Elers, J. (2012). Can therapeutic use of terbutaline be distinguished from doping use with a urine sample. Presentation 1393 at the 59th Annual Meeting of the American College of Sports Medicine, San Francisco, California; May 29-June 2, 2012.

This study examined urine and serum concentrations after therapeutic use of single and repetitive doses of inhaled terbutaline and supratherapeutic use of a single oral dose of terbutaline. Concentrations in asthmatics (N = 10) with regular use of beta2-agonists prior to the study and healthy Ss (N = 10) with no previous use of beta2- agonists were compared. Ss were administrated 2 mg inhaled and 10 mg oral terbutaline on two study days. The healthy Ss were also administrated 1 mg inhaled terbutaline every second hour (total 4 mg), which is the maximum permitted daily dose by the World Anti-Doping Agency (WADA). Blood samples were collected at baseline, 30 minutes, 1, 2, 3, 4, and 6 hours after the first inhalations. Urine samples were collected at baseline, 0-4 hours, 4-8 hours, and 8-12 hours after the first inhalations.

Median (IQR) urine concentrations peaked in the period 0-4 hours after inhalation with Cmax 472 (324) ng x mL-1 in asthmatics and 661 (517) ng x mL-1 in healthy Ss, and 4-8 hours after oral use with Cmax 666 (877) ng x mL-1 in asthmatic and 402 (663) ng x mL-1 in healthy Ss. All urine concentrations were corrected for the urine specific gravity.

There were no significant differences in urine and serum concentrations between asthmatic and healthy Ss. When urine and serum concentrations were compared after therapeutic inhaled doses and supratherapeutic oral doses, significant statistical differences were observed in both groups. There was high variability in urine concentrations between Ss in both groups. The variability between Ss was still present after the samples were corrected for urine specific gravity. When evaluating these results it was impossible to distinguish between permitted therapeutic use and prohibited supratherapeutic use based on doping tests with urine and blood samples.

Implication. WADA tests for the use of terbutaline are not sufficiently sensitive to discriminate between permitted and prohibited doses. The marked inter-individual variability makes it even more confusing to the point that the WADA tests for this substance are unreliable.

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