Rapid quantification of quinine by multi-stacking in a portable microchip electrophoresis system.

A new multi-stacking pre-concentration procedure based on field-enhanced sample injection (FESI), field-amplified sample stacking, and transient isotachophoresis was developed and implemented in a compact microchip electrophoresis (MCE) with a double T-junction glass chip, coupled with an on-chip capacitively coupled contactless conductivity detection (C4 D) system. A mixture of the cationic target analyte and the terminating electrolyte (TE) from the two sample reservoirs was injected under FESI conditions within the two sample-loading channels. At the double T-junction, the stacked analyte zones were further concentrated under field-amplified stacking conditions and then subsequently focused by transient-isotachophoresis and separated along the separation channels. The proposed multi-stacking strategy was verified under a Universal Serial Bus (USB) fluorescence microscope employing Rhodamine 6G as the model analyte. This developed approach was subsequently used to monitor the target quinine present in human plasma samples. The total analysis time for quinine was approximately 200 s with a sensitivity enhancement factor of approximately 61 when compared to the typical gated injection. The detection and quantification limits of the developed approach for quinine were 3.0 µg/mL and 10 µg/mL, respectively, with intraday and interday repeatability (%RSDs, n = 5) of 3.6 and 4.4%. Recoveries in spiked human plasma were 98.1-99.8%.

Quinine unbound concentration is the best marker for therapeutic drug monitoring.

Quinine monitoring should be based on unbound concentration due to variable unbound fraction in malaria patients.

Population pharmacokinetics of quinine in pregnant women with uncomplicated Plasmodium falciparum malaria in Uganda.

OBJECTIVES: Oral quinine is used for the treatment of uncomplicated malaria during pregnancy, but few pharmacokinetic data are available for this population. Previous studies have reported a substantial effect of malaria on the pharmacokinetics of quinine resulting from increased α-1-acid glycoprotein levels and decreased cytochrome P450 3A4 activity. The aim of this study was to investigate the pharmacokinetic properties of oral quinine in pregnant women with uncomplicated malaria in Uganda using a population approach. METHODS: Data from 22 women in the second and third trimesters of pregnancy with uncomplicated Plasmodium falciparum malaria were analysed. Patients received quinine sulphate (10 mg of salt/kg) three times daily (0, 8 and 16 h) for 7 days. Plasma samples were collected daily and at frequent intervals after the first and last doses. A population pharmacokinetic model for quinine was developed accounting for different disposition, absorption, error and covariate models. RESULTS: Parasitaemia, as a time-varying covariate affecting relative bioavailability, and body temperature on admission as a covariate on elimination clearance, explained the higher exposure to quinine during acute malaria compared with the convalescent phase. Neither the estimated gestational age nor the trimester influenced the pharmacokinetic properties of quinine significantly. CONCLUSIONS: A population model was developed that adequately characterized quinine pharmacokinetics in pregnant Ugandan women with acute malaria. Quinine exposure was lower than previously reported in patients who were not pregnant. The measurement of free quinine concentration will be necessary to determine the therapeutic relevance of these observations.

Residual antimalarial concentrations before treatment in patients with malaria from Cambodia: indication of drug pressure.

BACKGROUND: The Thai-Cambodian border has been known as the origin of antimalarial drug resistance for the past 30 years. There is a highly diverse market for antimalarials in this area, and improved knowledge of drug pressure would be useful to target interventions aimed at reducing inappropriate drug use. METHODS: Baseline samples from 125 patients with falciparum malaria recruited for 2 in vivo studies (in Preah Vihear and Pursat provinces) were analyzed for the presence of 14 antimalarials in a single run, by means of a liquid chromatography-tandem mass spectrometry assay. RESULTS: Half of the patients had residual drug concentrations above the lower limit of calibration for at least 1 antimalarial at admission. Among the drugs detected were the currently used first-line drugs mefloquine (25% and 35% of patients) and piperaquine (15% of patients); the first-line drug against vivax malaria, chloroquine (25% and 41% of patients); and the former first-line drug, quinine (5% and 34% patients). CONCLUSIONS: The findings demonstrate that there is high drug pressure and that many people still seek treatment in the private and informal sector, where appropriate treatment is not guaranteed. Promotion of comprehensive behavioral change, communication, community-based mobilization, and advocacy are vital to contain the emergence and spread of parasite resistance against new antimalarials.

