Interactions of calcium channel blockers with non-depolarising muscle relaxants in vitro.

The effects of two calcium channel blockers (verapamil and nicardipine) on indirectly elicited muscle twitch and possible interactions between these drugs and non-depolarising muscle relaxants (vecuronium, atracurium, pancuronium) were investigated using isolated rat phrenic nerve-hemidiaphragm preparations. Both verapamil 10(-5) M and nicardipine 10(-6) M caused significant depression of twitch amplitude. Verapamil significantly increased vecuronium- and atracurium-induced neuromuscular block, but not that produced by pancuronium. Nicardipine potentiated atracurium-induced neuromuscular block but had no effect on pancuronium- and vecuronium-induced twitch depression. Neostigmine 10(-6) M did not produce any significant changes in the maximal recovery of twitch depression induced with calcium channel blockers and muscle relaxants combinations; also, neostigmine had no effect on maximal recovery time of twitch depression.