For drug [Fluvastatin][1], [Fluvastatin [sodium salt]][2] (CAS-93957-55-2) is usually used for testing the potential of Fluvastatin. They have different structures, though it's slight difference. 

In [Drugbank][3], the Fluvastatin structure is at the beginning, while the salt form in the latter section of the webpage.

It seems the active form should be Fluvastatin ion in cell.

So which structure should be used when considering the structure ot this drug in chemoinformatics? Thank you.

Update:

Another example:

For [**tamoxifen**][4], one of its Synonyms is tamoxifen citrate shown in guidetopharmacology. In pubchem, they are different (CID [2733526][5] and [2733525][6]) with the latter includes a citrate. At least in the Connectivity Map, tamoxifen citrate [54965-24-1] (as a catalog name) was used instead of tamoxifen (as a cmap_name) [[ref1][7]]. I think they are just different, resulting in different effect on cells. In this situation, should I use the structure of tamoxifen to discover something in the Connectivity Map? It's a little odd. I'm wondering why they use tamoxifen citrate instead of tamoxifen, but name it as tamoxifen. Is it common for drug testing in chemistry?

 [1]: https://pubchem.ncbi.nlm.nih.gov/compound/1548972#section=Top
 [2]: https://pubchem.ncbi.nlm.nih.gov/compound/23663976#section=Top
 [3]: http://www.drugbank.ca/drugs/DB01095
 [4]: http://www.guidetopharmacology.org/GRAC/LigandDisplayForward?ligandId=1016
 [5]: https://pubchem.ncbi.nlm.nih.gov/compound/2733526#section=Top
 [6]: https://pubchem.ncbi.nlm.nih.gov/compound/2733525#section=Top
 [7]: http://www.connectivitymap.org/cmap/cmap_instances_02.xls
You have chosen a tricky one because it has salts, racemates, enantiomers and virtual deuteration

this adds up to 113 different representations http://www.ncbi.nlm.nih.gov/pccompound?cmd=Link&LinkName=pccompound_pccompound_parent_connectivity_pulldown&from_uid=1548972

Choices depends on exactly what cheminformatic operations you intend to perform, but stripping salts back to parents is usually advisable

To keep life simple just go with this GtoPdb entry

http://www.guidetopharmacology.org/GRAC/LigandDisplayForward?ligandId=2951