Effects of salbutamol and isoprenaline-phenylephrine in reversible airways obstruction

Abstract

Ventolin (salbutamol) and Medihaler-Duo (isoprenaline/phenylephrine combination) standard pressurized inhalers were used to administer doses of two or six "puffs" to 16 patients with known reversible airways obstruction. The doses were administered in random order over two days. Both the Ventolin and Medihaler-Duo inhalers substantially increased FEV(1), but in the doses used salbutamol was more effective than isoprenaline/phenylephrine (P < 0.01). There was no significant difference between two and six puffs of salbutamol, though there seemed to be an advantage of six puffs of isoprenaline/phenylephrine over two puffs (P < 0.05). Adrenaline (1/1,000) 0.5 ml and atropine 0.6 mg produced similar increases in FEV(1) to those produced by salbutamol.The Pao(2) fell more than 5 mm Hg in three patients after salbutamol and in three after isoprenaline/phenylephrine. There was no significant fall in mean Pao(2) in any of the treatment groups. It is concluded that the Ventolin inhalant, administered in the conventional dose of two puffs, is as effective a bronchodilator as subcutaneous adrenaline and atropine, is more effective than the Medihaler-Duo, and is without detectable side effects.