Crystalline warfarin sodium is an isopropanol clathrate containing 8.3% isopropyl alcohol (IPA) and 0.57% water upon receipt. The hygroscopicity and impact of moisture on IPA status as well as on the stability of the clathrate was studied at different relative humidities. The IPA loss and water uptake were simultaneous but they did not exchange at 1:1 molar ratio. At 58% relative humidity (RH) or below, the exchange process was insignificant. At 68% RH or above, the clathrate tended to lose IPA while absorbing water and reverting to the amorphous state. The rate of IPA loss and moisture uptake was a function of RH. The thermal stability of the crystalline warfarin sodium was also examined. Physical change occurred after isothermal storage for 24 hours at 80oC and 11 hours at 120oC. The rate of IPA loss was temperature dependent.

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Na2TeOa.5H20, M r = 311.6, is monoclinic, space group C2/c, with cell parameters a = 13.468 (2), b = 7.426 (1), c= 17.545 (3)/l,, fl = 97.79 (2)°, Z = 8, D m = 2.36 (2) and D x = 2.38 Mg m -3. 1994 independent reflexions were used in a full-matrix least-squares refinement; a final R value of 0.026 was obtained. The structure is built up from chains of Na(OH2) 6 octahedra parallel to the c axis, related by Na atoms in square-planar coordination, NaO2(OH2) z. This structure contains pyramidal TeO 2-ions with Te-O distances in the range 1.850-1.862 /I and O-Te-O angles close to 99.5°. Positions for the H atoms are proposed.

KEYWORDS: sublimation, vapor pressure, thermogravimetric analysis-infrared (TGA-IR) The purpose of this research is to investigate the sublimation process of DPC 963, a second-generation nonnucleoside reverse transcriptase inhibitor for HIV-1 retrovirus, and to better understand the effect of sublimation during active pharmaceutical ingredient (API) manufacture and formulation development, especially the drying processes. Sublimation of DPC 963 at 150°C and above was determined by thermogravimetric analysis-Fourier transform infrared (TGA-FTIR). The rates of sublimation at different temperatures were measured using isothermal TGA. Condensed material was collected and analyzed by differential scanning calorimetry (DSC), x-ray powder diffraction (XRPD), and infrared (IR) spectrometry. Benzoic acid was used as a reference standard to derive a linear logarithmic relationship between sublimation/evaporation rate and vapor pressure specific to the TGA system used in this study. Sublimation and evaporation of DPC 963 were found to follow apparent zero-order kinetics. Using the Eyring equation, the enthalpy and entropy of the sublimation and evaporation processes were obtained. The enthalpies of sublimation and evaporation were found to be 29 and 22 kcal/mol, respectively. The condensed material from the vapor phase was found to exist in 2 physical forms, amorphous and crystalline. Using benzoic acid as a reference standard, vapor pressure of DPC 963 at different temperatures was calculated using the linear logarithmic relationship obtained. DPC 963 undergoes sublimation at appreciable rates at 150°C and above but this is not likely to pose a serious issue during the manufacturing process. Vapor pressure estimation using thermogravimetric analysis provided sufficient accuracy to be used as a fast, simple, and safe alternative to the traditional methods of vapor pressure determination.

The pH-rate profile was consistent with a combination of a V-shaped profile in the pH range of 0-9 and a sigmoid-shaped profile in the pH range of 4-13. The plateau that began at pH 10-11 is a result of the ionization of the amine of the carbamate inhibiting the base-catalyzed hydrolysis of efavirenz, given that the ionized form of the carbamate is resonance-stabilized toward hydroxide-catalyzed degradation. Thus, increasing the pH resulted in a parallel decrease in the unionized fraction and increase in hydroxide ion concentration resulting in a constant k(obs) value.