Microbial test in stability sample

can we skip the microbial test in stability studies of solid dosage form ? like can we do at initial as well as final stage and not doing at in between stage such as 3rd,6th, 12th or 18th month duration?

Stability studies should include testing of those attributes of the drug product that
are susceptible to change during storage and are likely to influence quality, safety,
and/or efficacy. The testing should cover, as appropriate, the physical, chemical,
biological, and microbiological attributes, preservative content (e.g., antioxidant,
antimicrobial preservative), and functionality tests (e.g., for a dose delivery system).
Analytical procedures should be fully validated and stability indicating. Whether and
to what extent replication should be performed will depend on the results of
validation studies.
Shelf life acceptance criteria should be derived from consideration of all available
stability information. It may be appropriate to have justifiable differences between
the shelf life and release acceptance criteria based on the stability evaluation and the
changes observed on storage. Any differences between the release and shelf life
acceptance criteria for antimicrobial preservative content should be supported by a
validated correlation of chemical content and preservative effectiveness demonstrated
during drug development on the product in its final formulation (except for
preservative concentration) intended for marketing. A single primary stability batch
of the drug product should be tested for antimicrobial preservative effectiveness (in
addition to preservative content) at the proposed shelf life for verification purposes,
regardless of whether there is a difference between the release and shelf life
acceptance criteria for preservative content.
Therefore, it would be acceptable to conduct Microbiology limit tests at initial and at the end of shelf life, if above conditions are satisfactorily met.
Please refer ICH Guideline ICH Q1A (R2) of STABILITY TESTING OF NEW DRUG SUBSTANCES AND PRODUCTS.

For Microbial limit tests, the Acceptance criteria should be set for the total count of aerobic microorganisms, the total count of yeasts and molds, and the absence of specific objectionable bacteria (e.g., Staphylococcus aureus, Escherichia coli, Salmonella, Pseudomonas aeruginosa).
These should be determined by suitable procedures, using pharmacopoeial procedures, and at a sampling frequency or time point in manufacture which is justified by data and experience. (For Batch Release purpose). Please also refer ICH Q6A Guideline of SPECIFICATIONS: TEST PROCEDURES AND ACCEPTANCE CRITERIA FOR NEW DRUG SUBSTANCES AND NEW DRUG PRODUCTS:
CHEMICAL SUBSTANCES.

thanks. really helpful.

You are welcome…!!