Electrophysiological effects of oral isradipine (Lomir, Sandoz)

Electrophysiological effects of oral isradipine were studied. There are controversial references about the presence of its selective negative chronotropic influence from in vitro and in vivo studies using intravenous route. The authors administered 7.5 mg and 2.5 mg of isradipine orally in two groups of patients. Electrophysiological parameters were measured by use of the transoesophageal atrial pacing prior to the administration and 120 minutes after it. Significant fall in blood pressure was observed in both groups. Changes of atrioventricular nodal parameters such as stimulus-R interval. Wenckenbach point and probable effective refractory period of atrioventricular node showed positive dromotropic effect on artioventricular conduction, but the negative chronotropic action was not proved. On the contrary, the mean sinus cycle length shortened significantly in both groups and the maximal sinus node recovery time decreased after isradipine. The extent of changes of both sinus and atrioventricular nodal parameters is similar and is not consistent with selective effect of isradipine on sinus node.