opioidid

Opioids, known in Estonian as opioidid, are a class of drugs that act on opioid receptors in the brain and body to produce analgesia and other effects. They include natural opiates such as morphine and codeine, semi-synthetic opioids like heroin, oxycodone and hydrocodone, and fully synthetic opioids such as fentanyl, methadone and tramadol. The primary clinical use is relief of moderate to severe pain, but opioids are also used in anesthesia, for cough suppression and in the treatment of opioid use disorder in controlled settings.

Opioids exert their effects mainly by activating mu, delta and kappa receptors, which are G protein–coupled receptors. Activation of these receptors inhibits neuronal firing and neurotransmitter release through Gi/o signaling, leading to analgesia, sedation and, at higher doses, respiratory depression, constipation and mood alteration. Mu receptors mediate most analgesic and addictive effects; kappa receptors can cause sedation and dysphoria; delta receptors contribute to analgesia and mood effects. Some opioids (such as loperamide) act peripherally with limited central effects.

Clinical use requires careful dosing because tolerance, dependence and withdrawal can develop with repeated use. Overdose can cause coma, pinpoint pupils and life-threatening respiratory depression; treatment includes administration of naloxone, an opioid receptor antagonist. Long-term management of opioid use disorder may involve methadone or buprenorphine substitution therapy, psychosocial support and monitoring.

Opioids remain among the most effective analgesics for severe pain, but their use carries substantial risks of misuse, addiction and adverse effects. Public health measures include prescription monitoring, harm reduction and access to treatment.