Medicine taken orally (tablets, capsules, liquids) that exerts effects from inside the body; the opposite of topical drugs.
内服薬は必ず水で飲んでください。
Always take oral medicine with water.
外用薬ではなく内服薬を処方された。
I was prescribed an oral medicine rather than a topical one.
内服薬の服用時間は食前と書かれている。
The oral medication's administration time is listed as before meals.