Urinary and blood concentrations of β2-agonists in trained subjects:: Comparison between routes of use

We aimed to assess the plasma and urine concentrations of beta(2)-agonists and evaluate the difference between three routes of administration in trained adults in order to distinguish doping from prevention of exercise-induced asthma. Ten young healthy Caucasian male subjects received during a four treatment period study: 1) inhaled salbutamol (S-1) 2 x 100 mu g t.i.d. for 3 clays, 2) inhaled formoterol (F-1) 2 x 12 mu g b.i.d. for 3 days, 3) a single salbcutaneous injection of salbutamol (S-S) 0.5 mg, and 4) salbutamol 2 x 2 mg t.i.d. orally for 3 days (SO). Blood samples were taken during the first and the third day of experimentation at baseline, 30 min, 1 h, 2 h, 4 h and 6 h after administration; additional blood samples were drawn at 15 min for S-1, S-S and F-1 and at 42 h for F-1. Urinary samples were collected at baseline, 2 h, 4 h, 6 h and 12 h after administration. Urinary concentrations were 20 to almost 50 times higher after S-0 than after S-1. Mean urinary concentration after S-0 increased to above 800 ng . mL(-1) within the two hours and above 1000 ng . mL-1 at 6 to 12 hours post-drug administration. Urinary concentrations after S-S were maximal during the first 2 hours (mean: 340 +/- 172 ng . mL(-1)). Plasma concentrations were very low, whatever the routes of administration. Results showed that we could eliminate the use of S-1 (authorized) and S-S administration when individual urinary concentrations are higher than 230 ng . mL(-1) and 615 ng . mL(-1), respectively. Therefore, at rest, the cut-off value used to discriminate therapeutic from doping salbutamol intake could be fixed at 250 ng . mL(-1) instead of the 1000 ng . mL(-1) still authorized by international committees.