Distinction of inhaled and oral salbutamol by urine analysis using conventional screening procedures for doping control

Salbutamol administration in athletes is permitted only by inhalation, for the management of asthma. The authors discuss different criteria for suspecting oral use of salbutamol, taking into account the data obtained by application of two conventional screening procedures for doping control: gas chromatography/mass spectrometry (GC/MS) and enzyme-linked immunosorbent assay (ELISA). Urine samples obtained after administration of oral and inhaled salbutamol to asthmatic and nonasthmatic swimmers were analyzed using both analytical approaches. As expected, concentrations obtained by the ELISA rest (detection of total salbutamol) were higher than those obtained using the GC/MS procedure (detection of nonsulfated salbutamol). After oral administration, the ELISA test detected significantly higher salbutamol concentrations than those detected after inhalation, reflecting the greater doses administered orally. Urine samples with total salbutamol greater than 1400 ng/mL were obtained after oral doses, bur no sample reached this value after inhaled doses. Higher concentrations of nonsulfated salbutamol have also been detected after oral intake, although there is an overlap between the distributions of concentrations after oral and inhaled doses. A cut-off concentration of 500 ng/mL can be used for nonsulfated salbutamol to select suspicious samples, giving 11.8% false negative results and 4.3% false positive results. An additional criterion evaluated was the androsterone-salbutamol peak height ratio, which was lower after oral doses because of the higher concentrations of salbutamol in urine. This ratio was lower than 2 for all the samples collected after oral administration, although 6.8% false positive samples resulted because of low concentrations of androsterone in female urine. Several possibilities for detecting supsicious samples from athletes who have taken prohibited oral salbutamol are available with conventional screening procedures in doping control.