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.

Significant Pharmacokinetic Interactions Between Quinine and Ampicillin-Cloxacillin Combination.

INTRODUCTION: The co-existence of malaria with bacterial infections is common in the tropics, hence the concurrent use of antimalarials and antibiotics. OBJECTIVE: This study aimed to investigate the effect on pharmacokinetics and antimicrobial activity of co-administration of quinine and combined ampicillin-cloxacillin. METHODS: In total, 14 healthy adults received single oral doses of ampicillin-cloxacillin combination alone and with quinine in a randomized crossover manner. Urine samples collected at predetermined intervals over 48 h were analysed. The effect of quinine on minimum inhibitory concentrations (MICs) of ampicillin and cloxacillin were determined against Staphylococcus aureus by agar diffusion, agar dilution, and broth dilution. RESULTS: Quinine significantly reduced the rate and extent of excretion of ampicillin and cloxacillin (p < 0.0002). The total amounts of ampicillin and cloxacillin excreted unchanged (Du(∞)) alone were 217.10 ± 53.82 and 199.0 ± 64.29 mg versus 126.40 ± 50.63 and 135.20 ± 52.24 mg, respectively, with quinine. Respective maximum excretion rates (dDu/dt max) for ampicillin and cloxacillin were 43.55 ± 19.41 and 77.64 ± 29.65 mg/h alone versus 18.01 ± 8.52 and 53.16 ± 20.72 mg/h with quinine. This indicates a significant reduction in Du(∞)and dDu/dt max by 41.78 and 58.65 % for ampicillin and 32.06 and 31.53 % for cloxacillin. Conversely, the disposition of quinine was unaffected by ampicillin-cloxacillin (p > 0.1). The MIC of antibiotics alone versus with quinine, respectively, were 0.11 ± 0.04 and 0.78 ± 0.1 µg/ml for ampicillin, and 0.18 ± 0.1 and 0.92 ± 0.4 µg/ml for cloxacillin, with a five- to sevenfold increase (p > 0.01); indicating a decrease in antimicrobial activity by quinine. CONCLUSIONS: Quinine therefore, reduced the bioavailability and the antimicrobial activity of ampicillin-cloxacillin upon co-administration, which may have therapeutic implications. Caution is required with the co-administration of these medicines.

Quinine as a potential tracer for medication adherence: A pharmacokinetic and pharmacodynamic assessment of quinine alone and in combination with oxycodone in humans.

Effective strategies to monitor pharmacotherapy adherence are necessary, and sensitive biological markers are lacking. This study examined a subtherapeutic dose of quinine as a potential adherence tracer. Primary aims included examination of the plasma and urinary pharmacokinetic profile of once-daily quinine; secondary aims assessed pharmacokinetic/pharmacodynamic interactions with oxycodone (a CYP3A and CYP2D substrate). Healthy, nondependent opioid users (n = 9) were enrolled in this within-subject, double-blind, placebo-controlled inpatient study. Participants received the following oral doses: day 1, oxycodone (30 mg); days 2-4, quinine (80 mg); day 5, quinine and oxycodone (2 hours postquinine). Blood and 24-hour urine samples were collected throughout the study, and pharmacodynamic outcomes were assessed during experimental sessions (days 1, 4, 5). Quinine displayed a plasma Tmax ∼2 hours and t1/2 ∼10 hours. Oxycodone and noroxycodone parameters (Tmax , Cmax , t1/2 ) were similar with or without quinine present, although drug exposure (AUC) was slightly greater when combined with quinine. No pharmacodynamic interactions were detected, and doses were safely tolerated. During washout, quinine urinary concentrations steadily declined (elimination t1/2 ∼16 hours), with a 94% decrease observed 72 hours postdose. Overall, low-dose quinine appears to be a good candidate for a medication additive to monitor adherence for detection of missed medication.

Ultrasound assisted dispersive liquid-liquid microextraction followed by injector port silylation: a novel method for rapid determination of quinine in urine by GC-MS.

