Metabolic and cardiovascular effects of carbuterol and metaproterenol

Metabolic and cardiovascular responses to selective beta-adrenergic bronchodilators, carbuterol and metaproterenol, were studied during an asymptomatic period in 8 male subjects with bronchial asthma diagnosed as mild to moderate. On separate days each individual received either placebo, carbuterol 2 mg, carbuterol 4 mg, or metaproterenol 20 mg orally in a double-blind fashion. Subsequently, metabolic and cardiovascular responses were measured periodically for 5 hr. Carbuterol 2 mg was indistinguishable from placebo except for small elevations of glucose at 3 and 4 hr. Carbuterol 4 mg produced significant increases in glucose, insulin, lactate, and free fatty acids as well as in pulse rate and arterial pulse pressure. Metaproterenol produced increases only in plasma glucose and insulin. The majority of patients reported drug-related side effects which were all mild, after taking either carbuterol 4 mg or metaproterenol 20 mg. Fewer subjective side effects were noted with carbuterol 2 mg. These findings indicate that a 2-mg dose of carbuterol can be administered to typical asthmatic subjects without significant subjective or objective side effects. The larger dose (4 mg) may be accompanied by a greater frequency of side effects.