The QC had been carried out with the RSP-method and the USP-method was then applied. For this, the theoretical weight of a capsule was calculated taking the average weight of 5 empty capsules (0.0493g) as reference and the weight of the batch content (13.8g=dexamethasone (4g) + excipient (9.8g)) calculated in the compounding design being the acceptance interval 0.169-0.206g. ResultsThe RSP-method requires a sample of 20 capsules and uses their average weight as a reference, while the USP-method requires a sample of 5% or 10 capsules (whichever is less) and uses the theoretical weight of a capsule as a reference. The RSP-method admits a deviation of ± 10% or ± 7.5% depending on the average weight; and no >2 capsules can deviate from the limits and none more than double. The USP-method accepts a limit of ± 10% respect to the theoretical weight, and no capsule must deviate.Regarding the compounding method, the RSP allows elaboration by volumetric filling according to the Spanish-National-Formulary (excipients weight is not required). However, the USP-method requires knowing the theoretical capsule weight, which implies weighing the excipients.Since February-2020 to February-2021, 8 batches of dexamethasone 40mg were elaborated. They were accepted with the RFE-method. After applying the USP-method, none were rejected. Conclusion and RelevanceThe USP-method is safer than the RSP-method because for the same acceptance interval ( ± 10%) it does not admit any deviation. It also requires knowing the weight of all the excipients. Therefore, it is capable of detecting errors in the elaboration that the RFE-method would not detect (as long as the error is >10% and the capsules are homogeneous).Currently, the USP-method has been incorporated in the HPD as a reference of hard capsules QC, since it provides greater safety in their preparation.

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