tokens: H1 - and H2 - histamine antagonists or placebo were given before dosing with d - tubocurarine in a randomized double - blind fashion to four groups : group 1 - - placebo ; group 2 - - cimetidine , 4 mg / kg , plus placebo ; group 3 - - chlorpheniramine , 0 . 1 mg / kg , plus placebo ; and group 4 - - cimetidine plus chlorpheniramine .