From the Guidelines
Wellbutrin XL 150 mg is designed as an extended-release formulation, so 0% of the medication is absorbed into the bloodstream immediately. The extended-release technology ensures gradual absorption over 24 hours, with peak plasma concentrations typically occurring approximately 5 hours after administration 1. This controlled release mechanism is intentionally designed to provide steady blood levels throughout the day, reducing side effects and allowing for once-daily dosing. Some key points to consider about the pharmacokinetics of Wellbutrin XL include:
- The active ingredient, bupropion, is slowly released from the tablet matrix as it passes through the digestive system.
- The gradual absorption profile differs significantly from immediate-release formulations of bupropion (such as Wellbutrin IR), which release the medication quickly and require multiple daily doses.
- According to the study by the agnp-tdm expert group consensus guidelines, the absorption of bupropion is good from the gastrointestinal tract, but the maximum plasma concentration is reached within a short time after administration (tmax of about 0.5 to 4 h) 1.
- The high first-pass metabolism of bupropion results in a systemic availability of 10%-70% 1, which affects the amount of medication that actually enters the bloodstream. The extended-release nature of Wellbutrin XL helps maintain consistent therapeutic levels while minimizing fluctuations that could lead to increased side effects or reduced efficacy.
From the Research
Absorption of Wellbutrin XL 150 mg
- The absorption of Wellbutrin XL 150 mg is prolonged compared to the immediate release (IR) and sustained release (SR) formulations, with a T(max) of approximately 5 hours 2.
- Bupropion is absorbed rapidly after single-dose oral administration, with peak plasma concentrations generally attained within 2 hours 3.
- However, there is no specific information available on the percentage of Wellbutrin XL 150 mg that gets absorbed in the bloodstream immediately.
- Bupropion undergoes extensive first-pass metabolism, which may affect its absorption and bioavailability 3.
- The pharmacokinetic properties of bupropion, including its absorption, metabolism, and elimination, can vary between individuals and may be influenced by factors such as age, medical illnesses, and potential drug interactions 2, 4.