Modelling the Double Peak Phenomenon in Pharmacokinetics

Two approaches to describing the Double Peak Phenomenon in pharmacokinetics are compared. Both are based on compartmental modelling. The first assumes variability of absorption of the drug from the gut to the systemic plasma, with negligible absorption through the jejunum. This has the advantage of clear physiological interpretation, but the model has a comparatively large number of parameters to be estimated. The second approach assumes simultaneous input via two parallel pathways. This has considerably fewer parameters to be estimated, but it lacks the direct relationship to physiology. Almost equally good fits have been obtained from the two approaches when fitting to two data sets provided by AstraZeneca and to a data set from the literature.