What is Wellbutrin XL's Half-Life?
Wellbutrin XL (bupropion hydrochloride extended-release) has a half-life of about 21 hours for the parent drug bupropion after a single dose.[1] Steady-state half-life averages 24 (±9) hours following multiple dosing.[1]
Half-Life of Bupropion Metabolites
Bupropion metabolizes into three active compounds with longer half-lives:
- Hydroxybupropion: 20 (±5) hours
- Threohydrobupropion: 37 (±13) hours
- Erythrohydrobupropion: 33 (±10) hours[1]
These contribute to the drug's overall duration, with therapeutic effects lasting 24 hours per dose.
How Does Dosing Schedule Relate to Half-Life?
Wellbutrin XL is taken once daily due to its extended-release formulation and ~24-hour half-life, maintaining steady plasma levels. Peak concentrations occur 5 hours post-dose.[1]
Half-Life Changes in Special Populations
- Smokers: Half-life shortens to 20 hours due to CYP1A2 induction.[1]
- Renal impairment: Mild/moderate cases show similar half-lives; severe cases unstudied—avoid use.[1]
- Hepatic impairment: Mild cases extend to 29 hours; moderate to 44 hours—use lower doses.[1]
- Elderly: No specific changes noted, but monitor closely.[1]
Why Does Half-Life Matter for Missed Doses or Overdose?
With a 24-hour half-life, missing one dose typically requires resuming the next day without doubling up, as levels decline gradually. In overdose, prolonged elimination (up to 37 hours for metabolites) raises seizure risk—seek immediate care.[1]
[1]: Wellbutrin XL Prescribing Information (FDA)