No single word in English captures the play of signification of the ancient Greek word, pharmakon. Derrida traces the meanings assigned to pharmakon in Plato's dialogues: remedy, poison (either the cure or the illness or its cause), philter, drug, recipe, charm, medicine, substance, spell, artificial color, and paint. The word pharmakon is overdetermined, signifying in so many ways that the very notion of signification gets overloaded. A translation problem? Yes and no. In choosing one meaning translators often decide what in Plato's texts remains undecidable. But as indicated above, the problem is inherent in its very principle, situated less in the translation from one language to another, than already within the Greek language itself. And adopted within philosophical discourse, pharmakon does not suddenly become unambiguous, ready and suited for dialectic operations. (In Phaedrus, Socrates tries to distinguish between two kinds of words, the unambiguous - words about which we all agree - and the ambiguous - words about which we are at variance. In Plato, Derrida and Writing, Jasper Neel argues that in fact there are no unambiguous words.) Instead, words like pharmakon threatens the philosophical process, threatens dialectics from within. Plato's text itself is thus already the battlefield of an impossible process of translation.
 In Phaedrus, the god Teuth presents writing as a recipe (pharmakon) beneficial for memory to King Thamus. But the King refuses the gift saying that it will produce forgetfulness; it is not a remedy for memory, but for reminding. Writing is a poison (pharmakon) and Teuth has passed a poison off as a remedy. The pharmakon thus produces a play of oppositions: remedy-poison, good-bad, true-false, positive-negative. According to Derrida, this means that far from being governed by these oppositions, the pharmakon (writing) enables the coming into play of oppositions without allowing itself to be fully encompassed by them, without being subsumed under concepts whose contours it draws (cf. Dissemination, p.103).
 Socrates puts his most effective medicine (pharmakon teleotaton), living knowledge, opposite the other pharmakon, writing. 'Philosophy thus opposes to its other this transmutation of the drug into a remedy, of the poison into counterpoison', says Derrida. This is only possible due to the ambiguity of the pharmakon; it already bears its own opposite within itself. Presenting itself as a poison, it may turn out to be a cure. 'The 'essence' of the pharmakon lies in the way in which, having no stable essence, no 'proper' characteristics, it is not, in any sense (metaphysical, physical, chemical, alchemical) of the word, a substance ... It is rather the prior medium in which differentiation in general is produced' (Dissemination, p.125-6).
 (The working of) the word 'pharmakon' as related to the music of John Zorn is detailed on the pages entitled Saprophyte and Zorn's Pharmacy.