Comparison of a preliminary procedure for the general unknown screening of drugs and toxic compounds using a quadrupole-linear ion-trap mass spectrometer with a liquid chromatography-mass spectrometry reference technique

Liquid chromatography-tandem mass spectrometry (LC-MS-MS) might be a complement to GC-MS and HPLC-diode array detection for the general unknown screening (GUS) of drugs and toxic compounds, particularly when using information- or data-dependent acquisition (IDA or DDA), an auto-adaptive MS-MS product-ion scan mode where, at each unit time, the m/z ratios above a given intensity threshold are selected for fragmentation. A new quadrupole-linear ion-trap mass spectrometer (LC-QqQlinear ion-trap) was evaluated for GUS using IDA. For the first detection step (so-called "survey scan") the single quadrupole "enhanced" MS mode (EMS), where ions are accumulated then filtered in the Q3-linear ion-trap, was used. The so-called "enhanced" parent ion scan mode (EPI) used at two alternated fragmentation energies gave the best signal intensity and the best mass spectral information when adding mass spectra obtained in low and high fragmentation conditions, respectively, both in the positive (+20 and +50 eV) and negative (-15 and -40 eV) modes. Solid-phase extracts of serum spiked with eight test compounds (chosen for their retention times distributed along the 30-min long chromatogram and for ionising in both the positive and negative modes) were analysed in parallel with this LC-MS-MS technique and with a reference LC-MS method run on a single-quadrupole instrument where low and high in-source fragmentation conditions in the positive and the negative ion modes are alternated. A C(18), 5 microm (150 x 1 mm I.D.) column and a gradient elution of acetonitrile in pH 3, 2 mM ammonium formate, were used for both. Higher signal-to-noise ratios were obtained with the LC-QqQlinear ion-trap instrument than with the reference technique, resulting in mass spectra devoid of contaminant ions and at least as informative as the reconstructed single-MS spectra. After optimisation of the IDA intensity threshold for the detection of tiny chromatographic peaks in noise, five out of the eight compounds (milrinone, lorazepam, fluometuron, piretanide and warfarin) could be unambiguously identified at the concentration of 0.1 mg/l in serum, in the positive or negative modes, or in both, versus only two by LC-MS. All of them could be identified at 1 mg/l by both techniques. These preliminary results show that the sensitivity and mass structural information brought by this new LC-QqQlinear ion-trap instrument may help design an efficient toxicological GUS procedure.

Comparison of the prevalence of alcohol, cannabis and other drugs between 900 injured drivers and 900 control subjects: results of a French collaborative study

A collaborative case-control study was conducted in France in order to determine the prevalence of alcohol, cannabinoids, opiates, cocaine metabolites, amphetamines and therapeutic psychoactive drugs in blood samples from drivers injured in road accidents and to compare these values with those of a control population. Recruitment was performed in emergency departments of six university or general hospitals and comprised 900 drivers involved in a non-fatal accident and 900 patients (controls) who attended the same emergency units for a non-traumatic reason. Drivers and controls were matched by sex and age. Alcohol was determined by flame ionization-gas chromatography, drugs of abuse (DOA) by gas chromatography-mass spectrometry with the same analytical procedures in the six laboratories, and medicines by high performance liquid chromatography with diode array detection. Blood alcohol concentration exceeding 0.5 g/l (i.e. the legal French threshold) was found in 26% of drivers and 9% of controls. In the 18-27 years age range, alcohol was the only toxic found in blood samples of 17% drivers and 5% controls, leading to an odds-ratio (OR) of 3.8. A significant relationship was found between alcohol blood concentrations and OR values. All age groups confounded, the main active substance of cannabis, Delta(9) tetrahydrocannabinol (THC), was found in 10% of drivers and 5% of controls. In the less than 27 years old, THC (>1 ng/ml) was detected alone in the blood of 15.3% drivers and of 6.7% controls, giving OR=2.5, whereas there was no link between THC blood concentrations and OR value. THC was found alone in 60% of cases and associated with alcohol in 32%, with OR=4.6 between drivers and controls for this association. The difference in morphine prevalence between drivers (2.7%) and controls (0.03%) was highly significant (P<0.001), with OR=8.2. The number of positive cases for amphetamines and cocaine metabolites was too low for reaching any interpretation. The most frequently observed psychoactive therapeutic drugs were by far benzodiazepines, that were found alone in 9.4% of drivers and 5.8% of controls, which led to OR=1.7 (P<0.01). This study demonstrates a higher prevalence of opiates, alcohol, cannabinoids and the combination of these last two compounds in blood samples from drivers involved in road accidents than in those from controls, which suggests a causal role for these compounds in road crashes.

