Since 2010, the World Anti-Doping Agency (WADA) has introduced urinary thresholds for some beta2-agonists. In doping analysis urine samples of beta2-agonists are not corrected for the Urine Specific Gravity (USG) by the
WADA laboratories. Several studies have observed high differences in the urine concentrations of beta2-agonists when correction for USG is compared with no correction, as well as high inter-individual variability between subjects. However, no studies have measured the intra-individual variability after inhalation of the long-acting beta2-agonist salmeterol. As such, the purpose of this study was to measure the intra-individual variability in the urine concentrations of salmeterol and its metabolite a-hydroxysalmeterol. Furthermore, to highlight the variability between corrected and uncorrected urine samples for USG. Urine samples from 20 subjects were analyzed for USG, urine excretion and urine concentrations of salmeterol and a-hydroxysalmeterol. Seven of the subjects underwent a second visit with the same procedures. At each visit 100 µg salmeterol was administered by inhalation. Urine samples were collected before administration of the drug (T0) and 4 (T4), 8 (T8) and 12 (T12) hours after administration. The mean relative
differences in the urine concentrations of salmeterol and a-hydroxysalmeterol between USG corrected and uncorrected samples were 43 ± 44, 27 ± 42 and 56 ± 87% at T4, T8 and T12, respectively. The intra-individual variability in the
urine excretion of salmeterol and a-hydroxysalmeterol during visits one and two were 12.6 and 21.8%, respectively. The intra-individual variability of salmeterol and a-hydroxysalmeterol in the urine concentrations were significantly higher when uncorrected for USG with 43.0 and 43.7% versus 20.4% (p<0.01) and 28.0% (p<0.05), respectively. Correction for USG reduces inter-individual and intra-individual variability in urine concentrations of salmeterol and
a-hydroxysalmeterol.