Safety profile of enantiomers vs. racemic mixtures: it's the same?

Br J Clin Pharmacol. 2012 Nov;74(5):886-9. doi: 10.1111/j.1365-2125.2012.04262.x.


What is already known about this subject: The physicochemical properties of racemates and stereoisomers of medicines can differ significantly, and this may affect the side-effect profile in addition to the pharmacokinetics and intended pharmacology.

What this study adds: This is a study to investigate the profile of adverse drug reactions of racemic and enantiomeric forms of drugs. Our data suggest differences in the safety profile for ofloxacin and omeprazole. This area requires more work to investigate this for other compounds.

Aims: The objective was to investigate the safety profile of four drugs marketed as racemic and enantiomeric forms in France.

Methods: Data from the French PharmacoVigilance Data Base (January 2005 to June 2010) were analysed for four pairs of racemic/isomeric drugs. A case-noncase approach was used to measure the disproportionality of combination between adverse drug reaction (ADR) and exposure to drug.

Results: No significant difference in the number of ADRs was observed between Rac-cetirizine/(R)-cetirizine or Rac-citalopram/(S)-citalopram pairs. (S)-Omeprazole induced more haematological effects than Rac-omeprazole. Rac-Ofloxacin induced more haematological, renal and neuropsychiatric ADRs than (S)-ofloxacin, whereas levofloxacin was associated with more reports of musculoskeletal ADRs.

Conclusions: The profile of ADRs could differ for some drugs marketed as racemic and enantiomeric forms. Further studies would be necessary to confirm these data.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Adverse Drug Reaction Reporting Systems / statistics & numerical data
  • Aged
  • Aged, 80 and over
  • Cetirizine / adverse effects*
  • Cetirizine / chemistry
  • Citalopram / adverse effects*
  • Citalopram / chemistry
  • Databases, Factual
  • Female
  • Humans
  • Levofloxacin*
  • Male
  • Middle Aged
  • Ofloxacin / adverse effects*
  • Ofloxacin / chemistry
  • Omeprazole / adverse effects*
  • Omeprazole / chemistry
  • Stereoisomerism
  • Young Adult


  • Citalopram
  • Levofloxacin
  • Ofloxacin
  • Omeprazole
  • Cetirizine