Expert: Dr Alan Galbraith - 3/23/2009

Question
I've read that the difference between the two is that SR is designed to be taken in two 150mg doses daily.  I take one 300mg dose of SR daily...is that not the most effective course?  I would also like to know what technically makes these different...the both contain the same amounts of bupropion, so is it just some sort of binder that allows different rates of release?

Thanks for your help!

Answer
Dear Patricia

Drug companies do not normally release how their slow release preparations are exactly formulated. However, theoretically I would say that the 2 x150mg preparation will be more or less identical to taking 1 x 300 mg SR preparation per day. It may be that taking the 2 x 150 mg maintains more constant blood concentrations initially but after 5 doses the blood concentration of most drugs remains in what is known as steady state ie the blood concentration fluctuates only very slightly.

This be explained mathematically (usually shown graphically) and if you look up pharmacokinetics of drugs and steady state on the Internet you will find several sites that depict this.

Regards

Dr Alan Galbraith