Combined use of an
opioid with a psychostimulant is popular among drug abusers. Such "polydrug use" may increase
drug effects or attenuate adverse effects of either
drug alone. We proposed that a combination of
methamphetamine (meth) and
morphine may change physical
opioid withdrawal symptoms. Adult male rats were chronically injected with cumulative subcutaneous (s.c.) doses of
morphine, meth or a combination of both drugs within five days. On day six, a challenge dose of the same
drug was injected. Two hours later, precipitated
withdrawal symptoms were scored within 30 minutes after
naloxone (1mg/kg, i.p.) injection. Both frequency and incidence of jumping significantly increased in combined treated animals (P<0.05). The sole emergent symptom in combined treated animals was digging which we consider as another escaping behavior in addition to jumping. Our findings imply that combined use of meth and
morphine may exacerbate averseness of
morphine withdrawal which may cause more intense
opioid dependence.