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 Pr oventil are being phased out of production. In terms of delivery of albuter ol 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 a nd three actuations each of Spires and Ventolin (90- and 270-mu g albuterol base). A methacholine challenge (Cockcroft method) was initiated 3 h befor e and 0.25 h after albuterol. Predose PC20FEV1 values were not significantl y different between study days. Postdose PC20FEV1 results met standard bioa ssay study validity criteria: i.e., a significant dose-response relationshi p was present (p = 0.0002); tests for deviation from parallelism and overla p of dose-response curves were nonsignificant (p = 0.08, 0.69). By using Fi nney 2-by-2 bioassay analysis, we estimate that each Spires actuation deliv ers 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 differenc es in markers of systemic effects (vital signs, potassium, and blood glucos e concentrations). We conclude that Spires and Ventolin inhalers deliver co mparable quantities of albuterol to the airways.