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More and more people have died from mixing strong painkillers with tranquilizers like Xanax, leading federal health officials to strengthen warnings against doing so.

People who mix opioids with the sedatives can suffer from breathing problems, which can lead to comas and even prove fatal, the Food and Drug Administration said Wednesday.

A technician handles prescription drugs at the Whitman-Walker Clinic, a Washington, D.C.-based community health center focusing on HIV/AIDS care and lesbian, gay bisexual and transgender care. Macintosh / MCT via Getty Images

The FDA plans to add a black-box warning — the strongest warning — to nearly 400 drugs in the opioid and benzodiazepine classes.

"We said, 'we cannot wait' and called upon the FDA to save lives now," Baltimore City Health Commissioner Dr. Leana Wen said on a call with reporters Wednesday. Wen and other health professionals had petitioned the FDA to make the change.

“As an emergency physician, I have seen that in medical training and practice, it is common to prescribe opioid painkillers to a patient taking benzodiazepines for anxiety, and vice versa. This is not based on scientific research, but is routine clinical practice," Wen said.

Related: To Cut Opioid Abuse, Watch Doctors

"In recent years, we public health officials have noted an alarming trend: that nearly one in three unintentional overdose deaths from prescription opioids also involve benzodiazepines. We have also noted the growing biological evidence: that combining these medications increases sleepiness and slows breathing, increasing the likelihood of a fatal overdose," she added.

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The FDA said it had seen a 41 percent increase in the number of patients being prescribed both opioids and sedatives — about 2.5 million patients — between 2002 and 2014. Overdose deaths tripled between 2004 and 2011.

"Nearly one in three unintentional overdose deaths from prescription opioids also involve benzodiazepines."

"Opioids are used to treat pain and cough; benzodiazepines are used to treat anxiety, insomnia, and seizures," the FDA explained.

"In an effort to decrease the use of opioids and benzodiazepines, or opioids and other central nervous system depressants, together, we are adding Boxed Warnings, our strongest warnings, to the drug labeling of prescription opioid pain and prescription opioid cough medicines, and benzodiazepines."

The FDA has been heavily criticized for doing too little to stop overuse and abuse of opioids such as OxyContin, Vicodin and Percocet. The drugs, which are similar to morphine and heroin, are highly addictive and are easy to overdose on.

Deaths from opioid overdoses have hit an all-time record in the U.S.

They killed more than 47,000 people in 2014 — more than the 32,000 who died in road accidents, according to the Centers for Disease Control and Prevention.

The CDC estimates that in 2013 1.9 million people abused or were dependent on prescription opioid pain medication.

In March, the White House launched an initiative aimed at curbing America's opioid addiction epidemic, and the CDC issued new voluntary guidelines in May urging doctors to use caution in prescribing the potentially killer drugs.