Two random Hollywood guys, Mark Neveldine and Brian Taylor, co-wrote and co-directed “Crank.” It was their first time in charge of a movie, and it shows, both in the film’s enthusiastic disregard for filmmaking conventions, and in its mistakes.

The concept is at once ludicrous and irresistible. A Los Angeles hitman with the improbable name of Chev Chelios (Jason Statham) wakes up to discover he has been injected with a deadly poison. The only way to stave off death is to keep his heart pumping and to flood his body with adrenaline. Luckily, those are the natural side effects of what he was going to do today anyway, which is to find the S.O.B. who did this to him, and kill him.

The S.O.B. in question is an organized crime figure named Ricky Verona (Jose Pablo Cantillo), and why he chose to inject Chev with slow-acting poison instead of just, you know, KILLING him is anyone’s guess. Throughout the film he is furious that Chev is still alive, and even furiouser when Chev gets revenge by killing his (Ricky’s) brother.

To stay alive, Chev careens through L.A. in various vehicles, usually stolen ones, at one point driving his car through a shopping mall and later taking a hospital intern hostage to acquire some epinephrine, all in the interest of self-preservation. On the phone with him is his “doctor” (you’d use quote marks, too, if you saw the way this guy ran his practice), played by Dwight Yoakam, dispensing advice but insisting there’s no actual cure for what Chev’s been injected with.

Meanwhile, Chev has a girlfriend, Eve (Amy Smart), who doesn’t know he’s a hitman and who’s screamy and ditzy besides. I don’t really buy them as a couple, nor am I convinced the Chev character needed a girlfriend at all. She does help him create the most bizarre sex scene I’ve ever witnessed, though, when his heart begins to fail and he realizes a little fornication would be just the thing to boost his adrenaline. No problem, right? Except they’re in the middle of a sidewalk in Chinatown when they do it. No one order the chow mein today, OK?

Neveldine and Taylor direct the hell out of this thing, adding surreal touches like an image of the person Chev is on the phone with appearing in his rearview mirror, or randomly showing us an X-ray of Chev’s heart. When Chev gets into a fight in one scene, the exterior of the building bulges and pulses as if it were a cartoon. Later, one of the high-living crime bosses has three large plastic bubbles with bikini-clad women inside them, just sitting there next to the pool. Don’t be surprised if Girl In a Ball is on everyone’s Christmas list this year.

Such directorial excess is not always praiseworthy, but in a film about a man injected with drugs, who must constantly use drugs to stay alive, it makes a certain amount of sense. It seems likely that if Chev were to make a movie while in this condition, the movie would turn out looking like the crack nightmare that is “Crank.”

Unfortunately, the directors occasionally cross the line from outrageous and well-choreographed action violence into unnecessary cruelty. Cutting off the hand of a bad guy, fine. We’re down with that. But when innocent bystanders — cab drivers, cops, even a parakeet — start getting hurt, it’s hard to remain sympathetic toward the film’s “all in good fun” attitude. In fact, I worry about the psychological stability of a filmmaker who doesn’t realize that violence against a villain and violence against a civilian will elicit two very different audience reactions.

The occasional overindulgence aside, “Crank” is a zealously absurd action film, and one that doesn’t take itself too seriously. Statham made a name for himself as an over-the-top action star with the “Transporter” films, and while “Crank” doesn’t measure up to their level of proficiency, it’s enough to tide junkies over until the next big fix comes through.

B- (1 hr., 27 min.; R, abundant harsh profanity, a lot of sometimes-graphic violence, some strong sexuality, scattered bits of nudity.)