[Interactions between lithium/rubidium and six muscle relaxants. A study on the rat phrenic nerve-hemidiaphragm preparation].

The cumulative concentration-response curves for alcuronium, metocurine, d-tubocurarine, suxamethonium, pancuronium and vecuronium alone or in combination with lithium or rubidium were measured using indirectly evoked twitch tension in the isolated rat phrenic nerve-hemidiaphragm preparation. In the experiments with lithium and rubidium, 10% and 2% of the sodium ions (118 mmol/l) of Krebs solution were replaced by lithium (11.8 mmol/l = 0.082 g/l) or rubidium (2.36 mmol/l = 0.202 g/l) ions, respectively. At these concentrations, neither lithium nor rubidium alone affected twitch tension. Lithium led to a statistically significant enhancement of the myoneural blocking effects of suxamethonium, pancuronium and vecuronium, but not of the other myoneural blocking drugs. Rubidium behaved similarly to lithium, except that enhancement of the effect of vecuronium was not statistically significant. At higher concentrations, lithium and rubidium alone depressed twitch tension in a dose-dependent manner. Neither myoneural blocking drugs nor lithium and rubidium affected the directly evoked twitch tension. It is concluded that myoneural blocking drugs, especially the newer ones, should be used with caution in patients receiving lithium or other alkali metal therapy as it is not known what interactions may arise.