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  • 1.
    Blessborn, Daniel
    Högskolan Dalarna, Akademin Utbildning och humaniora, Kemi.
    Development of Analytical Methods for the Determination of Antimalarials in Biological Fluids2009Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    The aim of this thesis was to develop analytical methods for measuring antimalarial drugs in biological fluids. Solid phase extraction (SPE) was used for the enrichment and purification of the drugs. Automatic extraction procedures using a SPE robot were developed to reduce the workload for the analyst and to minimize variations in the extraction procedure. Liquid chromatography (LC) with either UV or mass spectrometric (MS) detection was used to determine sample concentrations. Determination of Pyronaridine in whole blood utilised a weak cation exchanger to extract Pyronaridine from blood. To improve LC separation between Pyronaridine and the internal standard, ion-pairing was utilized. For the simultaneous quantification of the highly lipophilic Atovaquone and the strong basic drug Proguanil with metabolites, a novel mixed mode solid phase extraction column was used. It combines the properties of a carboxylic acid (CBA) column and a non-polar octyl-silica (C8) column to extract the compounds from plasma; it also required a gradient LC separation. Stability is an important factor when developing new methods. A new approach was used to evaluate the stability of Amodiaquine in blood and plasma. This included the use of a stability marker, a stable compound which was added together with Amodiaquine when preparing the stability samples. This eliminated between-run variations and variations associated with preparation of new stock solutions. Lumefantrine (LF) is one of the active components in a new drug combination recommended by the World Health Organization as a replacement for older drugs which have lost their effect. The first of the two methods described for this compound is the determination of LF and a possible metabolite in plasma with a calibration range suitable for pharmacokinetic studies. In the second method, a capillary sampling technique is used where the blood is dried on a sampling paper and sent to the laboratory where the extraction and determination of LF concentrations take place. This method facilitates sample collection and will enable drug efficacy studies conducted in rural settings. To monitor a current change in treatment policy and self medication, a screening assay was developed. Its purpose is to be a complement to interviewing patients about their previous medication (in the previous few weeks) and to detect some of the more common drugs which might have been used.

  • 2.
    Blessborn, Daniel
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Kemiteknik.
    Römsing, Susanne
    Högskolan Dalarna, Akademin Utbildning, hälsa och samhälle, Kemi.
    Bergqvist, Yngve
    Högskolan Dalarna, Akademin Utbildning, hälsa och samhälle, Medicinsk vetenskap.
    Lindegardh, Niklas
    Assay for screening for six antimalarial drugs and one metabolite using dried blood spot sampling, sequential extraction and ion-trap detection2010Inngår i: Bioanalysis, ISSN 1757-6180, E-ISSN 1757-6199, Vol. 2, nr 11, s. 1839-1847Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: More parasites are becoming resistant to antimalarial drugs, and in many areas a change in first-line drug treatment is necessary. The aim of the developed assay is to help determine drug use in these areas and also to be a complement to interviewing patients, which will increase reliability of surveys.

    Results: This assay detects quinine, mefloquine, sulfadoxine, pyrimethamine, lumefantrine, chloroquine and its metabolite desethylchloroquine in a 100-mu l dried blood spot. Most of the drugs also have long half-lives that make them detectable at least 7 days after administration. The drugs are extracted from the dried blood spot with sequential extraction (due to the big differences in physicochemical properties), solid-phase extraction is used as sample clean-up and separation is performed with gradient-LC with MS ion-trap detection.

    Conclusion: Detection limits (S/N > 5:1) at 50 ng/ml or better were achieved for all drugs except lumefantrine (200 ng/ml), and thus can be used to determine patient compliance. A major advantage of using the ion-trap MS it that it will be possible to go back into the data and look for other drugs as needed.

  • 3. Jansson-Löfmark, Rasmus
    et al.
    Römsing, Susanne
    Högskolan Dalarna, Akademin Utbildning, hälsa och samhälle, Kemi.
    Albers, E
    Ashton, M
    Determination of eflornithine enantiomers in plasma by precolumn derivatization with o-phthalaldehyde-N-acetyl-L-cysteine and liquid chromatography with UV detection2010Inngår i: BMC Biomedical chromotography, ISSN 0269-3879, E-ISSN 1099-0801, Vol. 24, nr 7, s. 768-773Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A bioanalytical method for indirect determination of eflornithine enantiomers in 75?µL human plasma has been developed and validated. l- and d-eflornithine were derivatized with o-phthalaldehyde and N-acetyl-L-cysteine to generate diastereomers which were separated on two serially connected Chromolith Performance columns (RP-18e 100 × 4.6?mm i.d.) by a isocratic flow followed by a gradient flow for elution of endogenous compounds. The diastereomers were detected with UV (340?nm). The between-day precisions for L- and D-eflornithine in plasma were 8.4 and 2.3% at 3?µm, 4.0 and 5.1% at 400?µm, and 2.0 and 3.7% at 1000?µm. The lower limit of quantification was determined to be 1.5?µm, at which precision was 14.9 and 9.9% for L- and D-eflornithine, respectively

