Determination of ciprofloxacin concentrations in human serum and urine by HPLC with ultraviolet and fluorescence detection

Latanoprost Quantification in Ocular Implants and Tissues: HPLC-Fluorescence vs HPLC-UV

Anti-glaucoma latanoprost-loaded ocular implants provide prolonged delivery and enhanced bioavailability relative to the conventional eye drops. This study aims at the development and validation of a reversed-phase high-performance liquid chromatography method for quantitative analysis of nanogram levels of latanoprost in the eye, and for the first time, compares the use of fluorescence vs ultraviolet (UV) detectors in latanoprost quantification. The mobile phase was composed of acetonitrile:0.1% v/v formic acid (60:40, v/v) with a flow rate of 1 mL/min and separation was done using a C18 column at temperature 40°C. The fluorescence excitation and emission wavelengths were set at 265 and 285 nm, respectively, while the UV absorption was measured at 200 nm. The latanoprost concentration-peak area relationship maintained its linearity (R2 = 0.9999) over concentration ranges of 0.063-10 μg/mL and 0.212-10 μg/mL for the fluorescence and UV detectors, respectively. The UV detector showed better precision, while the fluorescence detector exhibited higher robustness and greater sensitivity, with a detection limit of 0.021 μg/mL. The fluorescence detector was selected for quantification of latanoprost released from ocular implants in vitro and in porcine ocular tissues. The developed method is a robust, rapid and cost-effective alternative to liquid chromatography-mass spectrometry for routine analysis of latanoprost released from ocular implants.

A simple and sensitive high-performance liquid chromatography method for determination of ciprofloxacin in bioavailability studies of conventional and gastroretentive prolonged-release formulations

Background:

A very simple, sensitive, and accurate high-performance liquid chromatography (HPLC) method with ultraviolet detector was developed and applied to determine ciprofloxacin in human plasma following administration of a gastroretentive formulation developed in our laboratory.

Materials and Methods:

HPLC analysis was performed on a C₁₈ μ-Bondapack column (250 mm × 3.9 mm) using acetonitrile: potassium dihydrogen phosphate solution 0.1 M (20:80, v/v, pH 3) at a flow rate of 1.5 ml/min and eluate was monitored at 276 nm. After addition of phenacetin as internal standard, plasma samples were treated with 0.1 M phosphate buffer (pH: 7) and followed by extraction with dichloromethane. The method was validated for linearity, precision, accuracy, limit of quantitation (LOQ), robustness, stability, and applied in bioavailability studies of our developed gastroretentive formulation in healthy volunteers.

Results:

The calibration curves were linear over the concentration range 0.025–4 μg/ml with the detection limit of 15 ng/ml. Accuracy % were within 93–115 and the coefficient of variance % ranged from 0.20 to 12.8. The very low LOQ (25 ng/ml) allowed avoiding fluorometric detection which is more expensive and is not available in all laboratories. Ciprofloxacin was stable in samples with no evidence of degradation during 3 freeze-thaw cycles and 3 months storage at –70°C.

Conclusion:

This validated HPLC method was successfully used for the determination of ciprofloxacin in human plasma following oral administration of controlled release formulation, conventional immediate-release tablets and when administered concomitantly with divalent and trivalent cations such as aluminum-, magnesium-, or calcium-containing products under which the bioavailability of ciprofloxacin is significantly reduced.

Bioanalysis of antitubercular drugs using liquid chromatography

Tuberculosis is a life threatening disease and second to HIV in terms of deaths due to infectious diseases. Drug resistance development of the first-line drugs is a major concern in the treatment of this disease. There is no comprehensive and critical review in the literature of the bioanalytical methods for the determination of anti-tubercular agents from last two decades. This work offers a detailed account on the liquid chromatographic methods reported in the literature for the estimation of various anti-tubercular drugs. Major emphasis is given to sample preparation process, sensitivity of method, chromatographic separation conditions and detection systems used in their bioanalysis.

