| 1. |
- Singtoroj, T, et al.
(författare)
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A new approach to evaluate regression models during validation of bioanalytical assays
- 2006
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Ingår i: J Pharm Biomed Anal. - : Elsevier BV. ; 41:1, s. 219-227
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Tidskriftsartikel (refereegranskat)abstract
- The quality of bioanalytical data is highly dependent on using an appropriate regression model for calibration curves. Non-weighted linear regression has traditionally been used but is not necessarily the optimal model. Bioanalytical assays generally benefit from using either data transformation and/or weighting since variance normally increases with concentration. A data set with calibrators ranging from 9 to 10000 ng/mL was used to compare a new approach with the traditional approach for selecting an optimal regression model. The new approach used a combination of relative residuals at each calibration level together with precision and accuracy of independent quality control samples over 4 days to select and justify the best regression model. The results showed that log-log transformation without weighting was the simplest model to fit the calibration data and ensure good predictability for this data set.
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| 2. |
- Tärning, Joel, 1977, et al.
(författare)
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Development and validation of an automated solid phase extraction and liquid chromatographic method for the determination of piperaquine in urine
- 2006
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Ingår i: J Pharm Biomed Anal. - : Elsevier BV. ; 41:1, s. 213-218
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Tidskriftsartikel (refereegranskat)abstract
- A sensitive and specific bioanalytical method for determination of piperaquine in urine by automated solid-phase extraction (SPE) and liquid chromatography (LC) has been developed and validated. Buffered urine samples (containing internal standard) were loaded onto mixed phase (cation-exchange and octylsilica) SPE columns using an ASPEC XL SPE robot. Chromatographic separation was achieved on a Chromolith Performance RP-18e (100 mm x 4.6 mm I.D.) LC column with phosphate buffer (pH 2.5; 0.1 mol/L)-acetonitrile (92:8, v/v). Piperaquine was analysed at a flow rate of 3 mL/min with UV detection at 347 nm. A linear regression model on log-log transformed data was used for quantification. Within-day precision for piperaquine was 1.3% at 5000 ng/mL and 6.6% at 50 ng/mL. Between-day precision for piperaquine was 3.7% at 5000 ng/mL and 7.2% at 50 ng/mL. Total-assay precision for piperaquine over 4 days using five replicates each day (n = 20) was 4.0%, 5.2% and 9.8% at 5000, 500 and 50 ng/mL, respectively. The lower limit of quantification (LLOQ) was set to 3 ng/mL using 1 mL of urine, which could be lowered to 0.33 ng/mL when using 9 mL of urine and an increased injection volume.
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| 3. |
- Tärning, Joel, 1977, et al.
(författare)
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Pitfalls in estimating piperaquine elimination
- 2005
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Ingår i: Antimicrob Agents Chemother. ; 49, s. 5127-8
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Tidskriftsartikel (refereegranskat)abstract
- By using a sensitive new assay, the terminal elimination half-life of the antimalarial piperaquine in a healthy volunteer was estimated to be 33 days, which is longer than estimated previously. This result illustrates the importance of extended sampling duration and sensitive assay methodologies in characterizing the disposition of slowly eliminated antimalarial drugs.
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| 4. |
- Tärning, Joel, 1977, et al.
(författare)
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Population pharmacokinetics of piperaquine after two different treatment regimens of dihydroartemisinin-piperaquine in patients with Plasmodium falciparum malaria in Thailand.
- 2008
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Ingår i: Antimicrobial Agents and Chemotherapy. - 0066-4804. ; 52:3, s. 1052-61
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Tidskriftsartikel (refereegranskat)abstract
- The population pharmacokinetics of piperaquine in adults and children with uncomplicated Plasmodium falciparum malaria treated with two different dosage regimens of dihydroartemisinin-piperaquine were characterized. Piperaquine pharmacokinetics in 98 Burmese and Karen patients aged 3 to 55 years were described by a two-compartment disposition model with first-order absorption and interindividual random variability on all parameters and were similar with the three- and four-dose regimens. Children had a lower body weightnormalized oral clearance than adults, resulting in longer terminal elimination half-lives and higher total exposure to piperaquine (area under the concentration-time curve from 0 to 63 days [AUCday 0–63]). However, children had lower plasma concentrations in the therapeutically relevant posttreatment prophylactic period (AUCday 3–20) because of smaller body weight-normalized central volumes of distribution and shorter distribution half-lives. Our data lend further support to a simplified once-daily treatment regimen to improve treatment adherence and efficacy and indicate that weight-adjusted piperaquine doses in children may need to be higher than in adults.
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