Half-Life of Bupropion
The mean elimination half-life of bupropion is 21 (±9) hours. 1
Pharmacokinetic Profile of Bupropion
Bupropion's pharmacokinetics are characterized by:
- Following oral administration, bupropion reaches steady-state plasma concentration within 8 days 1
- After single oral administration of bupropion extended-release (XL) formulation, the median time to peak plasma concentration is approximately 5 hours 1
- Bupropion is extensively metabolized in humans, producing three active metabolites 1:
- Hydroxybupropion (formed via hydroxylation)
- Threohydrobupropion (formed via reduction)
- Erythrohydrobupropion (formed via reduction)
Metabolites and Their Half-Lives
The active metabolites of bupropion have longer half-lives than the parent compound:
- Hydroxybupropion: approximately 20 (±5) hours 1
- Threohydrobupropion: approximately 37 (±13) hours 1
- Erythrohydrobupropion: approximately 33 (±10) hours 1
Formulation Considerations
Different formulations of bupropion have varying absorption profiles:
- Immediate-release (IR): Peak plasma concentration reached in approximately 1.5 hours 2
- Sustained-release (SR): Peak plasma concentration reached in approximately 3 hours 2
- Extended-release (XL): Peak plasma concentration reached in approximately 5 hours 2
Clinical Implications
The half-life of bupropion has important clinical implications:
- The relatively long half-life of bupropion and its metabolites allows for once-daily dosing with the XL formulation 2
- At steady state, the peak plasma concentration of hydroxybupropion (the primary active metabolite) is 7 times higher than that of the parent drug 1
- The AUC (area under the curve) of hydroxybupropion at steady state is about 13 times that of bupropion 1
Common Pitfalls and Caveats
When considering bupropion's half-life, be aware of:
- Earlier studies reported shorter half-lives (approximately 12-14 hours) 3, 4, but more recent and comprehensive pharmacokinetic analyses support the 21-hour half-life 1, 2
- No significant differences in pharmacokinetics have been observed between smokers and non-smokers 5
- Bupropion is 84% bound to human plasma proteins 1
- Bupropion is extensively metabolized by the liver, primarily through CYP2B6 enzyme pathway 1
- The half-life may be affected in patients with hepatic or renal impairment 1