1700 (n.), "an excessive dose," 1727 (v.), "to administer medicine in too large a dose" (trans.), from over + dose. Meaning "to take an overdose of drugs" is first attested 1973.
Main Entry: 1over·dose Pronunciation: 'O-v&r-"dOs Function: noun : too great a dose (as of a therapeutic agent) overdoseof exposure to the sun —Morris Fishbein>; also: a lethal or toxic amount (as of a drug)
Main Entry: 2over·dose Pronunciation: "O-v&r-'dOs Function: verb Inflected Forms: -dosed; -dos·ing transitivesenses : to give an overdose or too many doses to intransitive senses : to take an overdose