Opioid addiction is one of the biggest public health problems facing the United States, with more people succumbing to overdoses annually than dying in car accidents. Fortunately, there are many effective drugs that are used to treat opioid addiction, giving people an opportunity to turn their lives around and enjoy fulfilling and long-term recovery.
The Mechanism of Opioid Use
Medications to treat opioid addiction work in similar ways to how opioids themselves work. Whether the opioids are legal, like prescription painkillers, or illegal, like heroin or diverted fentanyl, the chemicals and mechanisms of action are the same or, at least, very similar.
Opioids themselves are chemical compounds that are derived from the opium in the poppy plant. For thousands of years, people in central Asia have used the poppy plant for its mildly painkilling and euphoric effects because the molecules in the opium bear a resemblance to the endorphins that are naturally produced in the brain. The region of the brain that processes endorphins is the nucleus accumbens, which regulates sensations of reward, pleasure, and anticipation. Endorphins also work on the nerve cells that communicate feelings of pain to and from the central nervous system, so they perform the double duty of boosting good feelings to offset any physical discomfort.
Opioid molecules work in similar ways as endorphins, but they are infinitely more powerful. While endorphins fight pain, opioids can completely cut off pain signals. While endorphins boost good feelings, opioids induce a surge of euphoria that is beyond any natural experience. PBS says that the feeling after a shot of heroin is comparable to “a heightened sexual orgasm.”
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Opioids and Neurotransmitters
What happens is that opioids attach to specific receptors in the brain. Different opioids have different effects on the receptors, but the most potent opioids—like heroin, fentanyl, and prescription painkillers—produce an intensely overwhelming calming effect. In the process, they cut off pain and reduce the breathing rate. Opioids mimic endorphins and even the body’s own natural opioids to the point where receptors are deceived into permitting them access. This allows the opioids to activate the receptors to unhealthy degrees, and cause wildly abnormal electrical signals to be transmitted throughout the brain and central nervous system.
The specific area of the brain targeted by the opioids is the nucleus accumbens, among others. The region is flooded with the dopamine neurotransmitter, which is what causes patients to feel supremely happy, relaxed, and even rewarded for their behavior. Dopamine is central to emotion, thought, motivation, and pleasure, so the artificial explosion of the neurotransmitter in the brain creates an instant and irresistible urge to experience it again. In this way, opioids take advantage of how the brain is configured. The more important an activity is to survival, such as consuming food or engaging in sexual intercourse, the more we associate those activities with pleasure or reward. Drugs use the same pathways to stimulate the reward circuit into associating the intake of drug with a feeling so overwhelmingly good that users are compelled to seek out more of the same without thinking of the consequences.
How Do Opioid Treatment Drugs Work?
The drugs that are used to treat opioid addiction use some of the same mechanics as the opioids responsible for the initial addiction. This is primarily done for the safety of the patient; the dependence on opioids can be so intense that immediately switching to nonopioid drugs can cause severely distressing and damaging withdrawal symptoms. Using opioids that are not as strong as the initial opioids allows patients to reduce their dependence on stronger opioids while avoiding the worst of withdrawal.
The approach is not without controversy. Medication-assisted treatment has been criticized for “replacing one opioid with another,” a perspective that has been challenged by public health and addiction specialists, but it is better than one of the alternatives. Trying to kick an opioid addiction “cold turkey” is extremely difficult, and according to Psych Central, less than 25% of patients who attempt to stop their opioid use by sheer willpower alone remain abstinent for the first year following their last opioid consumption. Medication-assisted treatment is an inherent part of a successful opioid addiction treatment program. When combined with counseling, therapy, and peer support, it offers patients the best chance of a fulfilling recovery.
The idea behind using opioids in addiction treatment is to keep individuals in a long-term recovery mindset and to keep them away from dangerous opioids in the short-term, explains the medical director of the Center for Neurobehavioral Research on Addictions at the University of Health Science Center in Houston. Even though withdrawing from opioids is not life-threatening in the same way that alcohol withdrawal is, the experience can be very painful, and it may lead to other health problems that will need to be addressed. Treatment centers use mild and slow-acting opioids as a substitute for the stronger and more immediate opioids that started the addiction in order to help the person get used to being on gradually smaller opioid stimulation, to the point where the opioid consumption is minimal or, in a best-case scenario, as nonexistent as possible.
The current spectrum of drugs that are used to treat opioid addiction range from opioid agonists to partial opioid agonists to opioid antagonists. The term agonist refers to a drug that activates specific receptors in the brain. A full agonist opioid, like heroin or oxycodone, activates those receptors to the fullest possible extent, resulting in a maximum opioid effect. Pain signals are completely dulled, the euphoria is immense, and the desire for more of the same is almost immediately formed. Similarly, partial opioid agonists have a much slower mechanism of action and do not fully activate a receptor cell.
