More than 1 in 5 Americans take opiates during their lifetime, either illegally or by prescription. Now, more people die of narcotic overdoses than automobile accidents. There is an increase in the use of heroin and other street opiates are 40% each year since 2010. More and more people are commonly misusing prescribed opiates and tragically, it’s showing no signs of reduction.
Opiates and narcotics get their classification by sharing a common effect, the most reliable one: pain relief. This is due to the drug's action in the thalamus. Some common prescriptions include vicodin and oxycontin, and approximately 300 million opiates are prescribed every year. When taken as directed, they can immensely help individuals suffering from acute and chronic pain to manage daily functions more easily.
Action:
The nucleus accumbens and the thalamus are the regions where opioids most concentrate. Along with the opioids acting on opioid receptors in the brain, one of the brain circuits that is activated by opioids is the mesolimbic (midbrain) reward system. This system generates signals that result in the release of the chemical dopamine (DA) in another part of the brain, the nucleus accumbens. This release of dopamine causes feelings of pleasure. The dopamine release also helps relieve pain, hence their use as pain relievers. Other areas of the brain create a memory that associates these good feelings with the environment in which they occur - in this case, consuming the drug. These memories, called conditioned associations, which often lead to the craving for drugs when the person is reminded of the event again, making them actively seek it out.
Prescription opiates are deemed safe by most people, but they can be dangerous when misused. The misuse of opiates is caused when the reward process is stimulated in the absence of any significant pain, which encourages the person to consume more of the drug, simply for pleasure. When used correctly, they effectively enhance the body’s ability to reduce pain and produce calming effects. But when taken excessively, that calm turns into a high euphoria, an intense feeling that soon overcomes the brain and convinces itself superior to the naturally occurring dopamine production in the brain.
Addiction:
From a scientific perspective, it is easy to see why opiates are so appealing. They work in the brain by mimicking endorphins. These endorphins are what you would describe to be a “runner's high”. Along with endorphins, there is another large class of chemicals called anti-opiates. These essentially produce the exact opposite effects of endorphins, and by extension, narcotics. They exist to restore the brain to its stable baseline, as part of our homeostatic system, and are essentially what causes dependence and adaptation to a drug.
Following exposure to recreational drugs including opiates like heroin, dopamine is released into the nucleus accumbens, released by neurons that originate in the midbrain, following the mesolimbic pathway. As mentioned before, addictive drugs derive pleasure by stimulating the mesolimbic pathway. The mesolimbic system evolved to encourage behaviors that are more focused on the “thrill” of pleasure, not essentially on maintaining a transient state or mood. The brain's response to a drug is to always facilitate the opposite state; therefore, the only way for any regular user to feel normal is to take the drug. So it functions normally with the drugs in the system, and abnormally when it's not.
Keeping this basic homeostatic principle in mind, perhaps, the most dangerous part of opioids, or any drugs in this instance is tolerance. Opioid tolerance occurs because the brain cells that have opioid receptors on them gradually become less responsive to the opioid stimulation. For example, more opioid is needed to stimulate the VTA brain cells of the mesolimbic reward system to release the same amount of dopamine. Therefore, more opioid is needed to produce pleasure comparable to that provided in previous drug-taking episodes.
Another is adaptation. Due to the release of dopamine-producing constant euphoric feeling in the individual, the anti-opiate system stimulates to create more pain in order to balance out the net effect. In order to oppose this pain, the body craves to go back into safety and escape the perceived danger, which is often just taking drugs in higher amounts and more frequently. This will eventually lead most people to an overdose.
Withdrawal and treatment:
As mentioned in the previous section, the higher the dose of the drug in the brain, the stronger the tolerance. The brain reduces the production of naturally occurring chemicals in the brain so it almost completely relies on dopamine and the pleasure derived from the external drugs. Take this away, the brain falls in a severe state of dysphoria, and the person experiences withdrawal symptoms. Oftentimes, after repeated use, the opiates no longer have a euphoric effect on the brain, but the person continues to use it to prevent the painful withdrawal symptoms.
Furthermore, due to its dependence, it has a reduced ability to handle pain on its own so it depends on opiates alone to relieve pain. When there is a deficit of this, the level of pain dramatically increases due to the brain’s ability to handle it alone, and this is essentially the reason why withdrawal can be so painful.
The most common method of treatment is medication-assisted treatments such as MATs like methadone, which aims to systematically satisfy the brain’s need for opioids but reduces its reliance over time. These also activate the opiate receptors but take a much longer time to absorb into the bloodstream and hence don’t cause instant euphoric feelings like general opiate drugs. They also discourage use by blocking out the effects of the drugs. This means that the person will not experience cravings associated with withdrawal. These types of drugs are classified as opioid agonists.
However, this does not come without its qualms. Methadone, like any other drug, can also be abused and can cause or increase addiction. They can also be used with other substances such as alcohol, which leads to serious reactions and present a risk of unconsciousness, coma, and even death. There are also studies on rats that challenge the long-term effect of the drug on the brain. It states its potential to significantly change the cognitive function and memory in the brain, but more research and study need to be done to confirm this.
Other drugs such as naltrexone are opioid antagonists and work by blocking the activation of opioid receptors and preventing any opioid drugs from producing rewarding effects. However, methadone still continues to be the most popularly used medication.
Citations:
Kosten, T. and George, T. (2002). The Neurobiology of Opioid Dependence: Implications for Treatment. Science & Practice Perspectives, [online] 1(1), pp.13–20. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851054/ [Accessed 22 Mar. 2021].
American Addiction Centers. (2020). Pros and Cons of Methadone Medication-Assisted Treatment. [online] Available at: https://americanaddictioncenters.org/methadone-addiction/pros-cons [Accessed 22 Mar. 2021].
Scholastic.com. (2007). The Science of Opioid Addiction | Scholastic: Nida. [online] Available at: http://headsup.scholastic.com/students/the-science-of-opioid-addiction [Accessed 22 Mar. 2021].
America’s Rehab Campuses. (2020). What Happens to Your Body During Drug Withdrawal? - America’s Rehab Campuses. [online] Available at: https://www.americasrehabcampuses.com/blog/what-happens-to-your-body-during-drug-withdrawal/ [Accessed 22 Mar. 2021].
Guide, B. (2018). Does Long-Term Opiate Use Change the Brain? (Guide). [online] MedMark Treatment Centers. Available at: https://medmark.com/does-long-term-opiate-use-change-the-brain/ [Accessed 22 Mar. 2021].
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