When GSK advertises that Wellbutrin XL comes in 150mg and 300mg tablets, that actually means that with 300mg, you are getting two doses of 150mg separated throughout the day, correct? Which would also mean that their 150mg tablet is actually two 75mg doses?

I have postulated this theory based on my understanding of how Shire's Adderall XL works. When they say its a 30mg XL capsule, you are actually getting 15mg at a time separated between 4 hours. But with regular Adderall, a 30mg pill means you GET 30mg of it instantly.

So is my theory about Wellbutrin correct?

When you are talking about "two doses" I think you have that a little wrong. There is another med called Wellbutrin SR where it does something like that. The way I understood it was that Wellbutrin XL was a SLOW release, made to "fix" the ups and downs that Wellbutrin and even Wellbutrin SR created. XL is **Supposed** to slow time release throughout the day. Hope this helps.