Speed of onset of bronchodilator response to salbutamol inhaled via different devices in asthmatics: a bioassay based on functional antagonism.
OBJECTIVE
To evaluate the speed of onset of bronchodilation following salbutamol administered via a metered-dose inhaler with a spacer (pMDI + Volumatic) and a dry-powder inhaler (Diskus), as well as the relative potencies of these devices in asthmatic patients with methacholine-induced bronchoconstriction.


METHODS
Eighteen patients inhaled methacholine (MCh) until FEV(1) decreased by 35% of control. Following administration of placebo, 200 microg salbutamol or 400 microg salbutamol through the pMDI + Volumatic or the Diskus, we calculated the time elapsed from drug administration and the appearance of a 90% increase in post-MCh forced vital capacity (FVC), FEV(1) and volume-adjusted mid-expiratory flow (recovery times). The salbutamol doses to be delivered by the two inhalation devices to achieve similar recovery times and the relative potencies of the devices were calculated by using the 2-by-2 Finney parallel regression method.


RESULTS
For all functional variables, recovery times were significantly (P < 0.01) shorter in pMDI + Volumatic than Diskus trials. The salbutamol doses to be delivered by the Diskus to achieve recovery times for FVC, FEV(1) and volume-adjusted mid-expiratory flow similar to those obtained with 200 microg salbutamol administered via the pMDI + Volumatic were 558 (95% CI 537, 579) microg, 395 (95% CI 388, 404) microg and 404 (95% CI 393, 415) microg, respectively, and corresponded to relative potencies of 2.79 (95% CI 2.68, 2.90), 1.98 (95% CI 1.94, 2.02), and 2.02 (95% CI 1.96, 2.07).


CONCLUSIONS
Administration of salbutamol via the pMDI + Volumatic provides faster reversal of induced bronchoconstriction than via the Diskus. The salbutamol dose targeting the lungs with the pMDI + Volumatic is approximately twice that with the Diskus.
Lavorini
Federico
F
Dipartimento di Area Critica Medico Chirurgica, Unità Funzionale di Medicina Respiratoria, Università degli Studi di Firenze, Italia. f.lavorini@dac.unifi.it
Geri
Pietro
P
Mariani
Laura
L
Marmai
Cecilia
C
Maluccio
Nazzarena Maria
NM
Pistolesi
Massimo
M
Fontana
Giovanni A
GA
D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D000420:Albuterol / Q000008:administration & dosage* / Q000493:pharmacokinetics; D001249:Asthma / Q000188:drug therapy* / Q000503:physiopathology; D016084:Bronchoconstriction / Q000187:drug effects; D001993:Bronchodilator Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D036501:Metered Dose Inhalers; D014797:Vital Capacity / Q000502:physiology
D001993:Bronchodilator Agents; D000420:Albuterol