Neil McManus bagged a hat-trick as the Saffrons won the Allianz NHL Division Two derby at Ballycran.
Karl Stewart was first to hit the net for Antrim before a brace from McManus, which included a penalty.
Antrim's Eddie McCloskey and Eoin Clarke of Down were sent-off as the visitors led 3-4 to 0-5 at the break.
McManus and Stewart netted again before Paul Braniff fired in Down's goal, while Mourne player Fintan Conway was dismissed late on.
McManus picked himself up after being hauled down to convert the penalty.
McCloskey and Clarke received straight red cards after being involved in an incident before half-time.
The win takes Antrim up to third on eight points while Down are four back in seventh.
Antrim: C O'Connell, A Graffin, Kieran McGourty, K Molloy, N McAuley, M Herron, J McCouaig, S McCrory, S McNaughton, P Shiels, K Stewart, E McCloskey, C McGuinness, N McManus, Barry McFall. Subs: S Hawes, M Armstrong, T McCann, J Black, C McFall, M Donnelly, K McKeegan, C Carson, S Shannon, L Kearns, C McCann, D Hamill, C Herron, K McKeague, C Donnelly, PJ O'Connell.