Fabrication of a highly sensitive and selective electrochemical sensor based on chitosan-coated Fe3O4 magnetic nanoparticle for determination of antibiotic ciprofloxacin and its application in biological samples

A simple and sensitive sensor has been developed for the electrochemical determination of ciprofloxacin (CF). The proposed sensor was designed by chitosan-coated Fe3O4 magnetic nanoparticle incorporated in the carbon paste electrode (CPE), which provides remarkably improved sensitivity for the electrochemical determination of CF. The proposed sensor was characterized with scanning electron microscopy and electrochemical impedance spectroscopy. Under optimum conditions, the sensor provides two linear differential pulse voltammetry responses in the range of 0.05–6 μmol/L and 6–75 μmol/L for CF with a detection limit of 0.01 μmol/L. The proposed sensor exhibited high sensitivity and good selectivity and was successfully applied for CF determination in serum and urine samples.

A Bioadhesive Nanoparticle-Hydrogel Hybrid System for Localized Antimicrobial Drug Delivery

Effective antibacterial treatment at the infection site associated with high shear forces remains challenging, owing largely to the lack of durably adhesive and safe delivery platforms that can enable localized antibiotic accumulation against bacterial colonization. Inspired by delivery systems mimicking marine mussels for adhesion, herein, we developed a bioadhesive nanoparticle-hydrogel hybrid (NP-gel) to enhance localized antimicrobial drug delivery. Antibiotics were loaded into polymeric nanoparticles and then embedded into a 3D hydrogel network that confers adhesion to biological surfaces. The combination of two distinct delivery platforms, namely, nanoparticles and hydrogel, allows the hydrogel network properties to be independently tailored for adhesion while maintaining controlled and prolonged antibiotic release profile from the nanoparticles. The bioadhesive NP-gel developed here showed superior adhesion and antibiotic retention under high shear stress on a bacterial film, a mammalian cell monolayer, and mouse skin tissue. Under a flow environment, the NP-gel inhibited the formation of an Escherichia coli bacterial film. When applied on mouse skin tissue for 7 consecutive days, the NP-gel did not generate any observable skin reaction or toxicity, implying its potential as a safe and effective local delivery platform against microbial infections.

Determination of ciprofloxacin in human plasma using high-performance liquid chromatography coupled with fluorescence detection: application to a population pharmacokinetics study in children with severe malnutrition

Clinical pharmacokinetic studies of ciprofloxacin require accurate and precise measurement of plasma drug concentrations. We describe a rapid, selective and sensitive HPLC method coupled with fluorescence detection for determination of ciprofloxacin in human plasma. Internal standard (IS; sarafloxacin) was added to plasma aliquots (200 μL) prior to protein precipitation with acetonitrile. Ciprofloxacin and IS were eluted on a Synergi Max-RP analytical column (150 mm×4.6 mm i.d., 5 μm particle size) maintained at 40°C. The mobile phase comprised a mixture of aqueous orthophosphoric acid (0.025 M)/methanol/acetonitrile (75/13/12%, v/v/v); the pH was adjusted to 3.0 with triethylamine. A fluorescence detector (excitation/emission wavelength of 278/450 nm) was used. Retention times for ciprofloxacin and IS were approximately 3.6 and 7.0 min, respectively. Calibration curves of ciprofloxacin were linear over the concentration range of 0.02-4 μg/mL, with correlation coefficients (r(2))≥0.998. Intra- and inter-assay relative standard deviations (SD) were <8.0% and accuracy values ranged from 93% to 105% for quality control samples (0.2, 1.8 and 3.6 μg/mL). The mean (SD) extraction recoveries for ciprofloxacin from spiked plasma at 0.08, 1.8 and 3.6 μg/mL were 72.8±12.5% (n=5), 83.5±5.2% and 77.7±2.0%, respectively (n=8 in both cases). The recovery for IS was 94.5±7.9% (n=15). The limits of detection and quantification were 10 ng/mL and 20 ng/mL, respectively. Ciprofloxacin was stable in plasma for at least one month when stored at -15°C to -25°C and -70°C to -90°C. This method was successfully applied to measure plasma ciprofloxacin concentrations in a population pharmacokinetics study of ciprofloxacin in malnourished children.

Methods for the analysis of fluoroquinolones in biological fluids

Methods for the analysis of ten selected fluoroquinolone antibiotics in biological fluids are reviewed. Approaches for sample preparation, detection methods, limits of detection and quantitation, and recovery information are provided for both single analyte and multi-analyte fluoroquinolone methods.

