A comparison of methacholine and histamine inhalations in asthmatics.

Bronchial provocation tests using aerosolized serially diluted histamine and methacholine were given to nearly 200 asthmatics. Results were usually reproducible for a given patient and corticosteroids did not influence the procedures. Those patients who could tolerate high doses of methacholine were statistically the least severe asthmatics as measured by their discharge dose of corticosteroids. Reaginmediated asthmatics could not tolerate the higher doses of histamine. These tests help delineate subgroups of asthmatics and may have clinical usefulness since, when combined with other data, they differentiate pathogenetic mechanisms in some patients and suggest therapeutic approaches in others.