BACKGROUND: Silylation is a widely used derivatization method for the analysis of polar analytes by GC-MS. Ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) is an ecofriendly, rapid and simple microextraction method. For the first time, a novel approach has been developed and applied for the analysis of quinine in urine by combining UA-DLLME with injection port silylation. RESULTS: The LOD and LOQ were found to be 5.4 and 18 ng/ml. The intra- and inter-day precisions were less than 5 and 8%, respectively. Mean recoveries of quinine were found to be in the range of 87 to 96%. CONCLUSION: Ultrasound-assisted dispersive liquid-liquid microextraction is rapid, simple and consumes less reagent for the analysis of polar analytes such as quinine.

On-line coupled capillary isotachophoresis-capillary zone electrophoresis in hydrodynamically closed separation system hyphenated with laser induced fluorescence detection.

An analytical method, based on a column coupling capillary ITP and CZE in a hydrodynamically closed separation mode hyphenated with the detection in the modular arrangement, was developed in this work. Analytical possibilities of this approach are demonstrated on the direct and ultrasensitive quantitative determination of quinine (QUI) in diluted real multicomponent ionic matrices (beverages, urine). The detection cell interface, with the rectangular arrangement of the optical channels inside, connected the separation capillary with the LIF detector via optical fibers in the on-column detection arrangement. ITP enabled the direct large volume (30 µL) injections of the diluted real matrices with an on-line sample pretreatment (preseparation, preconcentration) so that no external sample preparation (except for the dilution) was necessary for the separation of the analyte in the multicomponent ionic matrices. Due to the ITP sample preconcentration and intrinsic sensitivity of the LIF detection, very low concentration LOD (as low as 77 pg/mL), were reached at the same time. This was ca. two orders lower than the corresponding LOD achieved by the same 2D separation system with UV absorbance detection. Compared to the single column CE-LIF methods applied for this model analyte and matrix, this method was found to be superior in terms of concentration LOD, with acceptable selectivity and benefits of the on-line sample preparation. A food control and bioanalytical application clearly illustrates great practical possibilities and routine use of the proposed modular ITP-CZE-LIF technique.

Genome-wide association study reveals a complex genetic architecture underpinning-induced CYP3A4 enzyme activity.

Atypical cytochrome P450 3A4 (CYP3A4) enzyme activity-induced and inhibited-is thought to be the driver of numerous poor or adverse therapeutic responses to up to 50 % of all commonly prescribed drugs. We carried out a genome-wide association study to identify common genetic variants associated with variation in induced CYP3A4 activity. A total of 310 twins were included in this study. Each participant had already completed a 14 days course of St John's Wort to induce CYP3A4, which was quantified through the metabolic ratio of exogenous 3-hydroxyquinine to quinine. We failed to detect any genome-wide significant associations (P < 1 × 10(-8)) with variation in induced CYP3A4 activity although several genomic regions were highlighted which may play minor roles. We report the first GWAS of variation in induced CYP3A4 activity and our preliminary results indicate a complex genetic architecture underpinning induced CYP3A4 enzyme activity.

Polymer-modified glassy carbon electrode for the electrochemical detection of quinine in human urine and pharmaceutical formulations.

Glassy carbon electrode was modified by electropolymerization of 4-amino-3-hydroxynaphthalene sulfonic acid. Cyclic voltammetric study of quinine showed higher current response at the modified electrode compared to the bare and activated glassy carbon electrodes in pH 7.0 phosphate buffer solution. Under optimized conditions, a calibration curve was obtained by square wave voltammetry at the modified electrode. The linear relationship between the peak current and the concentration of quinine in the range of 1.0 × 10(-7) to 1.0 × 10(-5) M was I (pa) (in microamperes) = 6.26C (in micromolars) + 0.2997 (R (2) = 0.999). The detection limit calculated (S/N = 3) was 1.42 × 10(-8) M, which is much lower than similar reports. The method was successfully applied for the determination of quinine in spiked human urine, and pharmaceutical formulations and recovery values >90 % were obtained.

