Simultaneous interaction, degradation, and kinetic study of sparfloxacin with H2 receptor antagonist.

Sparfloxacin is a quinolone carboxylic acid derivative that shows activity as an antimicrobial agent, against a wide range of Gram-negative and Gram-positive organisms. It is clinically useful for the treatment of urinary tract infections, respiratory tract infections and gynecological infections. In this study in vitro drug-drug interaction of sparfloxacin has been carried out with famotidine and ranitidine. For these studies a two-component spectrophotometric process has been developed for sparfloxacin assay in the presence of famotidine or ranitidine. The reproducibility of the method is within ±5%. The technique has been applied to the development of sparfloxacin in methanol. The interaction studies of sparfloxacin with ranitidine and famotidine were carried out in methanol and methanol: Water mixtures (30:70, v/v; 50:50, v/v) and the kinetics of sparfloxacin degradation were evaluated in the presence and absence of famotidine and ranitidine. The decrease in the rate of degradation of sparfloxacin in the presence of famotidine or ranitidine, compared to that of sparfloxacin alone, indicated the possibility of interaction between the sparfloxacin and famotidine or ranitidine. The Thin layer chromatography (TLC) of the degraded solution showed the presence of a degradation product of sparfloxacin. The studies show that complexation with famotidine or ranitidine may affect the bioavailability of sparfloxacin.

In Vitro Analysis of N-Nitrosodimethylamine (NDMA) Formation From Ranitidine Under Simulated Gastrointestinal Conditions.

Importance: A publication reported that N-nitrosodimethylamine (NDMA), a probable human carcinogen, was formed when ranitidine and nitrite were added to simulated gastric fluid. However, the nitrite concentrations used were greater than the range detected in acidic gastric fluid in prior clinical studies. Objective: To characterize NDMA formation following the addition of ranitidine to simulated gastric fluid using combinations of fluid volume, pH levels, and nitrite concentrations, including physiologic levels. Design, Setting, and Participants: One 150-mg ranitidine tablet was added to 50 or 250 mL of simulated gastric fluid with a range of nitrite concentrations from the upper range of physiologic (100 µmol/L) to higher concentrations (10 000 µmol/L) with a range of pH levels. NDMA amounts were assessed with a liquid chromatography-mass spectrometry method. Main Outcomes and Measures: NDMA detected in simulated gastric fluid 2 hours after adding ranitidine. Results: At a supraphysiologic nitrite concentration (ie, 10 000 µmol/L), the mean (SD) amount of NDMA detected in 50 mL simulated gastric fluid 2 hours after adding ranitidine increased from 222 (12) ng at pH 5 to 11 822 (434) ng at pH 1.2. Subsequent experiments with 50 mL of simulated gastric fluid at pH 1.2 with no added nitrite detected a mean (SD) of 22 (2) ng of NDMA, which is the background amount present in the ranitidine tablets. Similarly, at the upper range of physiologic nitrite (ie, 100 µmol/L) or at nitrite concentrations as much as 50-fold greater (1000 or 5000 µmol/L) only background mean (SD) amounts of NDMA were observed (21 [3] ng, 24 [2] ng, or 24 [3] ng, respectively). With 250 mL of simulated gastric fluid, no NDMA was detected at the upper physiologic range (100 µmol/L) or 10-fold physiologic (1000 µmol/L) nitrite concentrations, while NDMA was detected (mean [SD] level, 7353 [183] ng) at a 50-fold physiologic nitrite concentration (5000 µmol/L). Conclusions and Relevance: In this in vitro study of ranitidine tablets added to simulated gastric fluid with different nitrite concentrations, ranitidine conversion to NDMA was not detected until nitrite was 5000 µmol/L, which is 50-fold greater than the upper range of physiologic gastric nitrite concentrations at acidic pH. These findings suggest that ranitidine is not converted to NDMA in gastric fluid at physiologic conditions.

Development and validation of RP-HPLC method for simultaneous determination of cefpodoxime proxetil and H2 receptor antagonists in pharmaceutical dosage forms.

