Teratogenic risk with etretinate and acitretin treatment

Etretinate (Tigason, Tegison) and its active metabolite acitretin (Neotigason, Soriatane) are known teratogens. Pregnancy should be avoided during treatment and until 2 years after treatment discontinuation. The question is discussed whether a dose or a blood concentration of the drug below which there is no teratogenic risk can be determined. Animal experimental and human pharmacokinetic data are reviewed. An evaluation of the outcomes of pregnancies which occurred in mothers exposed to etretinate or acitretin was performed. A threshold dose in human therapy below which there is no risk of congenital malformation cannot be determined based on animal experimental data. With regard to pharmacokinetics, there are currently no data suggesting that blood levels of the drug below the detection limit of 2 ng/ml are associated with a teratogenic risk. The most useful information is given by reports in women who were exposed to either retinoid before or during pregnancy. The data indicate that the risk of spontaneous abortion or congenital malformation is high when the drug is administered during the first trimester of pregnancy. After treatment discontinuation, the risk is low since the number of abnormalities seems not to exceed those observed in a general population. There are currently no available data which suggest that the pregnancy warnings are inappropriate in terms of duration of contraception.