Pharmacokinetic Evaluation of Ketorolac Tromethamine Sustained-Release Pellets after Oral Administration in Rabbits

To develop a sustained-release preparation containing ketorolac tromethamine, two sustained-release pellet formulations were evaluated with a pharmacokinetic study as compared with a conventional commercial tablets (10 mg , Roche Korea Ltd.). Two sustained-release formulations were as follows; formulation A was composed of an inner layer containing 75% of drug coated with RS 100 membrane and an outer layer containing 25% of drug mixed with NE30D, and formulation B was composed of only an inner layer containing 100% of drug coated with RS 100 membrane. The dissolution test was performed for two formulations. In case of conventional tablets, 2.5 mg of drug per a dose was administered orally into male Albino rabbit (2.0-2.3 kg of body weight) 3 times at intervals of 4 hours. In case of two sustained formulations, 7.5 mg of drug was administered once orally. Blood samples were withdrawn periodically after the administration, and the blood concentration was determined by HPLC. The conventional tablets showed very high peak-trough fluctuation between administered doses, but two sustained formulations showed less fluctuation. Formulation A with the loading dose showed the time to reach minimum effective concentration (MEC) i.e. the onset time was less than 20 min, while Formulation B had more than 1 hr of the onset time. Formulation A had the more constant plasma level than formulation B. However, formulation B had a time lag, so the plasma level was less than MEC for an initial period of 1 hr. In formulation A, the plasma level was maintained within the therapeutic window for a long period. Formulation A was thought to be an ideal sustained-release formulation for ketorolac tromethamine oral delivery system.