noun
specific remedy; targeted medicine
Refers to a medicine or treatment that is specifically suited to a particular illness, condition, or person, as opposed to a general cure-all. Often used in contrast to 万能薬 (panacea).
この症状には合い薬が必要だ。
This symptom requires a specific remedy.
万能薬ではなく、合い薬を探している。
I'm looking for a targeted medicine, not a panacea.
Compound of 合い (ai, 'fitting, matching') + 薬 (kusuri, 'medicine'). The exact historical derivation is uncertain, but the term transparently means 'medicine that fits (the condition)'.