From The Art and Popular Culture Encyclopedia
A pharmacon or pharmakon (from Greek: (φάρμακον), adapted from pharmacos) is a biologically active substance. It is used more broadly than the term drug because it includes endogenous substances, and biologically active substances which are not used as drugs. Typically the word pharmacon includes pharmacological agonists and antagonists, but also enzyme inhibitors (such as monoamine oxidase inhibitors). Spelt with a "k", is acceptable in English, but more common in German. In most cases pharmacon is the equivalent to active ingredient.
Unclear etymology, but most likely derived from Proto-Hellenic *pʰármakon. Cognate with Mycenaean Greek 𐀞𐀔𐀒 (pa-ma-ko /pʰármakon/).
Pokorny (1959) connects it to the Greek root φαρ- as in φάρος (pháros, “plough”) and φάρυγξ (phárunx, “throat”), from a Proto-Indo-European *bʰer- (“to cut, pierce, scrape”), i.e., a medicinal herb or root as something cut off or dug up, cognate with Proto-Germanic *burōną (“to drill”) – result of a conflation with *bazją (“berry”) – and Latin feriō (“hit, cut, slay, strike”). Compare furthermore Latvian burt (“to carve (marks, on a tree), to conjure magic”).
A Pre-Greek etymology has been proposed by R. S. P. Beekes.