of different drugs

A ll beta-blockers that are currently available possess anamino-alkanol side chain with an asymmetric carbon atom (Fig. 1), resulting in the existence of a d- and l-enantiomer which are mirror images [1] (Fig. 2). Although in vitro studies showed in the 1960s that the l-enantiomers are orders of magnitude more potent than the respective d-forms [2], most beta-blockers are still used as racemates in research as well as in clinical practice as though they were pure drugs. Within this context, it has been argued over a long period of time that “the limited experience from studies where these isomers had been used separately even suggests that they have no adverse effects at all. Based upon these considerations and in view of the sometimes cumbersome and expensive separation of the isomers, most beta-receptor blocking agents are now used as racemates [3]”. Indeed, specific effects of the non beta-blocking d-enantiomers of beta-blockers were unknown a