Naltrexone is a drug in the opioid antagonist group. The prescription drug is used in opioid withdrawal.
What is naltrexone?
Naltrexone is used in opioid addiction withdrawal and alcohol addiction treatment. Naltrexone is an opioid antagonist. Opioid antagonists are drugs that bind to opioid receptors and can partially or completely reverse the effects of opioids. However, the active ingredient is not only used in patients with opioid dependence. It is also an integral part of comprehensive treatment programs for alcohol addiction. Naltrexone is used to reduce the risk of relapse and support patients during the abstinence phase. In Germany, naltrexone is available only on prescription. Even with long-term treatment, there is no habituation effect. Neither physical nor psychological dependence symptoms are observed.
Pharmacologic effects
The exact mechanism of action of naltrexone is still unclear. The drug belongs to the opioid antagonists. These act as receptor antagonists at opioid receptors. They bind to these receptors and abruptly displace the opiates from the receptors. Thus, naltrexone serves as an antidote for opioid poisoning. But a different mechanism of action underlies the treatment of withdrawal symptoms. It is believed that the drug develops an interaction with the body’s opioid system. In this system, the body releases endorphins during profound emotional events, stress, or even pain. These have both analgesic and mood-enhancing effects. Presumably, alcohol abuse permanently and fundamentally stimulates this reward system. The result is an elevation of mood. Every further consumption of alcohol forces this situation, so that eventually a dependency develops. After withdrawal, even small amounts of alcohol are then enough to cause a relapse. The opioid antagonist reduces the risk of relapse by influencing the body’s own opioid system. It reduces alcohol cravings in both abstinent and nonabstinent patients.
Medical application and use
Following successful opioid detoxification, naltrexone can be used in the withdrawal treatment of opioid addicts. In this context, it is administered as a complement to psychotherapeutic and psychological treatment. However, the active ingredient is not only used for this purpose. In Germany, the United States and other European countries, naltrexone is also approved for relapse prevention in alcoholism. The drug is used to reduce the risk of relapse and to reduce alcohol craving. This is intended to support abstinence in former alcohol addicts. Treatment with naltrexone for borderline personality disorder and dissociative disorders also shows success. However, the agent is not approved for this indication, making it an off-label use. Naltrexone is also occasionally used off-label for autism and mental developmental disorders. Recent studies also show efficacy of low-dose naltrexone in multiple sclerosis. For example, study participants reported a significant reduction in spasticity after six months. The active ingredient appears to have a positive influence on the course of the disease. This is presumably due to an anti-inflammatory effect. Only one out of 40 participants showed a progressive reduction of the nerve sheaths. Fibromyalgia, amyotrophic lateral sclerosis (ALS), cancer, and opiate-induced constipation are other conditions that can be treated with naltrexone.
Risks and side effects
If opioid-dependent people are not opiate-free for at least one week before starting therapy with naltrexone, naltrexone can cause acute withdrawal syndrome. Therefore, to prevent this life-threatening situation and to confirm opiate freedom, a urine sample is usually analyzed before treatment is started. Common side effects associated with naltrexone include sleep disturbances, anxiety, and increased excitability. Furthermore, nausea, abdominal pain, joint pain, muscle pain, and headache may occur. If naltrexone is used concurrently with opiates, an overdose may occur. This is associated with potentially fatal respiratory disturbances.Therefore, patients must not take any opiates and other opioid-containing drugs such as codeine or loperamide during therapy with naltrexone. It should be noted that during treatment with naltrexone, opioid analgesics cannot exert their full effect. To relieve pain, the dose of these opioid analgesics would need to be increased. However, this can result in serious complications. At high doses, naltrexone has a toxic effect on the liver. Because of this hepatotoxic effect, administration of naltrexone is contraindicated in severe liver disease, such as cirrhosis. However, even in patients without preexisting liver damage, liver transaminases may increase and liver damage may occur. Because few study data are available for alcoholics younger than 20 years of age, treatment with naltrexone is usually not used in them.
