Alterations in response to somatic pain associated with anaesthesia. XXIII: Further study of naloxone.

Tibial pressure analgesimetry has been employed to study the antagonistic effects of small doses of naloxone in pethidine-induced analgesia. The dose of pethidine was 100 mg and the doses of naloxone 0.2, 0.1, 0.05 and 0.025 mg/60 kg body weight, and all drugs were given i.v. These doses of naloxone reduced the analgesia produced by pethidine and the degree of antagonism was probably dose-related. It was also found that naloxone antagonized the side-effects of pethidine, especially nausea.