Detection of substandard fixed-dose combination tuberculosis drugs using thin-layer chromatography.

SETTING: A convenience sample of 13 fixed-dose combination (FDC) tuberculosis (TB) drugs from 'The Fixed Dose Combination Project' was analysed in laboratories at the University of Botswana and the US Food and Drug Administration (FDA). OBJECTIVE: To determine actual versus stated content of drugs in these FDCs. DESIGN: Chemical analysis was performed using thin-layer chromatography (TLC) as a screening method, and ultraviolet (UV) spectrophotometry or liquid chromatography (LC) as confirmation. FDCs with content outside of 85-115% of stated concentration were defined as substandard. RESULTS: All 13 FDCs contained the stated drugs. However, four (31%) were substandard, including two (15%) with low rifampicin content, one (8%) with excessive rifampicin, and one (8%) with excessive pyrazinamide. Both FDCs with low rifampicin contained four drugs and failed TLC screening. The FDC with excessive rifampicin was not detected by TLC screening. Using UV as the gold standard, the sensitivity of TLC for low rifampicin was 2/2 (100%), and the specificity was 9/10 (90%). CONCLUSION: This study found that 31% of the FDCs in 'The Fixed Dose Combination Project' had substandard content, irrespective of bioavailability. Low rifampicin content, which can be reliably detected by TLC screening, was identified in both four-drug FDC products and is particularly worrisome. TB drugs should be screened for quality using TLC to optimise treatment outcomes and to prevent increases in acquired drug resistance.

Quality assurance in weighing.

Weighing is the most used step in any analytical procedure, and the balance is the one essential piece of laboratory equipment in all analyses. Yet weighing is a common source of error in final analytical results and can be difficult to detect. Analysts may become complacent and expect all weighings to be accurate. Our laboratory experienced a problem in weighing and found that the principal error was due to drift. The ensuing investigation into the cause led to a procedure for reducing drift, which, in turn, ensured accurate weighings that have improved quality assurance in our total operations.

Rapid screening of pharmaceuticals by thin-layer chromatography: analysis of essential drugs by visual methods.

A method for rapidly screening pharmaceuticals by thin-layer chromatography has been designed for use in areas with limited resources and by operators with limited training. An apparatus for performing the analysis in a plastic bag under equilibrium conditions was designed. Results can be reproduced by different operators and in different locations. The analysis can be performed without electricity or in a remote area, away from a laboratory. It is especially suited for field use in developing countries. The method is low cost, maintenance-free, fast, and reliable; it also uses limited volumes of solvents. The analyses can be performed without weighing if reference materials can be supplied in tablet form, provided the drug content is listed and only one unit is required for each analysis. All procedures were developed for the analysis of drugs from a partial list of essential drugs established by the World Health Organization. Three drugs were selected and prepared in the form of reference tablets. Comparisons with the analyses of the drugs in standard dosage forms were made by using reference tablets and primary USP standards. Comparable results were obtained, proving that the screening process can be conducted by using reference tablets and without weighing either the sample or the reference. The method has been successfully demonstrated and used in Swaziland, by high school teachers in the United States, and by personnel from the Ministry of Health in Saudi Arabia. Personnel can be trained in a short time to perform screening analysis of drugs.

A simple, inexpensive thin-layer chromatography method for the analysis of theophylline tablets.

A simple, low-cost thin-layer chromatography (TLC) procedure to estimate the quality of simple pharmaceuticals in tablet form is described together with easily built equipment to carry out the test in the field. The approach is demonstrated for theophylline, but can be used to assay the drug content of any tablet or to determine its dissolution or disintegration characteristics. The procedure can be used in the field without the need for any instrumentation.

Monitoring recombinant protein drugs: a study of insulin by H/D exchange and electrospray ionization mass spectrometry.

The increasing emergence of new protein- and peptide-based drugs makes necessary the development of rapid and sensitive methods to check consistency between and within batches of biotechnology pharmaceuticals to ensure product quality. We evaluated electrospray ionization mass spectrometry in combination with H/D isotopic exchange as a potential tool, taking as examples for this case study the four insulins used for treating insulin-dependent diabetes. Two (bovine and porcine) are produced naturally, and two are produced by recombinant biotechnology techniques [recombinant human (r-human) and its human insulin analog (LysPro)]. The extent of H/D exchange at a given time was measured with less than 2 micrograms (< 350 pmol) of sample and was sufficient for discriminating among the different insulins. After 60 min, bovine, porcine, r-human, and LysPro insulins exchanged on average 25, 28, 30, and 38 amide protons, respectively. After prolonged incubation with D2O for 24 h, bovine and porcine insulins exchanged 31 protons, whereas r-human and LysPro insulins exchanged 34 and 43 amide protons, respectively. The differences in H/D exchange are protein signatures that relate to differences in conformation and folding. The extent of exchange distinguishes among the insulin types and assures the consistency of batch preparations for a given insulin.

Algorithms for validating chiral properties of insulins.

The combination of chiral ligand exchange on Cu(II) complexes in aqueous base with circular dichroism spectropolarimetric detection provides excellent avenues to validate the chirality properties of oligopeptides and proteins. The method is quick and simple and has the potential for development into an automated, routine procedure for quality control applications. Target analytes used for this first study of a protein system are human, porcine, and bovine insulins prepared by different procedures and obtained from different sources, production lots, and manufacturers. The analytical specificity of the test makes the method a potentially useful technique for validating the chirality properties of many peptide and protein forms.

Pharmaceutical fingerprinting: evaluation of neural networks and chemometric techniques for distinguishing among same-product manufacturers.

The present study was undertaken to evaluate several computer-based classifiers as potential tools for pharmaceutical fingerprinting by utilizing normalized data obtained from HPLC trace organic impurity patterns. To assess the utility of this approach, samples of L-tryptophan (LT) drug substance were analyzed from commercial production lots of six different manufacturers. The performance of several artificial neural network (ANN) architectures was compared with that of two standard chemometric methods, K-nearest neighbors (KNN) and soft independent modeling of class analogy (SIMCA), as well as with a panel of human experts. The architecture of all three computer-based classifiers was varied with respect to the number of input variables. The ANNs were also optimized with respect to the number of nodes per hidden layer and to the number of hidden layers. A novel preprocessing scheme known as the Window method was devised for converting the output of 899 data entries extracted from each chromatogram into an appropriate input file for the classifiers. Analysis of the test set data revealed that an ANN with 46 inputs (i.e., ANN-46) was superior to all other classifiers evaluated, with 93% of the chromatograms correctly classified. Among the classifiers studied in detail, the order of performance was ANN-46 (93%) > SIMCA-46 (87%) > KNN-46 (85%) = ANN-899 (85%) > "human experts" (83%) > SIMCA-899 (78%) > or = ANN-22 (77%) = KNN-22 (77%) > or = KNN-899 (76%) > SIMCA-22 (73%). These results confirm that ANNs, particularly when used in conjunction with the Window preprocessing scheme, can provide a fast, accurate, and consistent methodology applicable to pharmaceutical fingerprinting. Particular attention was paid to variations in the HPLC patterns of same-manufacturer samples due to differences in LT production lots, HPLC columns, and even run-days to quantify how these factors might hinder correct classifications. The results from these classification studies indicate that the chromatograms evidenced variations across LT manufacturers, across the three HPLC columns and, for one manufacturer, across lots. The extent of column-to-column variations is particularly noteworthy in that all three columns had identical specifications with respect to their stationary-phase characteristics and two of the three columns were from the same vendor.