[The additive index--a new preclinical indicator of the addictive potential of analgesic agents]

A comparative study of analgesic and secondary-reinforcing properties of morphine, nalorphine, pentazocine and phencyclidine was carried out on mice. Different rations of their analgesic and reinforcement potencies were revealed. Based on these results, a new indicator--"addictive index" is proposed for characterization of the addictive potential of analgesics.