|Stoschitzky K et al.|
Racemic beta-blockers - fixed combinations of different drugs
Journal of Clinical and Basic Cardiology 1998; 1 (1): 15-19
PDF Summary Figures
Keywords: Betablocker, Chiralitšt, Enantiomer, Stereoselektivitšt, beta-blocker, chirality, enantiomers, stereoselectivity
Beta-blockers were introduced in clinical practice in the 1960s as racemic mixtures consisting of d- and l-enantiomers in a fixed 1:1 ratio. Little has changed on this issue although it has been clearly shown in vitro as well as in human studies that only the l-enantiomers exert beta-blockade when clinical doses of the racemic drugs are used, the d-enantiomers not contributing to this effect. In recent years numerous specific as well as non-specific effects of d-enantiomers of beta-blockers have been reported. Therefore, these non beta-blocking d-enantiomers may increase or even cause serious side effects on their own. In addition, pharmacokinetic properties of the l- and d-enantiomers vary widely even when they are given in the fixed 1:1 ratio of a racemic drug, particularly when exercise is performed. In conclusion, the data actually available on this issue demonstrate profound and clinically significant differences between the d- and l-enantiomers of beta-blockers. Therefore, the d- and l-enantiomers of beta-blocking drugs should be recognized and used as individual drugs on their own. We suggest that the so called ?chiral switch? be performed, ie, replace the currently used racemic mixtures with the optically pure l-enantiomers since the best available beta-blocking drugs should not be withheld from patients receiving beta-blockers. Such a procedure is further supported by the facts that the l-enantiomers can nowadays be provided easily and at low cost, and that the pure enantiomers give the full effect at half the dose of the currently used racemic mixtures. J Clin Bas Cardiol 1998; 1: 14?8.