A high-throughput LC-MS/MS method for simultaneous determination of isoniazid, ethambutol and pyrazinamide in human plasma

RATIONALE

Tuberculosis (TB) remains a challenging global infectious disease, mainly affecting the lungs. First-line anti-TB drugs play a crucial role in slowing down the rapid spread of TB. In addition, the patient might benefit from therapeutic drug monitoring since it has become an accepted clinical tool for optimizing TB treatment.

METHODS

A simple and sensitive liquid chromatography/tandem mass spectrometry method was developed to monitor the plasma level of isoniazid, ethambutol and pyrazinamide in plasma samples. A one-step extraction procedure using an Ostro™ plate was applied, and extracts were analyzed by gradient elution followed by detection on a mass spectrometer by multiple reaction monitoring mode.

RESULTS

The analytes were separated within 4.2 min and over the concentration range of 0.2-10 μg/ml for isoniazid and ethambutol and 1-65 μg/ml for pyrazinamide. The method was successfully validated according to the European Medicine Agency guideline for the selectivity, linearity and lower limit of detection, precision and accuracy, matrix effect, extraction recovery, carryover, dilution integrity and stability, and applied for quantification of analytes in clinical samples from TB patients.

CONCLUSIONS

The presented method allows sensitive and reproducible determination of selected anti-TB drugs with advantages such as low sample volume requirement, short run time of analysis, one-step sample preparation procedure with capabilities for phospholipids removal, and a low quantification limit as well as a high degree of selectivity.

Plain 1 H nuclear magnetic resonance analysis streamlines the quality control of antiviral favipiravir and congeneric World Health Organization essential medicines

Favipiravir is an established antiviral that is currently being assessed as an investigational drug for the treatment of COVID-19. Favipiravir is strikingly similar to two molecules that the World Health Organization (WHO) lists as essential medicines, which also consist of a six-membered aromatic N-heterocycle bearing a carboxamide function: the anti-tuberculosis agent, pyrazinamide, and nicotinamide, also known as vitamin B₃ . We demonstrate the utility of ¹ H nuclear magnetic resonance (NMR) profiling, an emerging pharmacopoeial tool, for the highly specific identification, selective differentiation of congeners, and subsequent detection of drug falsification or adulteration of these medicines. The straightforward comparison of basic 1-D ¹ H NMR spectra, obtained with benchtop or advanced NMR instruments alike, offers a rapid identity assay and works independently of physical reference materials. This approach accelerates and advances pharmaceutical quality control measures under situations of increased drug demand and altered economy, such as during a pandemic.

Potential of multisyringe chromatography for the on-line monitoring of the photocatalytic degradation of antituberculosis drugs in aqueous solution

In this study, a multisyringe chromatography system (MSC) using a C18 monolithic column was proposed for the on-line monitoring of the photocatalytic degradation of isoniazid (INH, 10 mg L(-1)) and pyrazinamide (PYRA, 5mgL(-1)) mixtures in aqueous solution using a small sample volume (200 μL) with an on-line filtration device in a fully automated approach. During the photocatalytic oxidation using TiO2 or ZnO semiconductor materials, total organic carbon (TOC) and the formed intermediates were analyzed off-line using ion chromatography, ion exclusion HPLC, and ESI-MS/MS. The results showed that TiO2 exhibits a better photocatalytic activity than ZnO under UV irradiation (365 nm) for the degradation of INH and PYRA mixtures, generating 97% and 92% degradation, respectively. The optimal oxidation conditions were identified as pH 7 and 1.0 g L(-1) of TiO2 as catalyst. The mineralization of the initial organic compounds was confirmed by the regular decrease in TOC, which indicated 63% mineralization, and the quantitative release of nitrate and nitrite ions, which represent 33% of the nitrogen in these compounds. The major intermediates of INH degradation included isonicotinamide, isonicotinic acid, and pyridine, while the ESI-MS/MS analysis of PYRA aqueous solution after photocatalytic treatment showed the formation of pyrazin-2-ylmethanol, pyrazin-2-ol, and pyrazine. Three low-molecular weight compounds, acetamide, acetic acid and formic acid, were detected during INH and PYRA decomposition. PYRA was more resistant to photocatalytic degradation due to the presence of the pyrazine ring, which provides greater stability against OH attack.

Isoniazid, pyrazinamide and rifampicin content variation in split fixed-dose combination tablets

Setting

In most developing countries, paediatric tuberculosis is treated with split tablets leading to potential inaccuracy in the dose delivery and drug exposure. There is no data on the quality of first-line drugs content in split fixed-dose combination tablets.