A new method on RP-HPLC is devised and validated, as per ICH guidelines, for the synchronous estimation of cefpodoxime proxetil and H2-receptor antagonits that are Cimetidine, Famotidine and Ranitidine. The method is simple, accurate, expeditious, reproducible, robust and precise. Chromatography was done on a C18 (250 x 4.6mm) column with methanol: water as mobile phae in the ratio of 70:30 (v/v), pumped at a flow rate of 1ml/min and pH was maintained using 85% ortho-phosphoric acid at 3. The λ max 240 nm was preferred for UV detection. A good linear relationship was attained, over the concentration ranges of 20-70 µg/ml and 5-30µg/ml, for cefpodoxime proxetil and H2 blockers respectively, with a correlation coefficient of R= 0.9987 to 0.9992. The method was validated and found precised (i.e. intra day and interday analysis) with RSD <2%. LOD and LOQ observations were under 0.4806 to 2.6069µg/ml which proved the method to be sensitive. The method provided satisfactory results of robustness and reproducibility, when validated and applied successfully for analysis of dosage forms.

Assessing the Detection Limit of a Minority Solid-State Form of a Pharmaceutical by 1H Double-Quantum Magic-Angle Spinning Nuclear Magnetic Resonance Spectroscopy.

The lower detection limit for 2 distinct crystalline phases by 1H magic-angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) is investigated for a minority amount of cimetidine (anhydrous polymorph A) in a physical mixture with the anhydrous HCl salt of cimetidine. Specifically, 2-dimensional 1H double-quantum (DQ) MAS NMR spectra of polymorph A and the anhydrous HCl salt constitute fingerprints for the presence of each of these solid forms. For solid-state NMR data recorded at a 1H Larmor frequency of 850 MHz and a MAS frequency of 30 kHz on ∼10 mg of sample, it is shown that, by following the pair of cross-peaks at a 1H DQ frequency of 7.4 + 11.6 = 19.0 ppm that are unique to polymorph A, the level of detection for polymorph A in a physical mixture with the anhydrous HCl salt is a concentration of 1% w/w.

Development of a Validated Comparative Stability-Indicating Assay Method for Some H2-Receptor Antagonists.

A comparative force degradation high performance thin layer chromatography (HPTLC) method was developed and validated for some H2-receptor antagonists. The studied H2-receptor antagonists were ranitidine (RAN), nizatidine (NIZ) and famotidine (FAM). The degradation behaviors of the studied H2-receptor antagonists were studied under different stress conditions (hydrolytic, thermal and oxidative) conditions as well as storage conditions according to International Conference on Harmonization (ICH) recommendations. A stability-indicating HPTLC method was optimized in order to separate the analyte from the degradation products formed under various stress conditions. Full separation of the drugs from their degradation products was successfully achieved on an HPTLC precoated silica gel plates. Densitometric measurements were carried out using a Camag TLC Scanner III in the absorbance mode at 320 nm for RAN and NIZ, and 280 nm for FAM. The limits of detection and limits of quantitation range were 5.47-9.37 and 16.30-31.26 ng/band, respectively, for all investigated drugs. The validation studies were performed according to ICH requirements. The developed method was simple, rapid and reliable hence it could be applied for routine quality control analysis of the investigated H2-receptor antagonists in dosage forms. The kinetic behavior, degradation rate constants and half-lives of the degradation of the investigated drugs were studied and compared at different stress conditions. The present study provides, for the first time, a new vision to compare the degradation kinetics of H2-receptor antagonists at the same degradation procedures.

Spectrofluorimetric analysis of famotidine in pharmaceutical preparations and biological fluids by derivatization with benzoin.