Simultaneous liquid chromatographic analysis of ritonavir, quinine and 3-hydroxyquinine in human plasma.

In regions with high prevalence of HIV and malaria, co-infection of both diseases is common; hence, there is a high possibility of concurrent administration of antiretroviral and antimalarial drugs. This study describes a new ion-pair reversed-phase high-performance liquid chromatographic (HPLC) method for simultaneous determinations of ritonavir (RTV), quinine (QN), and its major metabolite, 3-hydroxyquinine (3-HQN), in human plasma. Following a simple extraction with diethyl-ether under alkaline conditions, chromatographic separation was achieved on a 5-mum particle size C-18 column (200 mm x 4.6mm I.D.) using a mobile phase consisting of methanol:acetonitrile:0.02 M potassium dihydrogen phosphate (15:10:75) containing 75 mmol/L perchloric acid (pH 2.8). Retention times for RTV, 3-HQN, QN and the internal standard were 2.8, 4.0, 7.0 and 12 min, respectively. The limits of detection and validated lower limits of quantitation were 10 and 12.5 ng/ml for RTV while the corresponding values were 5 and 70 ng/ml for both QN and 3-HQN, respectively. The new HPLC method is simple, rapid, selective, reproducible and cost-effective. As demonstrated in three volunteers, it will facilitate the conducting of simultaneous therapeutic monitoring of quinine and ritonavir in patients concurrently receiving both drugs.

Fabrication of an imprinted electrochemical sensor from l-tyrosine, 3-methyl-4-nitrophenol and gold nanoparticles for quinine determination.

This study employed a molecularly imprinted composite (MIC) to develop a selective and very sensitive sensor for the determination of quinine. To fabricate the MIC sensor, 3-methyl-4-nitrophenol (MNP) and L-tyrosine (Tyr) were simultaneously electrodeposited in acidic media containing HAuCl4 to entrap Au nanoparticles (AuNPs) into the formed composite network. The effect of Tyr on the sensitivity and selectivity of the sensor and its electrochemical performance were evaluated. The signal reduction of the Fe2+probe during differential pulse voltammetry (DPV) was used to determine the concentration of quinine. The signal was found to be linear over the quinine concentration range of 0.1 to 1000 pM with a detection limit of 0.05 pM. The sensor was used to determine the quinine content of several plasma and urine samples.

Inflammation down-regulates CYP3A4-catalysed drug metabolism in hemodialysis patients.

BACKGROUND: Recent studies indicate that inflammation may also affect CYP3A4 activity. Associations of CYP3A4-mediated metabolism of quinine, with inflammatory biomarkers were investigated in patients undergoing maintenance hemodialysis (HD). METHODS: A single dose of 100 mg quinine was given to 44 HD patients and the plasma concentration of quinine and its metabolite 3-OH-quinine were measured 12 h after drug intake. The ratios of quinine/3-OH-quinine and 4ß-OH-cholesterol/cholesterol were used as markers of CYP3A4 activity. Inflammatory biomarkers, high-sensitive CRP (hsCRP), pentraxin 3 (PTX3) and orosomucoid were followed during 4 weeks prior to quinine administration. RESULTS: The quinine/3-OH-quinine ratio correlated with median concentrations of hsCRP (Rho = 0.48; p = 0.001) and orosomucoid (Rho = 0.44; p = 0.003), and also with interleukin-6 at 12 h after drug intake (Rho = 0.43; P = 0.004) but not PTX3. In multivariate regression analysis, the correlation between CYP3A4 activity and median hsCRP remained borderline significant (p = 0.05). 4ß-OH-cholesterol/cholesterol ratio correlated with quinine/3-OH-quinine (p = 0.008), but not with any of the inflammation markers. CONCLUSIONS: The association between CYP3A4 activity and inflammatory biomarkers suggest that the activity of CYP3A4 is reduced by inflammation in HD patients. Further studies are needed to confirm this finding and to assess to what extent magnitude and duration of inflammation as well as the microbiota affect drug metabolism.

