Crystallization of Amorphous Nifedipine Under Isothermal Conditions: Inter-laboratory Reproducibility and Investigation of the Factors Affecting Reproducibility.

High inter-laboratory reproducibility is required for conducting collaborative experiments among several laboratories. The primary aim of our evaluation of the physical stability of amorphous drugs, conducted in co-operation with eight laboratories, was to establish a protocol for isothermal storage tests to obtain data of the same quality from all the participating laboratories. Sharing a protocol that contained the same level of detail as the experimental section of general papers was insufficient for high inter-laboratory reproducibility. We investigated the causes of variations in the data from the various laboratories and restricted the protocol step-by-step to achieve high inter-laboratory reproducibility. The various experimentalists had very different levels of awareness regarding how to control the temperature of a sample as the samples were transferred into and out of thermostatic chambers. Specific instructions on how to conduct this operation, such as regarding the time required for the transfer and thermal protection of the container during the transfer, helped to reduce variation. Improved inter-laboratory reproducibility revealed that the physical stabilities of amorphous drugs differed when samples were prepared in differently shaped aluminum pans designed for various differential scanning calorimeters.

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Déclaration de conflit d'intérêts

Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Tamaki Miyazaki reports a relationship with National Institute of Health Sciences that includes: employment. Ryo Mizoguchi reports a relationship with Astellas Pharma Inc that includes: employment. Keisuke Ueda reports a relationship with Chiba University that includes: employment. Taeko Shinozaki reports a relationship with Daiichi Sankyo Co., Ltd. that includes: employment. Mie Kamoto reports a relationship with Eisai Co., Ltd. that includes: employment. Yoshihiro Takeda reports a relationship with Rigaku Corp. that includes: employment. Satoshi Sakuma reports a relationship with Shionogi & Co., Ltd. that includes: former employment. Naoya Ito reports a relationship with Sumitomo Pharma Co., Ltd. that includes: employment. Michiko Momo reports a relationship with Takeda Pharmaceutical Co., Ltd. that includes: employment. Kohsaku Kawakami reports a relationship with National Institute for Materials Science that includes: employment. This study was supported by grants from Japan Agency for Medical Research and Development.