Opioid Analgesics

By: Arooj Alvi

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Abstract: Pain “is a part of a rapid warning relay instruction of the motor neurons of the central nervous system to minimize detected physical harm.”
Analgesia simply means the absence of pain without losing consciousness.
“The analgesia system is mediated by 3 major components : the periaquaductal grey matter (in the midbrain), the nucleus raphe magnus (in the medulla), and the pain inhibitory neurons within the dorsal horns of the spinal cord, which act to inhibit pain-transmitting neurons also located in the spinal dorsal horn.”These areas are the areas in which the chemical mechanisms of opioid analgesics will take place.
Opioids are drugs derived from or related to the Opium.Opium is derived from the juice of the opium poppy, Papaver somniferum .Opium contains over twenty distinct alkaloids (morphine was the first alkaloid of opium to be isolated in 1806)
Opioid peptides are found in the central nervous system mainly in limbic and brainstem areas associated with pain reception, and the certain areas of the spinal cord. Their distribution corresponds to “areas of the human brain where electrical stimulation can relieve pain.” these opioid peptides interact with certain opioid receptors in the brain and certain other areas and produce their effects whether desirable or undesirable.
These opioid receptors includes mu, delta, kappa, orl-1.all of the opioid drugs act on these receptors and either modulate or potentiate their actions. Morphine is the prototype among such drugs. By acting on mu-receptors more strongly and less strongly on the other receptors, morphine induces its effect as sedation, analgesia, euphoria, respiratory depression, cough suppressant, decreased get secretions etc..
Tolerance is a major problem with all of the opioids and the physical and psychological tolerance of these drugs along with euphoria are the major reasons of drug addiction. For the withdrawal syndrome and addiction, some longer acting drugs that have mild withdrawal effects may be used as methadone. The opioid antagonists may also be used for the acute opioid toxicity as Naltrexone.