The term “opioids” refers to natural substances (for example, morphine) or synthetic substances (for example, heroin) that produce similar effects, primarily a state of profound calm that can progress to loss of consciousness (narcosis), accompanied by an intense sensation of pleasure throughout the body. The brain “detects” these substances through certain receptors and neural circuits that normally respond to substances produced by the brain itself, known as endogenous morphines or endorphins.
In medicine, opioids were initially used as sedatives and painkillers and, more recently, as medications for cough.
Regular use produces tolerance to their effects, so that, on the one hand, it becomes necessary to increase the dose in order to reproduce the initial effects, while on the other hand the person experiences physical and psychological discomfort if the next dose is not taken within a certain period of time. This discomfort is known as the withdrawal syndrome. It does not occur only with opioids and is temporary, usually lasting several days, although the initial phase tends to increase progressively in intensity.
Repeated use carries a relatively high risk of developing drug dependence. This risk applies both to people who use opioids for pleasure and to those who take them for medical reasons. Drug dependence consists of a loss of control over substance use, driven by an urgent and persistent craving that is relieved only after the substance has been taken.
Tolerance, with the associated problem of withdrawal, is not the mechanism underlying drug dependence. To eliminate the withdrawal problem, it would be sufficient to reduce the dose gradually, “going backward,” and then use the substance normally once tolerance had been eliminated. A person with drug dependence cannot carry out this process because they no longer have control over the substance and cannot use it at “lower” doses, but rather tend to use higher doses.
People who use opioids generally do so for pleasure, but use may initially continue because of the beneficial effects opioids can have on psychological distress and on genuine psychiatric disorders (self-medication). The dependence that subsequently develops, however, is no longer linked to any particular reason. Instead, it reflects a stable change in the brain’s relationship with the substance, characterized by a craving that does not disappear and, on the contrary, re-emerges even after long periods of abstinence.
Among all forms of drug dependence, opioid dependence—in recent decades, predominantly heroin dependence—is one of the most treatable. There is in fact a standard treatment suitable for most people with opioid dependence, consisting of a medication capable of suppressing and maintaining suppression of the excessive craving for heroin. In addition, residual craving tends to disappear because heroin no longer produces its usual effects, as its action is “blocked” by the medication. For a small proportion of people dependent on heroin, blocking its effects is sufficient, over time and with regular treatment adherence, to achieve cessation of heroin use. For the majority, however, it is necessary to suppress the craving in order to interrupt the behavior. The medications used for this purpose include methadone (the first and best-known), buprenorphine, and LAAM.
In some countries, people dependent on heroin who do not wish to undergo treatment in other ways are provided with heroin by the state. This procedure does not eliminate the disorder; rather, it maintains it while controlling some of its consequences, such as criminal behavior. Methadone treatment (and treatment with other medications) is based on a fundamental difference between medications and the abused substance: the medication reaches the brain “slowly” and does not produce a pleasurable effect comparable to that produced by drugs of abuse, and therefore does not induce the same pattern of addictive use. Being dependent on methadone therefore simply means taking methadone as a treatment in order to prevent relapse into heroin dependence. In order for the treatment to provide stable protection, it is generally necessary to continue it for long periods and at an appropriate dose.