| Infective endophthalmitis is a potentially blinding condition and remains a serious postoperative complication of such frequently performed eye surgeries as cataract or ocular trauma . Vancomycin , an antibiotic effective against all Gram-postive bacteria that interferes with cell-wall synthesis, has been increasingly recommended for the disease of Staphylococcus epiderimidis and S. aureus. endophthalmitis.In order to be able to treat this condition, optimally, detailed knowledge of the pharmacokinetics of relevant antibiotics is needed. Different methods have been used to study the pharmacokinetics of drugs in the vitreous , but they all have drawbacks.Microdialysis has gained wide recognition as standard sampling technique in the field of neurochemistry, as well as in sampling other tissues and fluid. This technique has also been employed successfully for sampling the vitreous and anterior chamber.To determine the pharmacokinetics governing the distribution and elimination of intravitreously injected vancomycin . We establish a conscious rabbit model for ocular harmacokinetic studies, the method of microdialysis was used for collecting series of samples from the rabbit vitreous, and delineate the ocular pharmacokinetic of vancomycin. In addition , the study was to compare the method with traditional pharmacokinetic sampling.Materials1. Animals New Zealand albino rabbits of other sex 36.2. Reagents Vancomycin hydrochoride ws supplied by Bli Lilly company.Acetonitrile was chromatographic grade. Monobasic K phosphate and all other chemicals used were analytical grade.Methods1. Experimental group( microdialysis group)(1). Animal Model: A 0.1ml solution containing approxinmately 2000cfu/ ml of suspension of S. aueus was injected slowly into the mid vitreous cavity of the right eye,72hours after inmoculation ,the endophthalimitis models were succeeded.(2). Microdialysis Probe: The microdialysis probe contains a membrance of regenerated celluose, the inlet and outlet , stiff plastic for collecting sample, and microdialysis syringe pump.(3 ). Surgical Procedure; Under general anesthetied, the conjuntion opened at the limbus to approximately 1/2 the circumference, the probe was inserted carefully into right eye approximately 2-3 mm below the sclera-limbus junction through the pars plana into the mid vitreous.(4) . Recovery of microdialysis probe: The ratio between the concentration of vancomycin in the outflow solution and the concentration in the viteous outside the probe is defined as recovery, and each experiment was preceded by perfu-sion of the implanted probe with a buffer containing a known amount of vancomycin (20ug/ml) at a constant flow rate of 2ul/min ,and samples were collected every 20min, then calculate the recovery .(5). Microdialysis Procedure: After probe implantation , the animals were allowed to stabilize for 24 hour prior to the initiation of any study. After intravit-real injection of vancomycin with a dose of 1mg/0.1ml, Ringers solution was used to perfuse the microdialysis probe with a flow rate of 2ul/min using micro-injection pump. The dialysate was collcted every 20min over a period of 6hours and assayed by HPLC-UV. Then 40ul sample was collected at 12. 24.48. 72and 84hour,and detected by HPLC-UV.2. Control Group: A vancomycin solution containing 1mg/0.1ml vancomycin was injected into mid vitreous cavity,four animals were killed atlh. 12h.24h. 48h. 72hand 84h hours post-injection , vitreous sample were obtained from the removed eyes and detected by HPLC.3. HPLC Analysis: The sample were analysis using an HPLC-UV system e-quipped with UV-visible detection, a reversed phase C18 column. The mobile phase of monobasicK phosphate 0. 05mol,ph =4. 0,containing 10% acetonitrile at a flow rate of 2ul/min, UV-detection was carried out at 210nm. The average quantitation limit obtained was 0.05ug/ml.Standard solutions were prepared from the stock solutions at a concentration of 200ug/ml by sequential dilution with water. The spike of the seque... |
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