According to IUPAC Glossary of Terms Used in Toxicology [1, ppp. 1211, 1245] these and similar notations are just ordinary upright characters with corresponding indices:
inhibitoryeffective concentration (ICEC)
Concentration of a substance that causes a defined inhibitionmagnitude of response in a given system. Note: IC50EC50 is the median concentration that causes 50 % inhibitionof maximal response.
inhibitory doseconcentration (IDIC)
DoseConcentration of a substance that causes a defined inhibition of a given system. NoteNote: IDIC50 is the median doseconcentration that causes 50 % inhibition.
- Duffus, J. H.; Nordberg, M.; Templeton, D. M. Pure and Applied Chemistry 2007, 79 (7). DOI: 10.1351/pac200779071153.