Prediction of the residue levels of drugs in eggs, using physicochemical properties and their influence on passive diffusion processes

Based on a physiologically based pharmacokinetic model, describing the relationship between the plasma concentration of a drug and its deposition into eggs, general transport constants into yolk and albumen were derived, for a number of compounds, using experimental data from literature. Using only generally accepted concepts in passive diffusion theory, these transport constants were used to derive and calibrate general equations, describing the transport into yolk and albumen, in terms of the physicochemical properties of a drug. It is shown that, in theory, it is possible to calculate/predict the transport constants, using the physicochemical parameters: pK a and plasma protein binding. For a number of sulfonamides, the model was used to predict their distribution between egg yolk and albumen; the outcome was compared to data found in literature. Within this dataset, the lipophilic nature of a drug does not seem to play a major role in explaining the distribution ratio of a drug between albumen and yolk.