Wellbutrin SR 100 mg Formulation Availability
Yes, Wellbutrin SR 100 mg tablets exist and are FDA-approved, though they experienced historical stability issues that were subsequently resolved through reformulation. 1, 2
FDA Approval and Formulation History
The FDA approved Wellbutrin SR 100 mg tablets on October 4,1996, making this a legitimate sustained-release formulation of bupropion hydrochloride. 2
Between 1996 and 2000, the original formulation experienced dissolution rate increases during storage due to acid hydrolysis of the release-controlling polymer, which initially limited shelf-life to 9–12 months. 2
The product was successfully reformulated using the same ingredients and manufacturing processes but with an adjusted ratio of release-controlling polymer to acid stabilizer, receiving FDA approval for the reformulation on October 11,2000. 2
The reformulated Wellbutrin SR 100 mg now carries a 36-month (3-year) shelf-life, confirming its stability and continued availability. 2
Clinical Use of the 100 mg SR Strength
Wellbutrin SR 100 mg is the appropriate starting dose for twice-daily regimens, with typical initiation at 100 mg once daily, then increasing to 100 mg twice daily after 3 days if tolerated. 3
For pregnancy and postpartum ADHD treatment, guidelines specifically recommend starting bupropion SR at 100–150 mg daily, with maintenance dosing of 100–150 mg twice daily. 3
The second daily dose of any SR formulation must be taken before 3 PM to minimize insomnia risk from bupropion's activating properties. 4
Comparison with Other Bupropion Formulations
Wellbutrin SR requires twice-daily dosing, whereas Wellbutrin XL (extended-release) is dosed once daily in the morning; the two formulations are not interchangeable in their dosing schedules despite delivering comparable total daily exposure. 4
The FDA label explicitly identifies Wellbutrin SR as the sustained-release formulation, distinct from both the immediate-release (IR) and extended-release (XL) products. 1
Patients unable to swallow large tablets whole may benefit from the smaller SR 100 mg tablets, and those requiring flexible dosing (e.g., a total of 150 mg daily) find SR easier to titrate. 4
Maximum Dosing for SR Formulation
- The recommended maximum for Wellbutrin SR is 400 mg per day (200 mg twice daily), though some guidelines cite 450 mg per day as an absolute ceiling; doses above 450 mg markedly increase seizure risk. 5, 6
Pharmacokinetic Evidence
Clinical pharmacokinetic studies have confirmed that bupropion SR 100 mg and 150 mg tablets exhibit linear pharmacokinetics, with no metabolic saturation observed across different release formulations. 7
In pediatric populations (ages 11–17), bupropion SR was studied at doses of 100 mg and 200 mg daily, demonstrating that youths metabolize bupropion faster than adults and supporting divided-dose administration. 8
Common Pitfalls
Do not combine multiple bupropion formulations (e.g., IR + SR + XL) because this can unintentionally exceed the 450 mg daily safety limit. 5
Wellbutrin SR 100 mg should not be crushed, divided, or chewed, as this alters the release rate and increases seizure risk. 1
Patients with seizure disorders, eating disorders, or conditions that lower the seizure threshold are absolutely contraindicated from receiving any bupropion formulation, including the 100 mg SR strength. 4, 5