On 28 May 2013, the FDA also finally published the ICH harmonised Guideline entitled "Evaluation and Recommendation of Pharmacopoeial Texts for Use in the ICH Regions on Bulk Density and Tapped Density of Powders - General Chapter (Q4B Annex 13)".
This ICH Guideline thus came into force in the USA, too.
The objective of the ICH Q4B Working Group is to reach mutual recognition by regulatory authorities in the ICH regions for all testing methods listed in the ICH Q6A Guideline on Specifications.
Through this, comparable testing laid down in the different pharmacopoeias shouldn't be performed separately when it has been assessed by authorities that those are similar and interchangeable.
Nevertheless, the FDA might request - if necessary - that a company demonstrates that the chosen method is acceptable and suitable for a specific material or product, irrespective of the origin of the method. This "Disclaimer" can be found in all the ICH Q4B Annexes. No one knows whether the FDA has already posed such questions.
For details please see the FDA Q4B - Annex 13.