Jamieson, Fausset and Brown on Ephesians 5:18

18. excess--worthless, ruinous, reckless prodigality.

wherein--not in the wine itself when used aright (1Ti 5:23), but in the "excess" as to it.

but be filled with the Spirit--The effect in inspiration was that the person was "filled" with an ecstatic exhilaration, like that caused by wine; hence the two are here connected (compare Ac 2:13-18). Hence arose the abstinence from wine of many of the prophets, for example, John the Baptist, namely, in order to keep distinct before the world the ecstasy caused by the Spirit, from that caused by wine. So also in ordinary Christians the Spirit dwells not in the mind that seeks the disturbing influences of excitement, but in the well-balanced prayerful mind. Such a one expresses his joy, not in drunken or worldly songs, but in Christian hymns of thankfulness.