The case of a 25-year-old male with methamphetamine dependence indicating the presence of synergism between methamphetamine and alcohol was reported. The three clinical features observed in the present case were: First, ingesting large quantities of alcohol after an intravenous injection of the psychostimulant induced psychomotor excitement, indicating that alcohol itself could potentiate the psychosis-inducing action of the psychostimulant. Second, repetition of the alcohol intake without the

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... rug injection reactivated a psychotic state, suggesting that there is a cross-reverse tolerance phenomenon to alcohol. Third, drug injection alone, twice aggavated the psychiatric symptoms, indicating the presence of reverse tolerance to the psychostimulant.