During Zac Efron's downward spiral into the world of drugs, he was partying it up with the notoriously fast-living Charlie Sheen, Breaking Celebrity News is exclusively reporting.

According to a source close the situation, Sheen and Efron were introduced by a mutual friend.

"Zac was in Charlie's inner circle for a few months. The two became very good friends. Zac was spending a lot of time at Charlie's Beverly Hills mansion and they were definitely partying together," the insider revealed.

"There were a lot of very good looking women hanging around."

The source says Sheen's friends were shocked to see the former Disney star partying with him — but he held his own.

"Some of Charlie's friends were very surprised to see Zac hanging around Charlie because he looked like such a clean cut guy," the source told Breaking Celebrity News.

"However, he could party with the big boys."

Sheen is known for his hard-core partying, admittedly snorting copious amounts of cocaine and smoking crack on a daily basis at times.

In 2012 after a brief period of sobriety, Sheen was back on drugs with a source telling Breaking Celebrity News, “For at least the last eight months or so Charlie has been having a quarter to half an ounce of cocaine delivered to him every single day and was spending nearly $2,000 a day on drugs. Sometimes he’d even get two to three quarters of cocaine in one day."

While hanging out with Sheen, Efron visited the set of his show Anger Management numerous times.