Aim To establish the pharmacokinetic principles of the zero-order release and the first-order release of mono-compartment drugs administered by non-parenteral route based on the release kinetics of the dosage forms and the intrinsic pharmacokinetic parameters of the active drug, such as the rate constants of the absorption and elimination, and the distribution volume of the drug. Methods By the Laplace transform and the compartmental analysis method, the pharmacokinetic behaviors of the zero-order release and the first-order release of mono-compartment drugs administered by non-parenteral routes were deduced with divisions of the dose being absorbed during the release phase and after the release has terminated. Results The pharmacokinetics of the non-parenteral administration of the zero-order release and the first-order release of mono-compartment drugs were established. Conclusion The pharmacokinetic theories of the zero-order release and the first-order release of mono-compartment drugs administered by non-parenteral route have been established. Since the zero-order release and the first-order release are the primary release patterns, the theory should be a key to explore the pharmacokinetics of the controlled/sustained release dosage forms.

Objective:To research the rule of melatonin nasal absorption.Methods: The stability of melatonin in rat nasal wash was studied, after that the in situ rat nasal recirculation methods were used as experimental animal model to study the rule of melatonin nasal absorption.Results:Melatonin was stable in rat nasal wash, its absorption in nasal cavity accorded with first order kinetic equation. The absorption rate constants did not vary with melatonin concentrations.Conclusion:The mechanism of melatonin nasal absorption is passive diffusion, the average absorption rate constant is 1.054?10 -2 min -1 .