Metabolism of cocaine by human placentas: implications for fetal exposure

Article Abstract:

Since one fetus out of every 10 in the United States is exposed to cocaine prior to birth, the role of the placenta in protecting the fetus from this drug is highly relevant. The ability of the placenta to metabolize cocaine (break it down into its constituent chemicals) was investigated by analyzing microsomes from 10 placentas. Microsomes are small vesicles within cells that contain enzymes, chemicals essential for metabolism to take place. The placentas were associated with problem-free, vaginal deliveries to mothers with no disease or drug abuse history. Microsomes were evaluated for the ability to metabolize cocaine during a 135-minute period; they were incubated with the drug at concentrations equivalent to those in the blood after typical intranasal (through the nose) cocaine use. Results showed that the concentration of cocaine declined by 20 percent during the experiment, with most of the decline occurring during the first 45 minutes. These effects were most probably due to the action of cholinesterase (an enzyme) in the microsomes. A discussion is provided of the effects of cocaine in pregnancy: these include actions on the vessels that control blood exchange between mother and fetus, and on uterine contractions. Consequences of cocaine use can include premature rupture of the membranes surrounding the fetus, abruptio placentae (premature detachment of the placenta), preterm (premature) labor, reduced birth weight, and fetal growth retardation. While the results indicate that the term (mature) placenta can exert some protection against cocaine, the protection offered by the placenta in earlier stages of development, when the fetus is more vulnerable, has not been determined. (Consumer Summary produced by Reliance Medical Information, Inc.)

Fetus, Drug abuse in pregnancy

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A new placental enzyme in the metabolism of cocaine: an in vitro animal model

Article Abstract:

The human placenta is able to metabolize cocaine with cholinesterase, and may be able to metabolize cocaine in the absence of cholinesterase. Researchers removed placentas from the bodies of rats and analyzed the effect of certain enzymes on cocaine metabolism. The rat placenta metabolized cocaine with cholinesterase, as does the human placenta. The rat placenta also metabolized cocaine with the enzyme N-demethylase, a reaction that has not been discovered before. This suggests that the placenta may protect the fetus from cocaine exposure by first metabolizing it. Women who use cocaine but who do not have adequate cholinesterase activity may be at greater risk of having babies with abnormalities from cocaine exposure.

Pregnant women, Drug use

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The maternal-fetal transfer of lamivudine in the ex vivo human placenta

Article Abstract:

The drug lamivudine may cross the placenta to the fetus without being inhibited by zidovudine. Zidovudine has been the primary treatment for HIV infection but is now being combined with lamivudine to overcome resistant viruses. Such treatment may reduce the transmission of HIV from mother to fetus. Researchers analyzed the ability of lamivudine to cross the placenta in nine delivered term placentas. Lamivudine crossed the placenta by simple diffusion and this did not change in the presence of zidovudine. The lowest effective concentration of lamivudine is unknown but should be determined for fetal health.

Prevention, Drug therapy, HIV infections, HIV infection in children, Pediatric HIV infections, Pregnancy, Antiviral agents, HIV infection in pregnancy

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