title: Terbutaline Accumulates in Blood and Urine after Daily Therapeutic Inhalation.
abstract: This study investigated pharmacokinetics of terbutaline after single and seven consecutive days of inhalation in exercising trained men.
  
  
  
  Twelve healthy trained men underwent two pharmacokinetic trials comparing single dose (2 mg) and seven consecutive days (2 mg·d) of inhaled terbutaline. After inhalation of terbutaline at each trial, subjects performed 90 min of bike ergometer exercise at 55%-65% of maximal oxygen consumption after which they stayed inactive. Blood and urine samples were collected before and after inhalation of terbutaline. Samples were analyzed by high-performance liquid chromatography-tandem mass spectrometry.
  
  
  
  Maximum serum concentration of terbutaline (Cmax) (6.4 ± 1.2 vs 4.9 ± 1.2 ng·mL, P = 0.01) (mean ± 95% confidence interval) and area under serum concentration-time curve from 0 to 4 h after inhalation (AUC0-4) (16 ± 3 vs 13 ± 2 ng·mL·h, P ≤ 0.005) were higher after 7 d of inhalation compared with the first day. Seven days of terbutaline inhalation resulted in accumulation of terbutaline in urine, in which total urine excretion of terbutaline was higher after 7 d of inhalation compared with the first day (274 ± 43 vs 194 ± 33 μg, P ≤ 0.001). These differences were partly attributed to systemic accumulation of terbutaline after consecutive days of inhalation, in that baseline serum and urine samples revealed incomplete elimination of terbutaline.
  
  
  
  Terbutaline accumulates in serum and urine after consecutive days of inhalation. For doping control purposes, these observations are of relevance if a urine threshold and decision limit is to be introduced for terbutaline on the World Anti-Doping Agency's list of prohibited substances because asthmatic athletes may use their bronchorelievers for consecutive days.
authors.affiliation: 1Respiratory Research Unit, Bispebjerg University Hospital, Copenhagen, DENMARK; 2Norwegian Doping Control Laboratory, Oslo University Hospital, Oslo, NORWAY; 3IOC Research Center Copenhagen, DENMARK; and 4Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, DENMARK.
authors.forename: Nanna
authors.initials: N
authors.lastname: Krogh
authors.forename: Sebastian
authors.initials: S
authors.lastname: Rzeppa
authors.forename: Anders
authors.initials: A
authors.lastname: Dyreborg
authors.forename: Yvette
authors.initials: Y
authors.lastname: Dehnes
authors.forename: Peter
authors.initials: P
authors.lastname: Hemmersbach
authors.forename: Vibeke
authors.initials: V
authors.lastname: Backer
authors.forename: Morten
authors.initials: M
authors.lastname: Hostrup
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D019540:Area Under Curve; D001993:Bronchodilator Agents / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D004334:Drug Administration Schedule; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D013726:Terbutaline / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine
chemical_list: D001993:Bronchodilator Agents; D013726:Terbutaline