Assay of artemether, methylparaben and propylparaben in a formulated paediatric antimalarial dry suspension

Antimalarial solid self-emulsifying system for oral use: in vitro investigation

AIM

The low aqueous solubility of artemether and lumefantrine makes them less bioavailable. It is expected that by formulating self-microemulsifying drug-delivery systems (SMEDDS), their aqueous solubility and absorption will thus be enhanced. Results & methodology: Optimized liquid SMEDDS containing artemether and lumefantrine was adsorbed on Neusilin US2^® employing spray drying technique to convert it into solid SMEDDS. Almost 90% of both drugs were released within 15 min in their respective official dissolution media. Drug assay and dissolution rate of solid SMEDDS remained unaltered after 3-month storage at 40°C and 75% relative humidity.

CONCLUSION

Reconstitution of solid SMEDDS in water yielded microemulsion with a globule size of 67.74 nm. Complete and faster in vitro release of both drugs from solid SMEDDS was observed as compared with that from marketed tablets.

LC-UV/MS quality analytics of paediatric artemether formulations

A highly selective and stability-indicating HPLC-method, combined with appropriate sample preparation steps, is developed for β-artemether assay and profiling of related impurities, including possible degradants, in a complex powder for oral suspension. Following HPLC conditions allowed the required selectivity: a Prevail organic acid (OA) column (250 mm×4.6 mm, 5 μm), flow rate set at 1.5 mL/min combined with a linear gradient (where A=25 mM phosphate buffer (pH 2.5), and B=acetonitrile) from 30% to 75% B in a runtime of 60 min. Quantitative UV-detection was performed at 210 nm. Acetonitrile was applied as extraction solvent for sample preparation. Using acetonitrile-water mixtures as extraction solvent, a compartmental behaviour by a non-solving excipient-bound fraction and an artemether-solubilising free fraction of solvent was demonstrated, making a mobile phase based extraction not a good choice. Method validation showed that the developed HPLC-method is considered to be suitable for its intended regulatory stability-quality characterisation of β-artemether paediatric formulations. Furthermore, LC-MS on references as well as on stability samples was performed allowing identity confirmation of the β-artemether related impurities. MS-fragmentation scheme of β-artemether and its related substances is proposed, explaining the m/z values of the in-source fragments obtained.

Relative response factor determination of β-artemether degradants by a dry heat stress approach

During the stability evaluation of β-artemether containing finished drug products, a consistent and disproportional increase in the UV-peak areas of β-artemether degradation products, when compared to the peak area decline of β-artemether itself, was observed. This suggested that the response factors of the formed β-artemether degradants were significantly higher than β-artemether. Dry heat stressing of β-artemether powder, as a single compound, using different temperatures (125-150 °C), times (10-90 min) and environmental conditions (neutral, KMnO(4) and zinc), resulted in the formation of 17 degradants. The vast majority of degradants seen during the long-term and accelerated ICH stability study of the drug product, were also observed here. The obtained stress results allowed the calculation of the overall average relative response factor (RRF) of β-artemether degradants, i.e. 21.2, whereas the individual RRF values of the 9 most prominent selected degradants ranged from 4.9 to 42.4. Finally, Ames tests were performed on β-artemether as well as a representative stressed sample mixture, experimentally assessing their mutagenic properties. Both were found to be negative, suggesting no mutagenicity problems of the degradants at high concentrations. Our general approach and specific results solve the developmental quality issue of mass balance during stability studies and the related genotoxicity concerns of the key antimalarial drug β-artemether and its degradants.

Counterfeit drugs: analytical techniques for their identification

In recent years, the number of counterfeit drugs has increased dramatically, including not only "lifestyle" products but also vital medicines. Besides the threat to public health, the financial and reputational damage to pharmaceutical companies is substantial. The lack of robust information on the prevalence of fake drugs is an obstacle in the fight against drug counterfeiting. It is generally accepted that approximately 10% of drugs worldwide could be counterfeit, but it is also well known that this number covers very different situations depending on the country, the places where the drugs are purchased, and the definition of what constitutes a counterfeit drug. The chemical analysis of drugs suspected to be fake is a crucial step as counterfeiters are becoming increasingly sophisticated, rendering visual inspection insufficient to distinguish the genuine products from the counterfeit ones. This article critically reviews the recent analytical methods employed to control the quality of drug formulations, using as an example artemisinin derivatives, medicines particularly targeted by counterfeiters. Indeed, a broad panel of techniques have been reported for their analysis, ranging from simple and cheap in-field ones (colorimetry and thin-layer chromatography) to more advanced laboratory methods (mass spectrometry, nuclear magnetic resonance, and vibrational spectroscopies) through chromatographic methods, which remain the most widely used. The conclusion section of the article highlights the questions to be posed before selecting the most appropriate analytical approach.

Quantitation of artemether in pharmaceutical raw material and injections by high performance liquid chromatography

The quantitation of artemether in both pharmaceutical raw material and injections was carried out by high performance liquid chromatography (HPLC) with ultraviolet detection. A Zorbax C18 column (150 x 4.6 mm; 5 μm), at 30 °C, and a mobile phase composed of acetonitrile and water (70:30), at a flow rate of 1ml/min, were used. The detection wavelength was 216 nm and the injection volume was 20 μL. The method proved to be linear (r²=0.9999), precise (RSD < 20% for intra-day and inter-day precision), accurate and selective regarding possible impurities and excipients of the samples. The detection and quantitation limits were 8 μg/mL and 25 μg/mL, respectively. The artemether content obtained in the raw material analysis was 99.26% and in the injections, 102.08%. The optimized and validated method may be successfully employed to perform routine quality control analyses.