  • 4.
    Römsing, Susanne
    Högskolan Dalarna, Akademin Utbildning och humaniora, Kemi.
    Development and Validation of Bioanalytical Methods: Application to Melatonin and Selected Anti-Infective Drugs2010Doktoravhandling, monografi (Annet vitenskapelig)
  • 5.
    Römsing, Susanne
    et al.
    Högskolan Dalarna, Akademin Utbildning och humaniora, Kemi.
    Blessborn, Daniel
    Bergqvist, Yngve
    Högskolan Dalarna, Akademin Utbildning och humaniora, Kemi.
    Lindegardh, Niklas
    Assay for screening for six antimalarial drugs and one metabolite using dried blood spot sampling, sequential extraction and ion-trap detection2010Inngår i: Bioanalysis, ISSN 1757-6199, Vol. 2, nr 10, s. 1839-1847Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [un]

    Background: More parasites are becoming resistant to antimalarial drugs, and in many areas a change in first-line drug treatment is necessary. The aim of the developed assay is to help determine drug use in these areas and also to be a complement to interviewing patients, which will increase reliability of surveys. Results: This assay detects quinine, mefloquine, sulfadoxine, pyrimethamine, lumefantrine, chloroquine and its metabolite desethylchloroquine in a 100-µl dried blood spot. Most of the drugs also have long half-lives that make them detectable at least 7 days after administration. The drugs are extracted from the dried blood spot with sequential extraction (due to the big differences in physicochemical properties), solid-phase extraction is used as sample clean-up and separation is performed with gradient-LC with MS ion-trap detection. Conclusion: Detection limits (S/N > 5:1) at 50 ng/ml or better were achieved for all drugs except lumefantrine (200 ng/ml), and thus can be used to determine patient compliance. A major advantage of using the ion-trap MS it that it will be possible to go back into the data and look for other drugs as needed

  • 6.
    Römsing, Susanne
    et al.
    Högskolan Dalarna, Akademin Utbildning, hälsa och samhälle, Kemi.
    Lindegardh, Niklas
    Bergqvist, Yngve
    Högskolan Dalarna, Akademin Utbildning, hälsa och samhälle, Medicinsk vetenskap.
    Determination of tafenoquine in dried blood spots and plasma using LC and fluorescence detection2011Inngår i: Bioanalysis, ISSN 1757-6180, E-ISSN 1757-6199, Vol. 3, nr 16, s. 1847-1853Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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 mu l of capillary blood applied onto sampling paper and in 100 mu l 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.

  • 7. Tchaparian, E.
    et al.
    Sambol, N.C.
    Arinaitwe, E.
    McCormack, S.A.
    Bigira, V.
    Wanzira, H.
    Blessborn, Daniel
    Högskolan Dalarna, Akademin Utbildning, hälsa och samhälle, Kemi.
    Bergqvist, Yngve
    Högskolan Dalarna, Akademin Utbildning, hälsa och samhälle, Medicinsk vetenskap.
    Aweeka, F.T.
    Parikh, S.
    Population pharmacokinetics and pharmacodynamics of lumefantrine in young Ugandan children treated with artemether-lumefantrine for uncomplicated malaria2016Inngår i: Journal of Infectious Diseases, ISSN 0022-1899, E-ISSN 1537-6613, Vol. 214, nr 8, s. 1243-1251Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background. The pharmacokinetics and pharmacodynamics of lumefantrine, a component of the most widely used treatment for malaria, artemether-lumefantrine, has not been adequately characterized in young children. Methods. Capillary whole-blood lumefantrine concentration and treatment outcomes were determined in 105 Ugandan children, ages 6 months to 2 years, who were treated for 249 episodes of Plasmodium falciparum malaria with artemether-lumefantrine. Results. Population pharmacokinetics for lumefantrine used a 2-compartment open model with first-order absorption. Age had a significant positive correlation with bioavailability in a model that included allometric scaling. Children not receiving trimethoprim-sulfamethoxazole with capillary whole blood concentrations <200 ng/mL had a 3-fold higher hazard of 28-day recurrent parasitemia, compared with those with concentrations >200 ng/mL (P =. 0007). However, for children receiving trimethoprim-sulfamethoxazole, the risk of recurrent parasitemia did not differ significantly on the basis of this threshold. Day 3 concentrations were a stronger predictor of 28-day recurrence than day 7 concentrations. Conclusions. We demonstrate that age, in addition to weight, is a determinant of lumefantrine exposure, and in the absence of trimethoprim-sulfamethoxazole, lumefantrine exposure is a determinant of recurrent parasitemia. Exposure levels in children aged 6 months to 2 years was generally lower than levels published for older children and adults. Further refinement of artemether-lumefantrine dosing to improve exposure in infants and very young children may be warranted. © 2016 The Author.

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