Metronidazole concentration in the bloodstream following its topical application, at different concentration levels, on experimental skin wounds during healing by secondary intention

Abstract Purpose: To characterize qualitatively and quantitatively the absorption of metronidazole solution, in greater concentrations and for longer periods, when applied topically to an experimental open skin wound model. Methods: An open skin wound, 2 cm in diameter and total skin thickness was prepared, under anesthetic, in the dorsal region of 108 Wistar rats weighing between 300 and 350 grams. The animals were allocated to groups of 18 animals in accordance with the concentration of metronidazole in the solution to be applied daily to the wound. In the control group (CG), 0.9% sodium chloride solution was used for application, and in the experimental groups (GI, GII, GIII, GIV and GV) metronidazole solution at 4%, 6%, 8%, 10% and 12%, respectively, was applied. After 3, 7 and 14 days of treatment. Blood samples collected through cardiac puncture were examined for the existence or non-existence of metronidazole, using high performance liquid chromatography (HPLC). Detected metronidazole values were compared statistically within each group (temporal analysis 3 days X 7 days X 14 days) and between the groups that used topical metronidazole (4% X 6% X 8% X 10% and 12%) using the Kruskal-Wallis test, considering a statistical significance of 95% (p<0.05). Results: Metronidazole was detected in all the samples at all times in all the groups in which topical metronidazole was applied to the wounds. Characteristically, there was no significant difference between the doses obtained within each group over time (3 days X 7 days X 14 days) GI=0.461; GII=0.154; GIII=0.888; GIV= 0.264 and GV=0.152. In the evaluation between groups, a similar degree of absorption was found after 3 days (p=0.829) and 14 days (p=0.751). Conclusion: The serum concentration of metronidazole that was achieved was not influenced by the concentration of the solution applied to the skin wound, with similar extend, or by the duration of the application.

rapid and sensitive HPLC method for the analysis of metronidazole in human plasma: application to single dose pharmacokinetic and bioequivalence studies

A sensitive, accurate and rapid reverse phase HPLC method was developed to quantitate plasma levels of metronidazole in order to conduct a comparative bioavailabllity studies. The drug and internal standard were added to plasma samples, vortexed and then zinc sulfate solution was added in order to precipitate the plasma proteins. Samples were centrifuged at 3000 rpm for 10 min. The supernatant layer was separated and analyzed on a phenyl [300 X 4.6mm] column, with 5% acetonitrile in 0.1 M KH [2] PO[4] buffer [pH = 4.5] at 324 nm. The standard curve covering 0.15-30 micro g/ml concentration range, was linear [r [2] = 0.9999], relative errors were within 2.48 to 9.15% and the CV% ranged from 2.999 to 10.796. The method is suitable for bioavailability, pharmacokinetic, and bioequivalent studies in human. The in-vivo study was carried out in 12 healthy volunteers according to a single dose, two-sequence, cross over randomized design. The bioavailabllity was compared using the total area under the plasma level versus time curve [AUC [0-48], AUC [0-infinity], peak plasma concentration [C[max]] and time to [C[max] [T[max]]. No statistically significant difference was found between the AUC [0-infinity], C[max] and T[max] values of the test and reference, Flagyl [R] [p > 0.05]. The 90% CI for the ratio of the AUC [0-infinity], [0.94-1.07] and C[max] [0.88-1.03] and the logarithmically transformed AUC[0-infinity] [0.99-1.01] and C[max] [0.94-1.01] values of the generic product over those of Flagyl [R] was calculated to be within the acceptable limit of 0.80-1.20 and 0.80-1.25, respectively. It was, therefore, concluded that the generic metronidazole was bioequivalent with the innovator formulation

Plasma hydroxy-metronidazole/ metronidazole ratio in hepatitis C virus-induced liver disease

It has been suggested that the measurement of metronidazole clearance is a sensitive method for evaluating liver function. The aim of this study was to evaluate the usefulness of plasma hydroxy-metronidazole/metronidazole ratios as indicators of dynamic liver function to detect changes resulting from the various forms of chronic hepatitis C virus (HCV) infection. A total of 139 individuals were studied: 14 healthy volunteers, 22 healthy, asymptomatic, consecutive anti-HCV-positive HCV-RNA negative subjects, 81 patients with chronic hepatitis C (49 with moderate/severe chronic hepatitis and 34 with mild hepatitis), and 20 patients with cirrhosis of the liver. HCV status was determined by the polymerase chain reaction. Plasma concentrations of metronidazole and its hydroxy-metabolite were measured by reverse-phase high-performance liquid chromatography with ultraviolet detection in a blood sample collected 10 min after the end of a metronidazole infusion. Anti-HCV-positive HCV-RNA-negative individuals demonstrated a significantly reduced capacity to metabolize intravenously infused metronidazole compared to healthy individuals (0.0478 ± 0.0044 vs 0.0742 ± 0.0232). Liver cirrhosis patients also had a reduced plasma hydroxy-metronidazole/metronidazole ratio when compared to the other groups of anti-HCV-positive individuals (0.0300 ± 0.0032 vs 0.0438 ± 0.0027 (moderate/severe chronic hepatitis) vs 0.0455 ± 0.0026 (mild chronic hepatitis) and vs 0.0478 ± 0.0044 (anti-HCV-positive, HCV-RNA-negative individuals)). These results suggest an impairment of the metronidazole metabolizing system induced by HCV infection that lasts after viral clearance. In those patients with chronic hepatitis C, this impairment is paralleled by progression of the disease to liver cirrhosis.

Plasma concentrations of oral metronidazole in the early post-laparotomy periods

The bioavailability of metronidazole after oral ingestion, in ordinary conditions, is quite similar to intravenous administration of the drug. However, the degree of its absorption is not known in the early periods after laparotomy. To determine plasma levels of metronidazole in pediatric patients following elective abdominal surgery. The study group was comprised of 25 pediatric patients with mean age of 8.25 years. They took 10 mg/kg metronidazole [ingested or taken via nasogastric tube] a few hours after operation, followed by every eight hours for a total of three successive doses. We obtained blood samples 1-2 hours after each drug intake. The mean +/- SD of plasma drug concentrations after the first, second and third doses were 1.43 +/- 0.81, 6.26 +/- 3.86 and 10.21 +/- 4.28 micro g/ml, respectively, showing a significant rise after each dose [p<0.001]. The majority of patients [84%] obtained a level equal to, or above the minimal bactericidal concentration [MBC] after the third dose. Ninety-two and 96% of patients achieved the plasma minimal inhibitory concentration or higher following the second and third doses, respectively, as compared to 4% after the first dose [p<0.00001]. Absorption of oral metronidazole after elective laparotomy is disturbed only temporarily, as in the majority of patients the drug attains an acceptable level before the second post-operative day. Therefore, parenteral metronidazole therapy, if necessary, is recommended only during the first 24 hours, and it may be replaced by oral preparation afterward