Abstract

Pharmacological studies with a synthetic compound, Benadryl (β-dimethylaminoethyl benzhydryl ether hydrochloride), revealed the following:

1. A dilution of 1: 50,000,000 proved effective in antagonizing the spasmogenic effects of histamine on intestinal muscle whereas much larger doses were required to antagonize the effects of acetylcholine and barium. Benadryl possesses a degree of specificity against histamine which approaches the specificity of atropine against acetyicholine. In view of weak antagonism of barium, the term anti-histamine compound describes Benadryl more specifically than use of the generic term, musculotropic antispasmodic.

2. Secretion from denervated gastric pouches in dogs following stimulation with histamine was reduced approximately 40 per cent by pre-treatment with Benadryl. Evidence of inconsistency in results and lack of a pronounced inhibitory effect reduces the probability that a direct antagonism of the secretogogue action of histamine was involved.

3. Depressor effects of small doses of histamine and acetylcholine were decreased by intravenous administration of Benadryl in dogs. The possibility exists, therefore, that the relaxing effect of histamine on vascular smooth muscle was antagonized, as well as the contracting effect as demonstrated on intestinal muscle.

4. Adequate doses of Benadryl augmented the pressor response to epinephrine. There was no evidence of epinephrine reversal which has been demonstrated with several other synthetic drugs which possess some degree of anti-histamine action.