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Thursday, July 23, 2009 grannyelaine, Community Member, asks

Q: What does SR and XL stand for and what is the difference in the two?

I am taking generic Wellbutrin and this time the prescription is for XL where the others have been for SR. What does this mean? The XL is double the cost of SR so I want to make sure there is a substantial difference.

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Answers (3)
Teri Robert, Health Guide
7/23/09 1:54pm



OK. I went to the FDA site and got the labeling information for both of these. Let's see what the difference is:


Wellbutrin SR: The SR stands for Sustained Release.


Wellbutrin XL: The XL stands for Extended Release.


Well, I'm having trouble finding the difference. Tell you what -- I'm going to email a doctor who will KNOW the difference and get back to you. OK?



Teri Robert, Health Guide
7/24/09 5:35pm

Hello again, Elaine,


I took your question to Dr. John Claude Krusz. He runs a multi-specialty practice in Dallas treating Migraine, headaches, pain, mood disorders, and sleep disorders. Here's his answer:


Dear grannyelaine:


The XL is more expensive but doles out the medication over 8-10hrs; the XR is sort of time-release - take 5-6 hours to release. Ultimately there should not be any difference if effect



I hope this helps. Please let me know?



gary4921, Community Member
2/25/12 1:25pm

SR stands for sustained-release and has a time to peak serum blood level of approximately 3 hours, whereas XL stands for extended-release and has a time to peak serum blood level of approximately 5 hours. Wellbutrin is 87% primarily excreted in the urine.  The SR form does not last as long in the body and usually needs a twice-daily dosing whereas the XL form stays longer in the body and only needs once-daily dosing.

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By grannyelaine, Community Member— Last Modified: 10/28/13, First Published: 07/23/09