Adapalene Monograph Revision Proposed for Solubility Issue

USP Compendial Notices

Published January 1st, 2026

Detected March 12th, 2026

Summary

The USP Small Molecules 3 Expert Committee intends to revise the Adapalene monograph to address a potential solubility issue in the Organic Impurities test. The proposed changes include allowing a larger volume of tetrahydrofuran for the standard stock solution, introducing a two-table format for retention times, and deleting the Limit of Triethylamine test.

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What changed

The United States Pharmacopeia (USP) has issued a Notice of Intent to Revise the Adapalene monograph, targeting an official date of January 1, 2027. The Small Molecules 3 Expert Committee proposes to amend the preparation of the Standard stock solution to address a solubility issue in the Organic Impurities test, Procedure 1, by permitting the use of a larger volume of tetrahydrofuran. Additionally, the revision includes introducing a two-table format for relative retention times and acceptance criteria, referencing <477> User Determined Reporting Thresholds, and deleting the Limit of Triethylamine test as it is now covered under <467> Residual Solvents. Minor editorial changes to align with current USP style are also proposed.

This proposed revision is expected to be published in the Pharmacopeial Forum 52(3) in May-June 2026, with a comment period closing on July 31, 2026. Regulated entities, particularly drug and pharmaceutical manufacturers, should review the proposed changes to the Adapalene monograph. In the absence of significant adverse comments, the revision will become official on January 1, 2027. Companies should prepare to implement these changes by the effective date to ensure compliance with USP standards.

What to do next

Review proposed revisions to the Adapalene monograph for solubility and organic impurities testing.
Submit comments on the proposed revision by July 31, 2026.
Prepare for implementation of revised monograph standards by January 1, 2027.

Source document (simplified)

Adapalene

Type of Posting: Notice of Intent to Revise
Posting Date: 30-Jan-2026
Targeted Official Date: 01-Jan-2027; Interim Revision Announcement
Expert Committee: Small Molecules 3

In accordance with the Rules and Procedures of the Council of Experts, this is to provide notice that the Small Molecules 3 Expert Committee intends to revise the Adapalene monograph.

On the basis of the comments received, the committee proposes revising the preparation of the Standard stock solution preparation to address a possible solubility issue in the test for Organic Impurities, Procedure 1. The proposed change would permit the use of a larger volume of tetrahydrofuran (about 10% of the final flask volume) to dissolve the components of the Standard stock solution. The committee also proposes introducing a two-table format style for relative retention times and acceptance criteria, and adding references to <477> User Determined Reporting Thresholds in the tests for Organic Impurities.

Additionally, the committee proposes deleting the test for the Limit of Triethylamine because triethylamine is currently covered by the <467> Residual Solvents. Additionally, the committee proposes minor editorial changes to update the monograph to the current USP style.

It is anticipated that the proposed revision will be published as an Interim Revision Announcement in Pharmacopeial Forum 52(3) [May-Jun. 2026] pursuant to the Rules and Procedures of the Council of Experts. The comment period for this revision ends on July 31, 2026. In the absence of any significant adverse comments, the proposed IRA will become official on January 1, 2027.

Should you have any questions, please contact Allan Leeks, Jr, Sr. Scientist I (atl@usp.org).