Pirbuterol hydrochloride: evaluation of beta adrenergic agonist activity in reversible obstructive pulmonary disease and congestive heart failure.
Pirbuterol hydrochloride is a beta 2 adrenergic agonist with a structure similar to that of albuterol, except for the substitution of a pyridine ring for the benzene ring. It is comparable in duration of action to albuterol when given by inhalation, but it is threefold less potent by weight. In man, pirbuterol and albuterol have similar beta 2 selectivity. In the acute therapy of chronic obstructive pulmonary disease, pirbuterol is most effective in oral doses of 15-20 mg, and by aerosol in doses of 400 micrograms or greater. Long-term studies of oral pirbuterol in doses between 30-60 mg/day are promising, but further research is warranted. The combination of pirbuterol's beta 2 and lesser beta1 activity has proven helpful in the therapy of refractory congestive heart failure. Improvement of function of both right and left ventricles and systemic and pulmonic circulations has been demonstrated acutely. Drug effect wanes, as with other beta adrenergic agonists, due to the development of tolerance; however, long-term benefit appears to persist in both pulmonary and cardiac patients. Pirbuterol will be marketed in the United States as 10 and 15 mg tablets and as a 200 micrograms per actuation metered dose aerosol for use in pulmonary patients only; it will not be approved for use in congestive heart failure. In terms of beta 2 selectivity, duration of action, potency and frequency of side effects, pirbuterol is comparable to the two beta 2 agonists already available in the United States, albuterol and terbutaline.