Ceruletide increases threshold and tolerance to experimentally induced pain in healthy man

Previous studies suggested that ceruletide might be endowed with analgesic and sedative properties. To investigate the effects of ceruletide on experimentally induced pain and on central nervous functions, two studies, each involving 24 healthy subjects, were carried out in random double-blind fashion. Every subject participated in three experiments one week apart. In study 1, 120 and 60 ng/kg/hr ceruletide IV increased threshold and tolerance to electrically and threshold to thermally induced cutaneous pain significantly more than saline (p<0.001), the higher dose being slightly more active. Only mild sedative effects occurred. Study 2 compared the effects of 60 and 6 ng/kg/hr ceruletide IV to those of 0.4 mg/kg/hr pentazocine IV and investigated whether these effects were naloxone reversible. Both ceruletide doses, 60 ng/kg/hr slightly more than 6 ng/kg/hr, elevated threshold and tolerance to electrically induced and threshold to thermally induced pain markedly, pentazocine acted stronger and longer than ceruletide (p<0.001). Naloxone reversed the effects of pentazocine but not of ceruletide. Conclusion: ceruletide (1) exerts potent naloxone resistant analgesic effects, which, however, are inferior to those of pentazocine, and (2) produces only mild sedation.