Controlled release oral dosage form

1. A pharmaceutical composition comprising:

(A) at least one pellet consisting of:

(i) a core which comprises an inert carrier, wherein said inert carrier is coated with bupropion or a pharmaceutically acceptable salt or stereoisomer thereof, and

(ii) a sustained release coating surrounding said core wherein said sustained release coating comprises at least one controlled release polymer for controlled release delivery of said bupropion or a pharmaceutically acceptable salt or stereoisomer thereof,

(B) said pharmaceutical composition further comprising bupropion or a pharmaceutically acceptable salt or stereoisomer thereof in an immediate release form, and

wherein the pharmaceutical composition is designed for once daily dosing.

2. The composition of claim 1 wherein the core further comprises at least one binder.

3. The composition of claim 2 wherein said binder comprises hydroxypropyl methylcellulose.

4. The composition of claim 1 wherein said controlled release polymer is water insoluble.

5. The composition of claim 4 wherein said water insoluble polymer comprises a methacrylic acid copolymer.

6. The composition of claim 4 wherein said water insoluble polymer comprises ethylcellulose.

7. The composition of claim 1 wherein said controlled release polymer is insoluble below about pH 7.

8. The composition of claim 1 wherein the composition is a tablet, caplet, or capsule.

9. The composition of claim 1 , wherein said composition provides 24-hour efficacy with once daily dosing, with less than 50% of the bupropion released at 10 hours.

10. The composition of claim 1 , wherein said composition provides therapeutic plasma levels for 12 to 24 hours.

11. The composition of claim 4 wherein said water insoluble polymer is selected from the group consisting of cellulose acylate, cellulose diacylate, cellulose triacylate, cellulose acetate, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, mono-, di- and tri-cellulose arylates.