Understanding opioid dependence

Opioids are drugs that work in the body the way opium does. Some are made directly from opium (for example, morphine, and codeine), while others are man-made but similar chemically to opium (for example, the painkillers oxycodone, hydrocodone, and fentanyl, better known by such brand names as OxyContin^®, Vicodin^®, Percocet^® and Actiq^®*). The illegal drug heroin is also an opioid.

All of these drugs are extremely powerful. For people with severe pain, opioids are very effective medicines, and most patients treated for pain with opioids do not become dependent on them. For some people, however, opioid dependence is an unexpected side effect of proper pain treatment. The problem comes when someone is unable to stop using the drug after the pain passes.

*All brand names above are the property of their respective owners. Vicodin is a registered trademark of Knoll Pharmaceuticals, now Abbott Laboratories. Percocet is a registered trademark of Endo Pharmaceuticals, Inc. Actiq is a registered trademark of Cephalon, Inc. OxyContin is a registered trademark of Purdue Frederick Company.

For many, the decision to begin taking drugs is voluntary: it may have started with medicine that your doctor prescribed for serious pain, or with recreational drug use with prescription pain medications or heroin. Regardless of how you became dependent, once dependence has developed it is considered a disease that requires treatment. And, once a person becomes addicted or dependent on a drug, he or she may find that willpower is no match for the chemical, behavioral, and psychological nature of opioid dependence.

Dependence on opioids—prescription pain medicine and heroin—has been defined as a long-term brain disease by the World Health Organization and the National Institute on Drug Abuse. It is a treatable medical condition that is caused by changes in the chemistry of the brain that occur as a result of the use of opioids.

A person who shows 3 or more of the following behaviors over a 12-month period is most likely opioid-dependent:

• Needing to take more of the drug to get the same effect—or getting a lesser effect from the same amount of drug
• Experiencing withdrawal symptoms when not using opioids, or taking other drugs to help relieve withdrawal symptoms
• Taking larger amounts of opioids than planned, and for longer periods of time
• Persistently wanting to quit, or trying unsuccessfully to quit
• Spending a lot of time and effort to obtain, use, and recover from taking opioids
• Working less, missing work, or, if unemployed, not seriously looking for a job
• Spending less time seeing friends who don’t use opioids; skipping recreational activities
• Continuing to use opioids despite negative consequences

The development of opioid dependence causes complex, long-term, changes in the structure and functioning of the brain. The significant changes to brain “circuitry” have led addiction, medical, and scientific experts to classify it as a disease that interferes with normal brain functioning.

Typically, the changes that cause opioid dependence will not correct themselves right away, even though the misuse of opioids has stopped. In fact, these changes can trigger cravings months and even years after someone has stopped using opioids. Consequently, overcoming opioid dependence is not simply a matter of eliminating drugs from the body.

There is a part of the brain that researchers refer to as the “reward circuit.” This is the area of the brain that, among other things, regulates pain and pleasure. Basic life functions—such as eating and sex—stimulate receptors in the brain’s “reward circuit” to release dopamine, a chemical that produces an intensely pleasurable feeling known as “euphoria.”

It doesn’t take long to learn that certain activities will be “rewarded”—that is, that they will prompt dopamine release and pleasurable sensation. This positive reinforcement is the brain’s way of encouraging behavior important for survival.

The ability to activate the reward circuit accounts for some drugs being viewed as potentially addictive. Opioids are among those drugs capable of activating the reward circuit to release dopamine and reinforce drug-taking behavior. Activating the reward circuit, together with the changes in the structure and functioning of the brain, have several powerful results.

One result of this euphoria is that drug-taking behavior is rewarded, thereby increasing the chances that the behavior will be repeated.

A second result of this reward is that the brain begins to think drug-taking is actually necessary for survival. To the brain, just the fact that an activity is rewarded at all means that activity must be important for survival.

A third result is that, by the time a person develops opioid dependence, his or her brain no longer functions normally without opioids.

A fourth result is that opioid-dependence can impair the mechanism by which information from certain areas of the brain—namely, those involved with judgment and caution—is received.

Additionally, the motivation to obtain opioids may come from:

• Physical pain and discomfort caused by withdrawal symptoms
• Increasing anxiety due to powerful, unsatisfied opioid cravings
• Stress resulting from the brain’s fear that the current lack of opioids presents a threat to its survival

Taken together, all of these results help explain the behaviors associated with opioid dependence.

