noun
internal medicine; medicine taken internally
Refers to medication that is swallowed or ingested, as opposed to external preparations. Common in medical and pharmaceutical contexts.
この内用薬は食後に服用してください。
Please take this internal medicine after meals.
外用薬 is medicine for external use (e.g., ointments, creams), while 内用薬 is taken internally.
Compound of 内用 (internal use) and 薬 (medicine). The exact historical derivation is uncertain, but the term is a straightforward modern medical compound.