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Abacavir / lamivudine / zidovudine Pregnancy and Breastfeeding Warnings

Abacavir / lamivudine / zidovudine is also known as: Trizivir

Abacavir / lamivudine / zidovudine Pregnancy Warnings

Abacavir/lamivudine/zidovudine has been assigned to pregnancy category C by the FDA. There are no adequate and well-controlled studies of abacavir/lamivudine/zidovudine in pregnant women. Reproductive studies with abacavir, lamivudine and zidovudine used separately have been performed in animals, however, there are no well-controlled studies of each agent used alone in human pregnancy. High-dose animal studies with abacavir have revealed evidence of developmental toxicity, fetal anasarca, skeletal malformations, and increased incidence of stillbirth. High-dose lamivudine studies in rats have failed to reveal evidence of fetotoxicity. There is some indication of early embryolethality in rabbit studies using doses proportional to normal human dosages of lamivudine. Zidovudine animal studies failed to reveal evidence of teratogenicity, although some studies demonstrated an increased incidence of fetal resorption. Early results from a study by the AIDS Clinical Trial Group (ACTG 076) indicated perinatal zidovudine administration reduced the incidence of HIV maternal-infant transmission from 25.5% to 8.3%. However, the long-term effects of zidovudine therapy during pregnancy are not known. Abacavir/lamivudine/zidovudine should only be given during pregnancy when there are no alternatives and benefit outweighs risks.

In February 1994, early statistical analysis of ACTG 076 revealed that perinatal administration of zidovudine reduced the transmission of HIV from mother to infant by approximately two-thirds (8.3% compared to 25.5% with placebo). At this point, the trial was ended and zidovudine was offered to those participants receiving placebo. Zidovudine had been initiated in HIV-infected women with a CD4 cell count greater than 200/mm3 who had received no antiretroviral therapy during their current pregnancy and were between 14 and 34 weeks gestation. Zidovudine 100 mg five times a day was given for the duration of pregnancy. During labor, intravenous zidovudine was given, beginning with 2 mg per kg over the first hour, followed by 1 mg per kg per hour until delivery. For six weeks after birth, infants received 2 mg per kg orally every six hours, beginning at 8 to 12 hours of life. During this study zidovudine was administered to 180 infants. The only fetal or infant toxicity reported was a mean decrease in hemoglobin of less than 1 g/dL, which resolved spontaneously following completion of therapy. Zidovudine crosses the placenta, with similar maternal serum and umbilical concentrations at delivery. The pharmacokinetics of zidovudine are not significantly affected by pregnancy. Several reports of the use of zidovudine in pregnancy, including during the first trimester, have not revealed teratogenicity or fetal toxicity, other than reversible anemia. No adverse effects were observed in HIV-uninfected children with in utero and neonatal exposure to zidovudine followed up for as long as 5.6 years. One series of 104 cases of intentional or inadvertent use of zidovudine during all stages of pregnancy was unable to demonstrate any specific abnormalities reasonably attributable to zidovudine use. Anomalies reported in infants exposed during the first trimester included low set ears, retrognathia, prominent epicanthal folds, hirsutism, triangular facies with blue sclera, hyperpigmented skin macules, prominent sacral dimple in one infant, multiple minor anomalies in one infant, and extra digits in one infant. Pectus excavatum was reported in two infants exposed in the second and third trimesters. An infant exposed during the third trimester exhibited albinism, congenital ptosis, oligohydramnios and intrauterine growth retardation. An Antiretroviral Pregnancy Registry has been established to monitor maternal-fetal outcome of abacavir/lamivudine/zidovudine exposures during pregnancy. To register patients, physicians should call 800-258-4263.

Abacavir / lamivudine / zidovudine Breastfeeding Warnings

In one study, lamivudine was measured in the milk of 20 HIV-infected women given 150 mg every 12 hours since week 38 of pregnancy. Mean lamivudine milk concentrations ranged from undetectable (less than 500 mcg/L) to 8200 mcg/L and was measured at any time relative to the dose. The breast milk to maternal serum ratio was approximately one to one. After administration of a single dose of 200 mg zidovudine to thirteen HIV-infected women, the mean concentration of zidovudine was similar in human milk and serum.

There are no data on the excretion of abacavir into human milk; however it is excreted into rat milk. Lamivudine and zidovudine are excreted into human milk. There are no data on the adverse effects in the nursing infant. The manufacturer recommends that due to the potential for serious adverse reactions in nursing infants, mothers should not breast-feed while taking this drug. In addition, HIV-infected mothers should not breast-feed their infants due to the risk of transmission of HIV via breast milk.

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