idiosyncratic drug reaction

initialism: IDR
https://doi.org/10.1351/goldbook.13251
Rare and unpredictable adverse drug reaction occurring only in susceptible individuals.
Note: A dose–response relationship may not be apparent within the dose range used clinically.
Source:
PAC, 2012, 84, 1113. (IUPAC glossary of terms used in immunotoxicology (IUPAC Recommendations 2012)) on page 1181 [Terms] [Paper]