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The half life of naltrexone is used to determine how long the medication will be effective at certain doses, but there are two half life measurements with naltrexone that come into play.
What You’ll Learn:
- Why knowing the half life of a medication matters.
- How naltrexone’s half life is measured.
- Naltrexone plasma half life
- Metabolite half life
- How the half life of naltrexone impacts dose timing.
- How the dosage of naltrexone affects half life.
Figuring out naltrexone half life duration can be a bit confusing since there’s more than one measurement. It’s also unique in that the medication leaves the bloodstream relatively quickly, but the opioid blocking effects that are essential for naltrexone alcohol treatment last much longer.
The half life of a medication is the time it takes for the concentration to drop to 50% in the body. It’s used to figure out:
- How long it takes to fully eliminate a medication.
- When a drug will reach peak effectiveness.
- When a drug will reach a steady state.
- Dosage frequency for a medication.
Extensive research is done to determine the half life because a number of factors can influence how quickly a drug is cleared. How the drug is processed and metabolism play a role, but there are also individual variables like a person’s weight and age that can cause variations in the half life of a medication.
Naltrexone Plasma Half Life
Plasma half life is a measure of how long the medication stays in plasma. The medication goes from the plasma to another bodily fluid, is destroyed by blood or is eliminated and removed from the body, usually through the liver.
The plasma half life of naltrexone is 4 hours. That may sound really short, but it’s only half the picture for naltrexone half life.
Naltrexone Active Metabolite Half Life
There is also an active metabolite produced by naltrexone called 6‑β‑naltrexol. It stays present in the body for much longer with a half life of about 13 hours.
This is the more important measurement for naltrexone because it’s 6‑β‑naltrexol that blocks opioid receptors and prevents people from getting a dopamine hit when they drink alcohol. As long as 6‑β‑naltrexol is present, naltrexone will be effective.
How Naltrexone Half Life Affects Dosage
Half life has significant importance for naltrexone because timing is crucial for the medication to be effective at curbing alcohol cravings. Clinicians use the half life of naltrexone to create a dosing schedule that will keep patients continuously covered.
A standard naltrexone 50 mg tablet is effective at blocking opioid receptors for about 24 hours. It makes dosing frequency relatively easy to determine. For constant coverage, the patient simply takes one pill each day at the same time.
For standard daily naltrexone used in alcohol treatment:
- Time of day is usually chosen to balance side effects and typical drinking patterns, because the 24‑hour blockade makes exact dose time less critical.
- Many prescribers recommend morning dosing with food to reduce nausea and to anchor it to a daily routine, improving adherence.
- If you tend to drink mainly in the evening, morning dosing still works because opioid receptor blocking happens across a 24‑hour period.
- Dosing also hinges on how you feel during the day. Some people prefer late afternoon dosing if they experience early‑day fatigue. Others prefer to take a dose at night before bed if they experience headaches, nausea or other side effects.
- Because people metabolize medications differently, it’s important to work with a clinician to determine if a lower or higher dose of naltrexone is needed for 24-hour coverage.
The key to naltrexone dose frequency is consistency. Because of its duration, taking it at the same time every day you’ll maintain steady receptor blocking, even if the plasma half‑life is relatively short.
The Connection Between Naltrexone Dosage and Half Life Length
So far, we’ve been looking at the standard 50 mg dose of naltrexone. If we were to examine a 100 mg dose of naltrexone we’d find that the half life duration is much longer. Higher doses of naltrexone can provide opioid receptor blocking for 48-72 hours.
While the medication will remain active in the body for longer, this has to be weighed along with a higher risk of experiencing side effects. For most people, the standard naltrexone dose is the perfect balance between dosage frequency and side effect management.
Key Takeaways:
- The half life of a medication indicates how long it takes for it to reach 50% concentration in the body.
- Naltrexone has a plasma half life and a metabolite half life, with the metabolite half life being the more important measurement for effectiveness.
- A standard 50 mg dose of oral naltrexone provides 24 hours of effectiveness.
- Clinicians often prescribe 50mg of naltrexone daily for alcohol use treatment, but a lower or higher dosage may be needed for 24-hour effects.
If you’d like to talk with a qualified clinician about getting an online naltrexone prescription and what dose will be effective, take our Alcohol Use Assessment. It provides baseline information about your drinking habits so that the best treatment options can be suggested.