Very small injected samples to study chloroquine and quinine in human serum using capillary-LC and native fluorescence.

A comparison between HPLC with conventional fluorescence detection and capillary-LC (microHPLC) with native laser-induced fluorescence (LIF) detection was done to determine chloroquine (CQ) and quinine (Q) in human serum. HPLC experiments were run with parameters of the conventional fluorimeter set at the highest level of sensitivity. Results were compared with those obtained on microHPLC coupled to a ZETALIF (He-Cd 325 nm) detector which provided a 50-fold increase in sensitivity. In microHPLC-LIF injection volumes were 200 nL instead of 10 microL in conventional HPLC. The separation was completed within 3 min (6 min on HPLC). The limit of detection on microHPLC-LIF was 1.9 and 1.3 fmol for CQ and Q, respectively. Both experiments were validated on serum samples. The mean recovery was more than 95% for CQ and Q. The intra- and inter-day precision and accuracy were found to be within the acceptable limits (<10%).

Increased uptake of quinine into the brain by inhibition of P-glycoprotein.

The impact of P-glycoprotein (P-gp) on the distribution of quinine between brain and plasma was studied experimentally in mice. Administration of quinine (20mg/kg, i.v.) to mdrla knockout mice resulted in enhanced brain concentrations of quinine as compared to the wild-type mice (7.9+/-1.4 microg/g versus 1.6+/-0.8 microg/g, respectively). Quinine concentrations and quinine-to-3-hydroxyquinine ratio in plasma were similar in normal and P-gp-deficient mice. The effect of intravenously administered drugs before quinine (20mg/kg, i.v.) was evaluated on brain uptake and biotransformation of quinine in mice. Cyclosporine A (50 mg/kg), erythromycine (40 mg/kg), verapamil (5mg/kg) or mefloquine (20 mg/kg) increased the brain-to-plasma quinine concentration ratio (by factors of 3.8-, 1.8-, 1.9- and 2.5-fold, respectively) and the quinine-to-3-hydroxyquinine ratio in plasma (by factors 2.1-, 3.7-, 1.8- and 2.0-fold, respectively). After cinchonine (40 mg/kg) and halofantrine (40 mg/kg) pre-treatment, the brain-to-plasma ratio for quinine increased by factor of 2.3 and 1.8, respectively without changes of quinine or metabolite concentrations in plasma. Doxycycline (20 mg/kg), artesunate (50 mg/kg) or artemether (50 mg/kg) did not alter quinine disposition. These results confirm in vivo that quinine is a substrate for mdr1a P-gp. Drug associations led not only to metabolic interactions but also increased quinine uptake by tissues protected by P-gp. Such interactions may have implications for the improvement of chemotherapy but should be also taken into account for potential enhancement of adverse effects.

Early treatment failure in severe malaria resulting from abnormally low plasma quinine concentrations.

A patient admitted with severe Plasmodium falciparum malaria in western Thailand had an early treatment failure with quinine, despite full dosing. Plasma quinine concentrations were subtherapeutic. Abnormal quinine pharmacokinetics may explain sporadic reports of quinine treatment failures in severe malaria.

Clinical-parasitological response and in-vitro sensitivity of Plasmodium vivax to chloroquine and quinine on the western border of Thailand.

This study was conducted during 2002-2004 at Mae Sot District, on the Thai-Myanmar border, an area of multidrug-resistant Plasmodium falciparum malaria. Sixty-two patients with P. vivax malaria were included in the study. All were randomized into two groups to receive a 3-day regimen of chloroquine or a 3-day regimen of quinine. Primaquine was given to patients in both groups for the elimination of hepatic stages. Results from the present study suggest that the standard regimen of chloroquine and a 3-day course of quinine at the dose regimens under investigation were very effective and well tolerated for the treatment of P. vivax malaria in this area. All patients responded well to both drug regimens; the cure rates with chloroquine or quinine, when given concurrently with the tissue schizontocidal drug primaquine, were virtually 100% within 28 days of follow-up. No significant correlations between parasite clearance time (PCT) or fever clearance time (FCT) and inhibitory concentration 50 (IC50) were found. Patients who had PCT < or = 24 h and those with PCT >24 h had comparable IC50 to chloroquine (alone and plus primaquine) and quinine, as well as similar concentrations of chloroquine/desethylchloroquine (in blood) or quinine (in plasma) at the investigated time points.

