[The analgesic action of d-phenylalanine in combination with morphine or methadone]

The analgesic action of D-phenylalanine (D-Phe) is well known. It has been demonstrated in hot-plate tests on mice that combining D-Phe with narcotic analgesics already with doses inactive on separate application. In combination with D-Phe, a dose of morphine less by half compared to its unique use does not reduce analgesic activity in rats, but after six weeks of treatment some undesirable side effects like dependence, behavioural disorders and growth retardation are markedly lowered. These results suggest the possibility to design a combined drug similarly effective as well-introduced narcotic analgesics, but better tolerated.