Therapeutic equivalence of spiros dry powder inhaler and ventolin metered dose inhaler - A bioassay using methacholine

Because chlorofluorocarbons (CFCs) contribute to depletion of stratospheric ozone, CFC-containing metered-dose inhalers (MDIs) such as Ventolin and Proventil are being phased out of production. In terms of delivery of albuterol to the lungs, we compared an alternative delivery system, the Spires dry-powder inhaler (DPI), with Ventolin, using a methacholine challenge-based clinical bioassay. Twenty-four adults and adolescents with asthma completed this double-blind, four-period crossover study. Doses evaluated were one and three actuations each of Spires and Ventolin (90- and 270-mu g albuterol base). A methacholine challenge (Cockcroft method) was initiated 3 h before and 0.25 h after albuterol. Predose PC20FEV1 values were not significantly different between study days. Postdose PC20FEV1 results met standard bioassay study validity criteria: i.e., a significant dose-response relationship was present (p = 0.0002); tests for deviation from parallelism and overlap of dose-response curves were nonsignificant (p = 0.08, 0.69). By using Finney 2-by-2 bioassay analysis, we estimate that each Spires actuation delivers 1.12 times as much albuterol to the airways as one Ventolin actuation (90% confidence interval, 0.68 to 1.94). There were no significant differences in markers of systemic effects (vital signs, potassium, and blood glucose concentrations). We conclude that Spires and Ventolin inhalers deliver comparable quantities of albuterol to the airways.