Adapting therapy with repeated short-infusions to inter individual variability between patients

Survey: calculation of the characteristics of oral diffusion-controlled release dosage forms related to the drug

Oral dosage forms with controlled release exhibit various advantages over their immediate release counterparts, but they must be built adequately by dispersing the drug through the well-defined polymer matrix. This study is concerned with diffusion-controlled dosage forms to resolve the problems that appear: in vitro tests generally used for determining the kinetics of drug release do not take into account the nature of the drug. On the contrary, the plasma drug profiles obtained through in vivo tests strongly depend on the nature of the drug, through their typical pharmacokinetic parameters. Moreover, the effect of the stirring rate is difficult to evaluate. Following the demand from the FDA concerned with the in vitro/in vivo correlation, a numerical model was built so as to evaluate the plasma drug profile obtained with any drug delivered from a diffusion-controlled release dosage form. The results are expressed by connecting the half-life times of the drugs obtained either with bolus injection or with the dosage forms, for various values of the parameters of interest: the diffusivity of the matrix polymer and the size of the dosage form. Thus, these diagrams make it possible to promptly determine the characteristics of the dosage forms able to give the desired plasma drug profile for any drug. Of course, for each drug being defined by its pharmacokinetic parameters, the polymer matrix should be selected as a function of its diffusivity. Finally, the evaluation of the plasma drug profile is of effective help to determine quantitatively the effect of the intervariability of the patients as well as the effect of the patient's noncompliance.

Evaluation of the characteristics of oral dosage forms with release controlled by erosion

This paper is concerned with oral dosage forms with controlled release based on the erosion of the polymer matrix. A numerical model taking all the facts into account, i.e., the kinetics of release and pharmacokinetic parameters of the drug, makes it possible to calculate the plasma drug level. Diagrams are built which connect the half life times obtained either through i.v. or with these dosage forms as a function of the full time of erosion of the polymer. Thus, it is possible to determine the right dosage form matrix associated with the desired therapy. Their interest stands for possible bioadhesion extending the gastrointestinal tract time.