Effect of sodium cromoglycate on histamine inhalation tests

Sixteen adult asthmatic subjects in a clinical steady state were included in the study. On day 1, after baseline assessment of spirometry (FEV1, FEV1/FVC, FEF25-75), they underwent three to four consecutive inhalation tests using twofold increasing doses of histamine to measure the provocative concentration causing a fall in FEV1 of 20% (PC20). Baseline FEV1 was back to +/- 5% of the initial assessment before each histamine inhalation test (HIT). On days 2, 3, and 4, after baseline spirometry which confirmed that FEV1 was within 10% of initial day 1 assessment, placebo-lactose (P) or 40 mg of sodium cromoglycate (SCG) were nebulized in a double-blind randomized 4.3.1. two-treatment crossover study design. Ten minutes later, spirometry was repeated and followed by an HIT. Baseline spirometry was not significantly different on each day or after P and SCG. There was no statistical difference between the geometric means of the three or four PC20's done on day 1, indicating that there is no tachyphylaxis induced by repeated HIT. There was no statistical difference between mean PC20 after P (0.52 +/- 3.3 (SD) mg/ml), after SCG (0.50 +/- 3.2), and of the three to four HIT done on day 1 (0.40 +/- 3.6). We conclude that in asthmatic subjects SCG has no acute bronchodilator effect and does not alter the response to inhaled histamine.