WordNet (r) 3.0 (2006):

patent medicine
    n 1: medicine that is protected by a patent and available
         without a doctor's prescription

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "patent medicine":
   balm, balsam, drops, drug, electuary, elixir, ethical drug,
   generic name, herbs, inhalant, lincture, linctus, materia medica,
   medicament, medication, medicinal, medicinal herbs, medicine,
   mixture, nonprescription drug, nostrum, officinal, pharmacon,
   physic, powder, preparation, prescription drug, proprietary,
   proprietary medicine, proprietary name, quack remedy, simples,
   snake oil, syrup, theraputant, tisane, vegetable remedies