The Collaborative International Dictionary of English v.0.48:

Potion \Po"tion\, n. [L. potio, from potare to drink: cf. F.
   potion. See Poison.]
   A draught; a dose; usually, a draught or dose of a liquid
   medicine. --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Potion \Po"tion\, v. t.
   To drug. [Obs.] --Speed.
   [1913 Webster]

WordNet (r) 3.0 (2006):

potion
    n 1: a medicinal or magical or poisonous beverage

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "potion":
   bag, bang, beverage, booster, booster dose, booster shot, brew,
   concoction, cup, deck, decoction, dose, draft, dram, draught,
   drench, drink, drop, dropping, drug packet, elixir, fix, gargle,
   guzzle, hit, injection, jigger, jolt, libation, mainlining,
   narcotic shot, nip, overdose, peg, popping, portion, potation,
   pull, round, round of drinks, shot, sip, skin-popping, snifter,
   snort, spot, suck, sup, swig, swill, tonic, wet