Opioids, such as codeine, morphine and oxycodone, have been used for years as prescription painkillers.  They are some of the most powerful tools available to stop pain, but an opioid addiction spreading across the United States has changed many doctor’s opinion on the drugs.

Photo courtesy of FDA.org

Many are justifiably concerned that patients will get hooked or share their pain pills with friends and family. And even short-term users risk dangerous side effects: The drugs slow breathing and can cause constipation, nausea, and vomiting. Data from IMS Health shows that U.S. doctors wrote about 30 million fewer opioid prescriptions in 2015 than in 2012. Although this is a positive change, restricting access doesn’t make pain disappear or stop addiction.

Opioids mimic molecules like endorphins, which are the body’s natural painkillers. Both endorphins and opioids latch on to proteins called opioid receptors on the surface of nerve cells.  When an opioid binds to a receptor in the peripheral nervous system, the nerve cells outside the brain, the receptor changes shape and stops pain messages from reaching the brain.  At low doses, the drug just makes people feel relaxed, but at high doses it can be deadly. Opioids are highly addictive because they mess with the brain’s reward system, triggering release of dopamine at levels higher than what the brain is used to. Gradually, the opioid receptors in the brain become less sensitive to the drugs, so the body demands higher and higher doses to get the same relieving feeling.

Scientists have been searching for a drug that kills pain as successfully as opioids without the harmful side effects.  They originally thought opioid receptors were simple switches, but more recent studies suggest that the same receptor can send multiple missives to different recipients.  There may also be a way to direct pain-killing messages specifically to the parts of a person’s body that are feeling pain. In one recent study, scientists described a molecule that bound to opioid receptors only when the area around the receptors was more acidic than normal. Inflammation from pain and injury raises acidity, so this molecule could eliminate pain where necessary, but wouldn’t bind to receptors elsewhere in the body, reducing the likelihood of side effects.

Despite the potential for new, better opioids, other researchers are focused on an altogether different set of pain-killing drugs: the cannabinoids.  The active molecules in marijuana do not have the same fast-acting pain-quenching abilities that opioids do, but with medical marijuana legal in 29 states plus the District of Columbia, the plant is getting more attention as a potential pain reliever, especially for chronic pain.  Although there are many cannabinoid receptors in parts of the brain that process pain messages, unlike opioid receptors, few exist in the brain stem. That means cannabinoids are far less likely to influence breathing than opioids.  Safer opioids or alternative painkillers would help people deal with their pain without risking addiction or death.

By: Skylar Andrade’18, Guest Writer