Inequality in quality? Regional and educational differences in treatment with fluoroquinolone in urinary tract infection of 236,376 Swedish patients

BACKGROUND

In an international effort to reduce antibiotic resistance, in part suggested to be the effect of inappropriate antibiotic use, several quality indicators for outpatient antibiotic use have been proposed. In this study, geographical and educational differences in fluoroquinolone prescription in the treatment of urinary tract infection in women are presented.

METHODS

The age-adjusted ratio of women who were dispensed fluoroquinolones (ciprofloxacin or norfloxacin) among all 236,376 women dispensed any of the following antibiotics used in the treatment of lower urinary tract infection were studied: ciprofloxacin, norfloxacin, pivmecillinam, trimethoprim and nitrofurantoin. Only the first prescription during July 2006 to June 2007 was studied. Prescription data were linked to information on geographical area, marital status, country of birth and educational attainment, which allowed multivariate analysis of the importance of these factors.

RESULTS

The rate of fluoroquinolone prescription varied from 29.5% to 17.1% in the 21 regions in Sweden. Middle-aged women with ≥15 years of schooling were more often prescribed fluoroquinolones compared to those with only 9 years (OR 1.28, 95% CI 1.23 to 1.34).

CONCLUSION

Quality indicators in healthcare should be developed bearing in mind the overall level of adherence to guidelines and whether there are regional or socioeconomic or other differentials in their distribution in the population because such differentials in healthcare quality might further contribute to inequalities in health.

National surveillance of surgical-site infection through register-based analysis of antibiotic use after inguinal hernia repair

BACKGROUND

Systematic surveillance of surgical-site infections is not standard. The aim of this retrospective cohort study was to evaluate the feasibility of using existing national health registers for surveillance of postoperative antibiotic treatment suggestive of surgical-site infection.

METHODS

Data from national registers on hospital admissions and drug use were combined. Antibiotic purchases by 8856 patients subject to ambulatory care for inguinal hernia repair in Sweden during 2006 were ascertained during a 30-day interval immediately after surgery (postsurgical period) and in an 11-month control period (6 months before and 5 months after the postsurgical period).

RESULTS

The incidence of first purchases of skin and soft tissue antibiotics was 245 per 8697 person-months in the first postoperative month and 180 per 52 612 person-months in the preoperative control period, representing a 1-month risk difference of 2.4 (95 per cent confidence interval (c.i.) 2.0 to 2.7) per cent. Hence, a 1-month risk of 2.4 per cent could be attributed tentatively to the surgery. The rate of episodes with antibiotics used mainly for skin and soft tissue infection was sevenfold higher in the first postoperative month than in the control period (rate ratio 7.01, 95 per cent c.i. 5.94 to 8.27).

CONCLUSION

The risk of antibiotic treatment during the postsurgical period was of the same order of magnitude as infection rates reported in the Swedish Hernia Register and review studies. Surveillance of postoperative antibiotic use may be considered as a resource-saving surrogate marker for surgical-site infections or an indicator of inappropriate use.

Equal access to treatment? Population-based follow-up of drugs dispensed to patients after acute myocardial infarction in Sweden

BACKGROUND AND OBJECTIVE

The establishment of national guidelines is one approach to creating equity in terms of access to care, and both internationally and in Sweden, guidelines have been developed for coronary heart disease. We have analysed drug treatment in Sweden according to national guidelines after acute myocardial infarction (AMI). The aim was to investigate whether there are differences between population groups according to sex, education, country of birth and diabetes.

METHODS

Information was obtained from the Swedish Prescribed Drug Register on drugs dispensed between July and October 2005 for incident cases of AMI during the period 2003-2004 (n=28,168). Data on socio-economic and demographic conditions were included. Dispensed drugs after AMI were compared to the recommended drug treatment according to Swedish and European guidelines--acetylsalicylic acid (ASA), beta-blockers, lipid-lowering drugs and angiotensin-converting enzyme inhibitors (ACE inhibitors).

RESULTS

We found that, in general, there were only small differences between the sexes and between educational groups. The greatest differences were found in comparisons between regions of birth. In particular, foreign-born patients resident in Sweden but originally from outside the EU25 countries used fewer drugs than Swedish-born patients. The OR (odds ratio) for ASA was 0.73 [95% confidence interval (CI) 0.63-0.85], for beta-blockers, 0.72 (0.63-0.83), for lipid-lowering drugs, 0.75 (0.65-0.86) and for ACE inhibitors, 0.76 (0.67-0.86).

CONCLUSIONS

In general, we found only slight differences--or none at all--between population groups in terms of drug treatment after AMI. Only among immigrants from outside the EU25 countries was there a tendency towards a lesser use of the recommended drugs according to the national guidelines.

Simple and cost-effective liquid chromatographic method for determination of pyrimethamine in whole blood samples dried on filter paper

A cost-effective HPLC method for determination of pyrimethamine (PYR) in human whole blood samples dried on filter paper (Whatman) is reported. Trimethoprim (TMP) was used as an internal standard. Whole blood spiked with PYR was transferred (100 microl) onto filter paper and dried at room temperature. Capillary blood samples (100 microl) after ingestion of three tablets of sulfadoxine-pyrimethamine (SP) by one subject were also tested. PYR and an internal standard (IS) TMP were extracted into di-isopropyl ether as bases and then re-extracted with 150 microl mobile phase. A C-18 column was used and the mobile phase consisted of phosphate buffer (0.05 M, pH 5):acetonitrile:concentrated perchloric acid (750:300:2.5, v/v/v). The absorbances of PYR and IS were monitored at 270 nm. The limit of quantification was 40 ng/ml. The within- and between-assay coefficient of variations were <10% at the limit of quantification.

