DOPA, racemic side-effects

Many of the side effects (e.g. granulocytopenia) encountered with racemic DOPA were not seen with levo-DOPA and therefore can be attributed to the (+)-enantiomer. For this reason the racemate is no longer given. Post-anesthesia reactions to the anesthetic and analgesic agent ketamine are overwhelmingly associated with the R(-) antipode. ... 

The thalidomide tragedy, described in chapter 7, started to focus the pharmaceutical industry on synthesis of single enantiomers rather than racemic mixtures. Even if there are no antagonistic or undesirable side effects from the other enantiomer, a racemic mixture may waste 50 percent of the mass of a drug. Optically pure compounds such as vitamin B]2, morphine, and L-dopa are available naturally. In some cases (e.g., vitamin B12), the natural source is really the only practical source. For simpler compounds like L-dopa, chemical synthesis is very practical but resolution of enantiomers may double the production cost. 

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