Naltrexone hydrochloride has been shown to produce complete blockade of the euphoric effects of opioids in both volunteer and addict populations. When administered by means that enforce compliance, it will produce an effective opioid blockade, but has not been shown to affect the use of cocaine or other non-opioid drugs of abuse.
There are no data that demonstrate an unequivocally beneficial effect of naltrexone hydrochloride on rates of recidivism among detoxified, formerly opioid-dependent individuals who self-administer the drug. The failure of the drug in this setting appears to be due to poor medication compliance.
The drug is reported to be of greatest use in good prognosis opioid addicts who take the drug as part of a comprehensive occupational rehabilitative program, behavioral contract, or other compliance-enhancing protocol. Naltrexone hydrochloride, unlike methadone or LAAM (levo-alpha-acetylmethadol), does not reinforce medication compliance and is expected to have a therapeutic effect only when given under external conditions that support continued use of the medication.
Naltrexone Hydrochloride Indications and Usage
Naltrexone Hydrochloride Tablets USP are indicated in the treatment of alcohol dependence and for the blockade of the effects of exogenously administered opioids.
Naltrexone Hydrochloride Tablets USP have not been shown to provide any therapeutic benefit except as part of an appropriate plan of management for the addictions.
Naltrexone hydrochloride is contraindicated in:
- Patients receiving opioid analgesics.
- Patients currently dependent on opioids, including those currently maintained on opiate agonists (e.g., methadone) or partial agonists (e.g., buprenorphine).
- Patients in acute opioid withdrawal (see WARNINGS).
- Any individual who has failed the naloxone challenge test or who has a positive urine screen for opioids.
- Any individual with a history of sensitivity to naltrexone hydrochloride or any other components of this product. It is not known if there is any cross-sensitivity with naloxone or the phenanthrene containing opioids.
After opioid detoxification, patients are likely to have reduced tolerance to opioids. As the blockade of exogenous opioids provided by naltrexone hydrochloride wanes and eventually dissipates completely, patients who have been treated with naltrexone hydrochloride may respond to lower doses of opioids than previously used, just as they would shortly after completing detoxification. This could result in potentially life-threatening opioid intoxication (respiratory compromise or arrest, circulatory collapse, etc.) if the patient uses previously tolerated doses of opioids. Cases of opioid overdose with fatal outcomes have been reported in patients after discontinuing treatment.
Patients should be alerted that they may be more sensitive to opioids, even at lower doses, after naltrexone hydrochloride treatment is discontinued. It is important that patients inform family members, and the people closest to the patient of this increased sensitivity ot opioids and the risk of overdose (see PRECATIONS, Information for Patients).
There is also the possibility that a patient who is treated with naltrexone hydrochloride could overcome the opioid blockade effect of naltrexone hydrochloride. Although naltrexone hydrochloride is a potent antagonist, the blockade produced by naltrexone hydrochloride is surmountable. The plasma concentration of exogenous opioids attained immediately following their acute administration may be sufficient to overcome the competitive receptor blockade. This poses a potential risk to individuals who attempt, on their own, to overcome the blockade by administering large amounts of exogenous opioids. Any attempt by a patient to overcome the antagonism by taking opioids is especially dangerous and may lead to life-threatening opioid intoxication or fatal overdose. Patients should be told of the serious consequences of trying to overcome the opioid blockade (see PRECAUTIONS, Information for Patients).
The symptoms of spontaneous opioid withdrawal (which are associated with the discontinuation of opioid in a dependent individual) are uncomfortable, but they are not generally believed to be severe or necessitate hospitalization. However, when withdrawal is precipitated abruptly by the administration of an opioid antagonist to an opioid-dependent patient, the resulting withdrawal syndrome can be severe enough to require hospitalization. Symptoms of withdrawal have usually appeared within five minutes of ingestion of naltrexone hydrochloride and have lasted for up to 48 hours. Mental status changes including confusion, somnolence and visual hallucinations have occurred. Significant fluid losses from vomiting and diarrhea have required intravenous fluid administration. Review of postmarketing cases of precipitated opioid withdrawal in association with naltrexone treatment has identified cases with symptoms of withdrawal severe enough to require hospital admission, and in some cases, management in the intensive care unit.
To prevent occurrence of precipitated withdrawal in patients dependent on opioids, or exacerbation of a pre-existing subclinical withdrawal syndrome, opioid-dependent patients, including those being treated for alcohol dependence, should be opioid-free (including tramadol) before starting naltrexone hydrochloride treatment. An opioid-free interval of a minimum of 7 to 10 days is recommended for patients previously dependent on short-acting opioids. Patients transitioning from buprenorphine or methadone may be vulnerable to precipitation of withdrawal symptoms for as long as two weeks.
If a more rapid transition from agonist to antagonist therapy is deemed necessary and appropriate by the healthcare provider, monitor the patient closely in an appropriate medical setting where precipitated withdrawal can be managed.
In every case, healthcare providers should always be prepared to manage withdrawal symptomatically with non-opioid medications because there is no completely reliable method for determining whether a patient has had an adequate opioid-free period. A naloxone challenge test may be helpful; however, a few case reports have indicated that patients may experience precipitated withdrawal despite having a negative urine toxicology screen or tolerating a naloxone challenge test (usually in the setting of transitioning from buprenorphine treatment). Patients should be made aware of the risks associated with precipitated withdrawal and encouraged to give an accurate account of last opioid use. Patients treated for alcohol dependence with naltrexone hydrochloride should also be assessed for underlying opioid dependence and for any recent use of opioids prior to initiation of treatment with naltrexone hydrochloride. Precipitated opioid withdrawal has been observed in alcohol-dependent patients in circumstances where the prescriber had been unaware of the additional use of opioids or co-dependence on opioids.
Cases of hepatitis and clinically significant liver dysfunction were observed in association with naltrexone hydrochloride exposure during the clinical development program and in the postmarketing period. Transient, asymptomatic hepatic transaminase elevations were also observed in the clinical trials and postmarketing period. When patients presented with elevated transaminases, there were often other potential causative or contributory etiologies identified, including pre-existing alcoholic liver disease, hepatitis B and/or C infection, and concomitant usage of other potentially hepatotoxic drugs. Although clinically significant liver dysfunction is not typically recognized as a manifestation of opioid withdrawal, opioid withdrawal that is precipitated abruptly may lead to systemic sequelae, including acute liver injury.
Patients should be warned of the risk of hepatic injury and advised to seek medical attention if they experience symptoms of acute hepatitis. Use of naltrexone hydrochloride should be discontinued in the event of symptoms and/or signs of acute hepatitis.
Depression, suicide, attempted suicide and suicidal ideation have been reported in the postmarketing experience with naltrexone hydrochloride used in the treatment of opioid dependence. No causal relationship has been demonstrated. In the literature, endogenous opioids have been theorized to contribute to a variety of conditions.
Alcohol- and opioid-dependent patients, including those taking naltrexone hydrochloride, should be monitored for the development of depression or suicidal thinking. Families and caregivers of patients being treated with naltrexone hydrochloride should be alerted to the need to monitor patients for the emergence of symptoms of depression or suicidality, and to report such symptoms to the patient’s healthcare provider.
Safe use of naltrexone in ultra rapid opiate detoxification programs has not been established (see ADVERSE REACTIONS).
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