[Nifedipine and vecuronium bromide. How does a patient treated with calcium antagonists react to nondepolarizing muscle relaxants? Brief scientific communication].

The muscle-relaxation reactions of Ca-antagonist (nifedipine) pretreated patients and a control group (5 in each group) were observed after administration of vecuronium bromide using the "priming principle." Twitch depression induced by the "priming dose" of vecuronium bromide (20 micrograms/kg body weight and T4/T1 ratio in the Ca-antagonist-treated patients (35 +/- 13% and 0.42 +/- 0.14%, respectively), was significantly different (P less than 0.01) when compared with the control group (1.2 +/- 2.7% and 0.75 +/- 0.15%). Similarly, the onset time to maximum blockade after the intubating dose of vecuronium bromide (60 micrograms/kg body wt.) was significantly shorter in the nifedipine group (40 +/- 21 s) when compared with the controls (100 +/- 17 s). The duration of the effect observed clinically (until 25% recovery) in the nifedipine group 32.9 +/- 7.3 min versus 25 +/- 8.15 min was enhanced; however, the difference between the treated group and the control group was not significant.