Evaluation of the releasing pharmacokinetics of depot preparations of Leuprolide

DIDIER, C.; OGGERO EBERHARDT, M.; KRATJE, R. B.; ETCHEVERRIGARAY, M.

Santa Fe. Pcia. Santa Fe. Argentina

Congreso; 3rd Mercosur Congress on Process Systems Engineering – 1st Mercosur Congress on Chemical Engineering (ENPROMER 2001); 2001

Facultad de Ingeniería Química (UNL); CERIDE (CONICET); INTEC (UNL-CONICET); INGAR (CONICET)

Leuprolide is a synthetic nonapeptide analogue of the naturally occuring Luteinizing Hormone Releasing Hormone (LH RH) that exert high gonadothropin releasing and ovulation inducing activities. The continuous administration of therapeutic doses of Leuprolide inhibits the growth of certain hormone dependent prostatic and mammary tumors. The aim of this work was to investigate the pharmacokinectics of Leuprolide after subcutaneous administration of different depot preparations of the analogue. Two immunochemical assays to quantify Leuprolide were developed: a competitive ELISA and a liquid phase RIA. Both methods were carried out using a polyclonal antiserum obtained in our lab in rabbits immunized with peptide-protein conjugates. The ELISA had a linear range between 20 ng/ml and 10 µg/ml with a detection limit of 2 ng. The RIA was linear in the range between 1 ng/ml and 62.5 ng/ml with a detection limit of 100 pg. Taking into account these results, we selected the RIA as a sensitive and reliable technique to evaluate the releasing kinetic of different depot preparations. Three samples were tested: a commercial preparation (considered as a reference) and two samples. Wistar rats were innoculated subcutaneously (1.25 mg/rat) and bled by vein puncture at different times: 1 hour, 4 hours, 12 hours and 1, 3, 7, 14, 21, 28, 35, 44 and 51 days post-injection. Statistical treatment consisted of the analysis of variance (ANOVA) in one way for the case of subsampling and non-orthogonal comparissons between the reference and the samples. The releasing kinetic of the drug was established and the releasing peak at 1 hour post-injection was also detected. No significative differences between the commercial reference and the samples were observed.