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Definition of opioids
Last reviewed: 04.07.2025
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Opioids are substances that cause physical and psychological dependence. Opium is obtained from the juice of the opium poppy (Papaver somniferum), it contains more than 20 different alkaloids, the most famous of which is morphine. Semi-synthetic alkaloids are obtained from morphine, including heroin (diacetylmorphine), codeine and hydromorphine. Synthetic opioids include trimeperidine, methadone, etc.
Of all the types of opiate addiction, heroin addiction is the most common. Heroin is much more active than morphine, is more soluble, and passes through the blood-brain barrier more quickly.
Opioids exert their action by binding to specific opioid receptors in the brain. Brain areas with high affinity for exogenous opioids contain high concentrations of certain endogenous peptides with opiate-like properties. These peptides are called endorphins (this term is somewhat confusing due to its similarity to the name of one of the main prototypes of opioid peptides, β-endorphin, so the term "opiopeptides" is used to designate the generic affiliation of natural opioid peptides, and the term "endorphin" is used for peptides closely related to β-endorphin).
The major effects of opioids are related to their action on the central nervous system. The most important of these include analgesia, euphoria, lethargy, respiratory depression, drowsiness, and clouding of consciousness; impaired judgment may occur.
A significant portion of opioids is converted into polar metabolites, which are then quickly excreted by the kidneys. Compounds with free hydroxyl groups (morphine) are easily conjugated with glucuronic acid and excreted with bile (but this is not the main route of excretion). Heroin (diacetylmorphine) is hydrolyzed to monoacetylmorphine, then to morphine, which is conjugated with glucuronic acid. Opioids are also subject to N-demethylation in the liver. The half-life of morphine is 2-4 hours, heroin - 1-1.5 hours, codeine - 2-4 hours.
Morphine and heroin addicts may take hundreds of milligrams of heroin; tolerant addicts take up to 5,000 mg of morphine (in intolerant subjects, death from overdose may occur with 60 mg of morphine). Morphine and heroin withdrawal syndrome begins 6-8 hours after the last dose, reaches its maximum intensity within 2-3 days, and continues for the next 7-10 days (sometimes up to 6 months).
The lethal dose of morphine when taken orally is 0.5-1 g, when administered intravenously - 0.2 g. The lethal concentration in the blood is 0.1-4 mg / l. All opioids are especially toxic for children of younger age groups. The lethal dose of codeine for children under 3 years old is 400 mg, heroin - 20 mg.
Diagnosis of opioid overdose is often straightforward (anamnesis, injection marks), but in other cases it can be very difficult (as with any comatose state of unknown etiology). In such cases, it is necessary to test urine for opiate content. Various methods are used for this, both qualitative and quantitative.
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