Determination of Stability and Degradation Rate for Combination Containing Amoxicillin and Dicloxacillin in Capsule Dosage Form

A study was carried out using Reverse Phase High Performance Liquid Chromatography to determine the stability of four different brands of formulation (capsules) containing Amoxicillin and Dicloxacillin. Five batches of four different brands expiring in consecutive months (7^th, 8^th, 9^th, 10^th and 12^th month of 2010) were obtained and studied. During 5 months study, all the five batches were stored at room temperature (NMT 25°C). The 5 batches were assayed periodically at one month interval by Reverse Phase High Performance Liquid Chromatography method. The Dicloxacillin content in all the 5 batches steadily decreased over the months indicating that formulations of Amoxicillin and Dicloxacillin, which are available in the market are generally unstable. The Dicloxacillin content also reached 0% in some of these batches.