Recent preclinical and clinical studies (Crain, Gan, Levine, Joshi) have shown that co-treatments with extremely low doses of opioid receptor antagonists can markedly enhance the efficacy specific to Morphine and related analgesics. Crain did studies using Naloxone, in-vitro and in-vivo, that show direct competitive antagonism of Gs coupled excitatory opioid receptor functions. This markedly enhances Morphine’s antinociceptive potency and simultaneously attenuates opioid tolerance and dependence.