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The impact of acute and chronic administration of short-acting β2-agonists on urinary pharmacokinetics and athletic performance

Molphy, J (2015) The impact of acute and chronic administration of short-acting β2-agonists on urinary pharmacokinetics and athletic performance. Doctoral thesis, Liverpool John Moores University.

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Exercise Induced Bronchoconstriction (EIB) is common amongst elite athletes. Short-acting β2-agonists represent the first-line treatment of EIB, however; limited data currently exists examining the ergogenic and pharmacokinetic impact of chronic short-acting β2-agonist administration. Furthermore, the ergogenic impact of acute and chronic administration of short-acting β2-agonists in asthmatic individuals is unknown. Whilst the short-acting β2-agonist salbutamol is permitted in and out of competition due to a known pharmacokinetic response, no urinary threshold has been established for the use of the alternative short-acting β2-agonist terbutaline.
The purpose of study 1 was to investigate the ergogenic potential of the WADA upper daily limit of 1600 μg·day-1 salbutamol every day for 6 weeks versus placebo, alongside combined resistance and endurance training. Findings highlighted improvements in; 1 repetition maximum (1RM) bench press (Baseline: 65.6 ± 5.4 kg vs. 64.3 ± 4.9 kg – 6 weeks: 70.3 ± 4.9 vs. 72.5 ± 5.4 kg) and leg press (Baseline: 250 ± 26.9 vs. 217.9 ± 19 kg – 6 weeks: 282.5 ± 22.5 vs. 282.8 ± 18.3 kg); vertical jump test (Baseline: 53.5 ± 4.1 vs. 50.4 ± 2.1 cm – 6 weeks: 55 ± 3.5 vs. 52.4 ± 1.7 cm); 3 km running time-trial performance (Baseline: 988.7 ± 68.7 vs. 1040.5 ± 66.3 s – 6 weeks: 947.5 ± 54.9 vs. 1004.3 ± 70.5 s); isokinetic dynamometry (Baseline: 196.1 ± 47.3 vs. 184.6 ± 35.0 n.m. – 6 weeks: 179.5 ± 48.9 vs. 195.2 ± 28.9 n.m.); and body composition (Baseline: 32.1 ± 13.9 vs. 34.9 ± 10.4 mm – 6 weeks: 32.4 ± 14.5 vs. 34.5 ± 10 mm) for both the salbutamol group and the placebo group, respectively, over the 6 week period, with no difference observed between groups, indicating long-term therapeutic use of salbutamol at the WADA upper daily limit has no ergogenic effect. Of note, one participant exceeded the urinary threshold, presenting with an adverse analytical finding (AAF) showing that the upper daily limit can lead to AAF’s in susceptible individuals.
Athletes who respond poorly to salbutamol treatment are able to apply for the use of the short-acting β2-agonist terbutaline via a therapeutic use exemption (TUE) certificate. Urinary upper limits are unknown for terbutaline and as such it is prohibited at all times without the presentation of a TUE. The purpose of study 2 was to investigate the urinary excretion of terbutaline following single and repeated use of inhaled or oral terbutaline. The aim of the study was to establish a differential distinction between routes of administration which could assist the WADA with regard to anti-doping policy and procedure. Results demonstrated a significant difference in urine concentration of terbutaline between inhaled and oral administration for female Caucasian (670.1 ± 128.3 vs. 361.8 ± 43.8 ng·ml-1; P=0.019; 680.8 ± 91 vs. 369.9 ± 41.9 ng·ml-1; P=0.006), male Afro-Caribbean (343.18 ± 45 vs. 231.3 ± 32.95 ng·ml-1; P=0.044; 389.73 ± 67.4 vs. 212.4 ± 50.3 ng·ml-1; P=0.008) and male Asian (266.4 ± 23.7 vs. 143.3 ± 22 ng·ml-1; P=0.004; 379.5 ± 50.4 vs. 197.5 ± 38.6 ng·ml-1; P=0.000) groups for single (5 mg oral vs. 2 mg inhaled) and repeated (4 x 5 mg oral vs. 8 x 1 mg inhaled) administration trials, respectively. No difference was observed in male Caucasians. High intra- and inter-individual variability between samples meant that a clear distinction between routes of administration could not be established. The study was able to identify an upper urinary threshold following inhaled administration of 1284.3 ng·ml-1 and an upper urinary threshold following oral use of 2376.3 ng·ml-1 which may inform the process of distinguishing between inhaled and oral use.
Athletes are permitted to use inhaled terbutaline therapeutically through the TUE process. The purpose of study 3 was to investigate the ergogenic effect of terbutaline at high (2 mg and 4 mg) therapeutic inhaled doses on 3 km running time-trial performance in males and females. The study found that inhaled terbutaline, when used at the highest therapeutic dose, has no impact upon 3 km time-trial performance in males (956.3 s vs. 982 s) and females (1249 s vs. 1214.7 s) for placebo vs. 4 mg inhaled terbutaline, respectively.
The majority of studies investigating the ergogenic potential of salbutamol have been in healthy individuals. It is not yet understood whether the exercise response differs in asthmatic individuals. The purpose of study 4 was to investigate the use of inhaled salbutamol (400 μg) during a 3 km running time-trial in eucapnic voluntary hyperpnoea positive (EVH+ve) and negative (EVH-ve) individuals, in a low humidity environment. Results demonstrated increased FEV1 in both groups following salbutamol inhalation, which did not translate to improved performance. No performance differences were found between salbutamol and placebo (Sal: 1012.7 ± 50 vs. 962.1 ± 37.5 s – Pla: 1002.4 ± 46.5 vs. 962 ± 28.8 s) in the EVH+ve group vs. the EVH-ve group, respectively.
This thesis is the first to investigate the effects of long-term use of salbutamol at the WADA upper daily limit on exercise performance. It is also the first study to establish upper urinary thresholds for terbutaline use, and the effects of therapeutic inhaled terbutaline on exercise performance. The effect of salbutamol on exercise performance at low humidity in asthmatic individuals has also never previously been investigated. Overall, the findings from this thesis support previous research that inhaled β2-agonist use does not provide any ergogenic potential. With β2-agonists being an essential therapy for the treatment of EIB their current position on the WADA List of Prohibited Substances and Methods is appropriate. Further research is warranted to fully elucidate the upper urinary threshold for terbutaline to inform WADA and support the re-introduction of terbutaline as a therapeutic tool in the treatment of EIB in athletes.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Short-acting Beta-2-agonists, Exercise, Pharmacokinetics, Performance, Salbutamol, Terbutaline, Anti-doping.
Subjects: R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions: Sport & Exercise Sciences
Date Deposited: 04 Nov 2016 12:35
Last Modified: 03 Sep 2021 23:26
DOI or ID number: 10.24377/LJMU.t.00004330
Supervisors: Whyte, G, Dickinson, J and Chester, N
URI: https://researchonline.ljmu.ac.uk/id/eprint/4330
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