Isradipine, a dihydropyridine-class calcium channel antagonist, attenuates some of d-methamphetamine's positive subjective effects:: a preliminary study

Rationale: Dopamine (DA) pathways in the midbrain mediate d-methamphetamine's rewarding effects associated with its abuse liability. Isradipine, a dihydropyridine-class calcium channel antagonist, reduces the rewarding effects of psychostimulants such as cocaine and d-amphetamine, presumably by antagonizing these central DA pathways. This is the first experiment to test the hypothesis that the rewarding effects of d-methamphetamine, like other psychostimulants, can be reduced by isradipine. Objective: We studied the effects of high dose isradipine (0.21 mg/kg orally), on the positive subjective effects associated with the abuse liability of low and high dose d-methamphetamine (0.21 mg/kg and 0.42 mg/kg orally, respectively). Methods: Using a double-blind, double-dummy, placebo-controlled, Latin-Square, cross-over design, 18 healthy male and female volunteers received each of the following six treatments separated by a rest period of 2-7 days: a) placebo+placebo; b) low-dose d-methamphetamine+placebo); c) high-dose d-methamphetamine+placebo; d) high dose isradipine+placebo); e) low-dose d-methamphetamine+high dose isradipine, and f) high-dose d-methamphetamine+high dose isradipine. Results: d-Methamphetamine produced orderly increases in positive subjective measures of both stimulation and mood. Pre-treatment with isradipine significantly reduced some of these positive subjective effects and craving for d-methamphetamine. Conclusion: Isradipine as an anti-reward or craving reducing medication is a promising therapeutic agent for the treatment of d-methamphetamine dependence.