Prof.Dr. Meral Tunçbilek
ISOMERISM IN DRUG
Biological activity of stereoisomers
– The body with its numerous homochiral compounds
being amazingly chiral selector, will interact with each racemic drug differently and metabolize each enantiomer by a separate pathway to generate different pharmacological activity.
– Thus, one isomer may produce the desired therapeutic
activities, while the other may be inactive or, in worst cases, produce undesired or toxic effects
The majority of racemic pharmaceuticals have
- one major bioactive enantiomer (called eutomer-eu),
- the other is inactive or less active (distomer-dis) or toxic or can exert other desired or undesired pharmacological properties
- Each enantiomer interacts differently with the receptor, elicits the response differently and potency of enantiomer depends on the eudismic ratio or eudismic index or stereospecific index of the compound
- Therefore Eudismic ratio is also an important tool in chiral drug designing
- The eudysmic ratio (also spelled eudismic ratio) represents the difference in pharmacologic activity between the
two enantiomers of a drug.
- In most cases where a chiral compound is biologically active, one enantiomer is more active than the other.
- The eudysmic ratio is the ratio of activity between the two. - A eudysmic ratio significantly differing from 1 means that they are statistically different in activity.
