Tetrazolast (also known as MDL 26,024GO) is a tetrazoloquinoline derivative patented by Merrell Dow Pharmaceuticals, Inc. as an antiallergic and antiasthmatic agent. Tetrazolast was shown to be an orally absorbed mediator release inhibitor in the rat passive cutaneous anaphylaxis and passive peritoneal anaphylaxis tests. In addition, the compound was shown to both elicit and inhibit elicitation of the Bezold-Jarisch reflex in the dog. Tetrazolast also significantly reduced Ascaris-induced changes in pulmonary mechanics in cynomolgus monkeys. The compound inhibited both early and late phase antigen induced-changes in Ascaris-sensitive sheep, as well as the increased airway hyperreactivity which normally follows antigen challenge.