局麻药

• 尸(body; cover)RADICAL
• 口(mouth; door)ASSOCIATIVE

A mouth confined under a roof is restricted to a limited scope.

• 广(eaves; spacious house)RADICAL
• 林(forest; many trees)ASSOCIATIVE

An oil hemp plant with thorns is grown and dried under the eaves like a small forest.

• 艹(grass; plant)RADICAL
• 约(promise; bind)PHONETIC

Medicine is made from grass and plants, sounding like "wish" or "promise".