2D capillary electrophoresis hyphenated with spectral detection for the determination of quinine in human urine.

The possibilities of a column coupling two-dimensional capillary electrophoresis (2D CE) combined with fiber-based diode array detection (DAD) for the direct, highly reliable and ultrasensitive quantitative determination of quinine in real multicomponent ionic matrices (human urine) are demonstrated in this work. The capillary isotachophoresis (CITP) stage provided an on-line sample pretreatment (elimination of interfering matrix constituents, preseparation and preconcentration of the analyte) before the capillary zone electrophoresis (CZE) separation. Due to the large volume (30 µL) sample injection and CITP sample preconcentration, a simple absorbance photometric detection was sufficient for obtaining very low concentration limits of detection (∼8.6 ng/mL). The combination of the different separation mechanisms (CITP and CZE) resulted in enhanced separation selectivity. This enabled us to obtain a pure analyte zone in the directly injected real samples suitable for qualitative and quantitative evaluation. The spectral DAD allowed (i) characterization of the purity (i.e., spectral homogeneity) of the analyte zone; and (ii) preliminary indication of structurally related compounds (i.e., potential biodegradation products of quinine), via characteristic spectra recorded in intervals of 200-800 nm. The CITP-CZE-DAD method was characterized by favorable performance parameters that are suitable for its routine biomedical use. One of the primary benefits of the CITP-CZE-DAD method is the possibility of performing direct injections of real biological samples while avoiding external sample preparation procedures and, therefore, enhancing the reliability and applicability of analyses and the potential for method automatization and miniaturization.

Genetic epidemiology of induced CYP3A4 activity.

AIM: The cytochrome P450 3A4 (CYP3A4) enzyme is implicated in the metabolism of more than 50% of all prescribed medications and its activity - including induced or inhibited activity - is deemed to be a crucial determinant of interindividual variability in drug disposition, poor therapeutic efficacy, and adverse response to medication. METHODS: We used the classical twin model in conjunction with an induction experiment to uncover the relative contribution of genetic and environmental factors to interindividual variation in induced CYP3A4 activity. A total of 367 healthy twins participated in the study. Each volunteer was administered a potent inducer of CYP3A4 (St John's Wort) for 14 days and the activity of CYP3A4 was quantified through the metabolism of the exogenously administered probe drug quinine sulfate. RESULTS: Baseline and induced CYP3A4 activity were highly variable with a seven-fold and 11-fold difference among our population, respectively. Alcohol consumption, BMI, and smoking were significantly associated with induced CYP3A4 activity, collectively explaining 20% of the variation (P<1×10(-4)). The narrow-sense heritability of induced CYP3A4 activity was estimated at 66%, whereas the remainder of the variation was attributed to unique environmental factors. CONCLUSION: To our knowledge, this is the first genetic epidemiological study of induced CYP3A4 activity. Our results motivate further research to identify common and rarer genetic variants that underpin the heritable component of variation in induced CYP3A4 activity.

Rapid quantification of quinine and its major metabolite (3S)-3-hydroxyquinine in diluted urine by UPLC-MS/MS.

A rapid UPLC-MS/MS quantitative assay for the quantification of quinine and (3S)-3-hydroxyquinine requiring minimal sample pre-treatment - dilute-and-shoot type approach - has been developed. The assay was run at 0.6mL/min using gradient elution with (pH 10; 10mM) ammonium bicarbonate and methanol with a total cycle time of 2.5min on a 50mm×2.1mm ID, 1.7µm Acquity BEH column. Peak shapes were highly symmetrical allowing for accurate peak integration. Calibration curves for both analytes were constructed from 1.00 to 20.00ng/mL, yielding R(2) values >0.995. Intra- and inter-batch assay precision and accuracy were evaluated using 6 injections of QC solutions on 3 separate days (n=18) and were found to be within ±10% and 90-110% respectively. The method was shown to be suitable for quantitatively determining the ratio of quinine to (3S)-3-hydroxyquinine for a cohort of samples from an epidemiological study.

