Products
Naltrexone is commercially available in the form of film-coated tablets (naltrexin). It has been approved in many countries since 2003.
Structure and properties
Naltrexone (C20H23NO4, Mr = 341.40 g/mol) is a synthetically produced opioid related to oxymorphone. It is present in drugs as naltrexone hydrochloride, a white, hygroscopic powder that is readily soluble in water. The drug has a similar structure to naloxone, but carries a cyclopropylmethyl group in place of an allyl group on the nitrogen and therefore can be administered perorally as a tablet. Naltrexone has a high first-pass metabolism and an active metabolite (6-β-naltrexol).
Effects
Naltrexone (ATC N07BB04) is a competitive antagonist at opioid receptors and abolishes the effects of exogenous and endogenous opioids. It is supportive for relapse prevention after opioid withdrawal. In alcohol dependence and craving, endogenous opioids such as endorphins play an important role. Therefore, naltrexone can also be used to influence alcohol dependence. Naltrexone itself has no opioid properties and is not addictive.
Indications
For withdrawal in opioid or alcohol dependence after successful detoxification. Use in other indications is being discussed, for example, in other addictive disorders. A fixed combination with morphine is available in the United States, and a fixed combination with bupropion was approved in 2014 for the treatment of overweight and obesity (see under naltrexone-bupropion).
Dosage
According to the prescribing information. Tablets are usually administered once daily. Alternative dosing regimens are also possible. During treatment, it is essential that the patient be opiate-free! Therefore, a naloxone test is performed in advance in medical treatment.
Contraindications
- Hypersensitivity
- Before and during an opioid withdrawal
- Severe liver or kidney disease
- Concurrent administration of opioid analgesics.
For complete precautions, see the drug label.
Interactions
Naltrexone also reverses the desirable effects of opioids, for example, when used as an analgesic or cough suppressant. In general, opioids should not be given during treatment. If this is still necessary in an emergency situation, the dose may need to be increased. Naltrexone does not appear to interact with CYP450.
Adverse effects
The most common possible adverse effects include abdominal pain, nausea, vomiting, muscle and joint pain, headache, sleep disturbances, restlessness, nervousness, weakness, and a mild increase in blood pressure. Naltrexone is liver toxic in a dose-dependent manner, may elevate liver enzymes, and may cause hepatic inflammation. It has a narrow therapeutic range. The naltrexone derivative nalmefene is not reported to be hepatotoxic (Selincro).
