title: Exercise increases plasma concentrations of (R)- and (S)-propranolol.
abstract: OBJECTIVE
  We recently reported a highly stereoselective increase in plasma concentrations of (S)-atenolol during exercise which is most likely due to a release of the drug from adrenergic cells. The objective of the present study was to investigate the influence of physical exercise on plasma concentrations of the (R)- and (S)-enantiomers of propranolol.
  
  
  METHODS
  Blood samples were taken immediately before and at the end of exercise in 12 patients receiving chronic treatment with racemic (R, S)-propranolol. Plasma concentrations of (R)- and (S)-propranolol were determined by HPLC.
  
  
  RESULTS
  In contrast to atenolol, mean plasma concentrations of (S)-propranolol were significantly higher (+20%) than those of (R)-propranolol at rest. During exercise there was an increase in plasma concentrations of both (R)-propranolol (+129%) and (S)-propranolol (+109%).
  
  
  CONCLUSIONS
  Based on information from in vitro studies we conclude that the increase in plasma concentrations of (S)-propranolol during exercise is caused by a release of the drug from adrenergic nerves, whereas the reason for the increase in (R)-propranolol remains to be determined. This release of the beta-adrenoceptor blocking (S)-enantiomer directly at the synaptic gaps might be one reason for the poor correlation between plasma concentration and effect of beta-adrenoceptor antagonists repeatedly described in the literature.
authors.affiliation: Institute of Pharmaceutical Chemistry, Karl Franzens University, Graz, Austria.
authors.forename: K
authors.initials: K
authors.lastname: Stoschitzky
authors.forename: M
authors.initials: M
authors.lastname: Schumacher
authors.forename: G
authors.initials: G
authors.lastname: Stark
authors.forename: H P
authors.initials: HP
authors.lastname: Dimai
authors.forename: R
authors.initials: R
authors.lastname: Stauber
authors.forename: P
authors.initials: P
authors.lastname: Stoschitzky
authors.forename: G J
authors.initials: GJ
authors.lastname: Krejs
authors.forename: W
authors.initials: W
authors.lastname: Klein
authors.forename: W
authors.initials: W
authors.lastname: Lindner
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000097:blood*; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001794:Blood Pressure / Q000187:drug effects; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D008968:Molecular Conformation; D011433:Propranolol / Q000097:blood*; D013237:Stereoisomerism
chemical_list: D000319:Adrenergic beta-Antagonists; D011433:Propranolol