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ABSORPTION, DISTRIBUTION, METABOLISM, AND EXCRETION
-Acetylmethadol (LAAM) and L-
-Acetyl-N-normethadol (norLAAM) by the Perfused Human Placental Lobule
Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, Texas (T.N.N., S.V.D., M.S.A.); Kansas City School of Pharmacy, University of Missouri, Kansas City, MO (R.M.); and Quintiles, Inc., Kansas City, MO (S.B.)
The agonists buprenorphine and L-
-acetylmethadol (LAAM)
were introduced as alternatives to methadone for treatment of the adult opiate
addict. The direct and indirect effects of these drugs on normal fetal growth
and development are currently under investigation in our laboratory. The goal
of this report is to provide part of the data necessary to assess the safety
of LAAM in treatment of the pregnant opiate addict. To achieve this goal, the
technique of dual perfusion of placental lobule was utilized to determine the
kinetics for transplacental transfer of LAAM and its effects on the viability
and functional parameters of the tissue. LAAM is rapidly metabolized to the
pharmacologically active norLAAM that was also included in this investigation.
The two opiates were transfused at their plasma levels in patients under
treatment, a concentration of 35 ng/ml. The drugs exhibited similar
pharmacokinetic profiles, characterized by an initial phase of distribution
into placental tissue followed by their low transfer to the fetal circuit.
During the 4-h experimental period, the transfused tissue retained significant
amounts of LAAM and norLAAM, and neither drug was metabolized. LAAM did not
affect placental tissue viability and functional parameters. However, norLAAM
caused a significant decrease in the release of human chorionic gonadotropin.
At this time, it is unclear whether a similar effect for norLAAM may occur in
vivo and, if so, what the consequences would be on its role in implantation
and normal fetal growth and development.
Address correspondence to: Dr. Mahmoud S. Ahmed, Department of Obstetrics and Gynecology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-0587. E-mail: maahmed{at}utmb.edu