Caffeine potentiates methamphetamine-induced toxicity both in vitro and in vivo

► Combination of non-toxic doses of methamphetamine and caffeine significantly reduces the viability of SK-N-SH cells. ► Combination of methamphetamine and caffeine increases the ROS production and Bax/Bcl-2 ratio in SK-N-SH cells. ► Co-administration of methamphetamine and caffeine decreases the survival rate of rats and increases the TBARS levels in striatal tissues. ► The results indicate that caffeine potentiates the toxic effects of methamphetamine both in vitro and in vivo.