Quantitative detection of inhaled formoterol in human urine and relevance to doping control analysis

Formoterol is a frequently prescribed β(2)-agonist used for the treatment of asthma. Due to performance-enhancing effects of some β(2) -agonists, formoterol appears on the prohibited list, published by the World Anti-doping Agency (WADA). Its therapeutic use is allowed but restricted to inhalation. Since the data on urinary concentrations originating from therapeutic use is limited, no discrimination can be made between use and misuse when a routine sample is found to contain formoterol. Therefore the urinary excretion of six volunteers after inhalation of 18 µg of formoterol was investigated. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of formoterol in urine samples. Sample preparation consists of an enzymatic hydrolysis of the urine samples, followed by a liquid-liquid extraction at pH 9.5 with diethyl ether/isopropanol (5/1, v/v). Analysis was performed using selected reaction monitoring after electrospray ionization. The method was linear in the range of 0.5-50 ng/ml. The limit of quantification (LOQ) was 0.5 ng/ml. The bias ranged between -1.0 and -6.8 %. Results for the urinary excretion show that formoterol could be detected for 72 h. The maximum urinary concentration detected was 8.5 ng/ml without and 11.4 ng/ml after enzymatic hydrolysis. Cumulative data showed that maximum 11.5% and 23% of the administered dose is excreted as parent drug within the first 12 h, respectively, non-conjugated and conjugated. Analysis of 82 routine doping samples, declared positive for formoterol during routine analysis, did not exhibit concentrations which could be attributed to misuse.