Evaluation of the quality of amodiaquine and sulphadoxine/pyrimethamine tablets sold by private wholesale pharmacies in Dar Es Salaam Tanzania

OBJECTIVE

There are several independent reports in Tanzania of treatment failures with commercially available sulphadoxine/pyrimethamine (SP) and amodiaquine (AQ) brands. The aim of this work was to assess the quality of SP and AQ tablets marketed by wholesale pharmacies in Dar Es Salaam, Tanzania.

METHODS

All eight wholesale pharmacies authorized to import medicines and located in Dar Es Salaam were included in the study. From each pharmacy, samples of all SP and AQ brands available at the time of sampling were bought, provided they had a shelf-life of at least 1 year. A sample was either an intact box of 100 tablets or a sealed tin of 100 tablets. To ensure blinding, 30 tablets of each sample were removed from their original containers, coded and sent to the quality control laboratory for analysis. The name, strength, batch number, manufacturer and the expiry dates of the tablets were recorded. In total 15 AQ and 18 SP samples were collected. Identity, assay for content of active ingredients and dissolution assay were performed as described in the United States Pharmacopoeia (USP).

RESULTS

All samples passed the identity test. Among the AQ samples collected, two of 15 (13%) failed the dissolution test but all passed the assay for content, whereas two of 18 (11%) and eight of 18 (44%) SP samples failed the assay for content and dissolution tests, respectively. None of the pharmacies stocked all AQ and SP brands.

CONCLUSION

This work reveals the availability of poor quality antimalarial drugs on the Tanzanian market. Use of substandard drugs could have serious clinical consequences to patients. The results support the need for continuous monitoring of the quality of marketed drugs to ensure safety and efficacy of these products in the treatment of malaria in endemic areas.

High-performance liquid chromatographic method for determination of amodiaquine, chloroquine and their monodesethyl metabolites in biological samples

A high-performance liquid chromatographic method for determination of amodiaquine (AQ), desethylamodiaquine (DAQ), chloroquine (CQ) and desethylchloroquine (DCQ) in human whole blood, plasma and urine is reported. 4-(4-Dimethylamino-1-methylbutylamino)-7-chloroquinoline was used as internal standard. The drugs and the internal standard were extracted into di-isopropyl ether as bases and then re-extracted into an acidic aqueous phase with 0.1 M phosphate buffer at pH 4.0 for AQ samples and at pH 2.5 for CQ filter paper samples. A C(18) column was used and the mobile phase consisted of methanol-phosphate buffer (0.1 M, pH 3)-perchloric acid (250: 747.5:2.5, v/v). The absorbance of the drugs was monitored at 333 nm and no endogenous compound interfered at this wavelength. The limit of quantification in whole blood, plasma and urine was 100 nM for AQ and DAQ (sample size 100 microliter) as well as for CQ and DCQ in blood samples dried on filter paper. For 1000 microliter AQ and DAQ samples, the limit of quantification was 10 nM in all three biological fluids. The within-assay and between-assay coefficients of variations were always <10% at the limits of quantification. Plasma should be preferred for the determination of AQ and DAQ since use of whole blood may be associated with stability problems.

Simultaneous determination of quinine and four metabolites in plasma and urine by high-performance liquid chromatography

The determination of quinine, (3S)-3-hydroxyquinine, 2'-quininone and (10R)- and (10S)-10,11-dihydroxydihydroquinine in plasma and urine samples is described. This is the first time the R and S configurations have been correctly assigned to the two metabolites of 10,11-dihydroxyquinine. One hundred microliter-plasma samples were protein precipitated with 200 microl cold methanol. Urine samples were 10-100 x diluted and then directly injected into the HPLC. A reversed-phase liquid chromatography system with fluorescence detection and a Zorbax Eclipse XDB phenyl column and gradient elution was used. The within and between assay coefficients of variation of the method for quinine and its metabolites in plasma and urine was less than 13%. The lower limit of quantitation was in the range of 0.024-0.081 microM.

[Clostridium difficile-associated diarrhea--a growing problem in geriatric care]

From 1994 to 1998 the incidence of Clostridium difficile-associated diarrhoea (CDAD) in the Department of Geriatric Medicine, Huddinge University Hospital increased from 0.5% to 2.2% of all admissions. Corresponding figures for the whole hospital were 0.3% and 0.6%, respectively. The increase in CDAD at the Department of Geriatric Medicine was parallel with a more than doubled consumption of antibiotics. All geriatric patients with CDAD had been treated with antibiotics before onset of diarrhoea. Out of the antibiotic prescriptions 48% were a cephalosporin (mainly cefuroxim). In a matched reference group of geriatric patients 51% had been treated with antibiotics during the hospital stay. The patients with CDAD spent 27 +/- 14 days in hospital as compared to 13 +/- 9 days (P < 0.05) in the reference population.

Comparative in vitro and in vivo study of a sugar-coated chloroquine preparation marketed in Tanzania versus an ordinary brand

OBJECTIVE

To investigate the absorption and the quality of a sugar-coated chloroquine (CQ) marketed in Tanzania.

METHOD

Twenty healthy volunteers were randomised to take either the test brand (group A) or a control chloroquine phosphate (group B). Each subject received 300 mg chloroquine base. Whole blood dried on filter papers were collected at time 0 and at 15 and 30 min and at 1, 2, 3, 4, 6, 8, 24, 36, 48, 72 and 168 h after drug intake. Urine samples were collected at time 0, 0-4 h, 4-8 h, 8-24 h, 24-48 h and 48-72 h after drug administration. In an in vitro study, six tablets from each of the two CQ preparations were checked for the amount of active drug contained in each tablet and their dissolution rates.

RESULTS

The blood concentration Area Under the Curve (AUC) of group B was about 10% larger than that of group A. The total amounts of CQ plus deethylchloroquine excreted with the urine during the 72-h study period were 5% for group A and 6% for group B. None of the pharmacokinetic parameters were significantly different between the two groups. All the tablets contained the labelled amount of chloroquine; however, one tablet from the test drug failed to fulfil the required dissolution rate.