The initial decision to take a drug, whether a prescribed medication or a “street” drug, would be considered under voluntary control. However, when someone develops a dependence on that substance, the person’s ability to exert self-control can become seriously compromised. Brain imaging studies from drug-dependent individuals show physical changes in areas of the brain that are critical to judgment, decision-making, learning and memory, and behavior control. Scientists believe that these changes alter the way the brain works, and may help explain the compulsive and destructive behaviors of drug dependence.

So, even though, logically, a person may know that opioids are not essential for life, as long as those parts of the brain in charge of survival behavior still believe opioids are necessary, they may override “higher reasoning.” Furthermore, to an opioid-dependent brain, not having enough opioids to satisfy cravings or suppress withdrawal is comparable to not having enough food to satisfy hunger.

The need to obtain opioids can become more important than that person’s safety because opioid-dependence can impair the mechanism by which information from certain areas of the brain—namely, those involved with judgment and caution—is received. The brain responds by taking whatever steps are necessary to see that its opioid “hunger” is met, which usually means pursuing opioids with all the drive of a basic instinct.

Medicine is important for managing both the short- and the long-term effects of opioid dependence. Over the short term, medication can help to relieve the opioid cravings and withdrawal symptoms that occur when use of heroin or opioid pain medicine is discontinued. Medication can be important over the long term as well.

The CSAT Clinical Guidelines for the Use of Buprenorphine recommend that patients stay on medication after they have “detoxed” from their drug of misuse. This gives patients time to learn new skills that can help them cope with cravings and other triggers that might otherwise make them vulnerable to relapse.

Since it is long-term, it is like other chronic illnesses, such as diabetes, asthma, or heart disease. It shares a lot in common with these other types of illnesses:

• It can be successfully managed, but not “cured”
• Both medication and behavior change can be helpful
• It has a genetic basis—it runs in families
• People can have periods of time when they are symptom-free as well as periods of time when they are symptomatic

With opioid dependence, there are also behavior changes that can reduce or end the need for medication-assisted treatment. But, sometimes, even those who have done everything they can to stop taking opioids might still experience overwhelming cravings and long-term withdrawal symptoms or other symptoms that put them at risk for relapse, and so may need to continue medication therapy for optimal treatment. Cravings and withdrawal symptoms can continue because some of the changes in their brains that resulted from the opioid dependence may be slow to recover, or permanent.

Most people who use opioids do not become opioid-dependent. This suggests that, while the reward circuit is responsible for opioids’ addictive potential, opioid dependence most likely involves additional factors.

Exactly why some people, and not others, become dependent on opioids (or any addictive substance) is not totally understood. However, certain factors appear to increase the likelihood of dependence, including:

• Genetic factors
• Psychiatric disorders (for example, depression or bipolar disorder)
• Stress (high stress seems to increase the desire to use drugs)
• Properties of the drug itself (for example, how quickly it creates a “high,” how long the effects of the drug last)
• Substance abuse, which can lead to dependence, is often highly influenced by societal norms and peer pressure
• Having a risk-taking or novelty-seeking personality

Scientists estimate that genetic factors account for between 40% and 60% of a person’s vulnerability to dependence, including the effects of environment on gene expression and function. Adolescents and individuals with mental disorders are at greater risk of drug abuse and addiction than the general population.

Treatment of chronic diseases involves changing deeply imbedded behaviors, and relapse does not have to mean treatment failure. The chronic nature of the disease means that relapsing to drug use can occur. Relapse indicates the need for treatment to be reinstated or adjusted to a more intensive level of care until the person is again stable and in treatment.

Science has taught us that stress, cues linked to the drug experience (for example, people, places, things, mood), and exposure to drugs, are the most common triggers for relapse, so strategies need to be developed to help minimize or avoid these triggers. Counseling and group therapy or self-help groups are strongly recommended to help develop these strategies.

In addition to functioning as a reward, dopamine is also the brain’s way of ensuring that the experience itself will not be easily forgotten. Dopamine release activates the areas of the brain involved in memory formation to record details about the environment where the event occurred.

Which details the brain chooses to record can range from the obvious (where the incident occured, who was there) to the obscure (a billboard passed on the way, the temperature outside). There is no way to know ahead of time what details the brain has stored. But whatever they were, when those circumstances are encounted in the future, they will trigger memories of the good feelings produced by dopamine, and, often, a desire to recreate that experience. The technical term for these memories is "conditioned associations," but most people familiar with opioid dependence refer to them as "triggers."