Limited sampling strategies using Bayesian estimation or multilinear regression for cyclosporin AUC(0-12) monitoring in cardiac transplant recipients over the first year post-transplantation

OBJECTIVE

The aim of this study was to develop routinely applicable limited sampling strategies for assessing cyclosporin (CsA) AUC(0-12 h), and possibly other exposure indices such as AUC(0-4 h) and C(max), in heart transplant patients over the first year post-transplantation.

METHODS

First, the individual pharmacokinetics (PKs) of 14 adult heart-transplant patients receiving Neoral were assessed at three post-transplantation periods, at the end of the first week (W1), the third month (M3) and the first year (Y1). To fit blood concentrations, a PK model specially developed for oral CsA was applied. Second, two statistical methods were compared for AUC(0-12 h) estimation using a limited sampling strategy (maximum of three blood samples): multiple regression analysis (MR) and Bayesian estimation (BE).

RESULTS

No significant difference was observed between the individual PK parameters at M3 and Y1, so population modelling was performed taking as a whole the concentration data collected at M3 and Y1. On the contrary, a significant difference ( P<0.05) was found for the C2/dose ratio between W1 and M3 and between W1 and Y1 (mean+/-SD =5.47+/-2.33; 7.78+/-1.05; 6.98+/-2.17 ml(-1 )for W1, M3 and Y1, respectively). Also, C(max)/dose and A were found significantly lower at W1 than at M3 ( P<0.01 and P<0.005, respectively), while lambda(1) was significantly higher at W1 than at both M3 and Y1 ( P<0.01). Using three sampling times (t0 h, t1 h and t3 h), BE allowed an accurate prediction of AUC(0-12 h) (mean bias =3.06+/-12.16%; +1.50+/-1.61%; and -0.20+/-11.42% at W1, M3 and Y1, respectively), AUC(0-4 h )and C(max). MR led to satisfactory estimation of AUC(0-12 h) using only two blood samples collected 2 h and 6 h post-dose (R=0.956-0.993; bias =-5.22 to +4.41; precision =6.38 to 9.90%), but this method is unable to estimate any other exposure index and requires strict respect of sampling times, contrary to BE.

CONCLUSION

Neoral monitoring based on full or abbreviated AUC is possible using BE or MR in heart transplant patients over the first year post-transplantation. BE provides a good description of the individual PK profiles and thus might be useful not only in case of potential discrepancies between C2 and clinical findings, but also for clinical trials aimed at finding optimum PK monitoring in heart recipients.

Bayesian forecasting of oral cyclosporin pharmacokinetics in stable lung transplant recipients with and without cystic fibrosis

