The Collaborative International Dictionary of English v.0.48:

Philter \Phil"ter\, v. t. [imp. & p. p. Philtered; p. pr. &
   vb. n. Philtering.]
   1. To impregnate or mix with a love potion; as, to philter a
      draught.
      [1913 Webster]

   2. To charm to love; to excite to love or sexual desire by a
      potion. --Gov. of Tongue.
      [1913 Webster]