Risk level in pregnancy: This medicine is classified as Category C.
It has been shown that both alfentanil and fentanyl cross the placenta. A study conducted on 21 women undergoing cesarean section showed that the mean concentration of alfentanil in newborn umbilical venous blood was 7.5 ng/ml (range 3.6-10.6 ng/ml), one third of maternal plasma concentration.
The studies conducted in rats and rabbits did not appear to have shown teratogenic effects. However, the administration of doses 2.5 times the maximum recommended in humans, has an effect embryocidal in experimental animals when administered in a range from 10 to over 30 days.
A study on monkeys of the species Macaca mulatta, exposed to meperidine or alfentanil has shown a higher incidence of infections, neurological features of immaturity and lower motor activity during the follow up period (14 weeks).
The manufacturer states the following warning:
Although animal experiments have not been observed acute teratogenicity or embryotoxicity, data available are not sufficient to assess the potential harmful effect on humans. Consequently, must be assessed cautiously the risk/benefit ratio before using alfentanil in pregnant women.
Not recommended administration (IV) of alfentanil in childbirth (including caesarean section) since the alfentanil crosses the placenta and the fetal respiratory center is particularly sensitive to the action of morphinics. In any case, if used this substance during labor must be available an antidote for the child.
Meaning of category C
Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.