Opioid

Crude opium, from which most opiates derive.

An opioid or opiate is any endogenous or exogenous agent that binds to opioid receptors located primarily in the central nervous system and gastrointestinal tract.

Although the term opiate is often used to refer to all drugs similar to opium, it is more appropriate to limit its scope to the naturally occurring alkaloids of opium and its semisynthetic derivatives. There are three broad classes of opiate substances: opium alkaloids, such as morphine (the prototypical opiate) and codeine; semi-synthetic opioids, such as heroin and oxycodone, and fully synthetic opioids, such as pethidine and methadone, which have a structure unrelated to opium alkaloids. The term opioid refers only to endogenous and exogenous substances with affinity for these receptors, such as endorphins, enkephalins, or dynorphins.

Opioids are frequently prescribed for their effective analgesic properties, that is, to relieve pain.

Pharmacology

Opioids bind to specific opioid receptors in the nervous system and other tissues. There are three main classes of opioid receptors: μ, κ, and δ (mu, kappa, and delta), although more than seventeen have been described, including ε, ι, λ, and ζ (epsilon, iota, lambda, and zeta) receptors.. In contrast, σ (Sigma) receptors are currently not considered to be opioids because their activation is not reserved to the opioid inverse agonist naloxone, they do not show high affinity for classical opioids, and they are stereoselective for dextro-rotary isomers. while the other opioid receptors are stereoselective for levorotatory isomers.

In addition, there are three subtypes of μ receptors: μ₁ and μ₂, and the recently discovered μ₃. Another receptor of clinical importance is the opioid receptor-like receptor 1 (ORL1), which is related to pain responses and the development of tolerance to μ-opioid agonists used as analgesics. They are all receptors linked to Gi/o protein which inhibit adenylate cyclase and decrease cAMP production, also promote the opening of potassium channels and the closing of presynaptic calcium channels, all of these actions together decrease neuronal excitability.

Opioids in the Clinic

Medications in this class (also known as narcotics) include morphine, codeine (methylmorphine), and heroin (diacetylmorphine); Of these three, heroin is the one with the greatest affinity for endorphin receptors, which is why it is more potent than morphine; however, it quickly fell out of favor in medical practice because of its poor safety profile and increased potential for abuse. Morphine is often used as an analgesic to relieve severe pain after surgery or severe cancer pain. Codeine, being less effective than morphine, is used for less acute pain. Other examples of opioids that are prescribed for pain relief include buprenorphine, oxycodone (OxyContin), propoxyphene (Darvon), hydrocodone (Vicodin), and hydromorphone (Dilaudid), as well as pethidine (Demerol) which is less used due to its side effects. In addition to their pain-relieving properties, some of these drugs, for example, codeine and diphenoxylate (Lomotil), can be used to relieve cough and diarrhea. Morphic derivatives: Fentanyl, Alfentanil, Sufentanil are powerful analgesics used during surgery. Currently there is Remifentanil, which is a powerful opioid with a very short half-life that is being used more and more during anesthetic acts. In veterinary medicine, etorphine, carfentanil and thiafentanil are used, especially in wildlife and zoo species, all of them reversible with naltrexone, diprenorphine or naloxone; The use of these drugs in this type of animal is justified because the reversal is achieved in a few minutes and with great safety for the animal and the people who perform the procedure.

Opioid analgesics are a group of drugs that possess great analgesic activity, mediated by the activation of specific receptors in the central and peripheral nervous system, which are natural derivatives of opium, or semi-synthetic or analogous derivatives with many common characteristics.

Formerly, opiates received other names:

• hypnoanalgesics: (hypnos = dream) and narcotic painkillers (narcos=stupor) for their ability to generate sleep or stupor.

• opiates: to group those natural and semi-synthetic derivative drugs of opium and endorphins, as a generic term involving the three families of endogenous peptides.

Today we consider the term opioids It is much more inclusive, including all agonists and antagonists with a morbidity, endogenous or exogenous activity, whether these are natural, semi-synthetic or synthetic, and it is the one that is accepted today.

History

Knowledge of the effects of opium and its use for therapeutic purposes dates back to the remote past: the clearest data come from the 3rd and 4th centuries BC: Hippocrates (460-366 BC) refers to to its analgesic properties with the motto "Divinum opus est sedare dolores".

It was always considered an almost miraculous medication, and Paracelsus came to consider it the "stone of immortality".^{[citation needed]}

In 1660, Thomas Sydenham made the tincture of opium that bears his name (Sydenham's laudanum), coining the famous phrase: "Among the remedies that Almighty God has deigned to give man to alleviate his sufferings, none is as universal and efficacious as opium."

But the most significant development in the history of opium use occurred when, in 1803, F. W. Sertümer -- a German chemist -- succeeded in isolating opium's main alkaloid, naming it morphine, in relation to Morpheus, the mythological god of opium. dreams.^{[citation needed]}

From this discovery, others quickly followed: codeine, in 1832, by Robiquet, and papaverine, by Merck, in 1848. From then on, the use of drugs began to spread in the medical world. pure alkaloids to replace opium preparations.^{[citation needed]}

• carfentanyl
• dihydrocodein
• hydromorphone
• morphine
• oxymorphone
• sufentanyl
• tapedol
• tramadol