Objective

To determine Isoniazid, Pyrazinamide and Rifampicin content uniformity in split FDC tablets used in the treatment of childhood tuberculosis.

Design

Drug contents of 15 whole tablets, 30 half tablets and 36 third tablets were analysed by high performance liquid chromatography. The content uniformity was assessed by comparing drug content measured in split portions with their expected amounts and the quality of split portions was assessed applying qualitative specifications for whole tablets.

Results

All whole tablets measurements fell into the USP proxy for the three drugs. But a significant number of half and third portions was found outside the tolerated variation range and the split formulation failed the requirements for content uniformity. To correct for the inaccuracy of splitting the tablets into equal portions, a weight-adjustment strategy was used but this did not improve the findings.

Conclusion

In split tablets the content of the three drugs is non-uniform and exceeded the USP recommendations. There is an absolute need to make child-friendly formulations available for the treatment of childhood tuberculosis.

Automated chemiluminometric screening of counterfeit drugs of the antituberculosis agent pyrazinamide

Finding counterfeit drugs presents a growing challenge in preventing these products from entering health systems and causing serious consequences for consumers, drug manufacturers, and governments. In this investigation a simple, low-cost, and expeditious chemiluminometric approach, relying on a fully automated multipumping flow system for screening pharmaceutical preparations of the antituberculosis drug pyrazinamide, was implemented. The developed chemiluminescent method was based on the scavenging effect of pyrazinamide on the oxidation of luminol by hydrogen peroxide in alkaline medium. For analytical signal monitoring, a homemade chemiluminescence detector relying on a photomultiplier module was developed. Linear calibration plots for pyrazinamide concentrations between 10 and 70 mg/L were obtained (R = 0.9931) with good precision (RSD < 0.99%; n = 21). The limit of detection was 5.79 mg/L, and the sampling rate was about 150 determinations per hour.

[Application of near infrared spectroscopy in rapid and simultaneous determination of essential components in five varieties of anti-tuberculosis tablets]

Since 1980s, tuberculosis has become increasingly serious. Rifampicin tablets, isoniazide tablets, pyrazinamide tablets, rifampicin and isoniazide tablets and rifampicin isoniazide and pyrazinamide tablets are currently relatively efficacious antituberculosis drugs. In the present paper, near infrared spectroscopy (NIRS) with partial least squares (PLS) was applied to the simultaneous determination of rifampicin (RMP), isoniazide (INH) and pyrazinamide (PZA) contents in 5 varieties of anti-tuberculosis tablets. As the results showed, all of the models for the determination of RMP, INH and PZA contents applied the original NIR spectra. The most efficacious wavelength range for the determination of RMP contents was 1981-2195 nm, it was 1540-1717 nm and 2086-2197 nm for the determination of INH contents, and it was 1460-1537 nm, 1956-2022 nm and 2268-2393 nm for determination of PZA contents. The root mean square error of the calibration set obtained by cross-validation (RMSECV) of the optimum models for the quantitative analysis of RMP, INH and PZA contents was 0.0494, 0.0257 and 0.0307, respectively. Using these optimum models for the determination of RMP, INH and PZA contents in prediction set, the root mean square error of prediction set (RMSEP) was 0.0182, 0.0166 and 0.0134, respectively. The correlation coefficient (r(p)) between the predicted values and actual values was 0.9864, 0.9989 and 0.9993, respectively. These results demonstrated that this method was precise and reliable, and is significative for in situ measurement and the on-line quality control for anti-tuberculosis tablets production.

CHIH-DFT determination of the molecular structure infrared spectra, UV spectra and chemical reactivity of three antitubercular compounds: Rifampicin, Isoniazid and Pyrazinamide

Three of the most frequent antitubercular agents employed against Mycobacterium tuberculosis are: Rifampicin, Isoniazid and Pyrazinamide. It has been proven that the use of these antitubercular agents together, shortens the treatment period from 12-18 months to 6 months [1]. In this work we use a new Density Functional Theory chemistry model called CHIH-DFT (Chihuahua-Heterocycles-Density Functional Theory) that reflects the mixture of Hartree Fock exchange and DFT exchange, according to a mixing parameter based on empirical rules suited for heterocyclic systems. This new chemistry model was used to calculate the molecular structure of these antitubercular compounds, as well as their infrared, UV spectra, chemical reactivity and electronic properties. The UV and infrared spectra were obtained by experimental techniques. The calculated molecular structure, UV and IR spectra values from CHIH-DFT were compared with experimentally obtained values and theoretical studies. These results are in good agreement with experimental and theoretical studies. We also predicted using the relative electrophilicity and relative nucleophilicity concepts as defined by Roy et al. [2] the chemical active sites for the three antitubercular compounds as well as their electronegativity, ionization potential, electron affinity, hardness, dipole moment, E(HOMO)-E(LUMO) gap energy, etc.

