Bupropion.bmpAndrx Pharmaceuticals has filed a patent infringement suit against the UK’s GlaxoSmithKline PLC over a version of the antidepressant Wellbutrin XL. Andrx filed the suit in the U.S. District Court for the Southern District of Florida, alleging that GlaxoSmithKline’s 150 milligram dose of extended-release Wellbutrin violates its patent covering a once-a-day form of bupropion hydrochloride, the active ingredient in Wellbutrin.

Andrx Pharmaceuticals’ US Patent No. 6,905,708, claims:

1. A once daily dosage form comprising 150 mg of an bupropion or salt of bupropion, said dosage form providing an in vivo plasma profile selected from:

(a) Mean Tmax of about 5 or more hours

(b) Mean Cmax of less than about 90 ng/ml, and

(c) Mean AUC0-120h of more than about 350 (ng-h)ml.

The original compound, bupropion hydrochloride, is described in U.S. Pat. Nos. 3,819,706 and 3,885,046 and is used as an anti-depressant and as an aid to smoking cessation. Bupropion hydrochlorideis an aminoketone-derivative. In some studies, a risk of seizures appears to be strongly associated, in part, with the use of instant release tablets.

The ‘708 patent describes a pelletization process, typified by the application of a bupropion/cellulose ether suspension to inert spheres and two formulations of sustained release coatings that are applied to separate active pellets. The formulation functions by membrane-controlled extended-release in a pH dependent manner.

This formulation can provide 24-hour efficacy with once daily dosing, with less than 50% of the drug released at 10 hours. Therapeutic plasma levels are maintained from 12 to 24 hours. The usual dosage range is 75-450 mg.

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