As nouns the difference between drug and tegafur is that drug is (pharmacology) a substance used to treat an illness, relieve a symptom, or modify a chemical process in the body for a specific purpose or drug can be (obsolete) a drudge while tegafur is a particular drug used to treat cancer.
As a verb drug is to administer intoxicating drugs to, generally without the recipient’s knowledge or consent or drug can be (drag).