Percutaneous absorption: multidose pharmacokinetics

A linear pharmacokinetic model has been derived previously to analyze percutaneous absorption data. The model, which contains four first-order rate constants, has been extended to assess the effects of repeated topical dosing. It has been shown in previously published data that the amount of hydrocortisone excreted is dependent on the dosage regimen adopted. The model successfully describes the excretion pattern of hydrocortisone over a two-week period in which the drug was applied daily. Good correlation has also been established for the percutaneous penetration of malathion following repeated dosing. The patterns of the excretion profile for these two substances are different due to the difference in their physicochemical properties. These properties are reflected in the four first-order rate constants in the pharmacokinetic model.