Effects of vecuronium-induced histamine N-methyltransferase inhibition on cutaneous responses to histamine

All muscle relaxants inhibit histamine N-methyltransferase in vitro, but vecuronium, a steroid-derived muscle relaxant, is the most potent inhibitor. It has been suggested that administration of vecuronium prior to giving a drug that releases histamine may exaggerate the hemodynamic or vascular effects. Volunteers were injected intradermally with 5×10^-4M concentrations of histamine, and the combination of vecuronium and histamine, to evaluate the in vivo significance. Vecuronium did not alter the measured wheal and flare responses to injected histamine at 5, 15, 30, 40, 50 and 60 mins. There is no evidence that inhibition of histamine N-methyltransferase in vivo will alter the vascular effects of histamine.