A sensitive and simple spectrofluorimetric method has been developed for the analysis of famotidine, from pharmaceutical preparations and biological fluids after derivatization with benzoin. The reaction was carried out in alkaline medium with measurement of fluorescence intensity at 446 nm with excitation wavelength at 286 nm. Linear calibration was obtained with 0.5-15 µg/ml with coefficient of determination (r(2)) 0.997. The factors affecting the fluorescence intensity were optimized. The pharmaceutical additives and amino acid did not interfere in the determination. The mean percentage recovery (n=4) calculated by standard addition from pharmaceutical preparation was 94.8-98.2% with relative standard deviation (RSD) 1.56-3.34% and recovery from deproteinized spiked serum and urine of healthy volunteers was 98.6-98.9% and 98.0-98.4% with RSD 0.34-0.84% and 0.29-0.87% respectively.

Extraction of ranitidine and nizatidine with using imidazolium ionic liquids prior spectrophotometric and chromatographic detection.

A new extraction medium was proposed for liquid-liquid extraction of the histamine H2 receptor antagonists ranitidine (RNT) and nizatidine (NZT). The ionic liquids with low vapor pressure and favorable solvating properties for a range of compounds such as 1-butyl-3-methylimidazolium hexafluorophosphate [C4mim][PF6] and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C4mim][Tf2N] were tested for isolation of analytes. The extraction parameters of RNT and NZT, namely, amount of ionic liquid, pH of sample solution, shaking and centrifugation time were optimized. The isolation processes were performed with 1 mL of the ionic liquids. The extracted samples (pH values near 4) were shaken at 1750 rpm. The influence of interfering substances on the efficiency of extraction process was also studied. Methods for the histamine H2 receptor antagonists (ranitidine and nizatidine) determination after their separation using imidazolium ionic liquids by high performance liquid chromatography (HPLC) combined with UV spectrophotometry were developed. The application of ionic liquids in extraction step allows for selective isolation of analytes from aqueous matrices and their preconcentration. The above methods were applied to the determination of RNT and NZT in environmental samples (river water and wastewater after treatment).

Determination of ranitidine, nizatidine, and cimetidine by a sensitive fluorescent probe.

A validated, simple, and sensitive fluorescence quenching method for the determination of ranitidine, nizatidine, and cimetidine in tablets and biological fluids is presented. This is the first single fluorescence method reported for the analysis of all three H(2) antagonists. The competitive reaction between the investigated drug and the palmatine probe for the occupancy of the cucurbit[7]uril (CB[7]) cavity was studied using spectrofluorometry. CB[7] was found to react with the probe to form a stable complex. The fluorescence intensity of the complex was also enhanced greatly. However, the addition of the drug dramatically quenched the fluorescence intensity of the complex. Accordingly, a new fluorescence quenching method for the determination of the studied drugs was established. The different experimental parameters affecting the fluorescence quenching intensity were studied carefully. At optimum reaction conditions, the rectilinear calibration graphs between the fluorescence quenching values (ΔF) and the medicament concentration were obtained in the concentration range of 0.04-1.9 µg mL(-1) for the investigated drugs. The limits of detection ranged from 0.013 to 0.030 µg mL(-1) at 495 nm using an excitation wavelength of 343 nm. The proposed method can be used for the determination of the three H(2) antagonists in raw materials, dosage forms and biological fluids.

Evaluation of non-aqueous capillary zone electrophoresis for the determination of histamine H2 receptor antagonists in pharmaceuticals.

A new non-aqueous capillary electrophoresis method is proposed for the separation and simultaneous determination of cimetidine, ranitidine, roxatidine, nizatidine and famotidine by using a 30-cm long × 75 µm i.d. fused silica capillary and UV detection at 214 nm. Using a temperature of 25°C, an applied voltage of 15 kV, and a background electrolyte consisting of methanol containing 10 mM ammonium acetate and 0.2% acetic acid allowed the analytes to be separated in less than 4 min. The limits of detection obtained ranged from 7 and 17 µg L(-1). The proposed method was successfully used to determine the analytes in pharmaceutical preparations and its results were checked against an HPLC method.

Development and validation of a RP-HPLC method for simultaneous estimation of naproxen and ranitidinehydrochloride.

