reserpine , 2 mg/kg 3 hr before drugs , potentiated catalepsy produced by analgesics , while haloperidol , 0.2 mg/kg , 2 hr earlier , did not influence morphine and codeine catalepsy , but moderately potentiated fentanyl-induced catalepsy . alpha-methyl-p-tyrosine potentiated the cataleptogenic action of fentanyl and codeine , and also , less markedly , the action morphine .
C0009214
codeine
C0026549
morphine