The aims of the current study were (1) to study Neoral pharmacokinetics (PK) in stable lung recipients with or without cystic fibrosis (CF), (2) to compare Neoral PK between these two groups, and (3) to design Bayesian estimators for PK forecasting and dose adjustment in these patients using a limited number of blood samples. The individual PK of 19 adult lung transplant recipients, 9 subjects with CF and 10 subjects without CF, were retrospectively studied. Three profiles obtained within 5 days were available for each patient. A PK model combining a gamma distribution to describe the absorption profile and a two-compartment model were applied. Different exposure indices were estimated using nonlinear regression and Bayesian estimation. The PK model developed reliably described the individual PK of Neoral in lung transplant patients with and without CF, and the values of the first and second half-lives were different in these two populations (lambda(1) = 4.14 +/- 3.01 vs. 2.16 +/- 1.75 h(-1); P < 0.01; lambda(2) = 0.36 +/- 0.11 vs. 0.49 +/- 0.12 h(-1); P < 0.01), while the mean absorption time and standard deviation of absorption time tended to be less in patients with cystic fibrosis (P < 0.1). Also, the patients with CF required higher doses than those without CF to achieve similar drug exposure. Consequently, population modeling was performed in CF and non-CF patients separately. Bayesian estimation allowed accurate prediction of AUC(0-12), AUC(0-4), C(max), and T(max) using three blood samples collected at T0h, T1h, and T3h in both groups. This study demonstrated the applicability and good performance of the PK model previously developed for oral cyclosporin and of the MAP Bayesian estimation of cyclosporin systemic exposure in CF and non-CF patients. Moreover, it is the first to propose a monitoring tool specifically designed for cyclosporin monitoring in patients with CF.

A general unknown screening procedure for drugs and toxic compounds in serum using liquid chromatography-electrospray-single quadrupole mass spectrometry

A complete general unknown screening procedure was developed using liquid chromatography-mass spectrometry (LC-MS), a coupling that can increase the range of compounds amenable to MS. Sample preparation was by solid-phase extraction on a mixed-mode support in parallel with serum deproteination in order to recover the most hydrophilic compounds. Chromatography employed a reversed-phase narrow-bore column (150 x 1-mm i.d.) and a 50-min gradient elution at low flow-rate (50 microL/min), compatible with the electrospray source used without splitting nor heating. The single quadrupole LC-MS instrument used was operated in the 100 to 1100 mu mass range in both the positive and negative modes, with two different, alternated collision-induced dissociation voltages in the source, in order to obtain the molecular or pseudo-molecular ions as well as fragments for the compounds analyzed. The addition of spectra obtained at low and high fragmentation voltages gave reconstructed spectra for each polarity, representing library entries. Finally, a program was created in order to detect the peaks of interest in the chromatographic noise using a very efficient signal processing algorithm, compute their relative retention time with respect to the internal standard (glafenine), draw their reconstructed spectra, search them in the libraries, and edit a report.

Absolute bioavailability of midazolam after subcutaneous administration to healthy volunteers

AIMS

Midazolam is given intravenously for induction of anaesthesia and conscious sedation and by subcutaneous infusion in patients in palliative care units. The objective of the present study was to determine the absolute bioavailability of subcutaneous midazolam and its pharmacokinetics in young, healthy, male volunteers.

METHODS

Eighteen volunteers were given single doses of 0.1 mg kg-1 midazolam i.v. and s.c. after a wash-out period of 7-15 days in an open-label, randomized, cross-over study. Blood samples were collected up to 12 h post-infusion. Plasma concentrations of midazolam and of its two metabolites, 1'-OHM and 4-OHM, were assessed using an h.p.l.c.-MS method (LOQ 0.5 ng ml-1 for each analyte). Vital signs, cardiac parameters and oximetry were monitored. Local tolerance was determined and adverse events were also monitored.

RESULTS

After s.c. infusion t(max) and C(max) were 0.51 +/- 0.18 h and 127.8 +/- 29.3 ng ml-1 (mean +/- s.d.), respectively. No statistically significant difference was detected in AUC(0, infinity ) after i.v. and s.c. administration. The mean (+/- s.d.) absolute bioavailability of subcutaneous midazolam was 0.96 (+/- 0.14) (CI 0.84, 1.03). Mean (+/- s.d.) t1/2 was similar after s.c. (3.2 (+/- 1.0) h) and i.v. infusion (2.9 (+/- 0.7) h), although a statistically significant difference was reached (P < 0.05). Mean CL and V of i.v. midazolam were 4.4 +/- 1.0 ml min-1 kg-1 and 1.1 +/- 0.2 l kg-1 (mean +/- s.d.), respectively. Plasma concentrations of 1'-OHM were higher than those of 4-OHM. Few mild and transient adverse events were noted and there were no clinically significant effects on EEG, blood pressure and laboratory parameters.

