What are opioids and how they work?

The term "opioids" refers to both natural compounds derived from the poppy plant (Papaver somniferum) and semisynthetic or synthetic substances that mimic their effects by interacting with opioid receptors in the brain. Opioids are known for their pain-relieving and sedative properties, with medications like morphine, codeine, and fentanyl commonly used to manage pain. Additionally, opioids such as methadone and buprenorphine are utilized in the treatment of opioid dependence. When taken, opioids can induce feelings of euphoria, which often leads to their misuse for non-medical purposes. Examples of opioids include heroin, morphine, codeine, fentanyl, methadone, and tramadol. However, due to their pharmacological effects, opioids can cause respiratory depression, and overdoses may result in death.

The non-medical use, prolonged misuse, or use without medical supervision can lead to opioid dependence and various health problems. Opioid dependence is characterized by a compulsive drive to use opioids, an inability to control usage, prioritizing opioid use over other activities, and continued use despite negative consequences. This condition may also include physiological symptoms such as increased tolerance, withdrawal symptoms upon cessation, and continued use to avoid these symptoms [^1].

Opioids act on receptors throughout the body, particularly in the brain, leading to changes that block pain and produce a sense of euphoria, often described as warmth or well-being. Opioids have been prescribed for centuries to treat pain, severe cough, and diarrhea, and under medical supervision, they can be safe and effective. Common prescription opioids include morphine, codeine, oxycodone, hydrocodone, fentanyl, and hydromorphone.

However, prescription opioids are often misused, shared, or sold illegally. Risky behaviors such as using opioids for non-prescribed purposes or altering their form of use (e.g., crushing or injecting) increase the chance of overdose. Sharing prescribed opioids can also put others at risk, as drugs obtained illicitly may contain unknown or lethal ingredients. Illegally manufactured fentanyl is often found in counterfeit pills that resemble prescription medications, or it may be mixed with other illicit drugs like methamphetamine or cocaine, further raising the risk of unintentional overdose.

Globally, about 296 million people (5.8% of the population aged 15–64) used drugs at least once in 2021, with approximately 60 million using opioids. Of these, 39.5 million people were living with drug use disorders. While heroin remains the primary opioid for many users, the use of prescription opioids is steadily increasing [^2].