Intravenous salbutamol and aminophylline in asthma: a search for synergy

The bronchodilation produced by increasing intravenous doses of aminophylline, salbutamol, and a combination of aminophylline and salbutamol given in random order was determined in 10 stable asthmatics on three consecutive days. On a fourth day, response to placebo injections was determined. Forced expiratory volume in one second (FEV1) was measured at two-minute intervals after each dose until FEV1 returned to a new baseline. At no dosage level was there synergy between the two agents in terms of either mean percentage increase in FEV1 or the integrated response. The failure to demonstrate synergy has implications both with respect to the clinical use and the underlying mechanism of action of these drugs.