Allergen-induced changes in adenosine 5'-monophosphate bronchial responsiveness: effect of nedocromil sodium.

Bronchial hyperresponsiveness to adenosine 5'-monophosphate (AMP) was studied after allergen challenge in allergic asthmatic patients. Measurements were made with and without nedocromil sodium pretreatment. Nedocromil sodium inhibited both the early and late asthmatic reactions (P < .01). After allergen challenge a significant decrease in PC20 AMP from 12.2 mg/mL to 4.47 mg/mL (P < .05) at three hours was found, returning almost to baseline values: 10.85 mg/mL (P > .05) at 24 hours. Nedocromil sodium, 6 mg, given before allergen challenge prevented the increased responsiveness to AMP at three hours [PC20 10.12 mg/mL (P < .05)], but caused a decrease in PC20 AMP at 24 hours to 6.32 mg/mL (P < .05). Desensitization of the adenosine receptor during the late asthmatic reaction, which is prevented by nedocromil sodium, may explain the lack of increased responsiveness at 24 hours. AMP may play a physiologic role in allergen-induced late phase reactions.