A simple technique for the detection of anti-malarial drug formulations and their presence in human urine.

A simple, sensitive, specific assay technique for the detection and semi-quantification of chloroquine, amodiaquine, quinine, primaquine, sulfadoxine and pyrimethamine in formulations and in human urine by using thin layer chromatography (TLC) was developed and tested in the laboratory. The method involved developing test samples spotted on TLC chromatogram by diethylamine-toluene-isopropanol (1:4:5 v/v/v) as the eluting solvent. The solvent system diethylamine-toluene-isopropanol (1:4:5 v/v/v) enabled the elution and detection of all the tested antimalarial drugs in solution and those spiked in human urine. Detection limits for chloroquine, amodiaquine, quinine and primaquine were the lowest at 0.00025 mg/ml. Sulfadoxine exhibited a detection limit of 0.0005 mg/ml whereas that of pyrimethamine was 0.001 mg/ml. The results indicate the suitability of this technique in antimalarial drug quality and bioavailability studies. It is envisaged that this technique will adequately address the role of drug absorption and excretion in the chemotherapy of malaria as well as to detect types of antimalarial drugs commonly used in the community.

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.

Carbon nanotubes as adsorbent of solid-phase extraction and matrix for laser desorption/ionization mass spectrometry.

A method with carbon nanotubes functioning both as the adsorbent of solid-phase extraction (SPE) and the matrix for matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) to analyze small molecules in solution has been developed. In this method, 10 microL suspensions of carbon nanotubes in 50% (vol/vol) methanol were added to the sample solution to extract analytes onto surface of carbon nanotubes because of their dramatic hydrophobicity. Carbon nanotubes in solution are deposited onto the bottom of tube with centrifugation. After removing the supernatant fluid, carbon nanotubes are suspended again with dispersant and pipetted directly onto the sample target of the MALDI-MS to perform a mass spectrometric analysis. It was demonstrated by analysis of a variety of small molecules that the resolution of peaks and the efficiency of desorption/ionization on the carbon nanotubes are better than those on the activated carbon. It is found that with the addition of glycerol and sucrose to the dispersant, the intensity, the ratio of signal to noise (S/N), and the resolution of peaks for analytes by mass spectrometry increased greatly. Compared with the previously reported method by depositing sample solution onto thin layer of carbon nanotubes, it is observed that the detection limit for analytes can be enhanced about 10 to 100 times due to solid-phase extraction of analytes in solution by carbon nanotubes. An acceptable result of simultaneously quantitative analysis of three analytes in solution has been achieved. The application in determining drugs spiked into urine has also been realized.

Artemether bioavailability after oral or intramuscular administration in uncomplicated falciparum malaria.

The antimalarial activity of artemether following oral or intramuscular administration in the plasma of 15 adults with acute uncomplicated Plasmodium falciparum malaria was measured by bioassay. The peak concentrations in plasma following oral administration were higher in patients with acute illness (median, 1,905 mmol of dihydroartemisinin [DHA] equivalents per liter; range, 955 to 3,358 mmol of DHA equivalents per liter) than in patients in the convalescent phase (median, 955 mmol of DHA equivalents per liter; range, 576 to 1,363 mmol of DHA equivalents per liter), and clearance (CL/F) was lower in patients in the acute phase (1.11 liters/kg/h; range, 0.21 to 3.08 liters/kg/h) than in patients in the convalescent phase (median, 2.76 liters/kg/h; range, 1.56 to 5.74 liters/kg/h) (P< or =0.008). Antimalarial activity in terms of the peak concentration in plasma (Cmax) after oral administration was a median of 16 times higher than that after intramuscular administration. The ratio of the area under the plasma concentration-time curve during the first 24 h (AUC(0-24)) after oral administration of artemether to the AUC(0-24) after intramuscular administration was a median of 3.3 (range, 1 to 11) (P=0.0001). In the acute phase, the time to Cmax was significantly shorter after oral administration (median, 1 h; range, 0.5 to 3.0 h) than after intramuscular administration (median, 8 h; range, 4 to 24 h) (P=0.001). Intramuscular artemether is absorbed very slowly in patients with acute malaria.

