As a succinct quality-by-association marketing tool, it's an increasingly common practice for new TV shows to piggy-back on the success of an older popular model. Case in point is the phrase "from the makers of The Sopranos", which we've all seen crop up in press ads and promo clips.

Usually, the focus has been on the most consistent award-winning writers of the feted New Jersey mob/family saga who've gone on be the creative lynchpins of their own series, starting a few years ago with Matthew Weiner (Mad Men), and continuing more recently with Terence Winter (Boardwalk Empire) and the duo of Robin Green & Mitchell Burgess (Blue Bloods).

But what of the on-screen talent? James Gandolfini's involvement in small screen projects has been largely restricted to narrating war documentaries for HBO (a subtle nod to Tony Soprano's own obsession with The History Channel) and executive producing an upcoming drama about Ernest Hemingway. As an actor, he's been most visible on the Broadway stage, garnering a Tony nomination (fittingly) for his role in the comedy God Of Carnage.

Next to Galdofini, it was Edie Falco as the put-upon but stoic Carmela Soprano who grabbed the lion's share of screen time, and she's an even more powerful presence as the title character in Nurse Jackie, arguably the most unsanitised and controversial hospital-based drama in American TV history. It's already earned her an Emmy (to add to the three she won for The Sopranos) and she'll undoubtedly be in the running again for Season Two, out now on DVD and Blu-ray.

On the surface, as established in the opening episodes of the first season which debuted in 2009, Jackie Peyton, RN, is a pill-popping maverick medic challenging authority and bending the rules to the point of almost breaking like a brittle fibea. So far, so House – but Jackie is a far more layered and complicated character than Hugh Laurie's wisecracking genius and his tiresomely formulaic "eureka!" moments of diagnosing bafflingly obscure ailments.

Nurse Jackie takes place at the sharp end of US healthcare, with Falco as the pivotal force in the emergency room of New York's cash-strapped All Saints Hospital, its typical visitors the down-at-heel and dispossessed with barely the insurance to cover the cost of a tongue depressor. However, it's not the damning indictments of a failing system that's prompted the most criticism, but the portrayal of Jackie herself, trading sex to feed her drug habit. In a monumental display of understatement, the New York State Nurses Association declared such behaviour "violated the nursing code of ethics".

Jackie isn't squeaky clean, you see. As capable as she might be in her job, her private life is a mess. Hooked on prescription painkillers, she disappears into cupboards and empty rooms for quickies with Eddie the pharmacist to get the pills she needs. Meanwhile, her bartender hubby takes care of two daughters while the missus is on night shift, oblivious to her double life.

Such storylines, in theory, mirror America's typically melodramatic daytime hospital soaps, as does each episode's brief 30-minute running time, suggesting the show may have started life as a parody of what went before. But Nurse Jackie is different; its refusal to sugar-coat its narrative pills not only exposes the vacuous nature of afternoon telly but presents the programme as the antithesis of the prime time soft focus scrubs-wearing banal chick-lit of Grey's Anatomy or the oh so jaded last few seasons of ER.

As played by Falco with a minimum of ego, Carmela Soprano's often vulgar nouveau riche Jersey housewife fashion crimes meant she was never what might be called a traditional sex symbol. Jackie is even less concerned with glamour, Falco willing to appear on screen without make-up and sporting, in notional TV terms at least, an unflattering but functional short crop. She never looks anything less than a real nurse.

Again, this is where the show has come in for some stick. Falco's portrayal is so authentic, so utterly believable, that she appears to have been fashioned as the ultimate poster girl for the health service. However, weighed against her likeability and innate professionalism is the other Jackie, the troubled Jackie, the conniving, manipulative and duplicitous Jackie. Rarely has a TV heroine had such gargantuan feet of clay.

This is not the place to dissect its myriad plot threads, in case some of you have been holding out for a marathon session with the DVDs. Suffice to say that Jackie comes even closer to dropping the work/family/mistress balls she's frantically juggling, and viewers become better acquainted with the splendid troupe of supporting characters.

Jackie's best pal and confidante Dr O'Hara (Eve Best, recently seen as Wallis Simpson in The King's Speech) continues to burn the candle at both ends in a flurry of designer skirts and posh lunches, and reveals a long-standing lesbian affair; the constantly Tweeting and self-obsessed Dr Cooper (Peter Facinelli) becomes a minor media celebrity, much to Jackie's annoyance; and stony-faced administrator Gloria Akalitus (Anna Deavere Smith) is still keeping a tight hold on the purse strings but is portrayed as less of an ogre and more a strong-willed "suit" who nonetheless has the patients' best interests at heart.

As well-fashioned and fully dimensional as all the above might be, there is only one player who comes close to matching Falco's own dazzling star power; Merrit Wever's daydreamy and idealistic Nurse Zoey is developing into one of 21st century television's most brilliant comic foils. It's an oddly mannered performance, all child-like pirouettes and innocent expressions, but totally convincing, allowing the programme's makers to use her character as the prism through which the viewer is fed vital narrative, much in the way Aaron Sorkin did with the ever-inquisitive Donna Moss in The West Wing.

It could have been a thankless role, but the Zoey character is being allowed to grow, to mature (like real nurses do after prolonged exposure to the horrors of emergency medicine), and Wever is more than up to the challenge. Her face when confronted with a particularly gruesome groin injury is laugh-out-loud funny, as is her attempt to mimic the accents of a couple fresh off the boat from Dublin – "We're Irish," she's told, "not pirates." Should Falco decide to call it a day, a Nurse Zoey spin-off would have serious legs.

For now, though, it's Falco at the helm of an ever-engrossing hospital saga, cutting a no-nonsense swathe through a world of administrative bullshit, shagging and shady consumption of unprescribed meds. The latest 12-episode course of treatment is just what the doctor ordered.

Nurse Jackie: Season Two is out now on Lionsgate DVD and Blu-ray