The authors have determined the degree of purity on different samples of aminophenazone (I) containing very small quantities of phenazone and amino-4-phenazone. The advantages of differential scanning calorimetry and the of transparency recording in the change from the solid to the liquid state during the fusion is shown.
After studying the thermal behaviour of the reactants the authors have established the diagrams of state of binary systems of aminophenazone form (I) with phenazone and with amino-4-phenazone by thermomicroscopy, differential scanning calorimetry and differential thermal analysis. Only one eutectic point is observed for each binary system, the fusion temperature and the composition of which have been determined.
We have determined the eutectic composition nordazépam (NDZ) polyoxyethylene glycol 6000 (PEG): 4% NDZ, 96% PEG (Tf=59,0±0,5°C ΔHf=155,9±2,4 J·g−1; NDZ succinic acid: 0,32n (NDZ) and 0,68n (succinic acid) (Tf=163,8±0,4°C and ΔHf=119,34±2,1 J·g−1). No solid solution has been found. The negative and high absolute value of mixing enthalpy indicates that the eutectic composition is formed by interactions between OH, CO, NH groups of carrier and drug with hydrogene bonds formation, confirmed by X-ray diffraction.
The thermal behaviour of khellin has been studied by thermomicroscopy, differential scanning calorimetry, differential thermal analysis and measurement of transparency. The polymorphism of this drug has been established; the commercial form (I) melting at 153.3° and the form (II) melting at 150.3° have been identified, and their enthalpies (7725±166 cal·mole−1, 6668±230 cal·Mol−1) and entropies (18.17±0.41,15.76± 0.54) of fusion evaluated, while the degree of purity of form (I) has been determined.
The solubility and rate of dissolution of a poorly-soluble active principle are of importance when substances are destined
for oral administration. Physical blends in wich drug and carrier are able to form particular compositions, such as a eutectic,
may exibit an increased rate of dissolution. In this work the interactions lorazepam and PEG 6000, were examined, the particular
thermal behaviour of lorazepam being taken into account. An eutectic was obtained and its composition was studied by means
of differential scanning calorimetry, thermomicroscopy, infrared spectroscopy and X-ray methods.
Authors:A. Chauvet, J. Canotilho, A. de Sousa, and J. Masse
We have established the phase diagram tolbutamide (TBM)-PEG 6000 and determined the eutectic composition 1/9 (w/w) in tolbutamide
and melting temperature 56.2°C±0.3; no solid solution has been found. Negative mixing enthalpies of physical mixture (−2.5
J·g−1) and solid dispersions coprecipitate (−3.9 J·g−1) melt (−9.9 J·g−1) for eutectic composition involve the existence of interactions between drug and carrier. We have determined the dissolution
kinetics: amount % dissolved (10 min) 65.87±0.55 (physical mixture), 78.02±0.02 (coprecipitate), 99.90±0.10 (melt). We have
observed a good agreement between dissolution kinetics and mixing enthalpies data.
Authors:A. Terol, A. Chauvet, G. De Maury, and J. Masse
The phase diagrams for aminophenazone-urea (a), aminophenazone-thiourea (b) and aminophenazone-noxythioline (c), established by differential scanning calorimetry, transparency method and thermomicroscopy, revealed the presence of definite compounds (1–3). These compounds are formed during eutectic fusion for (a) and (c); the definite compound for (b) displays non-congruent fusion.