RP-HPLC-DAD Method Development and Validation for Simultaneous Determination of Lansoprazole, Tinidazole, Amoxicillin, and Naproxen in Their Raw Materials and Combined Dosage Form: DOE Approach for Optimization of the Proposed Method.

BACKGROUND: Helicobacter pylori infection is a common cause of peptic ulcer disease and dyspepsia. In addition, it may result in gastric cancer and gastric mucosa associated lymphoid tissue lymphoma. First-line therapy usually consists of triple therapy containing clarithromycin or amoxicillin, one of the proton pump inhibitors, and metronidazole or tinidazole. In addition to the triple therapy, an analgesic is required to relieve pain such as naproxen. OBJECTIVE: A sensitive and selective method needs to be developed and validated for simultaneous determination of four drugs (amoxacillin, tinidazole, naproxen and lansoprazole), used for treating Helicobacter pylori infection, in their combined dosage forms. METHODS: With the aid of experimental design, the cited drugs were separated and quantified. HPLC with a diode array detector was used and metronidazole, one of the drugs also used for treatment, was the internal standard (IS). A Thermo Scientific BDS Hypersil C18 column (5 µm, 250 mm x 4.6 mm) with mobile phase composed of acetonitrile-water (40 + 60, by volume), pH 5 adjusted with phosphoric acid, at 30°C was used for the separation of the cited drugs. RESULTS: The method was linear over the concentration ranges 10-500 µg/mL for amoxacillin, 10-350 µg/mL for tinidazole, 10-250 µg/mL for naproxen, and 2-20 µg/mL for lansoprazole. The proposed method was fully validated according to International Conference of Harmonization (ICH) guidelines. Statistical analysis revealed no significant difference between the results obtained and the four reference methods for the investigated drugs. CONCLUSION: The method can be easily implemented in QC studies of the cited drugs in their dosage forms. HIGHLIGHTS: Experimental design was applied using Plackett-Burman design for preliminary screening of factors followed by Box-Behnken design for chromatographic method optimization.

Development and Bio-Analytical Validation of Chromatographic Determination Method of Rufinamide in Presence of its Metabolite in Human Plasma.

Rufinamide (RF), antiepileptic drug, is biotransformed to inactive metabolite. Frequent plasma monitoring is required for dose adjustment. This work is concerned with the development and validation of a sensitive and selective RP-HPLC method for the quantitative determination of RF in spiked human plasma in the presence of its main metabolite. Lacosamide was selected as internal standard. Preparation of plasma samples involved precipitation of plasma proteins using methanol. Isocratic elution mode was applied and the chromatographic separation was performed on Prontosil CN column (5 µm, 250 × 4.6 mm). Good resolution was achieved using acetonitrile: water (10:90, v/v, adjusted with 0.01 N aqueous solution of o-phosphoric acid to pH = 3) as a mobile phase at a flow rate of 1 mL/min, and UV detection was carried out at 210 nm. Linearity was observed over the concentration range of 0.5-50 µg/mL of RF in plasma. Bio-analytical validation of the developed method was carried out in accordance to the European Medicines Agency guidelines. The accuracy ranged from 95.97 to 114.13%, and the coefficient of variation of the assay intra-day and inter-day precision did not exceed 10%. The samples were stable under the employed experimental conditions. In conclusion, the findings of the present study revealed its usefulness for therapeutic drug monitoring, assessment of drug pharmacokinetics and application for bioequivalence study.

Determination of Rufinamide in the Presence of 1-[(2,6-Difluorophenyl)Methyl]-1H-1,2,3-Triazole-4 Carboxylic Acid Using RP-HPLC and Derivative Ratio Methods as Stability Indicating Assays to Be Applied on Dosage Form.

BACKGROUND: Rufinamide is a triazole derivative that is structurally dissimilar to other marketed antiepileptic drugs, has been assumed a marketing authorization, by the European Union and FDA, for use as a complementary therapy for seizures associated with Lennox-Gastaut syndrome. OBJECTIVE: This work is concerned with development of two methods for determination of rufinamide (RUF) in presence of 1-[(2,6-difluorophenyl)methyl]-1H-1,2,3-triazole-4 carboxylic acid as its alkaline degradation product in dosage form. METHODS: The first method was capable of determing RUF in the presence of its alkaline degradation product and in dosage form. Kromasil C8 column and mobile phase consisting of acetonitrile-water (50:50, v/v) were used and UV detection at 210 nm. In the second method, first derivative ratio spectrophotometry, RUF was determined by measuring peak amplitude at 269.5 nm over 5-30 µg/mL. RESULTS: The linearity range of RUF was 10-90 µg/mL for HPLC method covering its therapeutic range with r2 = 0.9999. Forced degradation under alkaline conditions was carried out, the degradation product was isolated and its structure was confirmed. Both methods were validated in accordance to ICH guidelines. Statistical analysis revealed no significant difference between obtained results and reported ones. CONCLUSION: The present study is useful for therapeutic drug monitoring and routine analysis of RUF in quality control laboratories. HIGHLIGHTS: Kinetics of the alkaline degradation of RUF was studied by following the concentration of the remaining drug until complete degradation was achieved.

