Danny DeVito’s directing used to be flashy and incendiary. Now he’s just hopelessly behind the curve. On the heels of last year’s horrid Barney-basher Death to Smoochy, itself five years too late, comes Duplex, a use-once-and-throw-away comedy that would have felt dated in 1993.

It has fine moments, notably murder gags hearkening back to Throw Momma from the Train and slow burns from Ben Stiller, whose whipping-boy glares glow with humorously passive rage.

But there are too many random gross-out moments (some unspeakably grotesque) featuring masturbation and vomit. Oh, it’s tasteless — it is, after all, about bumping off an old lady. But Drew Barrymore puking into Stiller’s mouth is a bit much.

The two play Alex and Nancy, a husband and wife looking for the home of their dreams. They find a Brooklyn duplex that’s perfect, except for Mrs. Connelly (Eileen Essel), the little old lady upstairs grandfathered in due to rent-control laws.

They at first accommodate her quirks, demands and misconstructions, but it quickly escalates to life-ruining proportions for the two, who come to the only conclusion possible: She must be killed.

With her deceptively sweet Irish brogue, Essel is the movie’s most consistent comedic asset. And a scene when Stiller and Barrymore contract a killer flu in hopes of infecting her is inventively demented.

But the movie never capitalizes on the obvious marital animosity between Alex and Nancy. And the ending, forgoing morbidity for Christmas Eve morality, is a left-field letdown. It’s an upper where it doesn’t need it, but Duplex sure could use some fixing.