Investigation of drug partition kinetics to fat in simulated fed state gastric conditions based on drug properties

The presence of fat in the gastric environment can affect the pharmacokinetic behaviour of drugs with mechanisms which have not been yet fully understood. The objective of the current study was to assess the drug partition to the lipid part of the fed gastric content under different emulsification conditions, using in vitro discriminating setups. The model drugs used in the study were selected on the basis of different physicochemical properties (lipophilicity, ionization, molecular weight and aqueous solubility) and different food effect observed in in vivo human studies. Fed State Simulated Gastric Fluid prepared with skimmed milk (FeSSGF _sk) and anhydrous milk fat were used as surrogates for the aqueous and fat portions of the fed gastric environment respectively. An optimized biphasic model was developed so as to predict the differences in partition rate constants to fat, for model drugs of a wide range of the properties mentioned above. The experimental data and the use of statistical analysis revealed that molecular weight, molecular weight and log D _{pH 5} interaction and negative food effect act as negative factors to the rate constants of fat partition, while absence of food effect and logD _{pH 5} interaction with aqueous solubility affect the rate constants of partition to fat favourably.