiretroviral management options. Drugs. 2004;64(5):471-88.
• Mirochnick M, Capparelli E. Pharmacokinetics of antiretrovirals in pregnant women. Clin Pharmacokinet. 2004;43(15):1071-87. Review.
• Rakhmanina NY, van den Anker JN, Soldin SJ. Safety and pharmacokinetics of antiretroviral therapy during pregnancy. Ther Drug Monit. 2004 Apr;26(2):110-5. Review.
• Sullivan JL. Prevention of mother-to-child transmission of HIV--what next? J Acquir Immune Defic Syndr. 2003 Sep;34 Suppl 1:S67-72. Review.

Inclusion Criteria:

• HIV infected
• At least 20 weeks pregnant. If a woman has completed P1026s and becomes pregnant again, she may be eligible to re-enroll in P1026s only if she is receiving a different drug or drug combination than that studied during the first enrollment in P1026s.
• Enrolled in PACTG P1025
• Must begin one of the study drugs or drug combinations by 34 6/7th week of pregnancy, and must be on the anti-HIV drugs for at least 2 weeks prior to PK sampling

Exclusion Criteria:

• Certain medications known to interfere with absorption, metabolism, or clearance of the anti-HIV drug(s) being evaluated
• Pregnant with more than one baby
• Signs of toxicity that, in the opinion of the site investigator, would be likely to require a change in medication during the study