ISSN:
1432-1041
Keywords:
Key words Propranolol; stereoselectivity
;
chirality
;
enantiomers
;
isomers
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Medicine
Notes:
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%). Conclusion: 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 β-adrenoceptor blocking (S)-enantiomer directly at the synaptic gaps might be one reason for the poor correlation between plasma concentration and effect of β-adrenoceptor antagonists repeatedly described in the literature.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002280050119
