A bio-analytically validated HPLC-UV method for simultaneous determination of doripenem and ertapenem in pharmaceutical dosage forms and human plasma: a dual carbapenem regimen for treatment of drug-resistant strain of Klebsiella pneumoniae.

The emergence of strains resistant to certain antibiotics is turning into an important issue worldwide that threatens global health with the increasing incidence of carbapenemase-producing Klebsiella pneumoniae (KPC). Thus, successful doripenem-ertapenem (DOR-ERTA) combination is highly recommended in treatment of bacteremic ventilator-associated pneumonia due to Klebsiella pneumoniae. Hence, a fast and highly-sensitive HPLC-UV method was developed for the estimation of the cited drugs simultaneously in their pure form, pharmaceutical dosage forms and in simulated synthetic mixtures. The DOR-ERTA mixture was successfully separated within 6 min on a reversed-phase ODS column using an isocratic elution; a mobile phase mixture consists of 0.05 M phosphate buffer (pH 3.0 adjusted by 85% ortho-phosphoric acid) : acetonitrile : methanol (86 : 12 : 2; % v/v/v). The proposed method was optimized and validated according to ICH guidelines, where the calibration graph was constructed from 0.04 to 50 µg mL-1 and from 0.05 to 50 µg mL-1 with low detection limits reached 1.7 and 1.4 ng mL-1 for DOR and ERTA respectively. The proposed method showed higher sensitivity than several previous methods, which allowed an effective estimation of the DOR and ERTA in human plasma after a simple extraction method with high recovery results ranged from 96.30% ± 1.55 to 97.90% ± 1.45 and without any interference from plasma components.

Applicability of ninhydrin as a fluorescent reagent for estimation of teicoplanin in human plasma using salting-out assisted liquid-liquid extraction technique.

The applicability of ninhydrin, a widely used derivatizing reagent, for determination of teicoplanin (TEIC) in its pure form, pharmaceutical vials, and in human plasma was investigated. The presented spectrofluorimetric method was based on a condensation reaction between ninhydrin and the primary amine group existing in TEIC (in the presence of phenylacetaldehyde) to produce a highly fluorescent product detected at 460 nm (λex ,390 nm). Calibration plots were constructed in the concentration range 60-600 ng mL-1 with a good correlation coefficient of 0.9998 and a low detection limit of 10.84 ng mL-1 . The method was subjected to a bioanalytical validation study according to US-FDA recommendations. The proposed method was applied for analysis of TEIC in commercial vials with high recovery result 101.88 ± 1.11%. In addition, the method was utilized efficiently for detection of TEIC in human plasma using salting-out assisted liquid-liquid extraction technique (SALLE) with a recovery range from 96.71 ± 1.08% to 97.71 ± 0.86%. SALLE is an effective approach used for extraction of TEIC from human plasma without interferences using ammonium sulphate. The proposed method is highly recommended to monitor TEIC in clinical laboratory samples and therapeutic drug monitoring systems.

Highly sensitive cadmium sulphide quantum dots as a fluorescent probe for estimation of doripenem in real human plasma: application to pharmacokinetic study.

Thioglycolic acid-capped cadmium sulphide quantum dots (TGA-CdS QDs) have been synthesized and utilized as a fluorescent probe for the estimation of doripenem (DOR). Monitoring of DOR in different biological fluids is required to estimate the efficient dose to avoid bacterial infections and resistance. The investigated method is based on the measurement of fluorescence quenching of TGA-CdS QDs after the addition of DOR. The synthesized TGA-CdS QDs were characterized using transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD) and ZETA sizer. The TGA-CdS QDs showed unique photophysical properties with high quantum yield (0.32) using a comparison method with rhodamine B. Different experimental parameters affecting the synthesis process of the TGA-CdS QDs and their behavior with the studied drug DOR were examined and optimized. The values of the fluorescence quenching were linearly correlated to DOR concentration over the range of 10-500 ng mL-1 with a good correlation coefficient of 0.9991. The proposed method showed higher sensitivity over several reported methods, with LOD reaching 2.0 ng mL-1. The method was effectively applied for the estimation of DOR in human plasma and urine with good recovery results ranged from 95.16% to 99.51%. Furthermore, the stability of DOR in the human plasma was studied and a pharmacokinetic study of DOR in real human plasma was conducted.

Development of sensitive benzofurazan-based spectrometric methods for analysis of spectinomycin in vials and human biological samples.

