Expert: Dr. Ravindra Bhaskar Ghooi - 5/24/2009

Question
I've received conflicting information regarding the time release mechanism of Wellbutrin XL. I wish to cut the pill in half, but I was advised by my the pharmacist not to because, he believes, the coating controls the time release. Is this really true, or is the time release mechanism built into the formulation? A mere coating would only govern the when it starts to work, now how slowly, it seems.

Answer
Hi David,
There are two or three types of mechanisms used for controlling drug release from a formulation. Coating is certainly one of them, matrix being the other common one, osmotic mechansims have been used but very rarely. Manufacturers are not obliged to disclose the mechanism that has been used to control release hence most pharmacist will tell you not to break the tblet into two.
The manufacturers of wellbutrin have not given the details of the mechanism used by them, in the absence ofthis information I too would go by the conventional advice not to break the tablet into two unless we are absolutely sure that its kinetics would not be adversely affected.
Ravi Ghooi