CONCLUSION

We found no major difference between the AUCs of the two CQ preparations, but the sugar-coated brand has shown to have variable dissolution rate.

Slow chloroguanide metabolism in Tanzanians compared with white subjects and Asian subjects confirms a decreased CYP2C19 activity in relation to genotype

BACKGROUND

We have previously found decreased CYP2C19 activity in Tanzanians tested with mephenytoin and omeprazole in relation to genotype when compared with white and Asian subjects.

OBJECTIVE

We investigated the impact of CYP2C19 genotype and phenotype on chloroguanide (INN, proguanil) metabolism to its metabolites cycloguanil and 4-chlorophenylbiguanide.

METHODS

A single oral chloroguanide dose was given to 25 healthy Tanzanian subjects with CYP2C19 genotypes (CYP2C19*1, CYP2C19*2, and CYP2C19*3). Homozygous wild-type and mutated genotype groups were chosen randomly, but the heterozygous genotype group was chosen with a range in phenotype. We used a novel HPLC method for drug determination.

RESULTS

Pharmacokinetics of chloroguanide did not differ between groups. Maximum plasma concentration (Cmax) and area under the plasma concentration versus time [AUC(0-infinity)] for cycloguanil was significantly lower (t test P < .05) in the homozygously mutated group compared with the homozygously wild-type group. There were similar significant group differences of median urinary excretion. The chloroguanide/cycloguanil ratio closely correlated (r(s) = .87) with omeprazole metabolic ratio, confirming that Tanzanian subjects are generally slower CYP2C19 metabolizers. It also confirms that CYP2C19 genotype and phenotype predicts cycloguanil formation. In addition, a 3-hour plasma sample metabolic ratio also seems to be a proper time for omeprazole phenotyping in Tanzanian subjects. Because the plasma concentrations of cycloguanil and 4-chlorophenylbiguanide covary (r(s) = .89), it is now suggested that their formation be catalyzed by the same enzyme (ie, CYP2C19) through a common intermediate, the structure of which is also presented.

CONCLUSIONS

As shown in an earlier study, also with a third substrate, Tanzanians have a lower capacity to form cycloguanil than white and Asian subjects. Individuals with two mutated alleles have lower metabolic capacity than individuals with two wild-type alleles or individuals in the heterozygous group, which may lead to chloroguanide therapeutic failure. This knowledge should be important when selecting appropriate patients and doses of chloroguanide in different populations.

Investigations of the metabolites of the trypanocidal drug melarsoprol

BACKGROUND

Melarsoprol remains the first-choice drug for trypanosomiasis (human African sleeping sickness). To contribute to the sparse pharmacologic data and to better understand the cause of the frequent serious adverse reactions, we investigated the metabolism of this 50-year-old organoarsenic compound.

RESULTS

The half-life of melarsoprol determined by HPLC was <1 hour compared with 35 hours determined by bioassay and atomic absorption spectroscopy, indicating the existence of active metabolites. One metabolite, melarsen oxide, was identified by ultraviolet HPLC after incubation of melarsoprol with microsomes. The maximum plasma concentration of melarsenoxide was reached 15 minutes after administration; the clearance was 21.5 mL/min/kg and the half-life of free melarsen oxide was 3.9 hours. Either melarsen oxide or a yet-undiscovered active metabolite is irreversibly bound to proteins, as shown by ultrafiltration, precipitation experiments, and atomic absorption spectroscopy. Because of the poor pharmaceutical properties of melarsoprol, the therapeutic potential of melarsen oxide was investigated. In a rodent model of acute infection, 20 of 20 mice were cured (0.1 to 1 mg/kg intravenously or 2.2 mg/kg intraperitoneally). In a rodent model of central nervous system infection, five of six mice survived for more than 180 days (5 mg/kg intravenously), indicating a sufficient melarsen oxide penetration across the blood-brain barrier.

CONCLUSION

The prospects for the future of trypanosomiasis treatment are deplorable. Investigations on the improvement of the use of the old drugs are therefore required. The results of this study may build a basis for further research on the cause of severe adverse reactions.

The roles of cytochrome P450 3A4 and 1A2 in the 3-hydroxylation of quinine in vivo

OBJECTIVE

To investigate the roles of CYP3A4 and CYP1A2 in the 3-hydroxylation of quinine in vivo.

METHODS

In a randomized, three-way crossover study, nine healthy Swedish volunteers received single oral doses of quinine hydrochloride (500 mg), quinine hydrochloride (500 mg) plus ketoconazole (100 mg twice daily for 3 days), and quinine hydrochloride (500 mg) plus fluvoxamine (25 mg twice daily for 2 days) on three different occasions. Blood and urine samples were collected before quinine intake and up to 96 hours thereafter. Plasma and urine samples were analyzed for both quinine and its main metabolite 3-hydroxyquinine with HPLC methods.

RESULTS

Coadministration with ketoconazole (which inhibits CYP3A4) decreased the mean apparent oral clearance of quinine significantly (P < .001) by 31% (from 8.7 to 6.0 L/h), whereas coadministration with fluvoxamine (which inhibits CYP1A2 and to some extent CYP2C19) had no significant effect (P > .05) on the mean apparent oral clearance of quinine. Coadministration with ketoconazole also decreased the mean area under the plasma concentration versus time curve (AUC) of 3-hydroxyquinine (from 28.4 to 19.7 micromol x h x L(-1); P < .001), whereas coadministration with fluvoxamine increased 3-hydroxyquinine AUC significantly (from 28.4 to 30.2 micromol x h x L(-1); P < .05).

CONCLUSION

Cytochrome P450 3A4 is important for the 3-hydroxylation of quinine in vivo. On the other hand, CYP1A2 had no significant effect on this metabolic pathway.

