Bioequivalence and Bioavailability Forum

Hi John,

as usual in the FDA’s guidances:

You can use an alternative approach if the approach satisfies the requirements of the applicable statutes and regulations. If you want to discuss an alternative approach, contact the Office of Generic Drugs.

❝ As per FDA guidance the in-vivo BE route for Minoxidil 5% topical requires a clinical endpoint study because the drug cannot be quantified in plasma due to its low system bioavailability (1.4%) when administered topically. Since this guidance was written in 2011, is it possible to suggest a PK BE study now since we have systems that are capable of measure drugs at very low concentrations?

Hi Jag009,
Approximately 1.4% of topical minoxidil is absorbed through the skin. It may be inadequate to establish bioequivalence using pharmacokinetic parameters alone, given that the final site of action is topical. Therefore, the FDA may still consider conducting a clinical endpoint study to demonstrate equivalence for Minoxidil 5% Topical aerosol foam. Furthermore, it is highly recommended to communicate with the FDA and submit the study protocol before initiating any pharmacokinetic study for minoxidil.