Naltrexone is a medication approved by the Food and Drug Administration (FDA) to assist in the treatment of both alcohol use disorder and opioid use disorder. It functions by blocking the euphoric and sedative effects associated with substance use, helping to reduce cravings. This medication is available in two main forms: an oral tablet and an extended-release injectable version.
Common Side Effects and Their Typical Duration
Naltrexone can cause side effects, with duration often depending on the medication form. For oral naltrexone, common side effects include nausea, headache, dizziness, insomnia, anxiety, and abdominal pain. These mild side effects subside within a few days to a week as the body adjusts.
Nausea is common when starting the oral tablet, but it usually improves within days or weeks. Headaches, dizziness, and fatigue are also common and diminish as the body adapts. The oral tablet has a short half-life of 4 to 6 hours, meaning the body eliminates most of it within 20 to 30 hours.
The extended-release injectable form, known as Vivitrol, is administered as a 380 mg intramuscular injection once a month. Due to its slow-release nature, Vivitrol’s effects and side effects can last up to a month. Common side effects for the injectable form include nausea, headache, and reactions at the injection site such as pain, swelling, or a hard lump. While mild, these injection site reactions can persist for several days.
Factors Influencing Side Effect Duration
The duration of naltrexone side effects can vary among individuals due to various factors. An individual’s metabolism influences how the body processes medications, affecting how long side effects last. For example, the half-life of oral naltrexone is 4 to 6 hours.
The specific form of the medication also impacts side effect duration. The oral tablet is eliminated from the body within about 20 to 30 hours, leading to shorter-lived side effects compared to the extended-release injectable form. The injectable version, Vivitrol, has a longer half-life of 5 to 10 days, extending the duration of its side effects.
Dosage is another factor; higher doses may lead to more pronounced or prolonged side effects. The presence of other medical conditions, particularly liver or kidney problems, can also prolong side effect duration. This is because these organs are involved in metabolizing and eliminating naltrexone from the body, and impaired function can slow this process.
Managing Side Effects and When to Seek Medical Attention
Mild side effects of naltrexone can be managed with simple adjustments. Taking the oral medication with food can help reduce nausea and other gastrointestinal issues. For headaches, over-the-counter pain relievers may provide relief. If insomnia is a concern, adjusting the timing of the dose or discussing it with a healthcare provider can be beneficial.
While most side effects are temporary and mild, certain symptoms warrant immediate medical attention. Severe abdominal pain that lasts more than a few days, dark urine, or yellowing of the skin or eyes can indicate liver problems.
Seek emergency care if you experience a severe allergic reaction, characterized by difficulty breathing, swelling of the face, lips, or tongue, or hives. Worsening depression or thoughts of self-harm also require immediate medical intervention. It is important to consult a healthcare provider before making any changes to your medication regimen.