Pharmacokinetics and distribution of diazepam and oxazepam in early pregnancy

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Abstract
The transfer of drugs from the mother to the fetus is important from the view of possible harmful as well as therapeutic effects on both mother and fetus. In the first trimester of pregnancy this has been sparsely investigated. In 66 first‐trimester pregnant women, who had applied for legal termination of the pregnancy, we have calculated different pharmacokinetic parameters of two benzodiazepine derivatives, diazepam and oxazepam, after administration of a single oral dose of 10 or 25 mg to the mother. The calculated pharmacokinetic parameters were within the normal range for healthy adults. The pharmacological active metabolite n‐desmethyldiazepam was measured in concentrations near the detection limit. The penetration of diazepam and oxazepam from maternal serum to placental tissue in a 4 h period after drug administration was 31.5% and 49%, respectively, indicating a rapid transfer.