Biomedical subjects
Publications and source records attributed to Y Bergqvist.
During determination of chloroquine (CQ) and its main metabolite desethylchloroquine (CQM) in blood samples applied to filter paper, we observed contamination of the paper by CQ. CQ and CQM in the dried spots were analyzed with two different high performance liquid chromatographic methods. The identity of the contamination was confirmed as CQ with mass spectrometry.
The kinetics of chloroquine and its major metabolite desethylchloroquine were studied in patients with rheumatoid disease after single oral doses of chloroquine phosphate corresponding to 150 and 300 mg chloroquine base. The findings strengthen the previous finding that the disposition of chloroquine involves rate limiting steps.
Pyrimethamine was extracted as a base, and sulphadoxine simultaneous as an ion pair with tetrabutyl-ammonium into methylene chloride. After re-extraction into an acidic aqueous phase separation of the drugs was performed by reversed-phase high performance liquid chromatography using Nucleosil C-18 as the support and acetonitrile-phosphate buffer pH 5.5 (28 + 72) as the mobile phase with tetrabutyl-ammonium as counter ion. Photometric detection at 240 nm was used for both substances. The within-day precision of the method was 5 to 10% for pyrimethamine within 50 to 1000 nmol/l (13 to 250 ng/ml) and for sulphadoxine 3 to 6% within 50 to 1000 mumol/l (16 to 310 micrograms/ml) in plasma. The method is suitable for simultaneous determination of plasma levels of pyrimethamine and sulphadoxine after therapeutic doses of Fansidar.
A new straightforward photometric method for the assay of the antimalarial drug chloroquine and its metabolites in urine is described. The method involves an ion-pair extraction procedure with dichloromethane using the acid-base indicator bromthymol blue as counter-ion. The ion pair formed with chloroquine in the organic phase is yellow, and absorbance is measured at lambda = 410 nm using a filter photometer. The absorbance is a linear function of concentration up to 400 mumol/l (120 mg/l) chloroquine. The method is suitable for the determination of chloroquine and its metabolites in urine down to a limiting concentration of about 10 mumol/l (3 mg/l). Additionally, the method is suitable for semiquantitative visual estimation of the concentration of chloroquine in urine. A single dose of 5 mg/kg chloroquine base could be determined in urine from two volunteers for at least 8 days after administration of the drug. The results obtained for the analysis of chloroquine and its metabolites with the colorimetric method described here correlate well with those obtained using high performance liquid chromatography.
A gas chromatographic method for the simultaneous determination of therapeutic levels of chloroquine, and the metabolites deethyl chloroquine and bideethyl chloroquine in human whole blood, plasma and urine has been developed by use of the capillary column technique. The analytes were extracted as bases with n-hexane-1-pentanol (90:10) and re-extracted into an acidic aqueous phase. After a further extraction to a small volume of chloroform, the substances were injected by the falling needle technique onto a fused-silica capillary column followed by nitrogen-selective detection. Limits of determination using 2 ml of the sample were found to be 10 nmol/l (3 ng/ml) for chloroquine and deethyl chloroquine and 30-40 nmol/l (10 ng/ml) for bideethyl chloroquine with a coefficient of variation of less than 15%. The precision of the method at the 100 nmol/l level was about 4% (n = 8) for chloroquine.
The kinetics and disposition of chloroquine (CQ) and its metabolite monodesethylchloroquine (CQM) were investigated in 5 healthy volunteers after incremental (150-300-600mg CQ base) single oral doses of CQ. The analytical method used (HPLC and fluorescence detection) is the most sensitive known method for CQ and CQM. Plasma and whole blood concentrations of CQ, CQM and a third metabolite, bidesethylchloroquine (CQMM), were determined. The kinetics of CQ was found to be unique. The best fit was obtained by a multicompartmental model. The biological half-life appeared to be between 30-60 days; the volume of distribution (Vd) was approximately 8001/kg, and the clearance approximately 11/h/kg when calculated from plasma data. The whole blood concentrations were approximately 8-10 times higher than in plasma, and consequently the Vd and whole blood clearance were approximately 10 times lower. The kinetics changed as the dose was increased. An indication of capacity-limited steps in CQ disposition was found, as the rate constants decreased even though the clearance remained the same. The intrinsic half-life of CQM was 1/4 of that of CQ, but was prolonged after the highest dose of CQ. The present knowledge of CQ kinetics could provide a basis for revision of current dosage regimens in malaria suppression and rheumatoid disease to ensure efficacious and safe therapy.
We evaluated the effect on drug concentration of the duration of sample storage in three different tubes for blood collection: SST (Becton Dickinson), AutoSep (Terumo), and Microvette (Sarstedt), all of which contain an inert barrier (e.g., gel) for cleaner separation of serum from coagulum during centrifugation. With two of the tubes (SST and AutoSep) we examined samples taken from patients undergoing treatment with phenobarbital, phenytoin, and carbamazepine. We found significant decrease in the drug, concentration after 24 h with the serum standing over the gel barrier in the SST tubes for phenobarbital and both the SST and AutoSep tubes for carbamazepine. Adding aqueous drug solutions or serum samples supplemented with the above drugs in therapeutic concentrations to the three types of tubes resulted in a more pronounced decrease of concentration in the SST and Auto-Sep tubes than in the Microvette tubes.
