Urinary and Blood Concentrations of β₂-Agonists in Trained Subjects: Comparison between Routes of Use

Abstract

We aimed to assess the plasma and urine concentrations of β₂-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_I) 2 × 100 µg t.i.d. for 3 days, 2) inhaled formoterol (F_I) 2 × 12 µg b.i.d. for 3 days, 3) a single subcutaneous injection of salbutamol (S_S) 0.5 mg, and 4) salbutamol 2 × 2 mg t.i.d. orally for 3 days (S_O). 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_I, S_S and F_I and at 12 h for F_I. 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_O than after S_I. Mean urinary concentration after S_O 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_I (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.

Key words

β₂-agonists - doping - asthma - plasma and urinary concentrations

References

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