"pertaining to pharmacy or the art of preparing drugs," 1640s (pharmaceutic in the same sense is from 1540s), from Late Latin pharmaceuticus "of drugs," from Greek pharmakeutikos, from pharmakeus "preparer of drugs, poisoner" (see pharmacy). Pharmaceuticals "medicinal drugs" is attested by 1881. Related: Pharmaceutically.
in the names of sciences or disciplines (acoustics, aerobics, economics, etc.), a 16c. revival of the classical custom of using the neuter plural of adjectives with Greek -ikos "pertaining to" (see -ic) to mean "matters relevant to" and also as the titles of treatises about them. Subject matters that acquired their English names before c. 1500, however, tend to be singular in form (arithmetic, logic, magic, music, rhetoric). The grammatical number of words in -ics (mathematics is/mathematics are) is a confused question.
<a href="https://www.etymonline.com/word/pharmaceutics">Etymology of pharmaceutics by etymonline</a>
Harper, D. (n.d.). Etymology of pharmaceutics. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/pharmaceutics