David E. Stanley writes in his new memoir My Brother Elvis: The Final Years that he used to have to physically reach into Elvis' mouth and remove food to prevent him from choking

When Elvis Presley died in August 1977, the world was shocked: the vibrant performer was only 42.

Decades later, it has become well-known that Presley’s final years were filled with drug use – the Blue Hawaii heartthrob was no more.

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In My Brother Elvis: The Final Years, a new memoir by the late star’s stepbrother David E. Stanley, the extent of Presley’s substance abuse is outlined in shocking detail.

“We had to watch Elvis around the clock, since he was taking so many drugs that he spent more time completely obliterated than not,” writes Stanley, whose mother was Dee Presley, Presley’s father Vernon’s second wife.

Only 16 when he became Presley’s road bodyguard, Stanley explains that his job requirements were more like “babysitting,” adding, “I felt more like a nursing home aide.”

Among his so-called duties were keeping up with Elvis’ medications – a combination of drugs that were crafted into what Stanley dubbed “attack packs.” Each “pack” included a variety of six to 11 pills, along with a shot or three of Demorol, an opioid pain medication.

Those pills, Stanley’s brother Rick told PEOPLE in 1989, included “all kinds of uppers – Dexedrine, Black Beauties. Then you’ve got the Class-A Percodan, Demerol, codeine. There were barbiturates – Tuinal, Seconal, Nembutal, Carbital… Needles.” The combinations were called “attack,” because, Rick said, “that’s what he wanted them to do, ‘attack’ him, knock him out.”

Stanley says in My Brother Elvis, that Presley would go through up to three “packs” a day – a schedule that often resulted in the singer passing out.

“Whomever was watching him had to make sure that the drugs didn’t kick in before he was done eating and put him to sleep, or else he risked choking to death, of which he had a couple of close calls,” Stanley writes. And, in the cases when he did fall asleep mid-meal, Stanley would have to physically reach into Presley’s mouth and remove the food.

Similarly, Rick previously recalled to PEOPLE, “Sometimes Elvis would get so out of it that during a meal he would be sitting there and he’d be nodding off, and you’d always have to watch him because he’d get a piece of hamburger meat hung in his throat.”

“On more than one occasion, I had to go in while he was choking in bed and reach down his throat and pull stuff out,” Rick explained. “Pound on his chest, And it was sad, you know. I mean, this guy’s 19 years older than me, and I’m holding him up, and I’d put my arms around him… He was just like a little bitty kid.”

During the late ’70s, Rick said, “Drugs were everywhere. In the latter part of his life they started taking complete control. He couldn’t think or act straight anymore.”

Stanley says that he thinks his stepbrother relied on the drugs to keep himself “numb from the outside world.”

He aided in the drug regimen, he says, because his youth blinded him to the harsh reality of the situation.

“I wasn’t able to fully grasp what was happening, and was no match for Elvis in the throws of addiction,” he explains. “He was more than a King to me, he was my father figure, and I never thought a day would come where he wouldn’t be there anymore. I had this naive belief that Elvis could do anything – even overcome a prescription drug addiction.”

Presley was found dead on the bathroom floor at his Memphis home, Graceland. His death was ruled as “hypertensive cardiovascular disease associated with atherosclerotic heart disease,” but there has long been a conspiracy over drug involvement in his demise.

“Beyond all the fame, fortune and hype, Elvis was a simple man who loved the Lord, his family, and his fans,” said Stanley. “A man who was haunted by demons and insecurities that plague us all, and eventually lost the battle of addiction, as too many often do.”