Reproductive and teratogenic effects of fentanyl in Sprague-Dawley rats

Female Sprague-Dawley rats were administered fentanyl continuously using chronically implanted osmotic minipumps for 2 weeks before breeding and during the entire period of pregnancy. Three different fentanyl dosage regimens were employed, i.e., 10, 100, and 500 micrograms/kg/day. Reproductive indices were determined and the 1,046 offspring delivered at cesarean section were examined for external, visceral, and skeletal abnormalities. There were no major or minor reproductive abnormalities or teratogenic findings in any of the fentanyl-treated groups. We conclude that fentanyl is devoid of adverse reproductive effects in this strain of rats up to dosages of 500 micrograms/kg/day administered by osmotic minipumps. From a methodologic point of view, osmotic minipumps facilitate study of the reproductive effects of narcotics as they allow delivery of dosages that ordinarily would not be tolerated without producing severe respiratory depression.