CONCLUSIONS

This study has shown that subcutaneous midazolam has excellent bioavailability and that administration of midazolam by this route could be preferable when the intravenous route is inappropriate.

[New drugs at "rave parties": ketamine and prolintane]

"Rave parties", all-night dance parties based on "techno" music, represent an increasing phenomenon in France. "Rave drugs" refers to a wide variety of drugs used by the young participants owing to their hallucinogenic or stimulant effects. Uncertainties about the sources of these substances, the possible contaminants and the multiplicity of the associations make it difficult to evaluate the toxic consequences that might be expected in this particular context. This report presents toxicological cases documented by analytical findings in which two pharmacological agents abused in "rave parties" in South-West of France were found. The day following a party, a 17 year-old girl showed a confused state with drowsiness and hallucinations. She confessed having consumed a white powder sold as "ecstasy", that sample analysis identified as pure ketamine. Ketamine is an anaesthetic agent primarily used in veterinary medicine and paediatrics. This drug seems to be abused, mainly by the intranasal route, owing to its hallucinogen effects. Its used in "rave-party" appears to be marked by unsuspected consumption. All long another party, a large quantity of orange tablets were sold and abused by several participants. Analysis performed on some fragments of these tablets revealed the presence of prolintane and ascorbic acid. Prolintane, an amphetamine-related substance, is a central nervous system stimulant. This compound is "freely" available in Spain in combination with several vitamins, under the form of tablets with orange coating named "Katovit" and sold at low price: 1.93 [symbol: see text]/20 tablets (200 mg of prolintane).

Nouvelles drogues de « rave-parties » : ketamine et prolintane

"Rave parties", all-night dance parties based on "techno" music, represent an increasing phenomenon in France. "Rave drugs" refers to a wide variety of drugs used by the young participants owing to their hallucinogenic or stimulant effects. Uncertainties about the sources of these substances, the possible contaminants and the multiplicity of the associations make it difficult to evaluate the toxic consequences that might be expected in this particular context. This report presents toxicological cases documented by analytical findings in which two pharmacological agents abused in "rave parties" in South-West of France were found. The day following a party, a 17 year-old girl showed a confused state with drowsiness and hallucinations. She confessed having consumed a white powder sold as "ecstasy", that sample analysis identified as pure ketamine. Ketamine is an anaesthetic agent primarily used in veterinary medicine and paediatrics. This drug seems to be abused, mainly by the intranasal route, owing to its hallucinogen effects. Its used in "rave-party" appears to be marked by unsuspected consumption. All long another party, a large quantity of orange tablets were sold and abused by several participants. Analysis performed on some fragments of these tablets revealed the presence of prolintane and ascorbic acid. Prolintane, an amphetamine-related substance, is a central nervous system stimulant. This compound is "freely" available in Spain in combination with several vitamins, under the form of tablets with orange coating named "Katovit" and sold at low price: 1.93 €/20 tablets (200 mg of prolintane).

Application of a gamma model of absorption to oral cyclosporin

BACKGROUND

Some drugs, such as cyclosporin, exhibit flat and delayed absorption profiles, with a correlation between the delay and the peak width. Such profiles can be described by an absorption model in which the absorption rate is derived from a gamma distribution (of which the classical first-order absorption model is a special case).

OBJECTIVE

To develop a model for the pharmacokinetics of extravascular administration of cyclosporin and apply it to a study of the pharmacokinetics of cyclosporin microemulsion in stable renal transplant recipients.