A simple, specific and accurate reverse phase liquid chromatographic method has been developed for the simultaneous determination of naproxen and ranitidine HCl. Both the drugs are official with British Pharmacopoeia 2007, but do not involve simultaneous determination of naproxen and ranitidine HCl. The separation was carried out using 4.6 × 250 mm Symmetry Shield TM RP 18 with a particle diameter of 5 µm and mobile phase containing 0.1M orthophosphoric acid: methanol (35:65, pH 3.1) in isocratic mode. The flow rate was 1.00 ml/min and effluent was monitored at 240 nm. The retention times (average) of ranitidine HCl and naproxen were 2.36 min and 12.39 min, respectively. The linearity for naproxen and ranitidine HCl was in the range of 5-35 µg/ml and 1.5-12 µg/ml, respectively. The potencies of naproxen and ranitidine HCl were found 99.40 % and 99.48 %, respectively. The proposed method was validated and successfully applied to the estimation of naproxen and ranitidine HCl in newly formulated combined tablet and in plasma.

Colorimetric assay of cimetidine in the presence of its oxidative degradates.

Three simple, accurate, and sensitive colorimetric methods for the determination of cimetidine (Cim) in pure form, in dosage forms, and in the presence of its oxidative degradates were developed. These methods are indirect, involve the addition of excess oxidant [N-bromosuccinimide (NBS) for method A; cerric sulfate [Ce(SO4)2] for methods B and C] of known concentration in acid medium to Cim, and the determination of the unreacted oxidant by measurement of the decrease in absorbance of amaranth dye for method A, chromotrope 2R for method B, and rhodamine 6G, for method C at a suitable maximum wavelength, lambda max: 520, 528, and 525 nm, for the 3 methods, respectively. Regression analysis of the Beer plots showed good correlation in the concentration ranges of 0.2-4.4 microg/mL for method A, and 0.2-3.4 microg/mL for methods B and C. The apparent molar absorptivity, Sandell sensitivity, and detection and quantitation limits were evaluated. The stoichiometric ratio between the drug (Cim) and the oxidant (NBS or Ce4+) was estimated. The validity of the proposed methods was tested by analyzing pure and dosage forms containing Cim with relative standard deviation < or = 1.18. The proposed methods could successfully determine the studied drug with varying excess of its oxidative degradation products, with recovery between 99.2 and 101.8, 100.2 and 102.8, and 99.8 and 102.0% for methods A-C, respectively.

Prediction of the stability of polymeric matrix tablets containing famotidine from the positron annihilation lifetime distributions of their physical mixtures.

The aim of the present work was to elucidate the impact of the structural changes of polymeric excipients during the course of storage on the drug release stability of tablets containing different polymers. Matrix tablets were formulated with famotidine as a model drug, using polyvinylpyrrolidone and carbopol matrix. Dissolution tests were carried out before and after storing the tablets under stress conditions for different time intervals. Parameters characterizing the release kinetics of matrix tablets, just as difference and similarity factors, were calculated to compare the release profiles as a function of storage time. Positron annihilation lifetime measurements were carried out to track the structural changes of the physical mixtures containing polymers during the course of storage. The changes in the positron lifetime distribution curves of the famotidine-polymer mixtures were in good correlation with the significant changes of release parameters of tablets. Thus the method would be a valuable tool for the screening of possible destabilizing interactions in the preformulation phase.

Acid-suppressive medications and risk of bone loss and fracture in older adults.