At the other end of the spectrum are antagonists, which attach to receptor cells and then prevent other opioids from connecting to the receptors and activating them. While partial and full agonists cause varying degrees of opioid effects, antagonists cause no such effect and can even displace agonists that have already attached to a target receptor. For this reason, opioid antagonists are sometimes used to reverse an opioid overdose in progress.
Methadone Use and Risks
When it comes to treating an opioid addiction, the first line of attack is usually methadone, an opioid agonist that is administered to prevent withdrawal. Methadone is intended for long-term treatment, where patients receive a dose once a day. It is effective at reducing the craving for stronger opioids that many patients experience as they transition away from their addictions.
Methadone is not without its risks. As a full agonist, it can induce some of the same side effects that heroin does, and large doses of methadone have been known to cause depressed breathing in some patients. There is also the danger of opioid-dependent patients developing a need for methadone, effectively becoming dependent on the methadone itself.
The American Family Physician journal writes that methadone is “the most widely known pharmacologic treatment for opioid dependence.” Research has shown that methadone not only reduces the use of illegal opioids, it also keeps patient in treatment and reduces their overall drug use. Long-term methadone treatment has been further shown to reduce the risk of contracting and transmitting bloodborne diseases as the result of using contaminated needles for intravenous opioid use.
If methadone is used early in treatment, it can reduce withdrawal symptoms and cravings for the short-acting opioids behind the addiction, and it prevents the characteristic euphoria of the short-acting opioids as well as narcotic sedation. Methadone has a long half-life (how long it takes for the amount of methadone in the body to be reduced by 50%), so 4–10 days of administration are necessary for the patient to receive steady doses to maintain effective opioid dosing. The longer the patient demonstrates abstinence from more powerful opioids, the better chance the methadone doses can be brought down. In the event of relapse or abuse of other drugs, methadone doses can be increased.
Buprenorphine and Naloxone
Another drug in the treatment of opioid addiction is buprenorphine, a partial opioid agonist. As a partial agonist, it causes fewer effects traditionally associated with opioids. It might still induce nausea and constipation, but unlike methadone, it will probably not put patients at risk of respiratory depression.
As a partial agonist, there is a limit to which buprenorphine can activate the opioid receptors it binds to. The American Family Physician journal describes this as a “plateau,” one that does not exist for methadone or heroin. This confers some benefits for buprenorphine in that it makes it unlikely that people with chronic opioid dependence will use buprenorphine to the point of transferring their dependence to the medication—a reality that does exist with methadone. Like an antagonist, buprenorphine can remove opioid molecules from certain receptors, which can induce withdrawal symptoms in patients who have grown accustomed to the presence of those molecules.
An example of an opioid antagonist is naloxone. Naloxone is often combined with buprenorphine to produce a medication called Suboxone, which works on two levels. Because naloxone is an antagonist, it removes opioid molecules that have bound to receptor cells and blocks other opioid molecules from reaching them. While this is useful in a life-or-death situation like overdose reversal, it means that a patient receiving pure naloxone will be sent into immediate withdrawal symptoms, as the body reacts violently to the sudden deprivation of the powerful opioid activation.
In order to ease this process, naloxone is bundled with buprenorphine, so patients can quickly start to move away from their opioids of abuse while still being protected from the full brunt of opioid withdrawal. Suboxone, the trade name for the combination medication, is widely used and approved to treat opioid addiction. In the first clinical trial, per the official journal of the American Medical Association, researchers noted that participants experienced a “substantial improvement” in their use of opioids and other drugs. Participants also demonstrated a better application of the treatment concepts than patients who were randomly assigned to a control group.
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Much like methadone, Suboxone is also prone to abuse. Reports detail how some patients become so psychologically dependent on their Suboxone prescriptions that they engage in the black market trade for extra filmstrips, dissolving them in water and injecting the liquid solution intravenously, much like how heroin is abused. This form of consumption negates the antagonist properties of naloxone. Once in the bloodstream, naloxone is activated much like an opioid agonist, meaning that those who abuse Suboxone in this way are effectively exposing themselves to two agonists (naloxone and buprenorphine). Some people do this because they are still struggling with an opioid use disorder, and some do it because they underestimate how dangerous Suboxone can be when misused.
Despite the risks, the National Institute on Drug Abuse writes that long-term buprenorphine or methadone treatment is a critical part of successful opioid addiction treatment, and it has been proven to reduce all forms of drug use. With tens of thousands of Americans dying from opioid abuse, and hundreds more suffering from overdoses and consequences from addiction, medication-assisted treatment for opioid addiction is currently the most effective form of therapy that exists for the many forms of opioid use disorder.