[On the interaction of combinations of nondepolarizing neuromuscular blocking drugs (author's transl)]

The interaction (addition or potentiation) of combinations of the ED20 and of the ED50 of pancuronium (0.01 and 0.0165 mg/kg), tubocurarine (0.06 and 0.10 mg/kg), and gallamine (0.25 and 0.41 mg/kg) was studied in 136 patients during general anaesthesia (methohexitone, fentanyl, droperidol, N2O; normoventilation). - 2. Neuromuscular blocking activity was quantified by means of mechanomyograms of the hand muscles following supramaximal electrical stimulation of the ulnar nerve (100-125 V, 0.2 ms, 0.2 Hz). - 3. The combinations of the ED20 and of the ED50 of the three muscle relaxants resulted in an nonlinear manner in 60% and 90% twitch inhibition. - 4. The duration of action of the combinations of the ED20 and of the ED50 did not exceed the duration of blockade by the longest acting individual component given alone. - 5. The nonlinear increase in response following the combination of equieffective doses of muscle relaxants corresponds with the nonlinear shape of dose-response curves and can be described as an additive interaction.