A comprehensive compatibility study of ganciclovir with some common excipients
Authors: Mishra Anoop , Sinha Vivek Ranjan , Sharma Sumit , Mathew Alen T. , Kumar Rajnish , Yadav Ashok Kumar 
Published: November 2023

Objectives:
The aim of the present study is to illustrate compatibility testing of ganciclovir (GCV) with some common excipients that would be used to manufacture solid oral dosage forms. Different spectroscopy techniques were utilized to see the interaction of GCV with excipients such as lactose, microcrystalline cellulose (MCC), magnesium stearate, and talc, and dicalcium phosphate. Further, a molecular docking study was also done to know the interaction of GCV with excipients. In vitro study of a physical mixture of GCV with excipients was performed to get the release of drug.

Material and Methods:
A number of analytical techniques (differential scanning calorimetry [DSC] using DSC-Q20, TA instruments, Fourier-transform infrared spectroscopy [FTIR] spectroscopy using Spectrum RX 1, nuclear magnetic resonance [NMR] using Bruker Advance Neo 500 MHz NMR spectrometer, etc.) have been used to explore the drug-excipient compatibility. Further, a suspected interaction was evaluated by thin-layer chromatography (TLC). In vitro dissolution studies in different sets of experiments were accomplished to determine the influence of hydrophobic and hydrophilic attributes of excipients (MCC, lactose, dicalcium phosphate, and talc) on the dissolution profile of GCV using USP1-type dissolution apparatus. Furthermore, in silico molecular docking studies were also performed to evaluate any probable molecular interactions among drugs and excipients using Auto Dock VINA 1.2.0 software and GROMACS 5.0 software.

Results:
Comparing FTIR and 1H NMR spectra of GCV and physical mixtures of GCV and excipients, no significant deviation of characteristic peaks in infrared spectroscopy and 1H NMR signals was observed. The DSC of GCV showed two sharp endothermic peaks at 238.82°C and 255°C. The endothermic peak of GCV in DSC thermogram of physical mixtures was observed in nearly the same position except with lactose and dicalcium phosphate. A slightly deviated peak of GCV with a physical mixture of drug and lactose and dicalcium phosphate indicated that there were suspected interactions between the drug with lactose and dicalcium phosphate. These interactions were evaluated by thin-layer chromatography (TLC) and it confirmed that there was no interaction between drugs and excipients. In vitro dissolution studies determined the influence of hydrophobic and hydrophilic attributes of excipients on the dissolution profile of GCV. The physical mixture of GCV with MCC displayed a maximum amount (66.48%) of drug release in 10 min. On the other hand, a physical mixture of GCV with talc showed a minimum amount (12.08%) of drug release in 10 min. Docking study predicted that the number of interactions were more between GCV and lactose (four nos.) in comparison to GCV and MCC (two nos.). This interaction supported the in vitro drug release of a physical mixture of GCV with MCC which was higher than a mixture of GCV with lactose.

Conclusion:
Compatibility testing of GCV with used excipients by analytical techniques confirmed that GCV should be compatible with used excipients. Drug dissolution of GCV and physical mixture of MCC exhibited the maximum amount of drug release whereas a mixture of GCV with talc released the minimum amount of drug for both short (10 min.) and long (60 min.) periods. Docking studies disclosed that the lactose complex showed less deviation with less root mean square deviation value in comparison to the microcrystalline complex. Thus, the lactose complex has more hydrogen bonds and it was more stable as compared with the MCC complex. GCV indicates that the total energy of the MCC complex is less than that of the lactose complex. This indicates that GCV is more soluble when combined with the microcrystalline complex. Therefore, GCV and used excipients could be used for solid dosage formulations.