Naltrexone is taken as a daily 50 mg oral tablet or as a 380 mg injection given once a month, depending on which form your provider prescribes. How you take it, when you take it, and what you need to do before starting all depend on your specific situation. Here’s what you need to know.
Standard Oral Dosing
The typical approach is to start low and work up. Most people begin with 25 mg per day for several days, then increase to 50 mg per day over about one week. This gradual ramp-up helps your body adjust and reduces the chance of side effects, especially nausea.
Take the tablet after a meal. Nausea and vomiting are significantly more likely when the drug is taken on an empty stomach. If you’re prone to stomach issues, eating a full meal beforehand can make a noticeable difference in how you feel during those first few days.
The Monthly Injection Option
The extended-release injectable form, sold as Vivitrol, delivers 380 mg into the muscle every four weeks. A healthcare provider administers it, so there’s no daily pill to remember. This can be a good fit if you have trouble sticking to a daily routine or simply prefer not to take a pill every day. The injection is given in the gluteal muscle, alternating sides each month.
The Sinclair Method: A Different Approach
Not everyone takes naltrexone daily. The Sinclair Method uses the oral tablet only on days you plan to drink alcohol, taken one hour before your first drink. The idea is to block the reinforcing effects of alcohol over time, gradually reducing cravings and consumption. This “as-needed” approach differs from standard daily dosing, and not all providers prescribe it this way, so it’s worth discussing specifically if this method interests you.
What to Do Before Starting
The most critical requirement before your first dose is being completely free of opioids. If you’ve been using short-acting opioids (including prescription painkillers or tramadol), you need to wait at least 7 to 10 days after your last use. For long-acting opioids like methadone or buprenorphine, the waiting period extends to 10 to 14 days. Taking naltrexone too soon triggers precipitated withdrawal, which is a sudden, intense onset of withdrawal symptoms that can be extremely uncomfortable and potentially dangerous.
If you’re starting naltrexone for alcohol use, practitioners typically wait until after the alcohol detox process is complete. Starting during active withdrawal can worsen nausea and other symptoms that already come with detox.
Your provider will likely order liver function blood tests before you begin. Naltrexone is processed through the liver, and most providers won’t prescribe it if liver enzymes are three to five times above normal levels. Periodic liver testing continues during treatment to catch any changes early.
Common Side Effects and How to Manage Them
Nausea is the most frequently reported side effect, especially in the first week. Other common effects include sleepiness, headache, dizziness, decreased appetite, joint pain, muscle cramps, and trouble sleeping. Most of these ease as your body adjusts to the medication.
The gradual dose increase from 25 mg to 50 mg exists specifically to soften these early side effects. Taking the tablet with a substantial meal further helps. If nausea persists beyond the first week or two, let your prescriber know, as they may be able to adjust the timing or explore other options.
Opioid Pain Relief Won’t Work While on Naltrexone
Naltrexone blocks opioid receptors in the brain. That means common opioid pain medications like morphine, oxycodone, and hydrocodone will not provide pain relief while you’re taking it. This becomes critically important in emergency situations, such as surgery or a serious injury, where opioid-based pain management is standard.
Carrying a medical alert card or wearing medical identification that states you’re on naltrexone is strongly recommended. Vivitrol’s manufacturer provides a printable emergency pain management card for exactly this purpose. Keep it in your wallet and make sure it includes your last dose or injection date, so emergency medical teams know when the blocking effect will wear off and can plan alternative pain management in the meantime.
Low Dose Naltrexone (LDN)
You may have also searched about low dose naltrexone, which is a separate, off-label use of the same medication at much smaller doses. LDN typically ranges from 0.1 mg to 4.5 mg per day, far below the standard 50 mg dose used for alcohol or opioid use. It’s most commonly explored for chronic pain conditions.
The effective dose varies widely from person to person. Some people respond to doses as low as 1 mg, while others need the full 4.5 mg. Because LDN isn’t FDA-approved for these uses, it’s usually compounded by a specialty pharmacy, and finding the right dose often involves a process of starting very low and gradually adjusting. The standard naltrexone tablets available at regular pharmacies are 50 mg and aren’t designed to be split into the tiny doses LDN requires.
If You Miss a Dose
If you forget to take your daily oral tablet, take it as soon as you remember. If it’s close to the time for your next scheduled dose, skip the missed one and continue your regular schedule. Don’t double up. A single missed dose won’t undo your progress, but consistently missing doses reduces the medication’s effectiveness over time. If you find yourself forgetting frequently, the monthly injection may be worth considering as an alternative.