Dose- and time-dependent effects of mirtazapine on the expression of cocaine-induced behavioral sensitization in rats.

Relapse to cocaine use is a major problem in the clinical treatment of cocaine dependence. Antidepressant medications have been studied as potential therapeutic drugs to relieve a cocaine dependence disorder. Mirtazapine is an antidepressant implicated in reducing behavioral alterations induced by drugs of abuse. We have reported elsewhere that 30mg/kg mirtazapine administered for 30 days during cocaine extinction significantly attenuated the induction and expression of cocaine-induced locomotor sensitization and decreased the duration of the cocaine-induced locomotor effect. This study focused on exploring whether different mirtazapine dosing regimens could optimize and/or improve the effect of 30mg/kg mirtazapine administered for 30 days on cocaine-induced locomotor activity during the expression phase of behavioral sensitization. Our study revealed that the daily dosing regimen with a fixed dose of mirtazapine (30mg/kg ip) over 60 days improved the decrease in cocaine-induced locomotor activity and behavioral sensitization obtained by dosing of 30mg mirtazapine for 30 days. In addition, it showed that a dosing regimen of 30mg/Kg mirtazapine for 30 days managed to reduce cocaine toxicity. These results suggested that dosage of mirtazapine for 30 consecutive days may be an effective therapy.