* Citalopram: steps were taken to separate the more potent enantiomer, escitalopram.
* Thalidomide is a drug whose two enantiomers cause distinctly different effects from one another. The unforeseen teratogenicity of the (R)-(+)-isomer caused it to become an important case study of stereochemistry in medicine. Although it is possible to chemically isolate just the desired (S)-(&minus;)-isomer from the racemic mixture, the two enantiomers rapidly interconvert in vivo; thus rendering their separation to be of little use.
* Methorphan is another drug whose two enantiomers possess very different binding profiles, with the L enantiomer being a potent opioid analgesic, and the D enantiomer being a commonly used over-the-counter cough suppressant which acts as an NMDA-antagonist but possesses nearly no opioid activity. In the case of morphinan, the eudysmic ratio is preserved after metabolism as the D and L metabolites possess the same pharmacological targets as the corresponding methorphan enantiomers, but are considerably more potent than their parent compounds. 
* Amino acids are also an example of eudysmic ratio.  Nearly all of the amino acids in the human body are called "L" amino acids; despite being chiral, the body almost exclusively creates and uses amino acids in this one configuration.  D amino acids, the enantiomers — or "mirror images" — of the amino acids in the human body cannot be incorporated into proteins.  D-aspartate and D-serine are two notable counterexamples, since they do not appear to ever be incorporated into proteins, but instead act individually as signalling molecules. However, mammals can metabolize significant amount of D amino acids by oxidizing them to alpha-ketoacids (most of which are non-chiral) and then transaminases can create L amino acids. There are no reasons to believe that humans are exceptional, they have all required enzymes (DDO, DAO). Some common foods contain near-racemic mixtures of amino acids.