Director Emmanuelle Bercot begins “150 Milligrams” with a rare stab at lyricism in what is otherwise a bluntly literal, plain-as-day procedural drama. As the opening credits flash by, a woman swims determinedly in a choppy ocean, her head nearly enveloped by Prussian blue waves; her legs are shown dangling vulnerably below the surface, as ominous synths swarm on the soundtrack. Uninformed viewers could be forgiven for expecting yet another “Jaws” knockoff, and that’s no accident: Bercot’s rather unsubtle visual metaphor instead sets her protagonist up for one corporate shark attack after another in the hazardous waters of Big Pharma.

Telling the true story of Irène Frachon, the French pulmonologist who, between 2009 and 2011, waged a one-woman war against the makers of a seemingly life-threatening diabetes drug, “150 Milligrams” will play to audiences in its native France as a ripped-from-the-headlines enterprise: The culmination of Frachon’s fight was extensively documented across the media there, while her own bestselling memoir filled in the gaps. Beyond borders, the film is counting on the irresistible, age-old popular appeal of the woman-against-the-system premise to work its magic: Many viewers may not know who Frachon is, but if they’ve seen “Erin Brockovich,” or even the less upbeat “Silkwood,” they’ll know how to invest in her. Would that the film, however, had quite as much gumption as its whistleblowing heroine: Televisually presented and arduously overlong at 127 minutes, “150 Milligrams” can’t always separate the compelling personal stakes of its narrative from its surfeit of informational minutiae.

Still, just as it was Frachon’s sheer, persistent force of personality that kept her little-supported campaign afloat through numerous legal and practical obstacles, Bercot’s film has a charismatic human face to carry viewers through its drier expanses of factual content. Fresh off a Cesar win for her French-language debut in last year’s “Courted,” Danish star Sidse Babett Knudsen (“The Duke of Burgundy,” TV’s “Borgen”) is an inspired choice to play the Brest-based Frachon, and not just for regional reasons: Knudsen’s best roles to date have called upon her guarded sense of cool, so it’s a surprise to see her channeling near-manic reserves of pluck here to play the good doctor. Frequently pop-eyed and given to animated gesticulation, whether in enthusiasm or anger, it’s a performance that occasionally teeters over the line from endearing to irritating — which, we’re led to believe, wasn’t untrue of Frachon herself.

The film’s earliest stages are perhaps its least digestible, as Bercot plunges viewers into a dense assemblage of medical facts and figures concerning the troubling effects of the prescription medication Mediator, which Frachon believes heightens the risk of valvular heart disease in patients. (“Digestible” certainly isn’t the word for the film’s commendably visceral sequences of open-heart surgery: Squeamish viewers are hereby advised to skip lunch beforehand.) Bercot, who adapted Frachon’s book with co-scribe Séverine Bosschem, has a lot of data to relay to her audience, but sometimes presents it in frustratingly prosaic ways: At one point, printed stats from a research report are superimposed on screen in a montage set to a thriller-by-numbers motif from composer Martin Wheeler, which hardly aids viewers’ comprehension of their larger implications. Meanwhile, calendar dates from Frachon’s two-year battle routinely pop up on screen, their particular significance not always conveyed.

Bercot, the actress-turned-helmer who opened last year’s Cannes fest with the low-key social realism of “Standing Tall,” seems somewhat torn between the thorough, academic methodology of docudrama and the romantic pull of a more character-driven underdog saga. Notwithstanding a couple of misjudged forays into overt, song-scored cutesiness, “150 Milligrams” actually fares better when it takes the more mainstream path, focusing on the fraught interpersonal relationships underpinning — and sometimes unpinning — Frachon’s quest.

Most conflicted and engaging among these is her love-hate collaboration with Antoine Le Bihan (Benoît Magimel), the medical researcher who provides the essential factual meat of her case, yet often balks at the uncompromising, sometimes unstrategic nature of her principle-led campaign. (“Limp dick,” she labels him, in not-quite-affectionate exasperation.) If there’s a heart-versus-head undertow to their squabbles, the film resists banally taking sides, often conceding both their points. Looking almost unrecognizably careworn and light-deprived, Magimel plays Le Bihan beautifully, countering and complementing Knudsen’s bullish bravado with more passively seething fury over the very same injustice — the moral commonality that survives their frequently opposed professional politics.

Bercot’s thespian instincts serve her well in identifying and encouraging such subtle chemistries among her players; incidental domestic scenes between Frachon and her alternately proud and befuddled husband (Patrick Ligardes) and children are likewise played with utmost care and conviction. The filmmaking around these delicate human dynamics can seem indifferently utilitarian by comparison: Guillaume Schiffman’s gray-toned lensing takes scant advantage of the widescreen format, while Julien Leloup’s editing assigns the same observational rhythm to rather too many conversational scenes. “Patience isn’t my forte,” our heroine blusters at one point; one occasionally wishes this no-nonsense but paradoxically undisciplined film would take after her a little more.

Film Review: ‘150 Milligrams’

Reviewed online, London, Sept. 15, 2016. (In San Sebastian Film Festival — opener; Toronto Film Festival — Special Presentations.) Running time: 127 MIN. (Original title: "La fille de Brest")

  • Production: (France) A Haut et Court production in co-production with France 2 Cinema in association with Cofinova 12, Soficinema 12, SofiTVCine 3, Palatine Etoile 13, Cinemage 10. (International sales: Wild Bunch, Paris.) Produced by Caroline Benjo, Carole Scotta, Barbara Letellier, Simon Arnal.
  • Crew: Directed by Emmanuelle Bercot. Screenplay, Bercot, Séverine Bosschem, based on the book "Mediator 150mg" by Irène Frachon. Camera (color, widescreen), Guillaume Schiffman; editor, Julien Leloup.
  • With: Sidse Babett Knudsen, Benoît Magimel, Charlotte Laemmel, Isabelle De Hertogh, Lara Neumann, Philippe Uchan, Patrick Ligardes, Olivier Pasquier, Gustave Kervern, Pablo Pauly, Myriam Azencot, Eddie Chignara, Raphael Ferret, Christophe Meynet, Gilles Treton, Garance Mazureck.