Evaluation of some cardiovascular effects of midazolam, an imidazobenzodiazepine

ABSTRACT

Interavenous administration of midazolam in three tested dose levels [0.7, 1.4 and 2.8 mg/kg] in rabbits was accompanied directly after injection by an abrupt fall in the blood pressure. The effect was decreased with time and at the end of the 30 minutes period of exposure to the drug, the mean blood pressure returned nearly to its normal value. During the administration of each dose of the drug the heart rate remained stable till the end of the 30 minutes period of investigation and no significant changes were observed in ECG patterns of animals. On isolated perfused rabbit's heart preparation midazolam at the three tested dose levels [0.3125, 0.625 and 1.25 mg] caused a marked reduction in both the amplitude and the rate of cardiac contracion. Midazolam in a dose level of 5 mg/kg restored the normal cardiac rhythm in anaesthetized guinea pigs in which cardiac dysthrythmia was induced by ouabain and barium chloride. The drug, however, failed to reverse the cardiac dyshyrthmias induced by aconitine and digoxin. A possible correlation between the antidysrthythmic activity of midazolam and cardiac electrolyte levels is discussed