Human volunteer studies of Alfentanyl (R39209), a new short-acting narcotic analgesic

Alfentanyl is a new narcotic analgesic with a rapid onset and very short duration of effect, and a potency about one third of that of fentanyl. The respiratory effects of 1.6, 3.2 and 6.4 micrograms/kg Alfentanyl were studied in a randomised controlled trial in five volunteers. Alfentanyl 6.4 micrograms/kg induced a significant increase in respiration at 1 minute, then significant depression of mean minute volume 3 and 4 minutes after slow intravenous injection, compared with saline control, and pre-injection values. Mean end-expired carbon dioxide concentration was increased after Alfentanyl 6.4 micrograms/kg, significantly from 2 to 9 min after injection, and highly significantly at 3, 4 and 5 minutes. Examination of the effect on expired CO2 concentration at 4 minutes reveals a highly significant dose-response relationship with the three doses of Alfentanyl. The transient effect of ALfentanyl was confirmed by the fact that no change in mean ventilatory response to carbon dioxide was demonstrable 30 or 50 minutes after any dose. When Alfentanyl was given 1 minute before testing the ventilatory response to carbon dioxide the response curves showed a highly significant dose-related shift to the right. There were no significant changes in heart rate or blood pressure after Alfentanyl, but the drug produces the typical subjective effects of the opiates.