Discrepancy in plasma melarsoprol concentrations between HPLC and bioassay methods in patients with T. gambiense sleeping sickness indicates that melarsoprol is metabolized

OBJECTIVE

With the use of a specific high-performance liquid chromatography (HPLC) method and a bioassay which determines trypanocidal activity, concentrations of melarsoprol were assessed in plasma, urine and cerebrospinal fluid (CSF) from 8 patients with late-stage Trypanosoma gambiense sleeping sickness. The aim was to unravel to what extent the bioassay codetermines biologically active metabolites of melarsoprol.

METHODS

Subjects were given one dose of melarsoprol i.v. per day for 4 days (1.2, 2.4, 3.0-3.6, 3.0-3.6 mg per kg b.w., respectively). Plasma samples were obtained before the first melarsoprol injection, immediately after and at 1 h, 24 h and 5 days after the 4th injection. Urine was collected before melarsoprol therapy and at 24 h after the 4th injection. CSF samples were taken once before treatment and at 24 h after the 4th injection.

RESULTS

HPLC analyses showed that plasma concentrations immediately after the 4th injection varied from 2200 to 15,900 nmol/l; dropping to 0-1800 nmol/l at 1 h; and to undetectable levels at 24 h. In urine small amounts of melarsoprol were recovered. Melarsoprol could not be detected in CSF by HPLC. Immediately after injection, bioassay analyses showed plasma concentrations of the same magnitude as HPLC assays but at 1 h they were 4-65-fold higher than the levels assessed by HPLC. Even 24 h and 5 days after the 4th injection there was significant but decreasing activity. Urine levels were 40-260-fold higher than the measured HPLC concentrations, whereas there was low but detectable activity in CSF.

CONCLUSION

Results indicate that melarsoprol is rapidly eliminated from plasma. The significant trypanocidal activity determined by bioassay and simultaneous low or undetectable levels of melarsoprol assayed by HPLC indicate that the compound is transformed into metabolites with parasiticidal activity.

High-performance liquid chromatographic method for the determination of the major quinine metabolite, 3-hydroxyquinine, in plasma and urine

The determination of 3-hydroxyquinine in urine and plasma samples is described. Extraction was performed using a mixture of toluene-butanol (75:25, v/v), followed by back-extraction into the mobile phase, which consisted of 0.1 M phosphate buffer, acetonitrile, tetrahydrofuran and triethylamine. A reversed-phase liquid chromatography system with fluorescence detection and a CT-sil C18 column were used. The within-assay coefficient of variation of the method was 2% at the higher concentration values in plasma, 2.95 microM, 4% at 227 nM and 9% at the lower limit of quantitation, 4.5 nM. In urine, the coefficient of variation was 11% at the lower concentration, 227 nM and was 3% at 56.8 microM. The between-assay coefficient of variation was 4% at the low concentration (5.1 nM) in plasma, 2% at 276.8 nM and 3% at 1.97 microM. In urine, the between assay coefficient of variation was 4% at 204.6 nM, 3% at 5.12 microM and 2% at 56.8 microM.

A malariometric survey in a rural community in the Muheza district, Tanzania: age profiles in the development of humoral immune responses

A malariometric survey was carried out in a rural community situated in a malaria holoendemic endemic area of Tanzania. A random sample (n = 228) of different age groups was taken to elucidate the association between anti-Pf155/RESA and anti-Pf332 antibody responses and classical malaria indices. Parasitaemia, fever, splenomegaly, haematocrit and antimalarial consumption were assessed. Antibody responses against Pf155/RESA and Pf332 peptides were determined by ELISA. The age profiles of parasite density, splenomegaly, fever, haematocrit values and prevalence of antibody responses indicated intensive malaria exposure and the highest impact of malaria in small children. Forty-five percent of the study population had detectable chloroquine and desethyl-chloroquine blood levels, and the highest frequency and concentrations were recorded in the 12-23 months old. There was no significant association between the presence of drug and parasite density in the different age groups, although in the < 15 years old there was lower parasite prevalence among the children positive for drug in their blood (P < 0.05). High prevalence of antibody responses to all antigens was observed already at an early age, but the mean anti-Pf155/RESA and anti-Pf332 antibody levels increased significantly only in the adult group (P < 0.01). Significantly lower mean parasite densities were observed in high responders to Pf155/RESA and Pf332 peptides for the > or = 10 years old. For the 1-9 years, a similar difference was only observed in the high responders to Pf332. For the whole material, anti-Pf155/RESA and anti-Pf332 antibody levels correlated positively with age. When the effect of age was allowed for in analysing the relationship between parasite density and antibody level against the different antigens, a significant negative correlation was found only with regard to Pf332 in the > = 10 years age group. These results suggest that anti-Pf332 antibodies appear to be a better indicator for antiparasitic immunity, but both antigens are important for immune protection.

Liquid chromatography-tandem mass spectrometry applied to a study of the metabolism of pentamidine. Discussion of possibilities and problems

Tandem mass spectrometry is usually employed to achieve rapid screening or structure elucidation. We have used liquid chromatography-tandem mass spectrometry in order to detect metabolites of the antiprotozoal drug pentamidine in urine. Samples of urine from rat and man were analysed both by direct injection and after solid-phase extraction. The present paper discusses advantages and disadvantages of using direct injection of urine samples, optimization of chromatographic conditions with regard to the performance of the mass spectrometer, automation and stability of the entire system.

Determination of melarsoprol in biological fluids by high-performance liquid chromatography and characterisation of two stereoisomers by nuclear magnetic resonance spectroscopy

The analysis of melarsoprol in whole blood, plasma, urine and cerebrospinal fluid is described. Extraction was made with a mixture of chloroform and acetonitrile followed by back-extraction into phosphoric acid. A reversed-phase liquid chromatography system with ultraviolet detection was used. The relative standard deviation was 1% at concentrations around 10 mumol/l and 3-6% at the lower limit of determination (9 nmol/l in plasma, 93 nmol/l in whole blood, 45 nmol/l in urine and 10 nmol/l in cerebrospinal fluid). Melarsoprol is not a stable compound and samples to be stored for longer periods of time should be kept at -70 degrees C. Plasma samples can be stored at -20 degrees C for up to 2 months. Chromatography showed that melarsoprol contains two components. Using nuclear magnetic resonance spectroscopy the two components were shown to be diastereomers which slowly equilibrate by inversion of the configuration at the As atom.

