It's enough to kill most people.
"I fell in love with the feeling of them. I just kept taking them and taking them and taking them," he said.
Barber's addiction began when he was prescribed Percocet for a tailbone injury.
"I got highly addicted to them. Next thing you know, I moved up, went to OxyContin. Your tolerance got higher and higher. Eventually, I was at my breaking point," he said.
Barber said he tried to go cold turkey in the past but said he quickly found himself back on opiates. But five years ago, he started taking a relatively new medication called buprenorphine, designed to block the cravings.
He places strips of the brand name medication Suboxone under his tongue once a day.
"In the five years, I've never relapsed at all," Barber said.
Suboxone and similar medications are opiates, but they don't get addicts high. Instead, they block cravings in the brain.
But buprenorphine is heavily regulated, limited to just 100 patients per doctor by federal law.
"I could shut down today and open up tomorrow as a pain clinic doctor, and I could have a thousand patients on OxyContin. It makes no sense at all," said Dr. Skip Sviokla.
Sviokla works with Barber and some 300 other patients as part of a team of doctors at Medical Assisted Recovery in Warwick.
To meet the demand in Rhode Island, clinics like his need multiple doctors on staff.
Sviokla lost his license after he became addicted to Vicodin while working as an emergency doctor, taking up to 150 pills a day.
He was arrested, but went to rehab and eventually got his license back. He wrote a book about his journey and now specializes in addiction medicine.
"I was very successful. I was a very lucky guy. Beautiful family. Great job. Beautiful home. All that stuff. And I went down just as hard as anybody else," Sviokla said.
He believes there's no reason to limit buprenorphine prescriptions, as long as doctors are specially trained and patients are tested for other drugs.
And he's not alone.
"It's not a cure. It's simply a tool that we have in treating addiction, and a very, very effective one," said Pam Scheer, addiction and psychiatric nurse.
Scheer runs Assisted Recovery, a Cranston clinic that also offers buprenorphine through specially trained doctors. She said the overdose epidemic in New England means it's time to take a second look at the 100 patient limit.
"It's like a wheel that keeps going, and it keeps picking up dirt and you can't stop it. It's like a bad train wreck," she said.
Walls at the Cranston clinic are covered with letters addicts write about their experiences, many saying Suboxone changed their lives.
Treatment professionals said without it, many addicts find the cravings never completely go away.
"Opiate addiction is for life," said Scot Scheer of Assisted Recovery. "Once the receptors are open to that, and exposed to that, the ship doesn't come back into the harbor."
But people like Barber say there is hope.
"I'm a better worker. I'm a better father. The Suboxone isn't just going to do it just by itself. You're going to have to want to," he said.
Raising the patient limit would mean changing federal law, but it's an uphill battle that an increasing number of doctors believe is worth fighting.