Inhibitory effect of diphenylhydantoin on myometrium from pregnant women in vitro. A comparative study with nicardipine and trifluoperazine.

In the isolated myometrium obtained from pregnant women, diphenylhydantoin inhibited both spontaneous and K(+)-evoked contractions within the same range of potency. Nicardipine was less effective in inhibiting spontaneous than K(+)-induced contractions, whereas trifluoperazine was only effective against spontaneous contractions. These results indicate that diphenylhydantoin may directly induce in vitro human myometrium relaxation by mechanisms that differ markedly from those induced by nicardipine and trifluoperazine.