Naltrexone comes in two forms: a pill and an injection. How long naltrexone takes to work depends on the form of the prescription you're using.
Injectable naltrexone starts working almost immediately and reaches peak concentrations in your blood about two hours after your shot.[1]
Oral naltrexone starts working about an hour after you take it.[2] The drug must move through your digestive tract, so it comes on a little slower than an injection.
How Long Does Naltrexone Last?
Oral Naltrexone lasts to prevent cravings in your body for alcohol for about a 24 hour period. It is for this reason that it is dosed once a day.
Naltrexone injections last in the body for about a month at a time.[3]
Every person’s body is different, and some people feel the impact of naltrexone faster, and they metabolize the prescription sooner too.
How quickly you'll process naltrexone depends on the following:
- Your age
- Your height and weight
- Your organ health
- Your personal genetics
- The severity of your cravings for alcohol
If you're using naltrexone and you feel it's wearing off too quickly or not covering cravings later in the day, talk with your doctor. You could need a dose adjustment to get the most effectiveness out of your medication.
Naltrexone Timing FAQs
Does naltrexone work the first day?
Yes, both oral and injectable naltrexone start working in the body the first day they are used.
How long does Naltrexone last in your body to prevent cravings?
Injectable naltrexone starts working almost immediately and reaches peak concentrations in your blood about two hours after your shot.[1] Oral naltrexone starts working about an hour after you take it.[2] The drug must move through your digestive tract, so it comes on a little slower than an injection.
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