Opioids are the compounds that bind to opioid receptors present in the central and peripheral nervous system and also in the gastrointestinal tract.
Opioids are generally used as an analgesic and given as a medicine for pain relief and also in diarrhoea. However, they are frequently taken as drugs to create euphoria. Opioids are one of the common drugs that are abused along with cannabinoids. Opioids and cocaine are known as narcotics. It causes addiction and overdose can be fatal. If they are stopped suddenly after long term use then the person may experience withdrawal symptoms.
How do opioids work?
Opioids work by blocking the pain signals sent from the brain. They bind to opioid receptors on the nerve cells and block the release of neurotransmitters from the neuron ending.
Opioid receptors are protein and known as G protein-coupled receptors. There are three types of opioid receptors found, mu, kappa and delta. ‘Mu’ receptors are involved in relieving pain and pleasurable effects of opioids.
Opioids can affect various parts of the nervous system. When they act on the limbic system, which controls emotion then they produce a feeling of relaxation and pleasure. The effect produced by their action on the brainstem is slow breathing, relief in cough and pain. If they act on the spinal cord, which connects all the peripheral organs to the brain, then they can even decrease the pain due to serious injuries.
Opioids are often prescribed to relieve pain, cough and diarrhoea. They are used for relieving mild pain as well as for chronic pain, fibromyalgia, cancer, etc.
Plant Source of Opioids
Opioids are present naturally in some plants and also synthesized for medicinal purposes.
Opioid drugs are extracted naturally from poppy plants, Papaver somniferum. Opium has been used since ages for medicinal and recreational purposes.
Morphine is extracted from the latex of the poppy plant. Friedrich Sertürner, a German chemist first isolated the alkaloid from opium. It has been the benchmark in modern drug research.
Thebaine or paramorphine is another opiate alkaloid, extracted from opium and used to synthesize opioid drugs. It is a stimulant rather than a depressant such as codeine or morphine.
Apart from poppy, opioids also occur naturally in Kratom and Salvia.
Opioid Drugs Examples
Heroin is the most dangerous opioid, it is commonly called ‘smack’ and a common drug that is abused. It is taken by snorting or injection. Heroin is prepared by diacetylation of morphine on treating it with acetic anhydride. Alder Wright synthesized heroin for the first time. It is not used for medicinal purposes.
There are many opioids, natural and synthetic which are used as a prescription drug, e.g.
Endorphins are endogenous peptides, which are opioid peptides, they also bind to opioid receptors.
Naloxone is an opioid antagonist, which reverses the effect of opioids.
Although opioids are effective pain relievers, they are highly addictive. The long term use of opioids leads to deleterious effects such as confusion, drowsiness, slow heartbeat, breathing and hypoxia. Overdose can even lead to death.