Effects of itopride hydrochloride on the delayed rectifier K+ and L-type Ca2+ currents in guinea-pig ventricular myocytes

The effects of itopride hydrochloride, a new drug used to regulate motility in the gastrointestinal tract, on the delayed rectifier K+ current (TK) an d the L-type Ca2+ current (I-Ca) were evaluated in guinea-pig ventricular m yocytes at concentrations of 1, 10 and 100 muM to determine whether the dru g has a proarrhythmic effect through blockade of I-K Itopride did not affec t I-K at concentrations of 100 muM or less, and no significant effects of 1 , 10 or 100 CI M itopride were observed on the inward rectifier K+ current (I-K1) responsible for the resting potential and final repolarization phase of the action potential. We next investigated the effects of itopride on L -type Ca2+ current (I-Ca). Significant inhibition of I-Ca was observed at i topride concentrations greater than 10 muM These results suggested that ito pride hydrochloride has an inhibitory effect on I-Ca at concentrations much higher than those in clinical use.