Lactose Monohydrate

Type of Posting: Notice of Adoption of Harmonized Standard

Posting Date: 17-Nov-2023

Official Date: 01-Dec-2024

Expert Committee: Simple Excipients

Coordinating Pharmacopeia: United States Pharmacopeia

A revision to the harmonized standard for Lactose Monohydrate has been approved by the Pharmacopeial Discussion Group (PDG) as described in its PDG Sign-Off Cover Page. Having reached Stage 4 of the PDG process, the Lactose Monohydrate monograph has been formally approved by the USP Simple Excipients Expert Committee in accordance with the Rules and Procedures of the 2020–2025 Council of Experts.

As indicated on the sign-off cover sheet of the recent Correction 2 to the Lactose Monohydrate harmonized standard, the major changes include the following:

  • Removed the thin-layer chromatography (TLC) method from the PDG harmonized attributes. However, the TLC test will be retained in the second identification series as a local requirement in European Pharmacopeia (Ph. Eur.) but using a solvent to replace hazardous ethylene dichloride. The Ph. Eur. correspondence to PDG stated that, according to the General Notices of Ph. Eur., a second identification series “may [only] be used in pharmacies provided it can be demonstrated that the substance or preparation is fully traceable to a batch certified to comply with all the other requirements of the monograph”. On the other hand, JP does not stipulate the TLC test in their monograph.
  • Although USP currently retains this TLC test as a local requirement in the monograph, USP has proposed in PF 49(5) to remove the TLC test from the Lactose Monohydrate monograph to align with USP policy contributing to global efforts on minimizing negative environmental impact. Most importantly, both Anhydrous Lactose and Lactose Monohydrate are sufficiently identified by their infrared (IR) spectra and can be differentiated from other sugars. Therefore, the TLC test does not provide additional confirmatory evidence. Once the PF 49(5) proposal becomes official, USP will submit a request to PDG to remove this test from USP’s local requirements on the PDG sign-off cover sheet.
  • Deleting “Heavy metals” test from JP’s local requirements on the PDG sign-off coversheet so that all three pharmacopeias in PDG have removed this test from their respective monographs.
  • Definition
    • Added (⧫⧫) symbols to the “[Note - Lactose Monohydrate may be modified as to its physical characteristics. It may contain varying proportions of amorphous lactose.]”
  • Microbial Enumeration Tests and Tests for Specified Microorganisms
    • Deleted (⧫⧫) symbols because this is a harmonized attribute.
    • Changed “5 x 101” to “50” to be consistent with the PDG sign-off document.
  • Packaging and Storage
    • Added (⧫⧫) symbols to make it clear that this is a non-harmonized attribute.
  • Labeling
    • Added (⧫⧫) symbols to make it clear that this is a non-harmonized attribute.
  • USP Reference Standards
    • On the PDG sign-off cover sheet, it states that “Each pharmacopeia will adapt the text to take account of local reference materials and reagent specifications.” Therefore, there is no need to add (⧫⧫) symbols around the reference standards as this is the default for all harmonization monographs.

Additionally, minor editorial changes have been made to update the monograph to current USP style.

The Lactose Monohydrate monograph will be incorporated into and become official with the USP-NF 2024 Issue 3 (December 1, 2024).

Should you have any questions about the Lactose Monohydrate monograph, please contact Dr. Tong (Jenny) Liu (240-221-2072 or For any questions about the PDG and its processes, please contact Richard Lew at (240-221-2060 or