IPA: /ˈmʌltiˌdrʌg/
KK: /mʌltiˌdrʌg/
Relating to or involving more than one type of medication or drug.
The patient was treated with a multidrug therapy to combat the infection.
Multidrug → It is formed from "multi-" (meaning many) and "drug" (from Old French *drogue*, meaning a substance used for medicinal purposes). The word "multidrug" refers to involving or affecting many drugs.
Think of 'many' ('multi-') substances used for medicine ('drug') — that's what multidrug means.
No commonly confused words.