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The amount of chloroquine and desethyl-chloroquine was determined in samples of total blood and in blood cell fractions from three normal subjects after one oral dose of 1000 mg of chloroquine diphosphate. About 70-85% of the total whole blood content of chloroquine and its metabolite desethyl-chloroquine were recovered in blood cells isolated from whole blood, indicating that these compounds have a high cell/plasma concentration ratio. They were mainly present in thrombocytes and granulocytes. A study of 40 patients taking chloroquine regularly as a treatment for rheumatoid arthritis showed significantly higher concentrations of chloroquine and desethyl-chloroquine in serum than in plasma. The concentration of chloroquine was about two times higher in serum than in plasma and for desethyl-chloroquine the concentration was about four times higher in serum than in plasma. These differences may be explained by a release of chloroquine and desethyl-chloroquine from thrombocytes during the coagulation of blood. The practical implication of the results is that the samples taken for chloroquine determination must be clearly identified as serum or plasma.
The steady state disposition of chloroquine and its major metabolites, monodesethyl and bidesethyl chloroquine, were determined in 6 patients on long-term treatment for rheumatic disease with 99-155 mg base/day. The total body clearance of chloroquine was 0.35 l/kg/h and that of its metabolites was much higher. The renal clearance was the same for all compounds measured, approximately equal to 0.1 l/kg/h. Currently recommended dosage schedules appear to be too high in certain cases.
A gas chromatographic method for the simultaneous determination of chloroquine and its metabolite desethylchloroquine in plasma described. Chloroquine, desethylchloroquine and internal standard are extracted as bases with n-hexane-pentanol (90:10) and then back-extracted to an acid aqueous phase. The aqueous phase is made alkaline and after re-extraction into chloroform and evaporation of the chloroform, acylation with trifluoroacetic anhydride is performed. Separation is achieved on an OV-17 column at 250 degrees C. Chloroquine and desethylchloroquine can be determined down to 0.1-0.2 mumol/l (30-60 ng/ml), with a coefficient of variation of 12%, using a nitrogen detector. The method shows good correlation (r = 0.98) with a recently developed liquid chromatographic method.
A method has been developed for the rapid quantitative analysis of chloroquine and its metabolite desethyl-chloroquine in plasma, blood and urine using high-performance liquid chromatography. An ethylene dichloride extract of the alkalinized biological samples was extracted with dilute acid and chromatographed on a reversed-phase column. Phosphate buffer in acetonitrile was used as the mobile phase with perchlorate as the counter-ion. Ultraviolet absorption at 254 or 340 nm or fluorescence detection was used. The fluorescence spectra and the fluorescence quantum yield of the substances were determined. Chloroquine and desethyl-chloroquine concentrations in the range of 10 nmol/l (UV-detection) and of 0.5 nmol/l (fluorescence detection) could be accurately measured with a relative standard deviation of 12%. The method should be adequate for therapeutic and pharmacokinetic studies.
A new method for determination of palmitic acid in amniotic fluid was developed. The dipalmitoyl lecithin was hydrolysed, and after extraction the palmitic acid was flash methylated in the injector of the gas chromatograph. The between batch coefficient of variation was 6.0% at 40 and 70 mumol/l of palmitic acid concentrations in 500 microliters amniotic fluid. The accuracy of the method was demonstrated by linearity, recovery and correlation studies. The correlation coefficient was 0.98 between the new and bortrifluoride methylating method. The concentrations of lecithin and palmitic acid in amniotic fluid showed a correlation coefficient of 0.97. If the concentration of palmitic acid falls below 80 mumol/l respiration distress syndrome is likely. The new method was simple and easy to carry out and could be adjusted for haemoglobin contamination of the amniotic fluid. It was concluded that the determination of palmitic acid in amniotic fluid was a reliable method for the assessment of fetal lung maturity that could replace the determination of lecithin concentration.
The most common method for determination of haemoglobin is the cyanmet-haemoglobin method which is recommended by the International Committee for Standardization in Haematology (ICSH). Determination of haemoglobin is one of the most used methods in hospital laboratories. One disadvantage with the method is the use of cyanide in the reagent, which demands cautious preparation and use. The intention of our investigation was to replace the cyanide reagent for Hemalog-8 with a reagent not containing cyanide. It is shown that the change of reagent did not influence the results of the analysis.
88 asymptomatic Tanzanian schoolchildren with Plasmodium falciparum parasitaemia were given all, half or quarter of the recommended standard therapeutic dose of sulfadoxine-pyrimethamine (Fansidar). All children cleared the parasites by day 3 and all remained negative during 28-42 days of follow-up. All 32 successful in vitro micro-tests showed full sensitivity. High performance liquid chromatographic methods were applied for drug determinations. Using 100 microliter capillary blood dried on filter paper for sulfadoxine determination the inter-individual variation during follow-up of the standard dose group was 2-4 fold and the median half life was 8.9 d. Sulfadoxine concentrations in the half and quarter dose groups were roughly proportional to those in the standard dose group. The median whole blood to plasma concentration ratio for sulfadoxine was 0.72 and the correlation coefficient 0.95. There was only a weak correlation (r=0.46) between plasma concentrations of sulfadoxine and pyrimethamine. The uniform efficacy of sulfadoxine-pyrimethamine in vivo, even when reduced doses were used, makes this combination a good alternative for treatment of P. falciparum in Tanzania.
The plasma concentrations of sulfadoxine, pyrimethamine, mefloquine and its major metabolite were determined in 18 healthy male volunteers who had regularly taken either 500 mg of sulfadoxine and 25 mg of pyrimethamine (Fansidar) weekly or 250 mg mefloquine regularly every 14 d during 6 months for malaria prophylaxis. The mean trough concentrations of sulfadoxine, pyrimethamine and mefloquine were 194, 0.28 and 1.48 mumol/litre and the mean half lives were 7.7, 4.2 and 25 d respectively. The variation in area under the curve for the 3 drugs was only 2-3 fold. The findings do not indicate that drug accumulation or induction of metabolism occurred during long-term usage.