Droperidol

Droperidol produces mild α-adrenergic blockade and peripheral vascular dilation. Droperidol has been shown to block potassium efflux in the myocardium in isolated animal ventricular myocytes, resulting in a dose-dependent delay in repolarization. Droperidol has also been shown to induce early depolarizations in isolated animal Purkinje fibers. ^[1]

Droperidol (0.01 mM-0.3 mM) increases in a dose-dependent fashion action potential duration (APD) without altering the other parameters in rabbit Purkinje fibers stimulated at 60 pulses/min. Droperidol (1 mM-3 mM) leads to the reversal of the prolonging effect in rabbit Purkinje fibers. Droperidol (10 mM-30 mM) produces shortening in APD at 50% repolarization concomitantly with a significant decrease in Vmax, action potential amplitude and resting membrane potential in rabbit Purkinje fibers. Droperidol exerts a dual effect on repolarization, prolongation with low concentrations with development of EADs and subsequent triggered activity in rabbit Purkinje fibers. ^[2] Droperidol (3 mg/kg, single dose) decreases dose dependently not only locomotion and rearing frequencies in the open-field but also the apomorphine effects of rats. Droperidol (3 mg/kg, long term administration) induces significant tolerance to all parameters of activity recorded in the open-field in rats. Droperidol withdrawn produces an augmented responsiveness to apomorphine-induced stereotyped behavior. ^[3]