More than half of opioid overdose deaths in the US involve a prescription opioid.
According to the Centers for Disease Control and Prevention (CDC), around 78 Americans die from an opioid overdose every day, and between 2000-2014, the drugs were responsible for almost half a million deaths in the US.
While many of these deaths are down to use of illegal opioids - such as heroin - more than half of opioid overdose deaths involve a prescription opioid; since 1999, deaths from prescription opioids have quadrupled in the US.
Health care professionals have put the significant rise in opioid deaths down to the dramatic increase in prescriptions of these drugs; more than 259 million opioid prescriptions were written in the US in 2012 - the equivalent to a bottle of pills for every adult in the country.
Such figures have led the use of prescription opioids to be labeled as a "silent epidemic," and last week, the CDC issued new prescription guidelines in a bid to tackle the problem.
Furthermore, the Food and Drug Administration (FDA) recently announced that new warnings would be added to all prescription opioid medications to inform doctors and patients of the risks associated with their use.
But are such changes likely to prove effective? Are they enough to significantly reduce the number of overdose deaths caused by prescription opioids? Or will they - as suggested by some individuals - prevent patients with chronic pain from getting the treatment then need? We investigate.
What are opioids, and how do they work?
Opioids are drugs that bind to proteins in the brain, spinal cord and gastrointestinal tract called opioid receptors. In doing so, the drugs block pain signaling to the brain, reducing the perception of pain.
The drugs are prescribed for patients with moderate to severe pain who do not respond well to other pain-relieving medications. This often includes patients who experience severe pain after surgery or as a result of advanced cancer.
Commonly prescribed opioids include oxycodone, hydrocodone, codeine, morphine and fentanyl.
When taken for a short time and under a doctor's instructions, opioids can be very effective for alleviating pain and are generally safe.
However, many individuals use the drugs long term - generally defined as 3 months or longer - despite many health care professionals claiming there is a lack of evidence to suggest that such treatment is effective.
Last February, for example, a systematic review of randomized trials and observational studies of long-term opioid use for chronic pain - published in the Annals of Internal Medicine - concluded that "evidence is insufficient to determine the effectiveness of long-term opioid therapy for improving chronic pain and function."
The risks of opioid use
Needless to say, there are major concerns regarding long-term opioid use. The drugs can become addictive. They act on the same brain reward system as the illegal opioid heroin, producing a sense of euphoria.
Side effects of opioids include increased pain sensitivity, nausea, vomiting, constipation, sleep problems, confusion, reduced energy and depression.
According to the CDC, around 1 in 4 people in the US who receive opioid prescriptions long term in a primary care setting have problems with addiction.
Additionally, opioid users are at an increased risk of unintentional overdose. Between 1999-2014, around 165,000 Americans died from prescription opioid-related overdose.
In part, this risk is driven by increased tolerance to the drug when taken for long periods; users may need to take more of the medication in order to feel any pain relief.
A recent study reported by Medical News Today suggests that the risk of opioid overdose may also be influenced by the dosage patients are prescribed, with researchers finding that patients who died of unintentional overdose were prescribed opioids at double the dose of those who did not overdose.
Other side effects of opioid use include physical dependence - where a user experiences withdrawal symptoms after opioid cessation - increased pain sensitivity, nausea, vomiting, constipation, sleep problems, confusion, reduced energy and depression.
On the next page, we look at how federal health agencies are planning to crack down on opioid prescribing in a bid to curb the overdose epidemic.