From the FDA Drug Label
Following single oral administration of bupropion hydrochloride extended-release tablets (XL) to healthy volunteers, the median time to peak plasma concentrations for bupropion was approximately 5 hours. The medication bupropion hydrochloride extended-release tablets (XL) reaches peak concentration levels approximately 5 hours after administration 1.
From the Research
Extended release Wellbutrin (bupropion XL) reaches peak concentration levels approximately 5 hours after administration. This delayed peak is by design, as the extended release formulation allows for a gradual release of the medication into the bloodstream over time. The pharmacokinetic profile of bupropion XL is characterized by a prolonged absorption phase, with a mean time to maximum concentration (Tmax) of approximately 5 hours, as reported in a study published in 2005 2. This differs from immediate release formulations which peak much earlier, typically within 1-2 hours.
The extended release mechanism provides more stable blood levels throughout the day, which helps minimize side effects while maintaining therapeutic effectiveness. This is supported by a study published in 2006, which found that the 24-hour area under the curve ratios of metabolites to bupropion ranged from 1.0 for erythrohydrobupropion to 16.4 for hydroxybupropion, indicating a sustained release of the medication and its active metabolites 3.
This pharmacokinetic profile is why Wellbutrin XL is typically dosed once daily, usually in the morning, as taking it later in the day might interfere with sleep. Patients should be aware that it may take several weeks of consistent dosing to achieve full therapeutic effects for depression or smoking cessation, even though peak concentrations for each individual dose occur within hours of administration. The efficacy and safety of bupropion XL have been established in several studies, including a review of its use in the management of major depressive disorder published in 2008 4.
Key points to consider when prescribing bupropion XL include:
- The medication reaches peak concentration levels approximately 5 hours after administration
- The extended release formulation provides a gradual release of the medication into the bloodstream over time
- The medication is typically dosed once daily, usually in the morning
- It may take several weeks of consistent dosing to achieve full therapeutic effects
- The medication has a sustained release of its active metabolites, which helps minimize side effects while maintaining therapeutic effectiveness.