Inhaled and oral salbutamol: How effective in the prophylaxis of asthma?
Inhaled and oral salbutamol were compared in 12 asthmatic patients for prophylaxis in antigen induced asthma. The patients were pretreated with 0.2- and 1.0-mg doses of inhaled salbutamol and with the standard oral 4- and 8-mg slow-release (SR) salbutamol preparations. Bronchodilatation was monitored over the ensuing 3 h and protection against antigen challenge at the end of the period. On each study day the degree of baseline airway hyperreactivity was determined by histamine challenge. Precautions were taken during the antigen challenge to ensure a reproducible response. Blood levels of salbutamol were monitored at hourly intervals for the 3 h after treatment and during the asthmatic reaction subsequent to challenge. Both the 0.2- and 1.0-mg inhalations caused immediate bronchodilatation as compared to a placebo (p < 0.05), but only the 1.0 mg dose protected subjects against antigen challenge (p < 0.05). In comparison to the placebo, no bronchodilatation was achieved with the standard 4-mg oral preparation in spite of measurable blood levels, nor were the patients protected against antigen challenge at 3 h after pretreatment. However, the 8-mg SR salbutamol caused significant bronchodilatation within 2 h and suppressed antigen challenge responses as compared to placebo (p < 0.05). It can be concluded that doses of inhaled salbutamol higher than the conventional 0.2- or the standard 4-mg oral preparations are required to protect asthmatics against inadvertent antigen exposure. In patients who are unable to use inhalers effectively, the SR preparation can be considered as an alternative.