Short answer: Naltrexone/Bupropion has a half-life of about 5 hours (naltrexone); about 21 hours (bupropion). Levels peak 2 hours (naltrexone); 3 hours (bupropion) after a dose. People vary, so treat these as estimates.
Naltrexone/bupropion is an extended-release tablet that combines naltrexone, an opioid blocker, with bupropion, an antidepressant also used to quit smoking. It is sold as Contrave for long-term weight management with diet and exercise.
Also known as: Contrave.
Each Contrave extended-release tablet contains 8 mg naltrexone HCl and 90 mg bupropion HCl. Tablets are not cut, chewed or crushed.
The Contrave label approves it, with a reduced-calorie diet and more activity, to reduce excess weight and keep it off long term in adults with obesity, or with overweight and at least one weight-related condition. Label dosing builds up over four weeks: 1 tablet in the morning in week 1; 1 morning and 1 evening in week 2; 2 morning and 1 evening in week 3; and 2 tablets twice a day from week 4 (32 mg naltrexone/360 mg bupropion a day). Response is checked after 12 weeks on that dose, and Contrave is stopped if weight loss is under 5%. It is not taken with a high-fat meal, which sharply raises drug levels and seizure risk.
Contrave has a boxed warning about suicidal thoughts and behaviors: it contains bupropion, and antidepressants raised that risk in children, teens and young adults in short-term trials, so everyone starting it is watched for mood changes. It is not used with uncontrolled high blood pressure, seizures, other bupropion products, anorexia or bulimia, long-term opioid use or opioid withdrawal, sudden stopping of alcohol, benzodiazepines or seizure medicines, or with MAO inhibitors. People need to be opioid-free for 7 to 10 days before starting. Other warnings cover blood pressure and heart rate, liver injury, mania and angle-closure glaucoma. In trials, nausea affected 32.5% vs 6.7% on placebo, constipation 19.2% vs 7.2% and headache 17.6% vs 10.4%. See Contrave side effects, Contrave dosing schedule, missed Contrave dose, how to store Contrave, and Contrave vs Qsymia, Wegovy vs Contrave and naltrexone vs Contrave.
The Contrave label says that after a single dose of two tablets, naltrexone peaked at 2 hours and bupropion at 3 hours. The mean elimination half-life was about 5 hours for naltrexone and about 21 hours for bupropion; bupropion and its metabolites build up with twice-daily dosing. With a high-fat meal, naltrexone exposure rose 2.1-fold (peak 3.7-fold) and bupropion exposure 1.4-fold (peak 1.8-fold).
Numbers shown are taken from the source above. Half-life varies from person to person.
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