We don't have synonyms for theriaca yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are theriac, theriacs and therian.
(n) :
Alternative spelling of theriac. [(pharmacology, historical) A universal antidote against all poisons, particularly medicines considered to derive from a recipe of the Roman physician Andromachus and representing an improvement on mithridate.]
(n) :
Alternative spelling of theriac. [(pharmacology, historical) A universal antidote against all poisons, particularly medicines considered to derive from a recipe of the Roman physician Andromachus and representing an improvement on mithridate.]