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# Alcon Wants Durezol Bioequivalence Requirements
- URL: https://www.fdaweb.com/alcon-wants-durezol-bioequivalence-requirements/
- Published: 2016-09-20T12:00:00.000Z
- Updated: 2026-09-14T21:33:39.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5136856

Alcon has petitioned FDA to change the bioequivalence testing requirements for any ANDA that cites its Durezol (difluprednate ophthalmic emulsion, 0.05%) as the reference-listed drug and also revise the product-specific bioequivalence draft guidance for difluprednate ophthalmic emulsion. “Petitioners believe that only *in vivo* pharmacokinetic testing or comparative clinical endpoint testing, and not *in vitro* testing, is sufficient to accurately, sensitively, and reproducibly measure bioequivalence of difluprednate ophthalmic emulsions,” the [petition](https://www.regulations.gov/contentStreamer?documentId=FDA-2016-P-2781-0001&attachmentNumber=1&disposition=attachment&contentType=pdf&ref=fdaweb.com) says.

According to Alcon, a January draft guidance on difluprednate said that an ANDA applicant could establish bioequivalence either through *in vitro* testing or an *in vivo* pharmacokinetic study in aqueous humor. The company wants the agency to require *in vivo* testing and drop the *in vitro* option.

If FDA denies the requests and retains the *in vitro* option, Alcon says, it should require additional *in vitro* testing as recommended in the petition to increase the likelihood that any meaningful differences between the *in vivo* bioavailability of generic difluprednant ophthalmic emulsion products and Durezol are detected.

A final guidance should be issued promptly, the petition says, with content that is consistent with the petition.