Both Methysergide and Methylergometrine displace the concentration-response curve of 5-HT to the right and depressed the maximum effect ; thus, both agents behaved as non-competitive antagonists of 5-HT. Methylergometrine is approximately 40-times more potent than Methysergide as an antagonist of the 5-HT-induced responses, since the calculated apparent pA2 values are 9.6 and 8.0, respectively.

Methylergometrine is more potent than Methysergide as a vasoconstrictor on bovine middle cerebral artery and human coronary arteries, an effect on 5-HT1B receptors. Subacute oral administration would result in metabolism of Methysergide to Methylergometrine.