(Reuters) - Addressing a growing "epidemic" of opioid overdoses and abuse of the prescribed painkillers in the United States, the Centers for Disease Control and Prevention on Tuesday released voluntary guidelines that instruct primary care doctors to sharply deter use of the medicines for chronic pain.

"Overprescribing opioids, largely for chronic pain, is a key driver of America's drug-overdose epidemic," said CDC Director Tom Frieden. Sales of the prescription therapies have quadrupled since 1999, causing 165,000 fatal overdoses over the same period and now growing at more than 40 per day, according to the agency.

Primary care doctors who treat adults for chronic pain in outpatient settings account for nearly half of all opioid prescriptions, the CDC said. It defined chronic pain as lasting longer than three months, or past the typical time it takes for normal tissue healing.

The new guidelines recommend non-opioids, including acetaminophen and ibuprofen, as preferred therapy for chronic pain unless patients have active cancer or are receiving palliative or end-of-life care.

When opioids are used, the lowest possible dose should be prescribed to reduce risks of opioid abuse and overdose and patients should then be closely monitored, according to the CDC guidelines. The drugs should also be combined with non-drug approaches to controlling pain, like physical therapy and exercise, the agency said.

Moreover, when starting opioid therapy for chronic pain, doctors should prescribe immediate-release formulations instead of long-acting versions, the guidelines say. They recommend doctors avoid prescribing opioids with sedatives called benzodiazepines.

When prescribed for acute, or short-term pain, doctors should prescribe the lowest effective dose of immediate release opioids.

"Three days or less will often be sufficient; more than seven days will rarely be needed," the guidelines say.

Some studies suggest only 5 percent of patients prescribed opioids receive them for chronic pain, but they account for 70 percent of overall opioid prescriptions and the majority of overdoses.

For the vast majority of patients taking opioids for chronic pain, risks from the drugs will outweigh benefits, Frieden said.

"The prescription overdose epidemic is doctor-driven," Frieden said, adding it can be reversed if doctors rein in their prescriptions of the painkillers.

The American College of Physicians on Tuesday said the new guidelines provide important guidance "at a time when many communities are being devastated by the adverse impact of opioid misuse."

The most widely used opioids include hydrocodone, which is the main active ingredient of Vicodin, and oxycodone, an active ingredient of OxyContin and Percocet. They are synthetic narcotics which work by binding to opioid receptors in the brain and are mostly available in pill form.

Nearly two million Americans aged 12 or older either abused or were dependent on prescription opioids in 2014, the CDC said.

Opioids also include heroin, an illegal injectable drug which has become a far cheaper alternative to oral opioids on the streets of many U.S. communities, causing many overdoses.

Other U.S. health officials on Tuesday said first responders should have wider access to Naloxone, a drug that can reverse opioid overdoses.

(Reporting by Ransdell Pierson, editing by G Crosse and Chizu Nomiyama)