Intravenous cocaine challenges during naltrexone maintenance: A preliminary study

Abstract

In 1976 Byck hypothesized that opioid antagonists would block the euphoric effect of cocaine, and recent clinical observations have suggested lower rates of cocaine abuse by people receiving naltrexone (NTX) than by those receiving methadone (Kosten et al 1989). Although early workers found that both rodents and primates maintained on antagonists showed no attenuation of cocaine self-administration (Killian et al 1978; Carroll et al 1986), more recent studies have found attenuation with NTX administration (Mello et al 1990; DeVry et al 1989; Ramsey and van Ree 1991). Furthermom, Bain and Kornetsky (1987), using rewarding brain stimulation in rodents, showed that the antagonist naloxone can reverse cocaine's potentiation of this stimulation. An early human study using cocaine administration found a potentiation rather than a reduction of cocaine effect after acute high-dose naloxcne (20 mg i.e.; Byck et al 1982), but this situation is clearly different from maintenance blocking with lower doses of NTX. We therefore undertook the current cocaine challenge study during chronic NTX.