Through its Active Pharmaceutical Ingredient Working Group (API-WG) the General European Official Medicines
Control Laboratory (OMCL) Network (GEON), co-ordinated by the European Directorate for the Quality of
Medicines & HealthCare (EDQM), regularly organises market surveillance studies for specific APIs for conformity
to their monograph in the European Pharmacopoeia. During the past years some studies were combined with a
fingerprint study of the APIs. The idea is to obtain a fingerprint for each manufacturer of the API under investigation,
allowing the OMCL network to identify future samples as well as to detect substandard and falsified
APIs.
This paper reports the results of the latest fingerprint study, organised on sildenafil citrate API samples.
Seventy-nine samples from 14 different manufacturers were collected throughout the Network. Fingerprint data
was collected through Mid-Infrared spectroscopy, Raman spectroscopy, liquid chromatography for related substances,
gas chromatography for residual solvents, X-ray diffraction and Nuclear Magnetic Resonance (NMR)
spectroscopy. Chemometrics applied to the collected data showed that all manufacturers could be discriminated
based on the data of only three of these tests, i.e. gas chromatography for residual solvents, X-ray diffraction and
proton NMR. Suspicious API samples for sildenafil citrate will therefore be analysed in the future with the
selected techniques in order to link the sample to a manufacturer or demonstrate the absence of such link. If the
sample cannot be attributed to one of the manufacturers, further analysis and research on provenance and
identity will be required. Of course, if the suspected sample claims to originate from one of the manufacturers
included in the study, analysis can be limited to the test distinguishing this manufacturer.