Chloroquine blood concentrations and malaria prophylaxis in Tanzanian women during the second and third trimesters of pregnancy

OBJECTIVE

Routine malaria prophylaxis with chloroquine (CQ) is recommended to pregnant semi-immune women in several countries in Africa. The dosage is empirically based. We investigated whether blood CQ concentrations and apparent oral blood clearance (CL/F) change during the course of pregnancy. We also studied whether malaria parasites could be detected together with low CQ blood levels.

METHODS

Forty nine semi-immune Tanzanian women were recruited in the 16th week of pregnancy. They were given 310 mg oral CQ base once per week as prophylaxis during the whole pregnancy. Capillary blood samples were taken for analysis of CQ before treatment and at weeks 26 and 36. Blood samples were dried on filter paper and analysed by HPLC. Blood was also drawn to detect occurrence of malaria parasites.

RESULTS

A total of 25 women fulfilled the sampling schedule. CL/F increased significantly from 160 ml.min-1 at week 26 to 180 ml.min-1 at week 36. In 7 of 25 women, CL/F increased > 20%. Trough blood CQ concentrations, determined on four occasions at week 26 and at week 36 varied between 200 and 900 nmol.l-1. No statistically significant differences between occasions were seen. Malaria parasites were seen in two individuals early in pregnancy.

CONCLUSION

Blood CQ CL/F showed a small increase during the course of pregnancy. The estimated mean blood CL/F values of 160 and 180 ml.min-1 (week 26 and 36, respectively) were higher than the mean CL/F of 125 ml.min-1 in non-pregnant individuals, published previously. Efficacy of higher dosages of CQ in malaria prophylaxis in pregnant women could, therefore, be evaluated in controlled trials in high-risk malaria areas.

In vitro susceptibility of Plasmodium falciparum to quinine: relation to parasite density and drug distribution in culture fractions

We have studied the importance of parasite density (2, 0.2, 0.02 and 0.002%) for the in vitro susceptibility of Plasmodium falciparum (F32 strain) to quinine. Shorter exposures (< or = 48 hours) only briefly inhibited parasites in wells with the highest initial density. Parasites reappeared after 3-5.5 days in wells with intermediate (0.2 and 0.02%) and lowest density (0.002%). Longer exposures (> or = 72 hours), however, inhibited them for much longer periods and parasites did not reappear in most of the wells with the lowest density during the 28 days of follow-up. The mean multiplication rate following reappearance was tenfold per parasite schizogony cycle. The mean elimination rate per schizogony cycle was calculated to be 99.91%. The elimination and multiplication rates were not correlated to initial parasite density. The mean ratio between quinine concentrations in erythrocytes and medium was 3.6 regardless of quinine concentrations and presence of parasites. Mean quinine-free fractions of 36 and 67% were found from total concentrations of 0.33 and 10.4 mumol/l. We conclude that initial parasite density determines the time to reappearance of parasites following quinine exposure while the elimination and multiplication rates are independent of the initial parasite density, and that quinine protein binding is concentration-dependent in vitro and lower than during treatment.

Mefloquine tolerability during chemoprophylaxis: focus on adverse event assessments, stereochemistry and compliance

This longitudinal study of travellers to Africa taking mefloquine (MQ) chemoprophylaxis aimed to quantify and assess non-serious adverse events (AE) occurring during short-term prophylaxis and relate these to concentrations of racemic MQ, its enantiomers and metabolite. A total of 420 volunteers (52% F) participated. AEs with some impact on activities were reported by 11.2% of participants including 7.9% of neurological/psychiatric symptoms. Women were more likely to report AEs (P = 0.02). The standardized questionnaires used showed more pathological indicators in travellers who reported subjective AE with significantly more dizziness, distress, sleep disturbances and a high total mood disturbance (TMD) in the AE group. There was, however, no significant performance deficit in computerized psychomotor tests in those experiencing AE. Furthermore, no significant differences were observed in enantiomer ratios, metabolite concentrations, or racemic MQ levels in participants with or without AEs suggesting that these factors are not the main predictors of mefloquine intolerability.

Metabolism is an important route of pentamidine elimination in the rat: disposition of 14C-pentamidine and identification of metabolites in urine using liquid chromatography-tandem mass spectrometry

This study assesses the contribution of metabolism for the disposition of pentamidine in the rat. With the use of 14C-labelled compound, the excretion of radioactivity in urine and faeces has been studied in four rats during 44 days after a single intravenous injection of the drug. The urinary and faecal excretion of the radioactivity were of equal importance; 22 +/- 2% (mean +/- S.D.) and 25 +/- 4% being detected in urine and faeces, respectively. The activity in organs and tissues at 44 days after drug administration was also measured and amounted to 21 +/- 5% of the administered dose. Using HPLC the proportion of metabolites in urine in relation to unchanged pentamidine increased with time after dose, being 76 +/- 15% (mean +/- S.D.) of the total excreted radioactivity on day 1 and 97 +/- 1% on day 6. HPLC--tandem mass spectometry was used for identification of metabolites in urine obtained from four rats given unlabelled pentamidine. Using synthetic reference compounds and the selective MS/MS mode four oxidized metabolites of pentamidine were identified either by direct injection into the system or by analyses of extracted urine. Thus, a substantial part of pentamidine is excreted as metabolites in urine.

