Measurement of ornidazole by high-performance liquid chromatography

Simultaneous determination of ornidazole and its main metabolites in human plasma by LC–MS/MS: application to a pharmacokinetic study

Background: Ornidazole is a 5-nitroimidazole antimicrobial agent used for almost 40 years. A novel LC–MS/MS assay was developed and validated for the simultaneous determination of ornidazole and its main metabolites (M3, M6, M16–1, and M16–2) in human plasma. Results: After extraction from 100 μl of plasma by protein precipitation with acetonitrile, all the analytes were separated on a Capcell PAK MG C18 column (100 × 4.6 mm, 5 μm) within 5.0 min and detected by ESI-MS/MS in the positive mode. The validation results met the acceptance criteria as per the US FDA and EMA guidelines. Conclusion: The validated method was successfully applied to a pharmacokinetic study after oral administration of 1000 mg ornidazole to six healthy Chinese volunteers.

Simultaneous Determination of Ofloxacin and Ornidazole in Solid Dosage Form by RP-HPLC and HPTLC Techniques

The objective of this work was to develop and validate simple, rapid and accurate chromatographic methods for simultaneous determination of ofloxacin and ornidazole in solid dosage form. The first method was based on reversed phase high performance liquid chromatography, on Intersil C₁₈ column (250 mm, 4.6 i.d.), using acetonitrile:methanol: 0.025M phosphate buffer, pH 3.0 (30:10:60 % v/v/v) as the mobile phase, at a flow rate of 1 ml/min at ambient temperature. Quantification was achieved with UV detection at 318 nm over a concentration range of 2-40 µg/ml for ofloxacin and 5-100 µg/ml for ornidazole. The mean retention time of ofloxacin and ornidazole was found to be 4.04 min and 5.83 min, 6.77 min (isomers), respectively. The amount of ofloxacin and ornidazole estimated as percentage of label claimed was found to be 100.23 and 99.61%, with mean percent recoveries 100.20 and 100.93%, respectively. The second method was based on TLC separation of these drugs using silica gel 60F₂₅₄ aluminium sheets and dichloromethane:methanol:25% ammonia solution (9.5:1:3 drops v/v) as mobile phase. Detection was carried out at 318 nm over the concentration range of 20-100 ng/spot for ofloxacin and 50-250 ng/spot for ornidazole. The mean R_f value of ofloxacin and ornidazole was found to be 0.16 and 0.56, 0.78 (isomers), respectively. The amount of ofloxacin and ornidazole estimated as percentage of label claimed was found to be 100.23 and 99.61% with mean percent recoveries 100.47 and 99.32%, respectively. Both these methods were found to be simple, precise, accurate, selective and rapid and could be successfully applied for the determination of pure laboratory prepared mixtures and tablets.

The ICH guidance in practice: stress degradation studies on ornidazole and development of a validated stability-indicating assay

The present study describes degradation of ornidazole under different ICH prescribed stress conditions (hydrolysis, oxidation and photolysis), and establishment of a stability-indicating reversed-phase HPLC assay. Degradation was found to occur in alkaline medium, under high acidic conditions, under oxidative stress, and also in the presence of light in acid conditions. Previously the drug is only known to decompose under alkaline conditions. Separation of drug and the degradation products under various conditions was successfully achieved on a C-18 column utilising water-acetonitrile in the ratio of 86:14. The detection wavelength was 310 nm. The method was validated with respect to linearity, precision, accuracy, selectivity, specificity and ruggedness. The response was linear in the drug concentration range of 5-500 microg ml(-1). The mean values (+/-RSD) of slope, intercept and correlation coefficient were 45251 (+/-1.59), 104418 (+/-2.49) and 0.9996 (+/-0.03), respectively. The RSD values for intra- and inter-day precision studies were <1 and <2.6%, respectively. The recovery of the drug ranged between 100-103% from a mixture of degradation products. The method was specific to drug and also selective to degradation products.

Quantitative assay of metronidazole by capillary zone electrophoresis with amperometric detection at a gold microelectrode

Capillary zone electrophoresis was employed for the determination of metronidazole using end-column amperometric detection with a gold microelectrode at a constant potential of -0.52V vs. saturated calomel electrode. To overcome interference of oxygen in the solution, a deaeration injector and a deaeration protector at the detection cell were used. The optimum conditions of separation and detection are 1.0 x 10(-3) mol/L potassium dihydrogen citrate (KH2C6H5O7) for the buffer solution, 20 kV for the separation voltage, and 5 kV and 10 S for injection voltage and injection time, respectively. The limit of detection is 6.0 x 10(7) mol/L or 0.78 fmole (S/N = 3). The relative standard deviation is 3.9% for the electrophoretic peak current. The method was applied to the determination of metronidazole in human urine.