Pharmacokinetics of fluoroquinolones in critical care patients: A bio-analytical HPLC method for the simultaneous quantification of ofloxacin, ciprofloxacin and moxifloxacin in human plasma

A high-performance liquid chromatographic (HPLC) method with fluorescence detection was developed and validated for the simultaneous quantification of ofloxacin, ciprofloxacin and moxifloxacin in human plasma. Sarafloxacin was used as internal standard. Chromatography was carried out using a Waters XBridge C(18) HPLC column and a gradient mobile phase consisting of CH(3)CN/MeOH/0.025M TBA.Cl/TFA (eluent A at 75/25/899/1 (v/v); eluent B at 150/50/799/1 (v/v); both at pH 3.5). Excitation/emission wavelengths were 279/442nm for ciprofloxacin and 290/500nm for ofloxacin, moxifloxacin and internal standard. Prior to chromatography, plasma samples were treated with acetonitrile for protein precipitation, followed by evaporation of the liquid layer and reconstitution in eluent A. The method was validated for the three fluoroquinolones over the clinically relevant concentration range from 0.02 to 7.50mug/ml. The method showed acceptable linearity with correlation coefficients, r(2)>0.995, as well as high precision (RSD% <7% in each case), accuracy (90.4-105.4%) and selectivity. The limit of quantification for the three fluoroquinolones was established at 0.02mug/ml. Ofloxacin, ciprofloxacin and moxifloxacin were extracted from plasma with a mean recovery of 95%, 86.4% and 94.2%, respectively. During validation, the concentration of the three fluoroquinolones was found to be stable after 3 freeze-thaw cycles and for at least 15h after extraction. This bio-analytical method was finally applied to the analysis of samples which have been obtained from patients, participating in a pharmacokinetic study on moxifloxacin.

An indirect atomic absorption spectrometric determination of ciprofloxacin, amoxycillin and diclofenac sodium in pharmaceutical formulations

A highly sensitive indirect atomic absorption spectrophotometric (AAS) method has been developed for the determination of very low concentrations of ciprofloxacin, amoxycillin and diclofenac sodium. The method is based on the oxidation of these drugs with iron(III). The excess of iron(III) was extracted into diethyl ether and then the iron(II) in the aqueous layer was aspirated into an air-acetylene flame and determined by AAS. The linear concentration ranges were 25-400, 50-500 and 60-600 ng ml-1 for ciprofloxacin, amoxycillin and diclofenac sodium, respectively. The results were statistically compared with the official method using t- and f-test at p < 0.05. There were insignificant interferences from most of the excipients present. The intra- and inter-day assay coefficients of variation were less than 6.1 % and the recoveries ranged from 95 to 103 %. The method was applied for the analysis of these drug substances in their commercial pharmaceutical formulations.

Sex-related differences in the pharmacokinetics of oral ciprofloxacin

The oral pharmacokinetics of ciprofloxacin were studied in healthy volunteers to assess the influence of sex on its disposition. Subjects (8 males, 7 females) received a single oral dose of ciprofloxacin 750 mg, blood and urine samples were collected, and ciprofloxacin concentrations were determined. A two-compartment open-model with two or three absorption phases, each one having a fitted independent lag time, best fit the data using a weighted least squares estimator. Univariate and multivariate regression analyses were performed to determine the influence of renal function, weight, and subject sex on the oral clearance (CL(S)/F) and apparent steady-state volume of distribution (V(ss)/F) of ciprofloxacin. Females had a median C(max) of ciprofloxacin that was 30% greater than males and a significantly smaller median (range) V(ss)/F: 81.1 (44.8-111.6) versus 170.9 (140.9-213.4), respectively (p < 0.01). In addition, females had increased exposure to ciprofloxacin, with a slower median (range) CL(S)/F of 28.3 L/h (24.5-33.4) compared to 44.4 L/h (41.4-53.7) for males (p < 0.01). Regression analyses revealed that subject sex was the only significant predictor of CL(S)/F (p < 0.001), but both body weight (p = 0.04) and subject sex (p < 0.005) were significant predictors of V(ss)/F. Fixed oral doses of ciprofloxacin will lead to higher maximum concentration and total drug exposure in females compared to males and do not appear to be solely related to weight-based differences.