A dose-response study of inhaled terbutaline administered via Nebuhaler or nebuliser to asthmatic children

Abstract

In 12, symptom-free, asthmatic children, aged 5-10 years, responses (increases in FEV1) were measured to cumulative doses of inhaled terbutaline delivered by two methods: a) 5 breaths from a 750 ml spacer (Nebuhaler) attached to a metered dose aerosol (doses were 0.5, 1, 2 and 4 mg); and b) by face mask attached to a Bennett twin-jet nebuliser containing terbutaline solution (doses were 1, 2, 4 and 8 mg in 2 ml). Responses were dose-related by both methods and the log dose-response lines were parallel. Twice the dose of nebulised terbutaline was required to give responses equivalent to those seen with the Nebuhaler (significant difference between the lines, ANOVA, P = 0.05). The highest doses given by either method resulted in achievement of at least 80% of the maximum possible improvement in respiratory function (i.e. predicted FEV1 (50th centile) minus basal FEV1) with no effects on pulse rate. Thus, the use of the Nebuhaler with terbutaline metered dose aerosol is at least as effective as administration of the same total dose by nebuliser in children who are not in acute respiratory difficulty. Also, it produces a dose-related bronchodilator effect, without pulse-rate effects, for doses of terbutaline between 0.5 to 4 mg (2 to 16 puffs of the metered dose (0.25 mg) aerosol).