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It is permissible for a firm to do the in vivo BE study against a
lower strength than what is recommended. However, if the firm ever
chooses to market the higher strength another in vivo BE study must be
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This is not always the case. For example, with Wellbutrin BE studies
were performed using the 150 mg dose strength. These studies supported
the marketing of the 300 mg dose strength for the generic. The FDA
stated that this approach was acceptable based due to safety concerns
with the use of the higher strength in normal volunteers. Details can
be found at http://www.fda.gov/CDER/drug/infopage/bupropion/TE_review.htm
.. Below is a brief extract from the webpage.
*What was the basis for approval of Teva's generic bupropion XL*?
The basis for approval of Teva's bupropion XL was that there was no
significant difference in the rate and extent of absorption as
measured by the plasma bupropion concentrations between 150 mg of the
Teva XL product and 150 mg of Wellbutrin XL. Because of the potential
risk of seizures at higher doses, the 300 mg strength was not studied.
This practice is used when evaluating the pharmacokinetic profile of a
drug in normal volunteers, especially when a drug's adverse effects
increase with dose. The pharmacokinetic profile is not expected to
differ between 300 mg and 150 mg doses of bupropion.
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