"Less Than Zero," an aptly titled tale of snooty California drug snorters, is dumber and duller than primordial ooze. It's one of those silly speed-bumps-in-the-fast-lane laments, though it does have a significant message: Get off the freeway or take the last exit ramp to the Betty Ford Clinic in the sky.

Andrew McCarthy, Jami Gertz and Robert Downey Jr. costar in this fatuous unintentional farce based on the best seller by Bret Easton Ellis. Like the book, the movie observes the alienated, affluent postadolescents of L.A., but portrays them less like heedless nihilists than the "St. Elmo's Fire" crowd gone to seed. Antiheroes become either heroes or sacrificial lambs to the movie's cause, which is ultimately lost to its melodramatic breast-beating.

McCarthy plays Clay, a college freshman who comes back to Beverly Hills for Christmas after his first semester at a school in the East. The movie makers seem to know little of this East, portraying it as a mysterious, apparently drug-free Ivy League mecca where West Coasters become clean cut; when he returns, Clay has lost the urge to abuse substances.

Only six months have passed since high school graduation day, but his old girlfriend Blair (Gertz), now a top fashion model with a runny nose, has developed either a terminal sinus infection or a taste for cocaine, and his best friend Julian (Downey) has degenerated into a pathetic male prostitute, with herpes and a freebasing habit.

Clay goes with his friends to various nightclubs and wild parties where the action is as aimless as the unsympathetic characters it involves. Women go to powder the insides of their noses and giggle over their nosebleeds ("rusty plumbing"). And Julian is a potential shish kebab, as he lights up his blow torch to freebase his drugs. Surly and slobbering, he joins his friends at home later to throw up and cry on their shoulders.

Meanwhile the saintly Clay and the bimboesque Blair rekindle their romance, with a passionate love scene in the middle of the freeway. Later, they enjoy a gymnastic moment against a garden wall -- thank God for garter belts -- and we get one of those French-kissing close-ups that directors find so sexy, but nobody else does.

If there is anything worse than looking up giant nostrils, it is looking at wide-screen questing tongues. It's less like sex than oral surgery. When these two lovebirds have spent their passion and gone to several more parties, they try to save Julian from an evil drug entrepreneur (James Spader) who is forcing him to work off a $50,000 debt by selling himself.

Spader, as the impersonal dealer, is easily the most effective member of the cast, though McCarthy exudes his curious appeal -- like a kissable TV anchorman. Downey, who had the title role in "The Pick-Up Artist," overplays his loser's part with visceral abandon. But he's got nothing on Gertz's Blair, a lost and listless woman-child with the brains of a small appliance. Gertz recalls Shirley Temple in tantrum mode as she coos and goos and moues.

British-born director Marek Kanievska of "Another Country" films this sorry soap opera in bright lights and big colors to give it an upbeat, glitzy look that subverts his purpose. Kanievska, making his American film debut, obsesses on L.A.'s florid, palmy decor, with punk passe' sets that would better suit a comedy. Then again, they are down and out in Beverly Hills, and it sure gets a lot of laughs.

"Less Than Zero" is noodle-headed and faint-hearted, a shallow swipe at a serious problem, with a happily-ever-after ending yet.

Just say no.

Less Than Zero, at area theaters, is rated R for profanity and sex.