The Collaborative International Dictionary of English v.0.48:

Medicate \Med"i*cate\, v. t. [imp. & p. p. Medicated; p. pr. &
   vb. n. Medicating.] [L. medicatus, p. p. of medicare,
   medicari. See Medicable.]
   [1913 Webster]
   1. To tincture or impregnate with anything medicinal; to
      drug. "Medicated waters." --Arbuthnot.
      [1913 Webster]

   2. To treat with medicine.
      [1913 Webster]

WordNet (r) 3.0 (2006):

medicate
    v 1: impregnate with a medicinal substance
    2: treat medicinally, treat with medicine [syn: medicate,
       medicine]