Spectinomycin hydrochloride (SPEC) is an aminoglycoside antibiotic that has a broad spectrum against several bacterial strains of humans and veterinary infections. However, SPEC lacks a fluorophore or chromophore and this lack makes its analysis a challenge. Our study provides a simple, sensitive and low-cost spectrofluorimetric/spectrophotometric method based on the reaction between secondary amine groups and a benzofurazan reagent using borate buffer (pH 9.2). The yielding compound was measured fluorimetrically at 530 nm (excitation at 460 nm) with colorimetry at 410 nm. The calibration curves ranged from 30 to 400 ng ml-1 and from 0.2 to 6 µg ml-1 for spectrofluorimetric and spectrophotometric analyses, respectively. The limits of detection were calculated to be 4.15 ng ml-1 and 0.05 µg ml-1 for spectrofluorimetric and spectrophotometric processes, respectively. The ultra-affectability and high selectivity of the proposed method permitted analysis of SPEC in the dosage form and in human plasma samples, with good recoveries of about 101.19 and 97.11%, respectively, without any matrix interference. The proposed strategy was validated using International Conference on Harmonization standards and validated bioanalytically using USFDA recommendations.

Utility of the fluorogenic characters of benzofurazan for analysis of tigecycline using spectrometric technique; application to pharmacokinetic study, urine and pharmaceutical formulations.

Tigecycline (TIGE) is the newest tetracycline derivative antibiotic with low toxicity, it is used for management of infectious diseases caused by Gram-positive and Gram-negative bacteria. Hence, an efficient, selective and sensitive method was developed for analysis of TIGE in commercial formulations, human plasma and urine. The spectrofluorimetric technique based on the reaction of secondary amine moiety in TIGE with 4-chloro-7-nitrobenzofurazan (NBD-Cl) in slightly alkaline medium producing a highly fluorescent product measured at 540 nm (λex at 470 nm) after heating for 15 min at 75°C. The proposed strategy was upgraded and approved by ICH rules and bio-analytical validated using US-FDA recommendations. A linear relationship between fluorescence intensity and TIGE concentration was observed over the concentration range 40-500 ng mL-1 with limit of quantification (LOQ) 21.09 ng mL-1 and limit of detection (LOD) 6.96 ng mL-1 .The ultra-affectability and high selectivity of the proposed strategy permits analysis of TIGE in dosage form, human plasma and urine samples with good recovery ranged from 97.23% to 98.72% and from 99.36% to 99.80% respectively, without any interfering from matrix components. Also, the developed strategy was used to examine the stability of TIGE in human plasma and applied for pharmacokinetic investigation of TIGE.

Spectrofluorimetric method for determination of some angiotensin II receptor antagonists.

A simple, rapid, accurate and highly sensitive spectrofluorimetric method has been developed for determination of some angiotensin II receptor antagonists (AIIRA's), namely Losartan potassium (Los-K), Irbesartan (Irb), Valsartan (Val) and Candesartan cilexetil (Cand) in pure forms as well as in their pharmaceutical dosage forms. All the variables affecting the relative fluorescence intensity (RFI) were studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9982-0.9991) were obtained over the concentration range from 0.006 µg/mL to 1.7 µg/mL. Good accuracy and precision were successfully obtained for the analysis of tablets containing each drug alone or combined with hydrochlorothiazide (HCTZ) without interferences from the co-formulated HCTZ or the additives commonly present in tablets.

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.

Sensitive indirect spectrophotometric method for determination of h2-receptor antagonists in pharmaceutical formulations.

A simple, accurate and sensitive spectrophotometric method has been developed and validated for determination of H2-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-dimethylaminocinnamaldehyde to give a red colored product (λmax at 464 nm). The decrease in the absorption intensity (ΔA) 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 the optimum conditions, linear relationships with good correlation coefficients (0.9985-0.9994) were found between ΔA values and the concentrations of the drugs in a concentration range of 1-16 µg ml(-1). The assay limits of detection and quantitation were 0.12-0.44 and 0.37-1.33 µg ml(-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 analysis of the investigated drugs in their pure and pharmaceutical dosage forms (recovery was 98.8-102.5 ± 0.79-1.72%) without interference from the common excipients. The results obtained by the proposed method were comparable with those obtained by the official methods.

A validated spectrofluorimetric method for determination of some psychoactive drugs.

Five psychoactive drugs namely, chlorpromazine HCl, thioridazine HCl, clomipramine HCl, imipramine HCl and desipramine HCl were analyzed by a simple spectrofluorimetric method. The method is based on oxidation of the studied drugs using cerium(IV) in presence of sulphuric acid and monitoring the fluorescence of the formed cerium(III) at lambda(ex.) = 254 nm and lambda(em.) = 355 nm. All variables affecting the reaction conditions such as; cerium(IV) concentration, sulphuric acid concentration, heating time, temperature and dilution solvents were carefully studied. The effect of potential interference due to common ingredients as glucose, sucrose, lactose, citric acid and propylene glycol were investigated. A validation study of the proposed method was carried out according to USP 2002. Beer's law was obeyed for all the studied drugs in the concentration range of 0.05-1.3 microg/ml. Limits of detection range was 0.035-0.038 microg/ml and limits of quantitation of 0.116-0.125 microg/ml were obtained. The method was successfully applied for the assay of the studied drugs in pure form and in pharmaceutical dosage forms. Results were compared with official methods. The t- and F-values were calculated and compared with the theoretical values, which indicate high accuracy and good precision of the proposed method.