Metabolism and elimination of quinine in healthy volunteers.

OBJECTIVES: The aims were to investigate: (1) The renal elimination of quinine and its metabolites 3-hydoxyquinine, 2'-quininone, (10R) and (10S)-11-dihydroxydihydroquinine and (2) the relative importance of CYP3A4, CYP1A2 and CYP2C19 for the formation of 2'-quininone, (10R) and (10S)-11-dihydroxydihydroquinine in vivo. METHODS: In a randomised three-way crossover study, nine healthy Swedish subjects received a single oral dose of quinine hydrochloride (500 mg), on three different occasions: (A) alone, (B) concomitantly with ketoconazole (100 mg twice daily for 3 days) and (C) concomitantly with fluvoxamine (25 mg twice daily for 2 days). Blood and urine samples were collected before quinine intake and up to 96 h thereafter. All samples were analysed by means of high-performance liquid chromatography. RESULTS: Co-administration with ketoconazole significantly increased the area under the plasma concentration versus time curve (AUC) of 2'-quininone, (10S)-11-dihydroxydihydroquinine, and (10R)-11-dihydroxydihydroquinine, the geometric mean ratios (90% CI) of the AUC were 1.9 (1.8, 2.0), 1.3 (1.1, 1.7) and 1.6 (1.4, 1.8), respectively. Co-administration with fluvoxamine had no significant effect on the mean AUC of any of the metabolites. A mean of 56% of the administered oral quinine dose was recovered in urine after hydrolysis with beta-glucuronidase relative to the 40% recovered before hydrolysis. CONCLUSION: Quinine is eliminated in urine mainly as unchanged drug and as 3-hydroxyquinine. The major metabolite of quinine is 3-hydroxyquinine formed by CYP3A4. There is no evidence for the involvement of CYP3A4, 1A2 or 2C19 in the formation of 2'-quininone, (10S)-11-dihydroxydihydroquinine and (10R)-11-dihydroxydihydroquinine in vivo. Glucuronidation is an important pathway for the renal elimination of quinine, mainly as direct conjugation of the drug.

Quinine 3-hydroxylation as a biomarker reaction for the activity of CYP3A4 in man.

OBJECTIVE: To investigate the usefulness of the 3-hydroxylation of quinine as a biomarker reaction for the activity of CYP3A4 in man and to study the interindividual variation in the metabolic ratio (MR), i.e. quinine/3-hydroxyquinine. METHODS: Data from a previous study (A) was used for determination of the MR of quinine in plasma and urine at different time points. In study B, 24 healthy Swedish subjects received 250 mg quinine hydrochloride first alone and later together with four other CYP probe drugs [losartan (CYP2C9), omeprazole (CYP2C19), debrisoquine (CYP2D6) and caffeine (CYP1A2)] administered on the same day. Plasma and urine samples were collected before quinine intake and 16 h thereafter and analysed for quinine and 3-hydroxyquinine using high-performance liquid chromatography. Plasma and/or urine were collected for the other probes at different time points. MRs of all the probes were determined and correlations to quinine MR were studied. RESULTS: In study A, the MR in plasma was stable over 96 h. The ratio increased from 5.8 to 12.2 (P=0.006) during co-administration with ketoconazole, whereas no significant difference (P=0.76) was observed during co-administration with fluvoxamine (from 5.8 to 6.0). In study B, there was no significant difference (P=0.36) between the mean MRs when quinine was given alone (4.7) or together with the four other drugs (4.5). There was a significant correlation between the MR of quinine and omeprazole sulphone formation (r=0.52, P<0.01), but not to the MRs of the other probes. There was a fivefold interindividual variability in the MR. CONCLUSIONS: The MR of quinine in plasma or urine may serve as a stable measure of the activity of CYP3A4 in man. These results together with in vitro data show that quinine is also a specific CYP3A4 probe.

