In conclusion, we showed that IRIS in combination with quantum-chemically computed IR spectra of candidate structures can aid in the structural elucidation of drug metabolites to support drug discovery and development. Comparing IR spectra of the drug itself and various metabolites gives direct information on the formation of new functional groups, whereas computed IR spectra aid in final identification of biotransformation sites. The work here was performed at an open-access free electron laser facility, but IRIS can also be implemented with table-top laser systems for easier and efficient application in pharmaceutical laboratories, although currently still over a restricted IR spectral range.