'extended-release' is a modern compound formed from the past participle 'extended' (from 'extend') combined with 'release' to describe a formulation that extends the time of drug release.

'extend' comes from Latin 'extendere' (ex- 'out' + tendere 'to stretch'), which passed into English via Old French; 'release' comes from Old French 'releser'/'relacher' (from Latin roots meaning 'loosen' or 'set free'). The pharmaceutical compound 'extended-release' developed in 20th-century English technical usage to describe timed-release drug formulations.

Individually, 'extend' originally meant 'to stretch out' and 'release' meant 'to set free'; combined in modern usage they specifically denote 'to let a drug out slowly over an extended period,' a sense that arose with advances in pharmaceutical dosage technology.