[Relationship between the pain-relieving action of narcotic analgesics and their effect on respiration].

Experiments with rabbits (30) and albino rats (110) demonstrated that morphine (1 mg/kg), promedol (trimeperidine) (2 mg/kg) and phentanyl (0.02 mg/kg), while raising by 21-24 per cent of the algesia threshold, produced an analgesic effect differeing in its duration (morphine-130 min, trimeperidine-70 min, phentanyl-17 min). This is attended by changes in respiration (greater on introduction of phentanyl, and lesser, following administration of morphine) and by shifts in the functional state of the tissues (greater on introduction of trimeperidine and lesser after aministration of morphine).