Determination of some antiemetic drugs through its native fluorescence or fluorescence quenching of cerrous ammonium sulphate.

The manuscript describes two fluorimetric methods for the determination of some antiemetic drugs namely granisetron HCl, ondansetron HCl and tropisetron HCl, used in the management of nausea and vomiting induced by cytotoxic chemotherapy and radiotherapy. Granisetron HCl solution exhibits a native fluorescence, which can be applied for its determination at 365 nm upon excitation at 305 nm. The method was applied for the determination of granisetron HCl in drug substance, drug product as well as in presence of its acid induced degradation products. The quantum yield was calculated. The second proposed method is based on measuring the quenching effect induced by ondansetron HCl or tropisetron HCl on the fluorescence intensity of cerrous ammonium sulphate at λem 348 nm upon excitation at 250 nm in acidic medium. The analysis of quenching data showed that quenching of cerrous ammonium sulphate induced by ondansetron HCl or tropisetron HCl is mainly through dynamic quenching. Various variables affecting fluorescence response were studied and optimized. The obtained results were found to be statistically agreed with those obtained from the official or reported ones. Moreover, the validity of the methods was assessed according to ICH guidelines.

Synthesis and biological evaluation of new prodrugs of etodolac and tolfenamic acid with reduced ulcerogenic potential.

Gastric irritation and ulcerogenic effect of the acidic NSAIDs are of the most challenging problems in designing novel anti-inflammatory agents. In this study, the new prodrugs were prepared through Steglich esterification reaction between the carboxylic acid functional group of etodolac or tolfenamic acid and thymol. The structures were confirmed by IR, 1H NMR, 13C NMR, mass spectroscopy and elemental analysis. Their chemical stability in addition to a kinetic study of their hydrolysis in 20% liver homogenate and 10% buffered plasma were investigated. In vitro enzymatic hydrolysis showed half-life times 88.84 and 106.61 min for the prodrugs of etodolac and tolfenamic acid, respectively. Their ability to inhibit paw edema and their ulcerogenic potential were assessed in rats and compared to their parent drugs. the prodrugs were found to be stable in different pHs at room and body temperatures. Both prodrugs proved to possess high percentage of inhibition of paw edema (94.68 & 97.1%) in rats comparable to that of the parent drugs (90.33 & 93.23%) and, most importantly with lower ulcerogenic potential. The prodrugs are expected to be converted to their parent drugs rapidly in plasma and liver in vivo and proved to be safer than their parent drugs. The study opens a perspective chance that can be a backbone for further investigations.

Validated Liquid Chromatographic Method for the Determination of (Canagliflozin, Dapagliflozin or Empagliflozin) and Metformin in the Presence of (1-Cyanoguanidine).

A simple and accurate liquid chromatographic method has been developed and validated for the determination of either canagliflozin, dapagliflozin propandiol monohydrate or empagliflozin and metformin in presence of metformin major degradation product;1-cyanoguanidine. The Liquid Chromatographic (LC) method was based on isocratic elution on Prontosil (Lichrosorb 100-5-NH2) column using a mobile phase consisting of NaH2PO4 buffer (10 mM, pH 2.8):acetonitrile (18.5:81.5, v/v), at a flow rate of 2 mL/min-1. Quantitation was achieved with UV detection at 225 nm. The validation of the method was assessed according to International Conference on Harmonization (ICH) guidelines. Linearity, accuracy and precision were satisfactory over the concentration ranges of 12.5-100, 3.75-30, 0.3075-2.46, and 0.3125-2.5 µg/mL for metformin HCl, canagliflozin, dapagliflozin propandiol monohydrate and empagliflozin, respectively. Limits of detection and quantitation were found to be 0.068, 0.135, 0.077 and 0.069 µg/mL and 0.206, 0.410, 0.233 and 0.210 µg/mL for metformin HCl, canagliflozin, dapagliflozin propandiol monohydrate and empagliflozin, respectively. The developed method is suitable for the quality control and routine analysis of the cited drugs separately or in combinations.

