Don't get me wrong. I can't get enough of the twisted humor of the pay channel's "Dexter," "Californication" and "Weeds" (10 p.m. Monday).

But then there's "Nurse Jackie" (10:30 p.m. Monday), the new Edie Falco series that's so unpleasant, it will make you question whether Showtime's whole over-the-top thing isn't being overdone.

Falco's Jackie is addicted to painkillers and carries on an affair with the pharmacist who supplies her habit. She steals from a patient and flushes his severed ear down the toilet. She forges a dead man's signature to make him appear to be an organ donor. And that's just in Monday's premiere.

She's outrageous, you see. She's also wholly unlikable. And that's the problem with this race to come up with ever more over-the-top series: Writers have started forgetting to make their characters worth caring about.

Dexter's a far worse person than Jackie -- he's a serial killer for crying out loud -- yet you can't look away from the guy. Jackie, on the other hand, makes you want to turn your head. And not just because of the distractingly short Supercuts 'do that gives her an unfortunate resemblance to Ben McKenzie of "Southland" and "The O.C." (Honestly. Look it up. It's uncanny.)

She's just a joyless woman trapped in a grim, bleak world. It was all I could do not to watch the sixth episode -- the last one that was made available for review, in which Jackie and her fellow nurses help euthanize a former colleague -- with my head in the oven.

And for all the fuss, Jackie's not even that original a character. An antisocial, rule-breaking drug addict who works in a hospital? Well, at least they didn't give her a scruffy beard and a limp.

Following the Toni Collette multiple-personalities comedy "United States of Tara," "Nurse Jackie" is the second straight Showtime original that feels more like an acting workshop than an actual series. They're creating a slippery slope that threatens to devalue the channel's entire lineup. After all, if everything's over-the-top, how special can "Weeds" and the others really be?

Now, I love a good over-the-top series -- I even enjoy "Over the Top," Sylvester Stallone's paean to arm wrestling -- and I complained early and often that the new "90210" wasn't over-the-top enough. But that's more about living up to expectations. You can't promise more casual sex and fancy cars than a dozen rap videos and then deliver story lines that feel like they were ripped from a very special episode of "Blossom."

The same goes for this fall's new version of "Melrose Place," which will be an abject failure if the first episode doesn't contain at least five of the following: amnesia, sex, demonic possession, inappropriate sex, a bikini splash-fight in the pool set to a Katy Perry song, really inappropriate sex, and Andrew Shue.

But as even Stallone's Lincoln Hawk knows, you can't go over-the-top all the time. You have to use that move sparingly.

Take HBO, which recently interrupted its roster of vampires, polygamists and assorted lowlifes to present "The No. 1 Ladies' Detective Agency." The gentle, family-friendly series served as a sort of palette cleanser, resetting the bar so that the pay channel's next new show -- "Hung," about the struggles of an overendowed high school basketball coach -- will seem all the more bold and shocking.

And Showtime, which has made a small fortune with over-the-top shows, should know better than to begin a series as unrelentingly dark as "Nurse Jackie" is at the outset. That level of despair really has to be earned.

Remember, it took four seasons of "Weeds" for Nancy Botwin (Mary-Louise Parker) to go from suburban soccer mom slinging a little pot on the side to her current predicament, where the only thing keeping a Mexican drug kingpin from shooting her in the head is the fact that she's carrying his baby.

But even as over-the-top as "Weeds" has become -- and I fully expect next season to begin with the entire cast chained up in a basement with the guy from "Saw" -- it never lost its sense of humor.

And that's something "Nurse Jackie" -- which, despite all evidence to the contrary, is still billed as a comedy -- never had.

It really is time for Showtime to go changing.

I loved it just the way it was.

Christopher Lawrence's Life on the Couch column appears on Sundays. E-mail him at clawrence@reviewjournal.com.