Pharmacokinetic and pharmacodynamic studies following percutaneous absorption of erythropoietin micropiles to rats.

To ascertain the pharmacological activity of erythropoietin (EPO) administered by self-dissolving micropiles (SDMP), four kinds of EPO SDMPs were prepared and were administered to rats in 4 consecutive days at 200, 500, 1000 and 2300 IU/kg. After the start of the experiment, blood samples were obtained once a day for 10 days and percent circulating reticulocytes were counted using Miller technique. At the lower doses, 200 and 500 IU/kg, pharmacological activity of EPO was not obtained. By increasing EPO dose to 1000 IU/kg, circulating reticulocytes significantly increased at days 4, 5, 6 and 7 after the start of the experiment and the average value for the change in reticulocyte levels during day 1 and day 5 was 170.9%. With the highest dose, 2300 IU/kg, higher circulating reticulocytes levels started to increase at the 4th day after the start of the experiment and maintained from day 5 to day 10. The average of the changes in reticulocyte from day 5 to day 10 was 251%. Dose-dependent circulating reticulocytes increase was observed at the higher dose range, 1000 and 2300 IU/kg. To study the linearity on the serum EPO level vs. time curves, pharmacokinetic experiment was performed with rats. After the administration of EPO SDMPs to rats, 200, 500, 1000 and 2300 IU/kg, serum EPO levels gradually increased and reached to the maximum level, C(max), at 18 h after administration. The C(max)s were 100.4+/-11.7 mIU/ml (200 IU/kg), 346.6+/-11.8 mIU/ml (500 IU/kg), 391.6+/-17.6 mIU/ml (1000 IU/kg), and 1094.9+/-114.8 mIU/ml (2300 IU/kg), respectively. AUCs were 1407+/-231, 3843+/-402, 5363+/-482 and 15,566+/-1894 mIU h/ml. Linear relation was obtained between serum EPO level and EPO dose administered as SDMP. With histological study, any adverse effect was not found out on the skin where SDMPs were administered for consecutive 4 days. These results suggest the usefulness of SDMP as a new percutaneous delivery system of EPO.

Pharmacokinetic and pharmacodynamic studies following oral administration of erythropoietin mucoadhesive tablets to beagle dogs.

Oral administration of mucoadhesive tablets containing erythropoietin (EPO) and an absorption enhancer Labrasol was studied in rats and dogs. Mucoadhesive tablets were prepared using Sylysia 550 holding the absorption enhancer and Carbopol 974P as a mucoadhesive agent. Mucoadhesive tablets were covered with a water-insoluble backing layer made of cellulose acetate and a pH-sensitive covering layer made of Eudragit L/Eudragit S. Tablet was administered into the rat jejunum at EPO dose of 100 IU/kg and serum samples were collected for 6h. Serum EPO level was analysed with a standard ELISA procedure. After administration, rats showed a maximum serum EPO level of C(max) 70.6 +/- 8.9 mIU/ml. Oral administration of a single tablet containing 100 IU/kg EPO to beagle dogs showed a C(max) of 24.6 +/- 4.1. When EPO dose was increased to 500 IU/kg and the number of tablets was also increased to 5, the C(max) was 54.8 +/- 9.0 mIU/ml. However, when EPO, 100 IU/kg dose was divided into five tablets, the C(max) was 15.5 +/- 1.8 mIU/ml. In the absence of absorption enhancer, the C(max) was 35.8 +/- 3.8 with 500 IU/kg dose distributed among five tablets. Pharmacodynamic studies were carried out following oral administration of mucoadhesive tablets for 6 consecutive days at an EPO dose of 500 IU/kg. Whole blood samples were collected and percent circulating reticulocytes were counted using Miller technique. The increase in percent circulating reticulocytes was found to be 1.7% on day 8 following oral administration. As a control study, EPO was administered by i.v. route at a dose of 300 IU/kg for 3 consecutive days and the percent circulating reticulocytes were counted. Mucoadhesive tablets showed promising results as an oral drug delivery system for protein therapeutics.