The Collaborative International Dictionary of English v.0.48:

Medication \Med`i*ca"tion\, [L. medicatio: cf. F.
   m['e]dication.]
   The act or process of medicating.
   [1913 Webster]

WordNet (r) 3.0 (2006):

medication
    n 1: (medicine) something that treats or prevents or alleviates
         the symptoms of disease [syn: medicine, medication,
         medicament, medicinal drug]
    2: the act of treating with medicines or remedies

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "medication":
   balm, balsam, curative measures, cure, drops, drug, electuary,
   elixir, ethical drug, first aid, generic name, healing arts, herbs,
   hospitalization, inhalant, lincture, linctus, materia medica,
   medical care, medical treatment, medicament, medicamentation,
   medicinal, medicinal herbs, medicine, medicines, mixture,
   nonprescription drug, officinal, patent medicine, pharmacon,
   physic, powder, preparation, prescription drug, proprietary,
   proprietary medicine, proprietary name, psychotherapy, regime,
   regimen, simples, syrup, therapeusis, therapeutics, theraputant,
   therapy, tisane, treatment, vegetable remedies