Analytical Investigation of the Possible Chemical Interaction of Methyldopa with Some Reducing Carbohydrates Used as Pharmaceutical Excipients

Modafinil-excipient compatibility study using differential scanning calorimetry

Drug excipient compatibility studies are considered important in successful formulation of drug products. Suggested methods for this purpose are thermal techniques under isothermal or nonisothermal conditions. In this study, modafinil, a wakefulness-promoting drug, was investigated under nonisothermal conditions using differential scanning calorimetry. Four different heating rates, 5, 10, 15, and 20°C/min, were performed for modafinil pure material and its physical mixtures with magnesium stearate (MgSt) or Gelucire 48/16. Activation energy (Ea) was calculated from the straight line of plotting a function of heating rate versus temperature and found that modafinil-Gelucire physical mixture increased Ea. This indicates drug-excipient interaction, supported by evidence from Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. No significant interaction was detected with MgSt.

Compatibility Study between Fenbendazole and Polymeric Excipients Used in Pharmaceutical Dosage Forms Using Thermal and Non-Thermal Analytical Techniques

The body of work described in this research paper evaluates the compatibility between Fenbendazole (Fen), which is a broad-spectrum anthelmintic with promising antitumor activity, and three polymeric excipients commonly applied in pharmaceutical dosage forms. The assessment of binary mixtures was performed by differential scanning calorimetry and thermogravimetric analysis/derivative thermogravimetry to predict physical and/or chemical interactions, followed by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), and high-performance liquid chromatography (HPLC) to confirm or exclude any interactions. Thermal studies suggested the presence of interactions between Fen and P 407, PCL, and PLA. To validate these data, XRD showed that Fen is compatible with PCL and PLA, suggesting some interaction with P 407. FTIR demonstrated that PCL and PLA can establish physical interactions with Fen; moreover, it suggested that P 407 interacts not only physically but also chemically, which was later proved by HPLC to be only new intermolecular interactions. This work supports the further application of P 407, PCL, and PLA for the development of new medicinal and veterinary formulations containing Fen, since they do not affect the physical and chemical characteristics of the active ingredient and consequently its bioavailability and therapeutic efficacy.

Evaluation the Effect of Amine Type on the Non-isothermally Derived Activation Energy for the Interaction of 3 Antidepressant Drugs with Lactose

Purpose: Evaluation of drug-excipients compatibility is an important stage during preformulation studies. In the present research, differential scanning calorimetry (DSC) at different heating rates (2.5, 10, 15°C/min) was applied for the kinetic evaluation of fluvoxamine (FLM), sertraline (SER) and doxepin (DOX) binary mixtures with lactose. Methods: Solid state kinetic parameters of the mixtures were calculated using two different thermal methods including ASTM E698 and Starink and the effect of amine type (pKa value) was investigated based on the calculated activation energies. Results: Based on obtained results mean activation energy calculated for FLM, SER and DOX with lactose using ASTM E698 and Starink methods are equal to 335.23, 132.02 and 270.99 kJ/ mol respectively. Conclusion: Results showed that the probability of drug-lactose interaction is higher in the SERlactose mixture in comparison with other two antidepressant drugs which is consistent with their pKa values.