Recent studies have suggested an increased fracture risk with acid-suppressive medication use. We studied two cohorts of men and women over age 65 who were enrolled in the Osteoporotic Fractures in Men Study (MrOS) and the Study of Osteoporotic Fractures (SOF), respectively. We used dual-energy X-ray absorptiometry and assessed baseline use of proton pump inhibitors (PPIs) and/or H2 receptor antagonists (H2RAs) in 5,755 men and 5,339 women. Medication use and bone mineral density (BMD) were assessed, and hip and other nonspine fractures were documented. On multivariate analysis, men using either PPIs or H2RAs had lower cross-sectional bone mass. No significant BMD differences were observed among women. However, there was an increased risk of nonspine fracture among women using PPIs (relative hazard [RH] = 1.34, 95% confidence interval [CI] 1.10-1.64). PPI use was also associated with an increased risk of nonspine fracture in men but only among those who were not taking calcium supplements (RH = 1.49, 95% CI 1.04-2.14). H2RA use was not associated with nonspine fractures, and neither H2RA use nor PPI use was associated with incident hip fractures in men or women. The use of PPIs in older women, and perhaps older men with low calcium intake, may be associated with a modestly increased risk of nonspine fracture.

Development and validation of a method for active drug identification and content determination of ranitidine in pharmaceutical products using near-infrared reflectance spectroscopy: a parametric release approach.

In this paper we describe the strategy used in the development and validation of a near-infrared diffuse reflectance spectroscopy method for identification and quantification of ranitidine in pharmaceutical products (granulates, cores and coated tablets) at-line, with a fiber optic probe. This method was developed in a pharmaceutical industry for routine application, to replace reference methods and was submitted and approved to the National Medicine Regulatory Agency (Infarmed). We consider that this is the first step of a broader parametric release approach to pharmaceutical products.

A sensitive spectrophotometric method for the determination of H2-receptor antagonists by means of N-bromosuccinimide and p-aminophenol.

A simple, accurate and sensitive spectrophotometric method for determination of H2-receptor antagonists: cimetidine (CIM), famotidine (FAM), nizatidine (NIZ), and ranitidine hydrochloride (RAN) has been fully developed and validated. The method was based on the reaction of these drugs with NBS and subsequent measurement of the excess N-bromosuccinimide by its reaction with p-aminophenol to give a violet colored product (lambda max at 552 nm). Decrease in the absorption intensity (Delta A) of the colored product, due to the presence of the drug, was correlated with its concentration in the sample solution. Different variables affecting the reaction were carefully studied and optimized. Under optimal conditions, linear relationships with good correlation coefficients (0.9988-0.9998) were found between Delta A values and the corresponding concentrations of the drugs in a concentration range of 8-30, 6-22, 6-25, and 4-20 microg mL(-1) for CIM, FAM, NIZ, and RAN, respectively. Limits of detection were 1.22, 1.01, 1.08, and 0.74 microg mL(-1) for CIM, FAM, NIZ, and RAN, respectively. The method was validated in terms of accuracy, precision, ruggedness, and robustness; the results were satisfactory. The proposed method was successfully applied to the analysis of the above mentioned drugs in bulk substance and in pharmaceutical dosage forms; percent recoveries ranged from 98.5 +/- 0.9 to 102.4 +/- 0.8% without interference from the common excipients. The results obtained by the proposed method were comparable with those obtained by the official methods.

Spectrophotometric determination of H(2)-receptor antagonists via their oxidation with cerium(IV).

A simple, accurate and sensitive spectrophotometric method has been developed and validated for determination of H(2)-receptor antagonists: cimetidine, famotidine, nizatidine and ranitidine hydrochloride. The method was based on the oxidation of these drugs with cerium(IV) in presence of perchloric acid and subsequent measurement of the excess Ce(IV) by its reaction with p-dimethylaminobenzaldehyde to give a red colored product (lambda(max) at 464nm). The decrease in the absorption intensity of the colored product (DeltaA), due to the presence of the drug was correlated with its concentration in the sample solution. Different variables affecting the reaction were carefully studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9990-0.9994) were found between DeltaA values and the concentrations of the drugs in a concentration range of 1-20microgml(-1). The assay limits of detection and quantitation were 0.18-0.60 and 0.54-1.53microgml(-1), respectively. The method was validated, in terms of accuracy, precision, ruggedness and robustness; the results were satisfactory. The proposed method was successfully applied to the determination of the investigated drugs in pure and pharmaceutical dosage forms (recovery was 98.3-102.6+/-0.57-1.90%) without interference from the common excipients. The results obtained by the proposed method were comparable with those obtained by the official methods.

