Structure of a new H2-receptor antagonist, 2-(2-{[5-(dimethylammoniomethyl)-2-furyl]methylthio}ethylamino)-2-methylamino-1-nitroethylene hydrogen oxalate (ranitidine hydrogen oxalate)

Effect of milling conditions on the solid-state conversion of ranitidine hydrochloride form 1

Powder samples of ranitidine hydrochloride forms 1 and 2 were milled using a vibrational ball mill (Retsch MM301) for periods up to 240min at 4, 12 and 35 degrees C. X-ray powder diffraction (XRPD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), solid-state nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC) were used to monitor solid-state properties of the milled samples. Milling of form 1 at 4 degrees C led to a powder temperature of 36 degrees C in the milling chamber and produced only amorphous drug; at 12 degrees C (powder temperature 45 degrees C) and at 35 degrees C (powder temperature 62 degrees C) progressive transformation of form 1 via amorphous drug to form 2 occurred. DSC of the milled samples showed a glass transition at 13-30 degrees C and a crystallization exotherm (T(c)) between 30 and 65 degrees C if the sample contained amorphous drug. The behaviour of the solid was speculated to be influenced by the relationship between powder temperature and T(c); at powder temperatures below T(c), amorphous drug is formed but no crystallization of form 2 occurs; at temperatures close to T(c), amorphous content initially increases with transformation to form 2 on continued milling. At temperatures much higher than T(c), at intermediate stages, less amorphous drug but both form 1 and form 2 are recovered, but continued milling gives only form 2. Form 2 did not transform to form 1 under any conditions used in this study.

Ketene aminal-based lactam derivatives as a novel class of orally active FXa inhibitors

N,N'-Disubstituted ketene aminals are good bioisosteres of thiourea functional groups. We report the design and synthesis of a novel class of ketene aminal-based lactam derivatives as potent and orally active FXa inhibitors.

Using Terahertz pulse spectroscopy to study the crystalline structure of a drug: a case study of the polymorphs of ranitidine hydrochloride

We describe the application of Terahertz pulse spectroscopy to polymorph identification. The particular compounds investigated were the different crystalline Forms 1 and 2 of ranitidine hydrochloride, both in the pure form and also obtained as a marketed pharmaceutical product. Identification was clear. The technique has advantages that excitation is not via a powerful laser source, as used in Raman spectroscopy, so phase changes or photochemical reactions in polymorphs do not occur. Terahertz absorption spectral interpretation and instrumentation are similar to basic Fourier transform infrared (FTIR) spectroscopy and therefore easy to understand. The sample preparation techniques used are the same as those used in FTIR and Raman spectroscopies. The data obtained is complementary to Raman Spectroscopy. As the selection rules are different between the two techniques, we are able to obtain new data set directly related to crystalline structure adding to that obtained by Raman spectroscopy. Terahertz pulse spectroscopy provides information on low-frequency intermolecular vibrational modes; these are difficult to assess in Raman spectroscopy due to the proximity of the laser exciting line. It is concluded that the method has a wide range of applications in pharmaceutical science including formulation, high throughput screening, and inspection in storage.