ABSTRACT
Design of an extended-release dosage form can be based on empirical data or on theoretical considerations supplemented by calculations according to the applied model. Absorption cannot proceed faster than the rate at which the drug dissolves. In this situation, the absorption process is dissolution-rate-limited and on this principle, extended-dosage forms can be designed. In the two-compartment model, the drug distribution balance between a central compartment and a deep compartment should be considered. Theoretical considerations and mathematical calculations can be verified only by in vivo testing of the drug level fluctuation in the blood over time or the amount of drug and/or metabolite in the urine. To obtain a satisfactory flat blood level curve using a first-order release pattern, the proper selection of dose fraction in the form of initial and maintenance dose and release constant of maintenance dose is necessary. For such a selection, a computer search of various combinations of initial and maintenance doses can be very helpful.
