8.1Pregnancy Pregnancy Exposure Registry
There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to lamivudine during pregnancy. Healthcare providers are encouraged to register patients by calling the Antiretroviral Pregnancy Registry (APR) at 1-800-258-4263. Risk Summary Available data from the APR show no substantial difference in the risk of overall major birth defects for lamivudine compared with the background rate for major birth defects of 2.7% reported in the U.S. reference population of the Metropolitan Atlanta Congenital Defects Program (MACDP).
The APR uses the MACDP as a U.S. reference population for birth defects in the general population. The MACDP evaluates women and infants from a limited geographic area and does not include outcomes for births that occur at less than 20 weeks’ gestation. Of over 12,900 women exposed to lamivudine in the APR, less than 2% were HBV mono-infected. The majority of women exposed to lamivudine in the APR were HIV-1-infected and were treated with higher doses of lamivudine compared with HBV mono-infected women.
In addition to lamivudine, HIV-1-infected women were also treated with other concomitant medications for HIV-1 infection [see Data]. The estimated rate of miscarriage for women exposed to lamivudine in the indicated population is unknown. The estimated background rate of miscarriage in clinically recognized pregnancies in the U.S. general population is 15% to 20%. Oral administration of lamivudine to pregnant rabbits during organogenesis resulted in embryolethality at systemic exposure (AUC) similar to the recommended clinical dose; however, no adverse developmental effects were observed with oral administration of lamivudine to pregnant rats during organogenesis at plasma concentrations (C max ) 60 times the recommended clinical dose [see Data] .
Data Human Data Based on prospective reports from the APR of over 12,900 exposures to lamivudine during pregnancy resulting in live births (including over 5,400 exposed in the first trimester and over 7,500 exposed in the second/third trimester), there was no difference between the overall risk of birth defects with lamivudine compared with the background birth defect rate of 2.7% observed in the U.S. reference population of the MACDP.The prevalence of birth defects in live births was 3.1% (95% CI: 2.7% to 3.6%) following first trimester exposure to lamivudine-containing regimens and 2.9% (95% CI: 2.5% to 3.3%) following second/third trimester exposure to lamivudine-containing regimens.
The pharmacokinetics of lamivudine in patients with HBV or HIV-1 infection and in healthy volunteers are similar at similar doses. Lamivudine pharmacokinetics were studied in pregnant women with HIV-1 infection during 2 clinical trials conducted in South Africa. The trials assessed pharmacokinetics in 16 women at 36 weeks gestation using 150 mg lamivudine twice daily (3 times the recommended daily dosage for HBV) with zidovudine, 10 women at 38 weeks gestation using 150 mg lamivudine twice daily (3 times the recommended daily dosage for HBV) with zidovudine, and 10 women at 38 weeks gestation using lamivudine 300 mg twice daily (6 times the recommended daily dosage for HBV) without other antiretrovirals.
Lamivudine concentrations were generally similar in maternal, neonatal, and umbilical cord serum samples. In a subset of subjects, amniotic fluid specimens were collected following natural rupture of membranes and confirmed that lamivudine crosses the placenta in humans. Based on limited data at delivery, median (range) amniotic fluid concentrations of lamivudine were 3.9- (1.2- to 12.8-) fold greater compared with paired maternal serum concentrations (n = 8).
Animal Data Lamivudine was administered orally to pregnant rats (at 90, 600, and 4,000 mg per kg per day) and rabbits (at 90, 300, and 1,000 mg per kg per day and at 15, 40, and 90 mg per kg per day) during organogenesis (on Gestation Days 7 through 16 [rat] and 8 through 20 [rabbit]). No evidence of fetal malformations due to lamivudine was observed in rats and rabbits at doses producing plasma concentrations (C max ) approximately 53 or more times higher than human exposure at the recommended daily dose.
Evidence of early embryolethality in the absence of maternal toxicity was seen in the rabbit at systemic exposures (AUC) similar to those observed in humans, but there was no indication of this effect in the rat at plasma concentrations (C max ) 60 times higher than human exposure at the recommended daily dose. Studies in pregnant rats showed that lamivudine is transferred to the fetus through the placenta. In the fertility/pre- and postnatal development study in rats, lamivudine was administered orally at doses of 180, 900, and 4,000 mg per kg per day (from prior to mating through postnatal Day 20).
In the study, development of the offspring, including fertility and reproductive performance, was not affected by maternal administration of lamivudine at plasma concentrations (C max ) 104 times higher than human exposure.
