The number of deaths related to abuse of opioid has been increasing in the U.S. as the substance has now become the leading cause of death from injuries in the country.  

In a bid to fight potentially deadly addiction to powerful painkillers, the FDA has come up with guidelines and warnings to deter its abuse, the latest of which is with a boxed warning on labels that caution users of serious risks related to use of pain-reducing drugs.

On Tuesday, the FDA announced that it now requires immediate-release opioid painkillers, which include the likes of oxycodone and fentanyl, to carry a "black box" warning, the strongest type of warning intended to educate doctors when they prescribe drugs to their patients.

The warning also serves to inform users of the risk of addiction, abuse, overdose and death related to the use of these powerful pain-killing medications.

The agency said 90 percent of opioid prescriptions in the U.S. are for immediate-release painkillers, which contain less opioid per dosage compared with extended-release painkillers but need to be administered more frequently.

The FDA said the labels would provide clear warning that immediate-release painkillers should only be given to patients suffering from severe pain when non-addictive drugs do not work well enough.

"Today's actions are one of the largest undertakings for informing prescribers of risks across opioid products," FDA commissioner Robert Califf said in a press release, "and one of many steps the FDA intends to take this year as part of our comprehensive action plan to reverse this epidemic."

Some, however, are not fully convinced that FDA's latest move can make a significant dent on opioid abuse in the U.S.

Michael Carome, director of consumer advocacy organization Public Citizen Health Research Group, said the boxed warning required in 2013 for the extended-release opioids made no sense and so is doing the same thing with immediate-release opioids.

"It will probably only make a small difference," Carome said. "This is just one small step of many steps that are going to need to be taken. It's not going to suddenly solve all the problems."

Figures from the Centers for Disease Control and Prevention (CDC), show that overdose deaths linked to prescription drugs have increased fourfold since 1999 following an increase in prescribing. Opioid overdoses now kill more than 40 people per day.

More people die each year from prescription narcotics than from car accidents.