keywords: Amoxicillin, diabetes, high performance liquid chromatography, metformin, metronidazole
Infection is common in diabetes and in the course of treatment metronidazole and amoxicillin may be co-administered with metformin. The study was designed to evaluate the effects of co-administration of metronidazole tablet and amoxicillin capsule on the pharmacokinetics of metformin in type II diabetic patients. Twelve patients with age ranging from 35 – 55 years, weight 50 – 70 kg and height 1.5 – 1.75 m participated in the study. The study was divided into two phases with a washout period of seven days between the phases. In phase one, metformin alone was administered to all the subjects with 150 ml of water after an overnight fasting. In phase two, the subjects were divided into two groups, with six subjects in each group. The first group received a single dose of metformin with metronidazole, while the second group received metformin co-administered with Amoxicillin. Blood samples were collected at 0, 0.5, 1.5, 3.0, 4.0, 6.0 and 8.0 h post drug administration and stored at – 40C before analysis. Plasma was obtained from the blood and the drug was extracted from the plasma using three times its volume of acetonitrile. The samples were analyzed for metformin using a reversed phase. High performance liquid chromatography (HPLC) method on a C–8column (4.6 x 150 nm), mobile phase acetonitrile/potassium dihydrogen orthophosphate (21:79) and a ultra violet (UV) detector at 236 nm. When metformin was co-administered with metronidazole, Ka increased to 0.59 ± 0.04 h-1, Cmax to 1.38 ± 0.35 µg/ml; while AUC and t1/2β increased to 536.71 ± 0.02 µgh/ml and 6.2 ± 0.02 h, respectively. These increments were found to be significant (p < 0.05). On the other hand, when metformin was co-administered with amoxicillin most of the changes were not significant (p > 0.05).
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