Optimization of a Stability-Indicating HPLC Method for the Simultaneous Determination of Rifampicin, Isoniazid, and Pyrazinamide in a Fixed-Dose Combination using Artificial Neural Networks

The aim of this study is to develop and optimize a simple and reliable high-performance liquid chromatography (HPLC) method for the simultaneous determination of rifampicin (RIF), isoniazid (INH), and pyrazinamide (PZA) in a fixed-dose combination. The method is developed and optimized using an artificial neural network (ANN) for data modeling. Retention times under different experimental conditions (solvent, buffer type, and pH) and using four different column types (referred to as the input and testing data) are used to train, validate, and test the ANN model. The developed model is then used to maximize HPLC performance by optimizing separation. The sensitivity of the separation (retention time) to the changes in column type, concentration, and type of solvent and buffer in the mobile phase are investigated. Acetonitrile (ACN) as a solvent and tetrabutylammonium hydroxide (tBAH), used to adjust pH, have the greatest influence on the chromatographic separation of PZA and INH and are used for the final optimization. The best separation and reasonably short retention times are produced on the micro-bondapak C18, 4.6 x 250-mm column, 10 microm/125 A using ACN-tBAH (42.5:57.5, v/v) (0.0002M) as the mobile phase, and optimized at a final pH of 3.10.

Effect of peritoneal dialysis on plasma and peritoneal fluid concentrations of isoniazid, pyrazinamide, and rifampin

OBJECTIVE

This study was performed to elucidate the pharmacokinetic profiles of antimycobacterial regimens for peritoneal dialysis patients.

PATIENTS

Nine patients on maintenance continuous ambulatory peritoneal dialysis (CAPD) were included in this study.

METHODS

After administering a conventional oral dose of antituberculosis medications, we measured plasma and peritoneal fluid concentrations of isoniazid by fluorometry, and rifampin and pyrazinamide by high performance liquid chromatography. The assay data were subjected to pharmacokinetic analysis.

RESULTS

Average peak plasma concentrations of isoniazid, rifampin, and pyrazinamide were 3.3 mg/L, 6.5 mg/L, and 30.9 mg/L, respectively, all of which much exceed the minimum inhibitory concentration (MIC) for Mycobacterium tuberculosis. Peritoneal fluid concentrations of isoniazid and pyrazinamide were maintained well above the MICs for M. tuberculosis; however, peritoneal fluid concentration of rifampin was below the therapeutic range most of the time.

CONCLUSION

For the treatment of systemic or pulmonary tuberculosis in CAPD patients, no dose adjustments are required for isoniazid, rifampin, or pyrazinamide. On the contrary, for the treatment of tuberculous peritonitis, oral rifampin therapy is not expected to be effective because of its low peritoneal fluid concentration.

Evaluation of the recently reported USP gradient HPLC method for analysis of anti-tuberculosis drugs for its ability to resolve degradation products of rifampicin

The recently notified USP gradient HPLC method for quantitative determination of rifampicin, isoniazid and pyrazinamide in fixed dose combination (FDC) formulations was evaluated to determine its ability to resolve major degradation products of rifampicin, viz. 3-formylrifamycin SV, rifampicin N-oxide, 25-desacetyl rifampicin, rifampicin quinone, and the newly reported isonicotinyl hydrazone, an interaction product of 3-formylrifamycin and isoniazid. The first observation was that the requirements of theoretical plates listed in the given method were met for rifampicin, but not for isoniazid and pyrazinamide, even on columns of different makes. The resolving power of the method was also dependent upon make of the column. On two of the three columns of the three tested, it was able to resolve most degradation products, except rifampicin N-oxide and 25-desacetylrifampicin, which were overlapping. The method was modified and an overall satisfactory resolution for all components was obtained by changing the buffer: organic modifier ratio of solution B in the gradient from 45:55 to 55:45 and decreasing the flow rate from 1.5 to 1.0 ml/min, keeping all other conditions constant.

