powdered medicine; medication in powder form (often dissolved in water or taken as a powder, used in dispensaries or for children).
医師の指示で粉薬を湯に溶かして飲ませた。
Following the doctor's instructions, I dissolved the powdered medicine in hot water and gave it to them.
小さな子どもには粉薬が処方されることが多い。
Powdered medicine is often prescribed for small children.
薬局で粉薬を粉末にしてもらった。
I had the pharmacy grind/mix the medicine into a powder.