Inhibitors of nitric oxide synthase and the opioid withdrawal syndrome

The NOS inhibitors L-NARG and L-NAME attenuate weight loss and wet dog shakes, two specific signs of opioid withdrawal in rats. NMMA is more potent than L-NAME, consistent with the in vivo actions of these compounds as inhibitors of NOS. In addition, NMMA antagonizes naloxone-induced jumping in morphine-dependent rats. The NOS inhibitors generally increase teeth chattering in precipitated withdrawal. The profile of the diminished withdrawal signs produced by these drugs differs from that produced by clonidine, which stimulates locomotor activity and does not increase teeth chattering in precipitated opioid withdrawal (Kimes et al. 1990). These findings suggest that administration of inhibitors of NOS may be an effective treatment of the opioid withdrawal syndrome alone or in combination with clonidine (U.S. patent #5,225,40).