You can have a look at Chemical Annotation Retrieval Toolkit available from:

http://cart.embl.de/

It matches an input list of chemical names to Pubchem IDs.

Later, bioactivity annotations (including pathways, protein targets) can be easily retrieved from CART.

Also, it is possible to perform chemical/drug annotation enrichment using the same toolkit.

Try searching for the drug name in the Reactome database e.g. paracetamol. There is ChEMBL and ChEBI too but not sure if they provide pathway information but worth investigating them further.

It turned out, KEGG has a special site:

http://www.genome.jp/kegg/drug/

It provides pathways at the bottom of the corresponding pages, like this one:

http://www.kegg.jp/pathway/hsa05010

Also, try to look at close biostar-posts.

Is There A Free Alternative To Ingenuity Pathway Analysis?

Biological Pathways And Drug Designing

You can search for your drug in PubChem too. They have a section called "Biomolecular interaction and pathways".

For example, search for celecoxib: https://pubchem.ncbi.nlm.nih.gov/compound/2662#section=Biosystems-and-Pathways

(or) check NCBI Biosystems directly too. https://www.ncbi.nlm.nih.gov/biosystems

please use: https://dsea.tigem.it/