excipient

in toxicology
https://doi.org/10.1351/goldbook.E02245
Any more or less inert substance added to a drug to give suitable consistency or form to the drug.
Source:
PAC, 1993, 65, 2003. 'Glossary for chemists of terms used in toxicology (IUPAC Recommendations 1993)' on page 2046 (https://doi.org/10.1351/pac199365092003)