Automated solid-phase extraction method for the determination of atovaquone in capillary blood applied onto sampling paper by rapid high-performance liquid chromatography

Quantification of atovaquone from amorphous solid dispersion formulation using HPLC: An in vitro and ex vivo investigation

Atovaquone (ATQ) is a poorly soluble drug. Therefore, formulating ATQ into its supersaturated state through solid dispersion for bioavailability enhancement can be of great value. However, due to fast crystallising properties of ATQ, the quantification of ATQ in a supersaturated solid dispersion system can be complicated. Therefore, in pursuit of accurate quantification of such sample, a simple HPLC analytical method utilising a C₁₈ column (250 × 4.6 mm ID, 5 μm) for the quantitation of ATQ has been developed and validated. Atovaquone elution using the proposed method demonstrated a retention time around 7.6 min with good linearity (R² > 0.999). The system suitability is also detailed with the tailing factor at 1.365 ± 0.002. The addition of solubilising agent as sample treatment step aided in ensuring the accurate quantitation of the fast crystallising ATQ. The developed HPLC quantitation method has been successfully employed in the analysis of ATQ from solid dispersion samples in in vitro dissolution as well as ex vivo permeation studies for formulation development.

Determination of tafenoquine in dried blood spots and plasma using LC and fluorescence detection

BACKGROUND

The growing problem of parasites developing resistance to the traditional antimalarial drugs makes the development of new effective and safe drugs crucial. Tafenoquine is a new promising antimalarial drug for prophylaxis and treatment.

RESULTS

A bioanalytical method for the determination of tafenoquine in 100 µl of capillary blood applied onto sampling paper and in 100 µl of plasma has been developed and validated. The Whatman 31 ET Chr paper was treated with 0.6 mol/l tartaric acid to improve the extraction recovery and solid-phase extraction was used for cleanup procedure of the blood samples. Plasma samples were precipitated with methanol. Tafenoquine and internal standard were separated on a Zorbax SB-CN column by reversed-phase LC and detected with fluorescence detection at 262 and 470 nm. The within- and between-day variations were below 10 and 14%, respectively, over the range 50-200 nmol/l for capillary blood on sampling paper and below 6 and 10% for plasma samples. The LLOQ of the method was 50 nmol/l.

CONCLUSION

The developed method has adequate sensitivity and is highly suitable for clinical studies in dried blood spots and plasma.

World Antimalarial Resistance Network (WARN) IV: clinical pharmacology

A World Antimalarial Resistance Network (WARN) database has the potential to improve the treatment of malaria, through informing current drug selection and use and providing a prompt warning of when treatment policies need changing. This manuscript outlines the contribution and structure of the clinical pharmacology component of this database. The determinants of treatment response are multi-factorial, but clearly providing adequate blood concentrations is pivotal to curing malaria. The ability of available antimalarial pharmacokinetic data to inform optimal dosing is constrained by the small number of patients studied, with even fewer (if any) studies conducted in the most vulnerable populations. There are even less data relating blood concentration data to the therapeutic response (pharmacodynamics). By pooling all available pharmacokinetic data, while paying careful attention to the analytical methodologies used, the limitations of small (and thus underpowered) individual studies may be overcome and factors that contribute to inter-individual variability in pharmacokinetic parameters defined. Key variables for pharmacokinetic studies are defined in terms of patient (or study subject) characteristics, the formulation and route of administration of the antimalarial studied, the sampling and assay methodology, and the approach taken to data analysis. Better defining these information needs and criteria of acceptability of pharmacokinetic-pharmacodynamic (PK-PD) studies should contribute to improving the quantity, relevance and quality of these studies. A better understanding of the pharmacokinetic properties of antimalarials and a more clear definition of what constitutes "therapeutic drug levels" would allow more precise use of the term "antimalarial resistance", as it would indicate when treatment failure is not caused by intrinsic parasite resistance but is instead the result of inadequate drug levels. The clinical pharmacology component of the WARN database can play a pivotal role in monitoring accurately for true antimalarial drug resistance and promptly correcting sub-optimal dosage regimens to prevent these contributing to the emergence and spread of antimalarial resistance.