Quinine levels revisited: the value of routine drug level monitoring for those on parenteral therapy.

Parenteral quinine is the most frequently used first line treatment for severe Plasmodium falciparum malaria in the developed world. Quinine is known to have a number of toxic side effects including cardiotoxicity, ototoxicity and ocular toxicity. Many therefore advocate routine monitoring of quinine levels for patients receiving parenteral therapy. This paper reviews current evidence on the usefulness of quinine level monitoring in the context of 73 adult patients with severe P. falciparum malaria managed by the Hospital for Tropical Diseases in London. Combining data from these patients with a comprehensive literature review, we conclude that routine quinine level monitoring in all patients receiving parenteral therapy is seldom appropriate.

Feasibility of using quinine, a potential multidrug resistance-reversing agent, in combination with mitoxantrone and cytarabine for the treatment of acute leukemia.

PURPOSE: We demonstrated previously that sera from quinine-treated patients reversed the multidrug resistance (MDR) of a human leukemic cell line. We now report a phase I and II clinical study that examined the toxicity of the combination of quinine with mitoxantrone and cytarabine (Ara-C). PATIENTS AND METHODS: Fifteen adult patients with relapsed or refractory acute leukemia were treated with quinine formiate (30 mg/kg/d in continuous intravenous (IV) infusion from day 1 through day 5 or 6) associated with Ara-C (1 g/m2 in 3-hour IV infusion twice a day for 5 days) and five increasing doses of mitoxantrone (from 8 mg/m2/d for 4 days to 12 mg/m2/d for 5 days). RESULTS: The main toxicity was severe myelosuppression: the mean times to leukocyte recovery (> 500/microL), granulocytes recovery (> 500/microL), and platelet count recovery (> 50,000/microL) were 23 days (range, 17 to 29 days), 30.6 days (range, 17 to 48 days), and 35.4 days (range, 14 to 75 days), respectively. The nonhematopoietic toxicity of this regimen was acceptable. Nausea and vomiting were common, but severe mucositis was observed in only two patients. Cardiotoxicity was limited to transient episodes of moderate supraventricular tachycardia and a clinically well-tolerated bradycardia. Tinnitus and vertigo were observed in 10 cases (67%), and mild hearing loss and transient increase of serum bilirubin were observed in six patients (40%). Total quinine serum levels reached a steady-state concentration between 6.4 and 18 mg/L in 24 hours. Complete remission (CR) was achieved in eight of 14 (57%) assessable patients, and partial response (PR) was achieved in two additional patients (14%). P-glycoprotein expression was detected on blast cells from five of 13 studied patients before treatment. A response was observed in all P-glycoprotein-positive cases. CONCLUSION: Quinine can be used safely as a potential reversing agent of MDR for the treatment of clinically resistant acute leukemias.

Recrudescence of imported falciparum malaria after quinine therapy: potential drug interaction with phenytoin.

Quinine remains a reliable treatment for falciparum malaria in most parts of the world. We report recrudescence of imported Plasmodium falciparum malaria following quinine treatment in the context of concurrent phenytoin use. Supported by a subtherapeutic quinine level, we hypothesise that a drug interaction with phenytoin may compromise the efficacy of quinine in the treatment of malaria.

Comparative effects of quinine and cinchonine in reversing multidrug resistance on human leukemic cell line K562/ADM.