Pharmacokinetics and adverse reactions after a single dose of pentamidine in patients with Trypanosoma gambiense sleeping sickness

1. Plasma concentrations of pentamidine were measured up to 1-8 months after a single 2 h i.v. infusion of 3.0 to 4.8 mg kg-1 pentamidine isethionate in 11 patients with late stage Trypanosoma gambiense sleeping sickness. 2. Maximum plasma drug concentrations varied between 713 and 2461 nmol 1-1. After termination of infusion, a rapid distribution phase over 10 min was followed by a slower distribution phase and an elimination phase prolonged over weeks to months. 3. The 'terminal' elimination rate constant could be determined in six patients and subsequent kinetic calculations showed a three to fourfold variation in plasma clearance and 'terminal' half-life (median 1126 (range 553-2036) ml min-1 and 265 (107-446) h, respectively). The median apparent volume of distribution (Vss) was 11,850 1. Renal clearance accounted for a median of 11% of total plasma clearance, indicating that metabolism is a major route of pentamidine elimination in man. 4. Side effects were few and mild and a slight or moderate decrease in blood pressure was the most common registered adverse reaction observed in four subjects. 5. The prolonged elimination of pentamidine seems inconsistent with the present recommended dosage regimen of pentamidine for treatment of trypanosomiasis of 7 to 10 parenteral doses given once daily or every second day.

Surfactant binding and micellisation in polymer solutions and gels: binding isotherms and their consequences

Transient networks are formed by many pairs of polymer and surfactant that associate into mixed micelles. Generally, for a given polymer concentration, the viscosity or the elastic shear modulus of such mixtures first increases and then decreases with the concentration of added surfactant. We point to the importance of considering the general features of the isotherm for the binding of the surfactant to the polymer when analysing these effects. We argue that a break-down of mixed micellar crosslinks between polymers should typically occur only when the added surfactant dominates in the mixed micelles. At this point, the concentration of monomeric surfactant should be of the same order as the relevant c.m.c. of the surfactant. The relevant c.m.c. is not generally the bulk c.m.c. but, rather, the c.m.c. in the same system but in the absence of those hydrophobic parts of the polymer that are responsible for the interpolymer crosslinking. We use this approach to analyse new and previously published experimental data on a range of ionic and non-ionic hydrophobically modified polymers mixed with surfactants that form spherical micelles, but have widely different c.m.c.s. A consistent picture of the mixed micellar stoichiometries at the point of the maximum viscosity, and at the point of final dissolution of the mixed micellar crosslinks, emerges from this analysis.

Malaria parasites and chloroquine concentrations in Tanzanian schoolchildren

Subtherapeutic doses of chloroquine (CQ) are considered to promote development of Plasmodium falciparum resistance but little is actually known about the drug levels in the population in endemic areas. We have therefore measured blood concentrations of CQ in Tanzanian schoolchildren and related these to parasite microscopy. A total of 163 children (median age 11 years) in a suburb outside Dar es Salaam were followed during four weeks. Thick and thin blood films were obtained once weekly. Parasites were counted in 200 visual fields. CQ and desethyl-chloroquine (DECQ) were determined with HPLC in 100 microliters of capillary blood. During the study P. falciparum trophozoites were detected in a mean of 78% of the children, P. falciparum gametocytes in 7.7% and P. malariae parasites in a mean of 13%. The cumulative prevalence of P. falciparum trophozoites and P. malariae parasites was 96% and 28% respectively. On day 0 and day 28, CQ was found in 78% and 80% of the children and DECQ in 21% and 31% of them. A total of 19% of all children had a verified CQ intake during the study and 35% had probably taken CQ. With a few exceptions (9% had CQ concentrations > 100 nmol/l) drug levels were not sufficient to affect parasites with a reduced CQ susceptibility but could possibly promote development of resistance by eradicating the most susceptibility part of the parasite population.

High-performance liquid chromatographic method for the enantioselective analysis of mefloquine in plasma and urine

An HPLC method for analysis of the enantiomers of the antimalarial drug mefloquine is presented. A complete resolution of (-)-(11S,2'R) and (+)-(11R,2'S) erythro-mefloquine from plasma and urine was obtained on a commercial AGP column. Mefloquine enantiomers were detected by UV at 222 nm. The separation factor (alpha) at +20 degrees C was 1.50. The limit of determination (coefficient of variation 4.0%) for the enantiomeric ratio (11S,2'R)/(11R,2'S) is 15:1 at a total mefloquine concentration of 1.6 mM.

Pentamidine accumulates in rat liver lysosomes and inhibits phospholipid degradation

The subcellular distribution and the effects of pentamidine on the ultrastructure of the rat liver were studied. Rats were given single or repeated daily intraperitoneal injections of 10, 25 or 50 mg pentamidine isethionate/kg b. wt. for 1, 4, 6, 9 or 16 days. The livers were removed for ultrastructural and biochemical analyses on the day after termination of each series of injections and in addition 7 and 35 days after the 16th injection. Electron microscopy of liver tissues showed that the general cellular architecture of the hepatocytes was preserved. The subcellular organelles were normal, except for the secondary lysosomes, which were severely altered and laden with multilamellar, myelin structures (myelin bodies) that gradually increased with dose and time course following repeated injections. These altered lysosomes were enriched in phospholipids. The alteration of the lysosomes persisted for up to 5 weeks after cessation of administration. Pentamidine was highly enriched in the lysosomal fraction (30-50 times more than in the liver homogenate). It was calculated that the lysosomal pentamidine accounted for practically all pentamidine distributed to the liver. The demonstrated accumulation of pentamidine in the lysosomes may explain the known large volume of distribution of this drug and may be one mechanism for organ toxicity.

Reversed-phase high-performance liquid chromatography determination of quinine in plasma, whole blood, urine, and samples dried on filter paper

The analysis of quinine in whole blood, plasma, urine, and samples dried on filter paper is described. Extraction was made with toluene followed by back-extraction into phosphate buffer. A reversed-phase liquid chromatography system with fluorescence detection was used. The within-day coefficient of variation of the method was 4-10% at the lower limit of determination (2 nM in plasma and 50 nM in whole blood, dried samples, and urine) and 2-4% at 10 microM. The quinine concentration was found to be lower in whole blood than in plasma (mean ratio, plasma-whole blood, 1.17). The concentration in capillary blood was lower than that in venous blood (mean ratio, capillary blood-venous blood, 0.93).

