Pharmacokinetics and pharmacodynamics of bambuterol, a long-acting bronchodilator pro-drug of terbutaline, in young and elderly patients with asthma.

Disposition and efficacy of bambuterol were studied in 10 younger (20 to 37 years) and 10 older (69 to 76 years) patients with asthma (nine men and 11 women) at steady state, after single daily doses of 20 mg (50 mumol) for 1 week. There was a greater area under the concentration versus time curve for terbutaline during a dose interval in older patients compared with younger patients (558 +/- 171 and 376 +/- 149 nmol.hr/L, respectively [mean +/- SD], p less than 0.021). This was reflected in a lower apparent plasma terbutaline clearance in older patients compared with younger patients (1.22 +/- 0.33 and 2.32 +/- 1.26 L/hr/kg, respectively, p less than 0.023). Peak drug concentration was not different by age. Plasma cholinesterase levels were depressed by about 70% in both groups compared with pretreatment activity. Peak expiratory flow rate increased in both groups. Improvement in forced expiratory volume in 1 second and forced vital capacity was detected only in the younger patients. A small decrease in heart rate and diastolic blood pressure occurred in both patient groups. Bambuterol appears to offer the possibility of once-daily therapy in both younger and older patients with asthma.