We have previously suggested that quinine and cinchonine could be good candidates for clinical circumvention of multidrug resistance (MDR) in hematological malignancies because of their tolerance and their retained efficacy in serum. In the present study, we have used the well-characterized multidrug resistant human leukemic cell line K562/ADM to compare the effect in vitro of quinine and cinchonine on doxorubicin, mitoxantrone, and vincristine uptake and cytotoxicity. In serum-free medium, quinine induced a dose-dependent increase of doxorubicin uptake reaching about 200% at 40 microM, while it had a slight and no effect on mitoxantrone and vincristine uptake respectively. In the same conditions, cinchonine induced a rapid and significant increase in the accumulation of the three drugs, reaching a plateau phase between 5 and 10 microM. Quinine and cinchonine induced both potentiation of doxorubicin, vincristine and mitoxantrone cytotoxicity in K562/ADM cells. However, quinine reached a plateau phase at 10 microM, while cinchonine had a maximal effect at 5 microM and was significantly more potent at low concentrations. When diluted in plasma, cinchonine was less bound to proteins than quinine. The free fraction of alkaloids was 37-55% for cinchonine and 20-30% for quinine. Cinchonine-induced enhancement of vincristine cellular accumulation was little modified by plasma proteins. When incubated in whole blood, the fraction of cinchonine trapped in red blood cells was rapidly and completely exchangeable with plasma. We conclude that cinchonine is a stronger inhibitor of MDR than quinine.

Simultaneous determination of quinine and chloroquine anti-malarial agents in pharmaceuticals and biological fluids by HPLC and fluorescence detection.

Even nowadays millions of people suffer and even die each year from malaria and hundreds of millions of people especially in tropical countries. Quinine (Q) a natural occurring alkaloid and chloroquine (CQ) a synthetic drug are widely used as anti-malarial agents. Herein an isocratic reversed-phase high performance liquid chromatographic (RP-HPLC) method is described for the simultaneous determination of quinine and chloroquine, at low concentrations, in pharmaceuticals and biological fluids. The present method is characterized by higher sensitivity and analytes are separated in less time than the already published methods. The analytical column, an MZ Kromasil, C18, 5 microm, 250 x 4mm, was operated at ambient temperature with backpressure values of 230 kg/cm(2). Mobile phase consisted of methanol-acetonitrile-0.1 mol/L ammonium acetate, (45:15:40 v/v) at a flow rate of 1.0 mL/min. Fluorescence detection was performed at excitation 325 nm and emission 375 nm, respectively. Salicylic acid was used as internal standard at a concentration of 0.5 ng/microL, resulting in a detection limit of 0.3 ng, while upper limit of linear range was 0.7 ng/microL for quinine and 0.5 ng/microL for chloroquine. Separation was completed within 5 min. The statistical evaluation of the method was examined performing intra-day (n=8) and inter-day calibration (n=8) and was found to be satisfactory, with high accuracy and precision results. Solid phase extraction provided high relative extraction recoveries from biological matrices: 92.1% for quinine and 105.4% for chloroquine from blood serum and 101.8% for quinine and 90.7% for chloroquine from urine.

Quinine-induced thrombocytopenia following intravenous use of heroin.

Profound thrombocytopenia developed in a 22-year-old man after intravenous use of heroin. A high-titer, quinine-dependent, platelet-specific antibody was detected in his serum using lysis of normal platelets labeled with chromium 51 and an electroimmunoassay for measurement of platelet-associated IgG. The antibody was specific for quinine and failed to react with platelets in the presence of quinidine hydrochloride or two structural analogues of heroin. Quinine, a common adulterant found in heroin, was detected in the patient's blood and urine. On the basis of these observations, the patient was judged to have quinine-induced immunologic thrombocytopenia. To our knowledge, this report is the first to confirm that quinine used as an adulterant can induce immunologic thrombocytopenia following an injection of heroin.

Aqueous two phase system based on ionic liquid for isolation of quinine from human plasma sample.

Aqueous two phase system was applied for selective extraction of quinine from human plasma. Bi-phase was constructed from ionic liquid: butyl-methyl-imidazolium chloride after addition kosmotropic salts K3PO4 or KH2PO4. Quinine was determined in plasma samples after drinking of tonic containing quinine. Determination was performed by HPLC on 5-µm Zorbax SB-CN column and eluent containing 40% acetonitrile (v/v), 20 mM phosphate buffer at pH 3 and 40 mM NaPF6 using external standard method. The spectrophotometric detection was set λ=214 nm. Selective fluorescence detection was performed at excitation of 325 nm and emission of 375 nm. Proposed strategy provides suitable sample purification and gives extraction yields in the range of 89-106%. The determination coefficient (R(2)) has a value ≥0.997 in the range of 50-800 ng/ml quinine concentration. The limit of quantification was set at 27.9 ng/ml and the detection limit was found to be 8.4 ng/ml under fluorescence detection.