A COMPARISON OF THE BRONCHODILATOR ACTIVITY OF BENADRYL WITH SOME OF ITS DERIVATIVES AND CERTAIN OTHER SUBSTANCES

¹ Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill

A comparison of the bronchial antispasmodic action of Benadryl, some of its derivatives and certain other substances has been made in isolated lungs and on bronchial muscle in situ.

In the isolated perfused guinea pig lungs, Benadryl and its monomethyl (S-59) and isopropyl (S-82) derivatives were the most effective compounds in preventing histamine constriction. Furthermore, these three compounds caused an additional dilatation of the lungs even in the presence of a constrictor dose of histamine. The other compounds investigated varied in effect from practically no antagonism to complete prevention of the histamine constriction.

On dogs' bronchi in situ, S-154 and S-59 appeared to relieve previously induced histamine bronchospasm faster than Benadryl. However, Benadryl was more consistent and reliable in producing bronchodilatation. S-82 was the least effective compound in relieving acute bronchial spasm.

The duration of action of the most effective S-compounds, following their injection prior to histamine, may be compared as follows: Benadryl > S-59 > S-82> S-154.

The other agents investigated (S-92, S-157 and S-158) were either weak in immediate antagonism to histamine or had a very short duration of action.