CHARLIE SHEEN has suffered at least FOUR potentially fatal drug overdoses in the last six months – and he’s alive today only because of the quick action of friends and staffers at his Beverly Hills mansion.

The drug-addled Two and a Half Men star – whose bizarre lifestyle and insane rants have become a national spectacle recently – grew so concerned that his routine cocaine benders would end in his death that he’s become a regular user of nitroglycerin tablets, say sources. The tablets contain a chemical compound commonly used to prevent cardiac arrest.

"Since Charlie’s latest tailspin began in October, he’s suffered at least four potentially fatal cocaine overdoses – maybe even more – but his life was saved each time by people who rushed to his side and rescued him," an insider told The ENQUIRER.

The actor’s overdoses have become so predictable that he now actually plans for them in advance, continued the insider. Charlie reportedly carries sublingual (under the tongue) nitroglycerin pills with him when he’s using cocaine.
When his drug intake reaches the point that his heart rate starts to increase dramatically, Charlie pops a pill – believing it prevents a deadly heart attack, says the insider.

But on at least four occasions, Charlie – who has been fired by CBS and Warner Bros. from "Two and a Half Men" – has found himself in a life-or-death situation when he couldn’t get to the pills on time, maintains the insider.

In each case, someone had to come to the 45-year-old actor’s aid after he collapsed in his home.

During three of the episodes, an assistant or a friend in the home found Charlie "strewn across the floor, sweating bullets, while he was going in and out of consciousness," continued the insider.

"Luckily, they got to him in time and were able to get a nitroglycerin pill under his tongue," which revived him.

Another time, Charlie was alone and couldn’t get to his pills when he needed them, divulged the insider. He was able to call a friend from his cell phone just moments before he collapsed.

By the time the friend arrived, Charlie appeared to be unconscious. "Fortunately, this pal knew exactly what to do – give Charlie a pill under his tongue – and he eventually came out of it."

While nitroglycerin can be used to prevent cocaine-induced heart attacks, it’s actually a secondary line of defense, according to one expert.

"Charlie’s very good at beating the system," added the insider. "The question is how long he’ll be able to play his deadly game."

Get all the details in the new ENQUIRER – still on sale.