Codeine, morphine, methadone and oxycodone are some opioid medications. Opioids are a class of narcotics generally prescribed as painkillers, notes WebMD. Opioids have the potential to be addictive and are not available over the counter as of 2015.
Opioid drugs bind to receptors in the brain, reducing the intensity of pain signals that the brain receives, notes WebMD. The drugs also affect certain areas of the brain that control emotion, which additionally reduces the strength of a pain reaction, according to the National Institute on Drug Abuse. The majority of opioids are prescribed to patients experiencing severe pain, after a traumatic injury or major surgical procedure, for example. Codeine is an opioid that may be prescribed for more minor pain, such as pain following dental work.
Opioid drugs are traditionally derived from a chemical found in poppies; however scientists have also managed to synthesize opioid drugs from bio-engineered yeast as of 2015, according to Reuters. Patients with severe pain may be prescribed a constant dose of opioids for round-the-clock pain relief, notes WebMD. Additional doses may help with pain that arises despite a consistent, lower dose. High doses of opioid drugs may cause side effects such as slowed breathing, confusion and constipation, notes Health.