Interaction of calcium and potassium with neuromuscular blocking agents

Dose-response curves for blockade of the indirectly elicited twitch of isolated guineapig nerve-lumbrical muscle preparations were determined for tubocurarine and pancuronium in the presence of potassium 2,4 and 6 mmol litre-1 and calcium 1,2 and 3 mmol litre-1. Increases in concentration of either ion decreased the sensitivity of the preparation to both drugs. Over the physiological range of concentrations of potassium and calcium, 36% and 27% variation in dosage can be expected.