Molecular interactions in pharmaceutical preformulation and supramolecular complexes. Structural properties governing drug-plasma protein binding and investigation of amino acids co-crystals

Abstract

The study of pharmaceutical preformulation includes the evaluation of pharmacokinetic, pharmacodynamic and physicochemical properties of the drug molecules that aid the formulation. However, it has a limited role in determining drug dosage optimisation in the formulation. The study of drug-Plasma Protein Binding (PPB), and the lipophilicity, solubility, and ionic behaviours of the desired drug molecules addresses the gap and enhances our undertraining related to the behaviour of the drug molecules in the body. The High-Performance Liquid Chromatography (HPLC) technique was used in the current study to assess drug-PPB interaction. Using Michael Abraham’s ‘Linear Free Energy Relationship’ (LFER) method, two major plasma proteins namely, Human Serum Albumin as HSA and α-1-Acid Glycoprotein as AGP, were used and the structural properties governing drug-plasma protein binding was determined. This is the first time that the effect of ionised species on PPB has been quantitatively evaluated. In addition, the molecular interactions also play a key role in the supramolecular complexes of co-crystals. The project also evaluated the co-crystallisation process and its effect on physicochemical properties of the drug. In the current study, amino acids (AAs) have been observed to be a prominent source of coformers. The AAs showed co-crystals formation with carboxylic acids, nonsteroidal anti-inflammatory drug (NSAID) and citric acid which overcome the hygroscopicity problems and improved the physical stability issues during storage. This study has also identified a new formulation which is helpful for improvement in the stability of effervescent tablets at various relative humidity (RH) conditions which will reduce the manufacturing cost associated with the production of effervescent tablets.