CEILING RESPIRATORY DEPRESSION BY DEZOCINE

Dezocine in equianalgesic i.v. doses depressed respiratory response to CO2 breathing of 6 healthy subjects to approximately the same degree as morphine but with a more rapid onset and higher peak depression. The depression was dose related up to 30 mg/70 kg but was not increased by an additional 10 mg/70 kg dose. Its duration of effect was approximately the same as that of morphine. Respiratory depression by dezocine was promptly and almost completely antagonized by 0.4 mg naloxone but antagonism lasted < 1 h. Healthy subjects found dezocine less pleasant than morphine and after large doses reported sensations suggestive of psychotomimetic effects. A ceiling of effect for respiratory depression has now been demonstrated for 3 agonist-antagonist analgesics: nalorphine, nalbuphine and dezocine. It is not yet clear to what extent this is a general characteristic of agonist-antagonist analgesics.