The Collaborative International Dictionary of English v.0.48:

antalgic \an*tal"gic\ ([a^]n*t[a^]l"j[i^]k), a. [Pref. anti- +
   Gr. 'a`lgos pain: cf. F. antalgique.] (Med.)
   Alleviating pain. -- n. A medicine to alleviate pain; an
   analgesic. [R.]
   [1913 Webster + AS] Antalkali