EVALUATION OF PLASMA AND URINARY SALBUTAMOL LEVELS IN COPD

Objective: To evaluate the use of trough plasma salbutamol and overnig ht urinary salbutamol excretion in the assessment of nebulised salbuta mol delivery in patients with chronic obstructive pulmonary disease (C OPD). Methods: Twenty in-patients with COPD receiving nebulised salbut amol, age 69.7 years, FEV(1) 38.1% predicted, were studied on two cons ecutive days, receiving four 2.5 mg doses of nebulised salbutamol on d ay 1 and four 5 mg doses of nebulised salbutamol on day 2, the first d ose at 8.00 h the last dose at 22.00 h. Salbutamol delivery was assess ed after the last dose by trough plasma salbutamol 8.00 h and overnigh t urinary excretion of salbutamol (22.00-8.00 h). Results: Levels of u rinary salbutamol were detectable in all 20 patients at both doses, wh ereas for plasma salbutamol detectable levels were only found in 16/20 cases at the 2.5 mg dose and in all cases at the 5 mg dose, For overn ight urinary salbutamol (mu g . 10 h(-1) n = 20) the results were 141 for 2.5 mg and 249 for 5 mg. The dose ratio for urinary salbutamol bet ween 2.5 mg and 5 mg doses was 1.83, Results for plasma salbutamol (ng /ml, n = 16) were 1.58 at 2.5 mg and 2.43 at 5 mg: dose ratio (geometr ic mean) 1.49. Conclusion: Overnight urinary salbutamol provides a sim ple and effective measure of nebulised salbutamol delivery in patients with COPD, which would be suitable for studying nebuliser performance and compliance.