Earlier this summer the FDA recommended a five-point scale to rate topical patch adhesion for drugmakers submitting abbreviated new drug applications (ANDA). However, the recommendations have only raised more questions.

The draft guidance, released in May, is used to determine whether the entire surface of a topical patch adheres to the skin for the duration of wear, according to the FDA. The scale includes:

• 0 = ≥ 90% adhered (essentially all of the patch is on the skin);
• 1 = ≥ 75% to < 90% adhered;
• 2 = ≥ 50% to < 75% adhered;
• 3 = > 0% to < 50% adhered; and
• 4 = 0% adhered (completely detached).

The community largely has been positive about the new scale. However, commenters want more detail on it as well as information on second and third generation products.

Perrigo takes issue with the FDA request for photographic documentation of patches so they can be graded. Perrigo says it is unclear what qualitative issues of an adhesion study photographic documentation would assess other than to confirm that the patch was applied flat against the skin to the correct application site.

Additionally, Perrigo adds that if four or more photographs are required to assess all of the edges of a patch, a study of 200 patients could mean that 7,200 photos will need to be taken.

AstraZeneca a Maryland-based company, said the document would benefit from more clarification on whether second- and third-generation transdermal systems are intended to be covered by this guidance or if there will be other standards/guidance to be considered.

Apotex, a Canadian generic drugmaker, requested further clarification on the acceptability of the adhesion studies that have already been designed and conducted based on the existing individual product-specific guidance documents that were released before this draft became available.

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