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.

Grapefruit juice has no effect on quinine pharmacokinetics.

OBJECTIVE: As quinine is mainly metabolised by human liver CYP3A4 and grapefruit juice inhibits CYP3A4, the effect of grapefruit juice on the pharmacokinetics of quinine following a single oral dose of 600 mg quinine sulphate was investigated. METHODS: The study was carried out in ten healthy volunteers using a randomised cross-over design. Subjects were studied on three occasions, with a washout period of 2 weeks. During each period, subjects received a pretreatment of 200 ml orange juice (control), full-strength grapefruit juice or half-strength grapefruit juice twice daily for 5 days. On day 6, the subjects were given a single oral dose of 600 mg quinine sulphate with 200 ml of one of the juices. Plasma and urine samples for measurement of quinine and its major metabolite, 3-hydroxyquinine, were collected over a 48-h period and analysed by means of a high-performance liquid chromatography method. RESULTS: The intake of grapefruit juice did not significantly alter the oral pharmacokinetics of quinine. There were no significant differences among the three treatment periods with regard to pharmacokinetic parameters of quinine, including the peak plasma drug concentration (Cmax), the time to reach Cmax (tmax), the terminal elimination half-life (t1/2), the area under the concentration-time curve and the apparent oral clearance. The pharmacokinetics of the 3-hydroxyquinine metabolite were slightly changed when volunteers received grapefruit juice. The mean Cmax of the metabolite (0.25+/-0.09 mg l(-1), mean +/- SD) while subjects received full-strength grapefruit juice was significantly less than during the control period (0.31+/-0.06 mg l(-1), P < 0.05) and during the intake of half-strength grapefruit juice (0.31+/-0.07 mg l(-1), P < 0.05). CONCLUSION: These results suggest that there is no significant interaction between the parent compound quinine and grapefruit juice, so it is not necessary to advise patients against ingesting grapefruit juice at the same time that they take quinine. Since quinine is a low clearance drug with a relatively high oral bioavailability, and is primarily metabolised by human liver CYP3A4, the lack of effect of grapefruit juice on quinine pharmacokinetics supports the view that the site of CYP inhibition by grapefruit juice is mainly in the gut.

Identification of quinine metabolites in urine after oral dosing in humans.

A gas chromatographic-mass spectrometric method was used to separate quinine and its metabolites present in urine after oral dosing of 300 mg quinine in humans. The technique allowed the separation of quinine and ten metabolites. Four of these metabolites were definitely identified as 3-hydroxyquinine, 2'-quinone, O-desmethylquinine and 10,11-dihydroxydihydroquinine, by comparing their methane chemical ionization mass spectra with those of authentic standards prepared by organic synthesis. Six other metabolites are described for the first time in human urine. From their electron impact and chemical ionization mass spectra, we propose these compounds to be 3-hydroxy-2'-quinone, O-desmethyl-2'-quinone, O-desmethyl-3-hydroxyquinine, O-desmethyl-3-hydroxy-2'-quinone, 10,11-dihydroxydihydro-2'-quinone and 10,11-dihydroxydihydro-O-desmethylquinine. These secondary metabolites probably arose from further biotransformation of the four primary metabolites.

Detection of quinine and its metabolites in horse urine by gas chromatography-mass spectrometry.

After oral administration of quinine sulfate to a thoroughbred mare, seven urine samples were obtained over a 45.5 h period. Using gas chromatography -electron impact ionization and positive-ion chemical ionization mass spectrometry, quinine and five putative metabolites were detected and tentatively identified in enzyme-hydrolysed post-administration urine; all metabolites involved some form of oxidation. The parent drug could be detected for about 16 h and some phase I biotransformation products for up to 40 h post-administration.