Determination of antitubercular drugs by micellar electrokinetic capillary chromatography (MEKC)

A method for the determination of isoniazid (ISO), pyrazinamide (PYR) and rifampicin (RIF) in pharmaceutical products, by micellar electrokinetic capillary chromatography (MEKC) with ultraviolet detection is described. The influence of pH, concentration of surfactants, buffer and organic solvents, over the separation were studied as experimental variables. The optimal separation was carried out at 30 degrees C and 20 kV, using a 40 mM borate buffer and 100 mM sodium dodecylsulphate (SDS) adjusted to pH 8.5. Under these conditions, the analysis is accomplished in about 8 min. The method was applied to the determination of these compounds in different pharmaceuticals with good results when compared with a reference liquid chromatographic (LC) method.

Validation of a RP-LC method for the simultaneous determination of isoniazid, pyrazinamide and rifampicin in a pharmaceutical formulation

A simple and accurate liquid chromatographic method was developed and validated for estimation of isoniazid (ISN), pyrazinamide (PYR) and rifampicin (RIF) in combined dosage forms. Drugs were chromatographed on a reverse phase C18 column using a mobile phase gradient and monitored at the corresponding maximum of each compounds. Peaks were identified with retention time as compared with standards and confirmed with characteristic spectra using diode-array detector. Solution concentrations were measured on a weight basis to avoid the use of an internal standard. The method does not require any specific sample preparation except the use of a guard column. The method is linear (r(2)>0.999), precise (RSD%: 0.50% for ISN, 0.12% for PYR and 0.98% for RIF), accurate (overall average recovery yields: 98.55% for ISN, 98.51 for PYR and 98.56% for RIF) and selective. Due to its simplicity and accuracy the method is suitable for routine quality control analysis of antitubercolosis combination dosage form.

Liquid chromatographic determination of isoniazid, pyrazinamide and rifampicin from pharmaceutical preparations and blood

Isoniazid (IN), pyrazinamide (Pz) and rifampicin (Rf) are separated on YMC-ODS column. IN was derivatized with 2-fluorene-carboxaldehyde (FA). The separation was achieved using ethanol-chloroform-acetonitrile water by isocratic elution and detected at 337 nm. The detection limits were 0.11 ng, 0.2 ng and 13 ng/injection (5 microl) for IN, Pz and Rf, respectively. The method of analysis was applied to the pharmaceutical preparations and in the blood samples of the patients suffering from tuberculosis after undergoing chemotherapy with IN, Pz and Rf. The amounts quantitated in blood showed 0.97 to 1.58 microg/ml IN, 3.44 to 4.09 microg/ml Pz and 1.98 to 3.5 microg/ml Rf with coefficient of variations 0.8-1.8%, 0.9-1.3% and 0.8-2.1%, respectively.

High-performance liquid chromatographic determination of pyrazinamide in human plasma, bronchoalveolar lavage fluid, and alveolar cells

A technique is presented for the measurement of pyrazinamide in human plasma, bronchoalveolar lavage, and alveolar cells by reversed-phase column chromatography. The assay utilizes acetazolamide as an internal standard, ultraviolet detection at 268 nm, and an acetonitrile-based mobile phase. Preparation of plasma samples requires a simple deproteinization step, resulting in the development of sharp peaks with retention times of 8.4 and 17 minutes for pyrazinamide and acetazolamide, respectively. Bronchoalveolar lavage and alveolar cell suspensions require an acid extraction with ethyl acetate, evaporation to dryness, and reconstitution. This method provides specific, rapid, and reliable determinations of drug concentrations and therefore is suitable for pharmacological studies, particularly those that are designed to quantitate the intrapulmonary concentrations of pyrazinamide.

The colorimetric analysis of anti-tuberculosis fixed-dose combination tablets and capsules

SETTING

The perceived need to demonstrate whether or not the actual amounts of rifampicin, isoniazid and pyrazinamide in fixed-dose combination tablets or capsules correspond to their stated drug contents.

OBJECTIVE

To adapt specific, robust and simple colorimetric methods that have been previously applied to measuring plasma and urinary rifampicin, isoniazid, pyrazinamide and ethambutol concentrations to estimate tablet and capsule drug contents.

DESIGN

The methods were applied to the analysis of 14 commercially manufactured fixed-dose combinations: two capsule and three tablet formulations containing rifampicin and isoniazid; seven tablet formulations containing rifampicin, isoniazid and pyrazinamide; and two tablet formulations containing rifampicin, isoniazid, pyrazinamide and ethambutol.

RESULTS

All the combined formulations contained near to their stated drug contents. Replicate analyses confirmed the excellent precision of the drug analyses.

CONCLUSION

Such methods are not only rapid to perform but should be practical in many Third World situations with relatively modest laboratory facilities.

