I found an assessment report of the Sitagliptin Accord, which includes the different salt forms from the sitagliptin phosphate monohydrate.
According to the report, three impurities described in the Ph. Eur. in the monograph of sitagliptin phosphate monohydrate are Impurity A (enantiomer), Impurities B, and C. And Impurities B and C are unspecified.
This sitagliptin was considered free from nitrosamine. Please see the following excerpt from the report.
P16.
The Applicant updated the risk assessment to include the discussion on potential nitrosamines likely to be introduced based on the manufacturing process of the drug substance and interactions between the components of the drug substance, excipients and packaging materials. All nitrosamines that could potentially be formed taking into account all parent amine entities (secondary, tertiary and quaternary) that could be present in the components of the drug product (drug substance, excipients, water and packaging materials) have been considered. Based on the additional information provided, overall it was accepted that no risk was identified of the possible presence of nitrosamine impurities in the active substance or the related finished product. This is sufficient and confirmatory testing is not required. The batch results provided by the Applicant (NDMA, NDEA, NDIPA, NEIPA and NDBA in three active substance batches, and NDMA and NDEA in 6 finished product batches for each strength) are considered supportive. The analytical methods used have been adequately described and appropriately validated in accordance with the ICH guidelines.
I’m not sure whether this sitagliptin includes impurity3 or not. I guess it could be identified through risk assessment if contained. And as @Diego_HM pointed out, I’m concerned with acid hydorisis through DP manufacturing or storage. Significant degradation was observed in acidic stress studies of API. What do you think?