The Comparative Bronchodilator Properties of Alkyl Quaternary Salts of Promethazine

Several salts of thiazinamium, a quaternary analogue of promethazine, administered by aerosol, possessed equipotent anticholinergic activity in anesthetized guinea pigs but the duration of this effect differed somewhat. N-Butyl substitution in the side chain, but not the corresponding ethyl or n-propyl substitutions, reduced the aerosol anticholinergic potency and duration. There was also a tendency for a corresponding reduction in antihistaminic activity with different alkyl substitutions and for a greatly reduced duration of this effect.