Development and Validation of Spectrophotometric Methods for the Determination of Canagliflozin or Gliclazide and Metformin in the Presence of Metformin Impurity (1-Cyanoguanidine).

Background: Quantitative multicomponent analysis is considered an analytical goal to save time and cost in analysis. Objective: This work aimed to provide sensitive and selective [successive ratio subtraction coupled with constant multiplication (SRS-CM) and chemometric] methods for the determination of coformulated antidiabetic drugs, namely canagliflozine and metformin or gliclazide and metformin in presence of metformin degradation product, 1-cyanoguanidine. Methods: SRS-CM method was developed for the determination of canagliflozin and metformin at 292 and 237 nm, respectively, using 14 µg/mL canagliflozin as a divisor in the first step to cancel the spectrum of canagliflozin. Then, 18 µg/mL metformin was used as a divisor in the second step to cancel the spectrum of metformin. Finally, we obtained the spectrum of cyanoguanidine. Chemometric method was applied for the determination of the gliclazide and metformin mixture in a 225-235 nm range. Sample enrichment technique was used to increase the concentration of canagliflozin or gliclazide to allow its simultaneous determination with metformin without prior separation. Results: Validation parameters according to the International Conference on Harmonization guidelines were satisfactory over the concentration ranges of 5 to 16 µg/mL for canagliflozin and metformin as well as 2.5 to 12.5 and 6 to 24 µg/mL for gliclazide and metformin, respectively. Conclusions: The method provides sufficient selectivity and accuracy to be applied for routine analysis and quality control in laboratories for the cited drugs. Highlights: This work shows two examples to how to select a suitable UV spectrophotometric method to overcome the spectral overlap.

Simultaneous HPLC Determination of Betamethasone Esters-Containing Mixtures: Analysis of Their Topical Preparations.

Topical pharmaceutical preparations containing betamethasone esters are widely prescribed for treatment of severe inflammatory skin conditions. Some betamethasone esters-containing preparations are formulated with either an antibacterial or an antifungal agent or a vitamin D3 derivative. A fast reversed-phase high-performance liquid chromatography method has been developed for the simultaneous determination of three betamethasone esters-containing binary mixtures along with the excipients of their dosage forms using clobetasone butyrate as internal standard. The first mixture was betamethasone valerate and fusidic acid (Mixture I) with chlorocresol as preservative. The second mixture was betamethasone dipropionate (BTD) and clotrimazole (Mixture II) with benzyl alcohol as preservative. The third mixture was BTD and calcipotriol monohydrate (Mixture III). Optimized chromatographic separation was achieved on a Discovery® C18 (4.6 × 250 mm, 5 µm) column, using water: acetonitrile (35:65, v/v) as mobile phase at flow rate of 1 mL/min with UV detection at 230 nm. The method was validated according to ICH guidelines. The regression coefficients were > 0.999 for all drugs. The method was successfully applied for the determination of the studied drugs in bulk, synthetic mixtures and dosage forms. The developed method is accurate, sensitive, selective and precise and can be used for routine analysis in quality control laboratories.

Determination of four antiepileptic drugs in plasma using ultra-performance liquid chromatography with mass detection technique.

Status epilepticus (SE) is considered the second most frequent neurological emergency. Its therapeutic management is performed using sequential antiepileptic drug regimens. Diazepam (DIA), midazolam (MID), phenytoin (PHT) and phenobarbital (PB) are four drugs of different classes used sequentially in the management of SE. A sensitive, selective, accurate and precise method was developed and validated for simultaneous determination of the four antiepileptic drugs in human plasma. Their separation and quantification were achieved using ultra-performance liquid chromatography (UPLC) with mass detection using carbamazepine as internal standard (IS). For the first three drugs and the IS, UPLC-MS/MS with electrospray ionization working in multiple reaction monitoring mode was used at the following transitions: m/z 285 → 193 for DIA; m/z 326 → 291 for MID; m/z 253 → 182 for PHT; and m/z 237 → 194, 237 → 192 for IS. For the fourth drug (PB), a molecular ion peak of PB [M + H] + at m/z 233 was used for its quantitation. The method was linear over concentration ranges 5-500 ng/mL for DIA and MID and 0.25-20 µg/mL for PHT and PB. Bioanalytical validation of the developed method was carried out according to European Medicines Agency guidelines. The developed method can be applied for routine drug analysis, therapeutic drug monitoring and bioequivalence studies.

Quantitative analysis of anti-inflammatory drugs using FTIR-ATR spectrometry.

