Zac Efron content with life

Zac Efron wouldn't want his life and career "any other way" at the moment.

The former High School Musical actor caused widespread shock last month when reports surfaced that he'd been treated for cocaine addiction in rehab.

His latest movie Parkland opens this month and although he hasn't expressly referred to the speculation, the 25-year-old star has insisted he is in a good place.

"I'm doing what I set out to do," he told Chicago Sun-Times.

"You have to go for it. You have to try. I want to challenge myself with tough parts. I wouldn't want it any other way."

Parkland follows the aftermath of the assassination of US President John F. Kennedy, who was taken to Parkland Memorial Hospital in Dallas after he was shot and later died at the facility.

The movie focuses on what happened within the treatment facility in the hours after the incident, with Zac portraying a doctor called Jim Carrico.

The actor had little knowledge of the event before the cameras started rolling and was amazed by what he learnt.

"He's a young resident who suddenly has the most important man in the world thrust in front of him with fatal injuries. He's called to action in a big way. You can't ask for more to do as an actor," he enthused.

"I didn't know all that much about the details. The film is eye-opening. This was in a time before Twitter and cell phones. People watched this unfold for days on TV."

The film also stars Paul Giamatti and Billy Bob Thornton, while Zac is also gearing up for the release of his film with Seth Rogen Neighbors which hits screens next year.

It was while shooting the comedy that Zac's personal problems are said to have worsened, with claims he was late to set as his supposed addiction took hold.

The speculation isn't something the actor comments on, instead he focuses on the positive aspects of his work.

"As an actor, my goal has always been to continue to challenge myself and learn and grow as an artist. I've been very lucky to have the chance to work alongside of great actors and directors. I couldn't ask for anything better," he said.