A new sensitive flow-injection chemiluminescence method for the determination of H(2)-receptor antagonists.

Based on the chemiluminescence (CL) intensity generated from the potassium ferricyanide [K(3)Fe(CN)(6)]-rhodamine 6G system in sodium hydroxide (NaOH) medium, a new sensitive flow-injection chemiluminescence (FI-CL) method has been developed, validated and applied for the determination of three kinds of H(2)-receptor antagonists: cimetidine (CIMT), ranitidine (RANT) hydrochloride and famotidine (FAMT). Under the optimum conditions, the linear range for the determination was 1.0 x 10(-9)-7.0 x 10(-5) g/ml for CIMT, 1.0 x 10(-9)-5.0 x 10(-5) g/mL for RANT hydrochloride and 5.0 x 10(-9)-7.0 x 10(-5) g/mL for FAMT. During 11 repeated measurements of 1.0 x 10(-6) g/mL sample solutions, the relative standard deviations (RSDs) were all <5%. The detection limit was 8.56 x 10(-10) g/mL for CIMT, 8.69 x 10(-10) g/mL for RANT hydrochloride and 2.35 x 10(-9) g/mL for FAMT (S:N = 3). This method has been successfully implemented for the analysis of H(2)-receptor antagonists in pharmaceuticals.

The application of sub-2-microm particle liquid chromatography-operated high mobile linear velocities coupled to orthogonal accelerated time-of-flight mass spectrometry for the analysis of ranitidine and its impurities.

Impurity profiling of pharmaceutical drug substances or dosage formulations require methods involving high sensitivity and resolution from LC and MS alike as well as an acceptable analysis time. While throughput can be increased, it is usually at the expense of chromatographic resolution. The application of sub-2-microm stationary phases and high mobile linear velocities has been combined with orthogonal acceleration (oa)-TOF MS for the impurity structural characterization analysis of small-molecule pharmaceutics. A pharmaceutical drug substance was forcefully degraded and used to test the proof of concept of developing an impurity profile method by ultra performance liquid chromatography (UPLC). Optimum conditions were identified by use of method development simulation software as well as traditional approaches of method scouting with columns and a varied range of pH. Further analysis illustrated the effectiveness of applying oa-TOF MS techniques to assist in achieving exact mass coupled with MS/MS to define the structural characterization of the related substances relative to the pharmaceutical active ingredient and identification of any unknown impurity substances. The barriers with trade-offs between resolution and speed are overcome by the application of UPLC, whereas the increased sensitivity provides for superior exact mass oa-TOF MS.

Validation of a new high-performance liquid chromatography assay for nizatidine.

An expedient high-performance liquid chromatography (HPLC) assay for nizatidine measurement in human plasma was developed and validated. After deproteinization of 200 microL of plasma by filtration, nizatidine and 4-amino-antipyrine (internal standard) were separated (capacity ratio 3.0 and 6.63, respectively) on Nova-Pak C18 cartridge at room temperature (RT), and detected spectrophotometrically at 320 nm. The mobile phase, 0.02 mol/L disodium hydrogen phosphate, acetonitrile, methanol, and triethylamine (80:10:10:0.05 vol/vol), was delivered at 1.5 mL/min. Calibration curves were linear (r2 > or = 0.999) in the range 0.02 to 5 microg/mL, detection and quantification limits were 0.01 and 0.02 microg/mL, respectively, intra-run and inter-run coefficients of variation were < or = 3.5% and < or = 4.2%, respectively, and recovery was >90%. Nizatidine was stable for at least 4 hours at RT, 12 weeks at -20 degrees C, and 3 freeze-thaw cycles in plasma; 16 hours at RT and 48 hours at -20 degrees C in deproteinized plasma; and 6 hours at RT and 3 weeks at -20 degrees C in water.