Four simple, accurate, sensitive and economic Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopic (ATR-FTIR) methods have been developed for the quantitative estimation of some non-steroidal anti-inflammatory drugs. The first method involves the determination of Etodolac by direct measurement of the absorbance at 1716cm-1. In the second method, the second derivative of the IR spectra of Tolfenamic acid and its reported degradation product (2-chlorobenzoic acid) was used and the amplitudes were measured at 1084.27cm-1 and 1056.02cm-1 for Tolfenamic acid and 2-chlorobenzoic acid, respectively. The third method used the first derivative of the IR spectra of Bumadizone and its reported degradation product, N,N-diphenylhydrazine and the amplitudes were measured at 2874.98cm-1 and 2160.32cm-1 for Bumadizone and N,N-diphenylhydrazine, respectively. The fourth method depends on measuring the amplitude of Diacerein at 1059.18cm-1 and of rhein, its reported degradation product, at 1079.32cm-1 in their first derivative spectra. The four methods were successfully applied on the pharmaceutical formulations by extracting the active constituent in chloroform and the extract was directly measured in liquid phase mode using a specific cell. Moreover, validation of these methods was carried out following International Conference of Harmonisation (ICH) guidelines.

Simultaneous determination of timolol maleate in combination with some other anti-glaucoma drugs in rabbit aqueous humor by high performance liquid chromatography-tandem mass spectroscopy.

In this work, a sensitive, selective, accurate and precise LC-MS/MS method has been developed for the simultaneous determination of an anti-glaucoma ß-blocker, timolol maleate (TIM) with other co-administered anti-glaucoma drugs of different classes, namely; dorzolamide hydrochloride (DOR), brinzolamide (BRZ) and brimonidine tartrate (BRM) in rabbit aqueous humor (AH) using eslicarbazepine as an internal standard (IS). Liquid-liquid extraction was used for the purification and pre-concentration of analytes from rabbit AH matrix. The chromatographic separation was achieved using a mobile phase consisting of 10mM ammonium formate pH=7: methanol: acetonitrile (5: 50: 45, v/v/v) in isocratic mode of elution at a flow rate of 0.8mL/min on an INERTSIL(®) C18 ODS-3 column (150mm×4.6mm, 3.5µm). The method was operated using electrospray ionization source in the positive ionization mode prior to detection by multiple reaction monitoring (MRM) at the following transitions: m/z 317.2→261.0 for TIM, m/z 325.1→199.0 for DOR, m/z 384.2→281.0 for BRZ, m/z 292.1→212.0 for BRM and m/z 255.0→237.0 for IS. The separation was done in only 3min and the lower limit of quantitation (LLOQ) was (50ng/ml) for all cited drugs. A detailed validation of the bio-analytical method was performed as mentioned in US-FDA and EMA guidelines and the standard calibration curves were found to be linear in the range (50-5000ng/ml) for all drugs with good mean regression coefficient for all drugs.

Validated stability-indicating derivative and derivative ratio methods for the determination of some drugs used to alleviate respiratory tract disorders and their degradation products.

Derivative and derivative ratio methods are presented for the determination of butamirate citrate, formoterol fumarate, montelukast sodium, and sodium cromoglycate. Using the second derivative ultraviolet (UV) spectrophotometry, butamirate citrate and formoterol fumarate were determined by measuring the peak amplitude at 260.4 and 261.8 nm, respectively, without any interference of their degradation products. Butamirate citrate degradation product, 2-phenyl butyric acid, was determined by the measurement of its second derivative amplitude at 246.7 nm where butamirate citrate displays zero crossing. Formoterol fumarate degradation product, desformyl derivative, could be evaluated through the use of the first derivative at peak amplitude of 264.8 nm where interference of formoterol fumarate is negligible. In the first mode, the zero-crossing technique was applied at 305 nm for the determination of montelukast sodium in the presence of its photodegradation product, cis-isomer. The derivative of ratio spectra of montelukast sodium and its cis- isomer were used to determine both isomers using the first derivative of the ratio spectra by measuring the amplitudes of the trough at 305 nm and the peak at 308 nm, respectively. The later technique was also used for the determination of a ternary mixture of sodium cromoglycate and its two degradation products using zero-crossing method. In the derivative ratio spectra of the ternary mixture, trough depths were measured at 271.6, 302.8 and 302.2 nm, using the second, the first, and the second mode to evaluate sodium cromoglycate, degradation product (1) and degradation product (2), respectively. All the methods were applied successfully to the pharmaceutical preparation and were validated according to ICH guidelines.