Simultaneous determination of rifampicin, isoniazid and pyrazinamide in tablet preparations by multivariate spectrophotometric calibration

The use of multivariate spectrophotometric calibration is presented for the simultaneous determination of the active components of tablets used in the treatment of pulmonary tuberculosis. The resolution of ternary mixtures of rifampicin, isoniazid and pyrazinamide has been accomplished by using partial least squares (PLS-1) regression analysis. Although the components show an important degree of spectral overlap, they have been simultaneously determined with high accuracy and precision, rapidly and with no need of nonaqueous solvents for dissolving the samples. No interference has been observed from the tablet excipients. A comparison is presented with the related multivariate method of classical least squares (CLS) analysis, which is shown to yield less reliable results due to the severe spectral overlap among the studied compounds. This is highlighted in the case of isoniazid, due to the small absorbances measured for this component.

Therapeutic monitoring of antituberculosis drugs by direct in-line extraction on a high-performance liquid chromatography system

A direct in-line pre-column extraction technique in which guanidinium and ammonium sulfate are used, followed by column switching, was employed to analyze serum, plasma and cerebrospinal fluid samples of patients treated for tuberculous meningitis. Resolution of a wide range of polar to non-polar xenobiotics was obtained on a C8 silica column by using a linear gradient from a binary system consisting of solvent A (0.05 M KH2PO4) and solvent B (acetonitrile-isopropanol, 4:1, v/v). Apart from the antituberculosis drugs (isoniazid, pyrazinamide, ethionamide and rifampicin) the patients received up to sixteen different medicines for prevention of complications and the treatment of symptoms. Qualitative resolution of all the drugs was obtained by the chromatographic system. Quantitation of pyrazinamide and ethionamide was achieved with high precision and low inter-sample variation.

[Microdetermination of pyrazinamide and its metabolites (pyrazinoic acid, 5-hydroxypyrazinoic acid, 5-hydroxypyrazinamide and pyrazinuric acid) in plasma and urine with liquid chromatography]

The method reported here for determining pyrazinamide and its metabolites (2-pyrazinoic acid, 5-hydroxypyrazinamide, 5-hydroxypyrazinoic acid and pyrazinuric acid) consists of diluting urine or acid deproteinisation of serum followed by chromatography on a cation-exchange column. The column length and the detection system (ultraviolet or fluorimetry) allow for a very good separation of the different compounds; the sensitivity of the method makes it suitable for pharmacokinetic studies.

High-performance liquid chromatographic determination of pyrazinamide in cerebrospinal fluid and plasma in the rabbit

A simple procedure for the determination of pyrazinamide in plasma and cerebrospinal fluid in the rabbit is described. The assay involves a preliminary extraction of the drug and an internal standard, paracetamol, from the acidified sample (pH 4.2). The extract is evaporated to dryness at 45 degrees C and the residue is redissolved in methanol (50 microliters). A 25-microliters aliquot is injected into the liquid chromatograph and eluted with acetonitrile-10 mM phosphate buffer of pH 3.5 (10:90, v/v) on a 30-microns C8 pre-column linked to a 5-microns C8 reversed-phase column at ambient temperature (25 +/- 1 degree C). The eluate is detected at 215 nm. The method has been used to investigate the disposition of pyrazinamide in plasma and cerebrospinal fluid in six rabbits.

Chromatographic analysis of antituberculosis drugs in biological samples

Numerous chromatographic and non-chromatographic methods of analysis for anti-tuberculosis drugs and metabolites in biological tissues have been discussed in this review. Depending upon the analytical methodology selected, limits of detection range from microgram to picogram levels. A number of examples have been given of the correlation between different types of assay procedures. The metabolism and pharmacokinetics have been described along with some of the commonly associated problems of sample collection and storage.

Mass fragmentographic determination of pyrazinamide and its metabolites in serum and urine

A combined gas chromatographic-mass spectrometric technique is described for the simultaneous determination of pyrazinamide and its two main metabolites, pyrazinoic acid and 5-hydroxypyrazinoic acid. Serum (200 microliter) is deproteinized and evaporated to dryness; urine (20 microliter) is evaporated. The crude residues are silylated and selected ions are monitored in the chemical-ionization mode with isobutane as both chromatographic carrier and reagent gas. The sensitivity is 10 ng/ml for pyrazinamide and pyrazinoic acid and 20 ng/ml for the 5-hydroxy metabolite in a single analysis. Nicotinic acid and nicotinamide are internal standards. Both unchanged drug and metabolites were identified and quantified in the serum and urine of human subjects.