Abstract: Repetitive administrations of cocaine over a period of days causes the animal body to become more sensitive to the drug. A dose of cocaine that was not toxic to a novice user may be toxic or even lethal to an habituated user. These toxic effects include craving, seizures, brain ischemia and death. The mechanism of action of these toxic effects appears to be through the glutamatergic neurotransmitter system as evidenced by blocking with antagonists for N-methyl-D-aspartate receptors. However, these antagonists have undersirable side effects. Applicant demonstrates that the toxic effects of repetitive cocaine administrations can be reversed by the administration of inhibitors of the enzyme nitric oxide synthase which is also involved in the neurotransmitter system. The drugs which inhibit the enzyme nitric oxide synthase include N-nitro-L-arginine and N-nitro-L-arginine methyl ester. The method of treatment with these drugs includes administration in various forms by various routes.