Beeswax-Lecithin SLMs of Erythromycin Ethyl Succinate for Treatment of Acute Bacteremia in Infected Mice

The aim of this work was to increase the efficacy of erythromycin ethyl succinate by encapsulation in beeswax lipid matrix using Myrj 52 as emulsifier. Different batches of SLM’s (solid-lipid microparticles) were formulated and stable ones were selected. The encapsulation efficiency and loading capacities were calculated. The batch with the highest loading capacity was used for further assays. The particle size was determined by light microscopy. The sensitivity of different clinical bacterial isolates to erythromycin was tested using in vitro cultures and E. coli was selected for efficacy tests. The activity of the formulated drug was tested in the in vitro culture and compared to that of the unformulated drug. White albino mice were infected with E. coli and left for one day to develop significant bacteremia. They were then divided into 4 groups (n = 4) and treated with the formulation and unformulated drug at a dose of 7.14 mg/kg 8 hourly for 56 hours. A third group was given SLM’s that do not contain drug, while another group was left untreated. The selected batch has an encapsulation efficiency of 94.83% with a loading capacity of 3.88%. The particle size was 17 ± 4 μm. At the end of the three day period of treatment, the group treated with unformulated erythromycin had much stooling and weakness in the mice, and some deaths were recorded, while that treated with the formulation had 33.8% bacteremia and the clinical signs had largely subsided. The other two groups recorded deaths the following day after bacteremia induction. The results show marked improvement in efficacy of erythromycin ethyl succinate by formulation in SLMs with beeswax and lecithin as lipid matrix.