Chronic pain is a persistent issue in the United States, affecting more than 100 million Americans.  Treatment and management of chronic pain is notoriously challenging. Opioids are often the solution, as these drugs are considered to be the most effective treatment for chronic pain. However helpful, opioid use can often come with serious side effects. Many people seek alternative or complementary pain management methods which may provide efficacy while avoiding discomfort, harm, and addiction. Whether personally dealing with chronic pain, helping a loved one, or treating a client, it is important to understand the basics of opioids.
The term “opioids” refers to all compounds that bind to specific proteins, called opioid receptors, in the body. Opioids act as neurotransmitters and neuromodulators at these receptors, sending signals through the body and to the brain.  Two major categories of opioids are endogenous and exogenous.
Endogenous opioids are naturally occurring in the body. There are different families of opioid peptides in the body, including endorphins, enkephalines, dynorphins, and endomorphins. Each of these compounds has different precursors, locations, and roles; they help to form then complex communication systems within our bodies. Endogenous opioids are involved in regulating pain perception (nociception), stress, reward, arousal, and homeostasis of the autonomic, cognitive, limbic, and neuroendocrine systems. For example, most people have heard about endorphins as a “natural pain reliever” or “feel-good chemical” produced during strenuous exercise, excitement, pain, and orgasm. [1, 3]
Although endogenous opioids are essential in many body functions, these opioids are not exactly the same as the prescription drugs that come to mind when you think of opioids. Our bodies can’t make enough natural endogenous opioids to produce negative side effects or overdose, but they also are unable to produce enough to stop severe or chronic pain. 
Exogenous opioids are not made within the human body. These include natural, synthetic, and semi-synthetic opioids. 
Natural opioids, also called opiates, are derived from the poppy plant, papaver somniferum. These include opium, morphine, codeine, and thebaine.
Synthetic opioids are human-made and do not occur in nature. Fentanyl, methadone, and propoxyphene are synthetic opioids.
Semi-synthetic opioids are created, or synthesized, from natural opiates. Examples of semi-synthetic opioids are heroin (made from morphine), oxycodone, and oxymorphone (made from thebaine).
These drugs act similarly to endogenous opioids by binding to opioid receptors and sending signals. Some opioid receptors function in pain modulation, located in the central and peripheral nervous systems. [3, 5, 7]
When the natural, semi-synthetic, or synthetic opioid binds to the receptor and sends the signal, feelings of euphoria, joy, and general calmness generally ensue. [4, 5] Opioids can block pain perception and interact with neurotransmitters involved in pain modulation. Although opioids can be extremely effective in reducing chronic pain, they can also cause unwanted side effects. Constipation is the most common side effect, as opioids reduce peristalsis. Sleepiness, mental clouding, dizziness, vomiting, sedation, and respiratory depression may also occur. [2, 5] In some people, short-term or long-term opioid use may result in tolerance or physical dependence. This can lead to opioid overuse, abuse, and addiction, affecting individuals’ wellness in all dimensions (physical, emotional, environmental, social, occupational, intellectual, financial, and spiritual). [5, 7]
Many of the synthetic and semi-synthetic opioids are created in the hopes of making potentially less addictive drugs for pain management. Additionally, individuals will react differently to the various types of opioids.  Having a variety can help people receive treatment that offers the most benefits with the least amount or severity of side effects. Even with the possibility of less addictive or harmful opioids, many people seek other pain-management methods that can work with opioids and potentially reduce their use. Burgeoning research explores complementary and alternative methods that may be safe, effective, and accessible. The connection between opioids and neurotransmitters may warrant assessment of individuals’ neurotransmitter levels to see how imbalances in this system can play a role in chronic pain. Additionally, utilizing the power of meditation can also offer benefits, as a recent study shows that mindfulness meditation modulates pain via endogenous opioid pathways. 
In summary, endogenous and exogenous opioids both act in the body by binding to opioid receptors. Endogenous opioids are produced in the body and have a variety of functions, including influencing pain perception. Exogenous opioids can be natural, synthetic, or semi-synthetic, and are highly effective at reducing chronic pain. Due to side effects such as constipation and suppressing respiration, as well as the high potential for abuse and addition, many people look to complementary and alternative therapies supported by research to address the challenge of managing chronic pain.
1. Holden, J. E., Jeong, Y., & Forrest, J. M. (2005). The endogenous opioid system and clinical pain management. AACN Advanced Critical Care, 16(3), 291-301.
2. Khansari, M., Sohrabi, M., & Zamani, F. (2013). The useage of opioids and their adverse effects in gastrointestinal practice: a review. Middle East journal of digestive diseases, 5(1), 5.
3. Koneru, A., Satyanarayana, S., & Rizwan, S. (2009). Endogenous opioids: their physiological role and receptors. Global J Pharmacol, 3(3), 149-153.
4. Opiates/Opioids. The National Alliance of Advocates for Buprenorphine Treatment. NAABT, n.d. Retrieved from https://www.naabt.org/education/opiates_opioids.cfm
5. Rosenblum, A., Marsch, L. A., Joseph, H., & Portenoy, R. K. (2008). Opioids and the treatment of chronic pain: controversies, current status, and future directions. Experimental and clinical psychopharmacology, 16(5), 405.
6. Sharon, H., Maron-Katz, A., Simon, E. B., Flusser, Y., Hendler, T., Tarrasch, R., & Brill, S. (2016). Mindfulness Meditation Modulates Pain Through Endogenous Opioids. The American journal of medicine.
7. Trang, T., Al-Hasani, R., Salvemini, D., Salter, M. W., Gutstein, H., & Cahill, C. M. (2015). Pain and poppies: the good, the bad, and the ugly of opioid analgesics. The Journal of Neuroscience, 35(41), 13879-13888.