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T. Das, B. Raju, T. Bali, G. Thiagarajan, V. Rao, S. Sharma; Physicochemical Properties and Antibacterial Activity of the Precipitate of Vancomycin and Ceftazidime: Implications in the Management of Endophthalmitis. Invest. Ophthalmol. Vis. Sci. 2007;48(13):676.
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To study the physicochemical properties, bioavailability and microbicidal activity of vancomycin and ceftazidime in the precipitate formed by the two antibiotics in mixture.
The precipitation of the antibiotics prepared in buffers in the pH range 5.8 - 8.9, in normal saline (NS), in balanced salt solution (BSS) and in Ringer Lactate (RL) was studied by light scatter analysis. Bioavailability and antibacterial activity of the precipitate and the supernatant were estimated using high-performance liquid chromatography (HPLC) and microbiologic assay respectively.
The scatter analysis showed precipitation of vancomycin alone at pH 7.5 and in BSS. The antibiotics mixture precipitated within the pH range 6.8 - 8.0 and in all solutions. HPLC of both supernatant and precipitate demonstrated presence of antibiotic and the microbiologic assay confirmed its inhibitory activity against bacteria. The precipitate had greater activity against gram-positive bacteria and the supernatant had greater activity against gram-negative bacteria.
This study shows that vancomycin’s pH dependent precipitation occurs regardless of presence of ceftazidime. The precipitate as well as the supernatant retains significant antibacterial activity thus confirming the efficacy of the combination therapy of vancomycin and ceftazidime in management of bacterial endophthalmitis.
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