Miscibility and interactions between 17β-estradiol and Eudragit® RS in solid dispersion

Solid State and Thermal Behavior of 17β-Estradiol in Ammonioethyl Methacrylate Ester Copolymer

“…The first endotherm (onset at 110 C) and second endotherm (onset at 174 C) in the first heating run corresponded to the partial release of hydrogen bonded water and the complete loss of water lattice, respectively. The water loss observed in the first scan was agreed with a weight loss of 3.2 % of E 2 measured by thermogravimetric analysis (TGA) as illustrated in Figure 6(B) (Wiranidchapong 2006;Wiranidchapong 2008 On cooling (DSC; 182-0 C at 20 K/min) the glass transition temperature (T g ) was observed around 84.2 C, correlating to that observed in the second heating (DSC; 0-250 C at 10 K/min). This aspect revealed an appearance of amorphous E 2 after E 2 -hemihydrate had been melted and then rapidly cooled.…”

“…The most common form of E 2 is the hemihydrates (Variankaval 2000;Wiranidchapong 2008). However, E 2 can exist in various kinds of pseudopolymorphs as hemisolvates, dependent on the type of solvent used in the crystallization.…”

“…This can lead to serious implications of physical stability in dosage forms (Niazi 2007). E 2 can exist in the amorphous form and at least three crystalline forms, including E 2 -hemihydrate (Variankaval 2000;Wiranidchapong 2006;Wiranidchapong 2008). Differential scanning calorimetry (DSC) curve reveals that the three crystal forms and amorphous form of E 2 are inter-convertible under various thermal conditions as displayed in Figure 6(A) (Wiranidchapong 2006;Wiranidchapong 2008).…”

“…This aspect revealed an appearance of amorphous E 2 after E 2 -hemihydrate had been melted and then rapidly cooled. In the second heating the amorphous E 2 in glassy state was changed to that in rubbery state when the temperature reached the T g , followed by recrystallization into ED form as stated by Variankaval et al (Variankaval 2000) and anhydrous E 2 exhibiting their melting points at 169.6 C and 179.2 C, respectively (Variankaval 2000;Wiranidchapong 2006;Wiranidchapong 2008).…”

“…E 2 -hemihydrate demonstrates characteristic peaks at 13.14, 15.74, 18.26, 22.62, and 26.58° (Latsch 2003;Park 2005;Wiranidchapong 2006;Wiranidchapong 2008). Anhydrous E 2 prepared by heating E 2 -hemihydrate from 0-175 °C and 0-180.5 °C at heating rate of 5 K/min exhibited the characteristic peaks at 13.60, 16.78, 21.00, and 24.72°, which were not observed in the diffraction pattern of E 2 -hemihydrate.…”