Determination of metronidazole in vaginal tissue by high-performance liquid chromatography using solid-phase extraction

A sensitive high-performance liquid chromatographic (HPLC) method for the determination of metronidazole in vaginal tissue is reported. The method uses a Zorbax SB phenyl column with a 0.01 M aqueous monobasic potassium phosphate buffer (pH 4.0)-absolute methanol (85:15, v/v) as mobile phase at a flow-rate of 1.0 ml/min and detection at 313 nm. Tinidazole was used as the internal standard. The method employed homogenization of tissue followed by solid-phase extraction. The quantitation was achieved within 30 min with sensitivity in the ng/g range. Metronidazole was linear in the 100-2000 ng/g range. The accuracy and precision were in the 1-4% range for the drug and the limit of detection was approximately 100 ng/g based on a signal-to-noise ratio of 3 and a 1009-microliters injection.

Pharmacokinetics and tissue penetration of a single dose of ornidazole (1,000 milligrams intravenously) for antibiotic prophylaxis in colorectal surgery

Levels in serum and tissue penetration of ornidazole were studied after a single intravenous injection of 1,000 mg given to 14 patients for prophylaxis of surgical infection. They were scheduled for elective colorectal surgery. Adequate levels in blood (greater than or equal to MIC for 90% of Bacteroides fragilis strains tested) were found in all patients throughout the procedure and up to hour 24. Mean-maximal (15 min) and last-determined (24 h) ornidazole levels in serum were 24 +/- 5.2 and 6.3 +/- 1.4 mg/liter, respectively. beta-Phase elimination half-life was 14.1 +/- 2.7 h, and clearance and apparent volume of distribution were 47 +/- 12 ml/min and 0.9 +/- 0.13 liters/kg, respectively. In all patient, adequate levels in tissue were found in the abdominal wall and the epiploic fat at time of incision and in the colonic wall at time of anastomosis. At time of closure, all but one patient had adequate levels in tissue in the abdominal wall and the epiploic fat. No anaerobic nor aerobic infection occurred in the study patients.

Pharmacokinetics of ornidazole in neonates and infants after a single intravenous infusion

The single dose pharmacokinetics of ornidazole has been evaluated in 12 neonates or infants (aged 1 to 42 weeks) after the infusion of 20 mg/kg over 20 min. Plasma disposition was described by a two-compartment open model. The distribution phase was short (T1/2 (1) = 0.31 h) and was followed by an elimination phase (t1/2 (2) = 14.67 h). The mean apparent volume of distribution was 0.961/kg-1. These results did not differ from data previous by reported in adults. Total plasma clearance was between 0.4 and 1.4 ml X min-1 X kg-1. The plasma concentration 24 h after the infusion was 7.32 mg X l-1, which was above the minimum inhibitory concentration for clinically significant anaerobic bacteria. Based on the pharmacokinetic results and residual concentrations at 24 h, a single daily infusion of ornidazole 20 mg X kg-1 appears adequate for therapy in neonates and infants.

Drug level monitoring: chromatography of some minor groups of drugs

Some important facts about the chromatographic separation of a number of selected categories of drugs are summarized. The data refer to the chromatographic method of choice, stationary phase, mobile phase (carrier gas), detection procedure and (where available) method sensitivity. Also, fundamental instrumental parameters, namely injector, column and detector temperature, carrier gas and mobile phase flow-rate and gradient set-up are reported here. In all cases also the source material used for analysis is specified. The data are presented in table form, each table dealing with a particular category of drugs. The following categories of drugs are being dealt with: anthelmintics, antiarteriosclerotics, antibacterials, anticholinergics and cholinergics, anticoagulants, antidiabetics, antiemetics, antimycotics, antihistamines, antimalarials, antiparasitics, antiparkinsonics, antitussives, antiulcer drugs, antiviral compounds, appetite depressants and immunosuppressives.

Pharmacokinetics of ornidazole in patients with renal insufficiency; influence of haemodialysis and peritoneal dialysis

The pharmacokinetics of ornidazole (Tiberal) was studied after intravenous administration of a single 500 mg dose in eight patients with advanced chronic renal failure (ACRF) (creatinine clearance 2-16 ml/min), in seven patients treated by haemodialysis (residual renal creatinine clearance 0-5 ml/min) and in five patients treated by continuous ambulatory peritoneal dialysis (CAPD) (residual renal creatinine clearance 0-6 ml/min). In ACRF patients, the half-life of ornidazole was 10.8 +/- 1.4 h, the total plasma clearance 46.3 +/- 2.3 ml/min and the volume of distribution 0.73 +/- 0.06 l/kg. During haemodialysis, ornidazole was partly removed: the dialyser extraction ratio was 42 +/- 5% and the dialysis clearance 64 +/- 7 ml/min. During CAPD, peritoneal excretion was low: the dialysis clearance was 3.0 +/- 0.4 ml/min and in 48 h 6.0 +/- 1.1% of the administered dose was found in the peritoneal fluids. In these patients, the half-life of ornidazole was 11.8 +/- 0.8 h and total plasma clearance was 48.3 +/- 5.5 ml/min, values which were close to those determined in non dialysed patients. In patients with end-stage renal disease, the half-life of ornidazole is comparable to that of subjects with normal renal function. This is due to the predominantly extra-renal elimination of the drug. Therefore, there is no need to modify the usual dosage of ornidazole for these patients. Because of the large elimination of the drug during haemodialysis it is necessary to administer the drug after the dialysis session.