Source : Webster's Revised Unabridged Dictionary (1913)

Materia medica \Ma*te"ri*a med"i*ca\ [L. See {Matter}, and
   {Medical}.]
   1. Material or substance used in the composition of remedies;
      -- a general term for all substances used as curative
      agents in medicine.

   2. That branch of medical science which treats of the nature
      and properties of all the substances that are employed for
      the cure of diseases.

Source : WordNet®

materia medica
     n : the science or study of drugs: their preparation and
         properties and uses and effects [syn: {pharmacology}, {pharmacological
         medicine}]