The reproducibility of quinine bioavailability

Plasma concentrations of quinine were measured in six healthy volunteers after a duplicate administration of 15 mg kg-1 of quinine hydrochloride orally and the administration of 15 mg kg-1 of quinine dihydrochloride as an infusion over 6 h. Quinine absorption rate devised by deconvolution was shown to be complete in less than 2 h. The mean (+/- s.d.) fraction available (F) was 0.76 (0.11) after both oral doses and maximum plasma drug concentrations occurred at 1.90 (0.83) h and 2.00 (0.30) h, respectively. The reproducibility of absorption was high, with a within-subject coefficient of variation of less than 10% for Cmax, AUC and F. Thus, quinine absorption is extensive, fast and reproducible in healthy volunteers.

Pentamidine concentrations in plasma, whole blood and cerebrospinal fluid during treatment of Trypanosoma gambiense infection in Côte d'Ivoire

Pentamidine concentrations in plasma, whole blood and cerebrospinal fluid (CSF) were determined in 11 patients with Trypanosoma gambiense infection without involvement of the central nervous system in Côte d'Ivoire. Blood samples were drawn during a 48 h period after the first and last dose of pentamidine dimesylate given as 10 intramuscular injections on alternate days. Maximum plasma concentrations were generally attained within one hour after injection but varied extensively (420-13420 nmol/litre). The median plasma concentration 48 h after the last dose was approximately 5 times higher than that after the first dose. The ratio between whole blood and plasma concentration was approximately 2. Small amounts of the drug were found in the CSF after the last dose. The findings showed inter-individual differences in the pharmacokinetics of pentamidine. The currently recommended daily dose regimen could be questioned, as drug accumulation was pronounced. All patients were cured and the concentrations attained should be considered as parasiticidal. Further studies on the kinetics and distribution after single and multiple doses of pentamidine as well as studies on the possible relationship between adverse effects and plasma concentrations are, however, needed.

Determination of metrifonate and dichlorvos in whole blood using gas chromatography and gas chromatography-mass spectrometry

Analytical methods for determining metrifonate and dichlorvos in whole blood and a sampling procedure suitable for pharmacokinetic studies in man are described. Metrifonate concentrations were determined after chloroform extraction using gas chromatography-nitrogen-phosphorus detection. The within-assay coefficients of variation were 4 and 9% at 19.4 and 0.8 mumol/l (limits of determination), respectively. Dichlorvos was determined using gas chromatography-mass spectrometry of toluene extracts. The within-assay coefficients of variation were 2 and 5% at 225 and 50 nmol/l (limits of determination), respectively. Since both substances are chemically unstable, the blood was collected by dripping it directly from the vein into 0.74 M phosphoric acid.

Isolated malaria outbreak in Somalia: role of chloroquine-resistant Plasmodium falciparum demonstrated in Balcad epidemic

A study was conducted in Balcad in December 1988 during a reported outbreak of malaria in order to investigate possible factors contributing to the outbreak. The slide positivity rate of 71% among fever patients, which was significantly higher than the usual rate, suggests the existence of a fresh malaria outbreak in the area. High parasite densities together with the pronounced malaria symptoms among both resident children and adult immigrants indicated little, if any, malaria experience in these patients. This outbreak could not be explained by gross climatic changes, e.g. unusual rainfalls. The in-vivo response of P. falciparum to the standard therapeutic regimen of chloroquine showed a high degree of resistance, with 31 of 36 patients showing resistance, including five RI responses and 26 RII-RIII responses. Micro in-vitro tests for chloroquine susceptibility showed resistance in 33 out of 37 isolates with a mean EC50 and EC99 of 1.50 and 10.97 X 10(-6) mol l-1 blood, respectively, indicative of a high degree of chloroquine resistance. All isolates tested against sulphadoxine/pyrimethamine showed a sensitive response. The frequent presence (78%) of detectable chloroquine levels prior to treatment did not apparently alter the in-vitro parasite growth. This is a sign of widespread use of this drug resulting in a high 'drug pressure' in the area. The proportion of sensitive parasites was inversely related to the pretreatment chloroquine concentration providing evidence of the selection of resistant parasites by the previous drug intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Metrifonate in healthy volunteers: interrelationship between pharmacokinetic properties, cholinesterase inhibition and side-effects

Metrifonate concentrations in plasma, its inhibition of blood cholinesterase, and side-effects were studied in 16 healthy volunteers who received a single oral dose of 2.5, 5, 7.5 or 15 mg/kg in a randomized double-blind study (4 subjects for each dose). Metrifonate was determined by a gas chromatographic method. Peak plasma levels were reached within 2 hours; the half-life in plasma, oral clearance, and normalized Cmax and AUCs did not differ significantly between the four groups. Plasma cholinesterase (BuchE) was inhibited to low levels in all subjects, while erythrocyte cholinesterase (AchE) was affected in a dose-dependent fashion. The occurrence of side-effects correlated strongly with peak plasma levels but not with maximum AchE inhibition or with increase in salivation. This study shows that the absorption of metrifonate was not significantly different for doses between 2.5 and 15 mg/kg. The plasma levels of this drug correlated with the occurrence of side-effects.

