Effect of nialamide and methyldopa on the analgesic action of morphine in rats and mice

Abstract

Methyldopa and nialamide enhance the analgesic action of morphine when administered separately in the rat. However, the association of both drugs in the same animal diminishes the effect of the analgesic. Results observed in mice differ from those found in rats, whereas methyldopa induces a slight increase in morphine analgesic effect, nialamide is ineffective. The administration of both drugs in combination increases morphine effect in a way similar to that obtained when methyldopa and morphine are administered together.