Biotransformation of terodiline. V. Stereoselectivity in hydroxylation by human liver microsomes

The stereoselective hydroxylation of N-tert-butyl-4,4-diphenyl-2-butylamine (Terodiline) was studied in human liver microsomes. Formation of the two main metabolites, N-tert-butyl-4(4-hydroxyphenyl)-4-phenyl-2-butylamine (II) and N-(2-hydroxymethyl-2-propyl)-4,4-diphenyl-2-butylamine (VI), was found to be stereoselective. R-Terodiline was preferentially transformed by phenolic hydroxylation to the 2R,4S-II and 2R,4R-II forms with a pronounced selectivity for the former. The formation rate ratio 2R,4S-II/2R,4R-II was about 6, obtained from two liver preparations. S-Terodiline was mainly hydroxylated to the alcohol 2S-VI although phenolic hydroxylation to the 2S,4S-II and 2S,4R-II also occurred, yielding about equal amounts of the two phenols.

Distribution of chloroquine in human blood fractions

The uptake of chloroquine (CQ) in blood cells in vitro is proportional to the concentration added to whole blood and follows the rank order of capacity: erythrocytes greater than platelets greater than granulocytes greater than lymphocytes. The accumulation of CQ in granulocytes and lymphocytes was linearly proportional to the concentration in whole blood. In average, the cellular compartment accumulated in vitro 90.6% of the total CQ amount in blood. The sum of CQ amount in isolated and washed blood cells was approximately 62.8%. The amount of CQ in erythrocytes was 4.05 to 8.4 times higher in comparison with platelet poor plasma. The number of platelets limits the uptake of CQ. With 1.5 x 10(-4) mol/l concentration in whole blood each platelet accumulated about 120 pg of CQ. The mechanism by which CQ accumulates in blood cells is not known. Possibly an active, but most probably a membrane perturbing, mechanism may play a role in CQ uptake. The compartmentation of CQ in blood must be taken into consideration when evaluating the disposition and pharmacokinetics of CQ in man.

Biotransformation of terodiline. III. Opposed stereoselectivity in the benzylic and aromatic hydroxylations in rat liver microsomes

1. Terodiline (N-tert-butyl-4,4-diphenyl-2-butylamine) is a racemic drug with anticholinergic and/or calcium antagonistic activity, which is subject to renewed interest as a potential remedy for urinary incontinence. As part of the current investigations on terodiline, the metabolism of its enantiomers is being investigated. 2. The metabolism of the enantiomers of terodiline in rat liver microsomes is slow, as for the racemate, though the S-enantiomer is metabolized more rapidly than its optical antipode. Phenobarbitone pretreatment of the rats enhances the metabolism with a marked increase in the conversion of the S-enantiomer. 3. While aromatic p-hydroxylation greatly exceeds benzylic oxidation in the metabolism of R-terodiline, this situation is reversed in the metabolism of S-terodiline. Moreover, the rate of aromatic p-hydroxylation of racemic terodiline follows that of R-terodiline, while the rate of benzylic hydroxylation of racemic terodiline follows that of S-terodiline. Phenobarbital pretreatment of the rats had little or no effect on aromatic p-hydroxylation but markedly increased benzylic oxidation. 4. Separation of the mixture of p-hydroxylated metabolites into diastereomeric pairs showed that their composition is highly dependent on which form of terodiline is used as substrate. 5. The results from the study are compatible with the participation of multiple forms of cytochrome P-450 enzymes.

Hydroxylation of desmethylimipramine: dependence on the debrisoquin hydroxylation phenotype

The 2-hydroxylation of desmethylimipramine (DMI) was studied in 14 healthy subjects previously phenotyped with respect to debrisoquin hydroxylation. After a single oral dose (25 mg), slow hydroxylators of debrisoquin had significantly lower total and metabolic clearances and longer plasma half-lives of DMI and excreted less 2-hydroxydesmethylimipramine than did rapid hydroxylators. These findings strengthen the hypothesis that the hydroxylations of debrisoquin and DMI may be under common enzymatic control.

The disposition of chloroquine in healthy Nigerians after single intravenous and oral doses

The pharmacokinetics of chloroquine after single oral (600 mg) and intravenous (2 mg kg-1) doses were studied in healthy black Nigerian students. The plasma concentrations of chloroquine and its desethylmetabolite were determined using a high performance liquid chromatography technique. Concentrations as low as 3 ng ml-1 were reproducibly determined. After i.v. dosage, the half-life ranged between 144 and 298 h; the total plasma clearance was between 282 and 1130 ml min-1 and the volume of distribution between 142 and 398 1 kg-1. Renal clearance was about 52% of plasma clearance. The estimated total urinary recovery of chloroquine and desethylchloroquine was 77% of the oral dose. There was no significant difference in the pharmacokinetics between the oral and the i.v. administration. The pharmacokinetic properties of chloroquine, in these black subjects did not differ from those previously demonstrated in Caucasians.

Enantioselective analysis of chloroquine and desethylchloroquine after oral administration of racemic chloroquine

An enantioselective high-performance liquid chromatographic method for chloroquine and desethylchloroquine was developed using a chiral alpha 1-acid glycoprotein column. This method was used to determine concentrations of chloroquine and desethylchloroquine enantiomers in plasma and urine from volunteers given single oral doses of racemic chloroquine. The disposition of the enantiomers was different. The renal clearance of the chloroquine enantiomers was indicative of stereoselective renal secretion of the drug, and evidence for stereoselective metabolism also was found.

Protein binding of chloroquine enantiomers and desethylchloroquine

The protein binding of racemic chloroquine, its enantiomers and desethylchloroquine to plasma, purified human albumin, and alpha 1-acid glycoprotein (alpha 1-AGP) was determined by equilibrium dialysis. The binding was not concentration dependent. (+)-Chloroquine bound more to plasma (66.6 +/- 1.9%) and albumin (45.9 +/- 0.8%) than (-)-chloroquine (48.5 +/- 2.4% and 35.3 +/- 0.6%, respectively). These differences were statistically significant. (-)-Chloroquine bound more to alpha 1-AGP (47.5 +/- 0.7%) than (+)-chloroquine (34.5 +/- 0.5%). The binding of desethylchloroquine to alpha 1-AGP is higher than to albumin (38.9 +/- 0.9% and 21.1 +/- 0.4%, respectively.