PATIENTS AND PARTICIPANTS

21 renal transplant patients receiving oral cyclosporin microemulsion 75 to 175 mg twice daily.

METHODS

The equation of the plasma concentration-time curve after oral administration was expressed as a convolution product between the absorption rate and a multi-exponential impulse response. The convolution integral was computed analytically and expressed in terms of the incomplete gamma function. Cyclosporin was assayed by liquid chromatography/mass spectrophotometry. The model was fitted by nonlinear regression, using a specially developed program.

RESULTS

The gamma model yielded a good fit in all of the 21 patients studied. Attempts to fit the same data by a classical exponential with lag-time model failed in most patients.

CONCLUSIONS

This model could simplify the Bayesian monitoring of cyclosporin therapy.

Fatal intoxications with chloral hydrate

An alcoholic man, treated with chloral hydrate (CH) syrup to which he was dependent, was discovered comatose and in respiratory arrest. Death occurred on the ninth day of hospitalization following cerebral oedema. A woman, alcohol addicted, depressed, and epileptic was admitted in the Intensive Care Unit with heart and respiratory failure following CH absorption. She died three days later after a deep coma. In these two cases, CH intoxication was confirmed by toxicological analysis: CH and its major metabolite, trichloroethanol (TCE), were identified and determined in serum and urine using headspace-capillary gas chromatography-mass spectrometry. The concentrations measured were compared with those found in previously published fatalities. The analytical method used can be proposed for both clinical and forensic cases.

Sensitive and specific multiresidue methods for the determination of pesticides of various classes in clinical and forensic toxicology

Original and sensitive multiresidue methods are presented for the detection and quantitation, in human biological matrices, of 61 pesticides of toxicological significance in human. These methods involved rapid solid-phase extraction using new polymeric support (HLB and MCX) OASIS cartridges. Gas chromatography-mass spectrometry (GC-MS) was used for volatile (organophosphate, organochlorine, phtalimide, uracil) pesticides and liquid chromatography-ionspray-mass spectrometry (LC-MS) for thermolabile and polar pesticides (carbamates, benzimidazoles). Acquisition was performed in the selected ion monitoring (SIM) mode. Extraction recovery varied owing to the nature of pesticides, but was satisfactory for all. Limits of detection (LODs) and limits of quantitation (LOQs) ranged, respectively, from 2.5 to 20 and from 5 to 50ng/ml. An excellent linearity was observed from LOQs up to 1000ng/ml for all the pesticides studied. The proposed procedures yielded reproducible results with good inter-assay accuracy and precision. A few cases of intoxication are presented to demonstrate the diagnostic interest of these methods: in two cases were determined lethal concentrations of endosulfan and carbofuran; in four other cases, the procedures helped diagnose intoxication with, respectively, parathion-ethyl, the association of bromacil and strychnine, bifenthrin and aldicarb.

Determination of N-acetylation phenotype using caffeine as a metabolic probe and high-performance liquid chromatography with either ultraviolet detection or electrospray mass spectrometry

A rapid, sensitive method using liquid chromatography-electrospray mass spectrometry (LC-ES-MS) was developed and evaluated for the simultaneous quantitative determination of caffeine metabolites 1U, 1X and AAMU in human urine. This method involved a simple dilution of urine samples. The chromatographic separation was achieved on a C18 reversed-phase column using a gradient of acetonitrile in 2 mM, pH 3.0 ammonium formate as mobile phase. After ionisation in an electrospray source, mass spectrometric detection was performed in the negative ion, selected ion monitoring mode. This method yielded acceptable accuracy and precision within the range 0.25-50 microg/ml. This analytical method was applied to investigate the N-acetylator phenotype of HIV-infected patients and compared with high-performance liquid chromatography with UV detection. Its specificity was better, which appeared to be absolutely necessary to prevent errors in metabolic ratios and phenotype interpretation.

Multiresidue determination method for organophosphorus pesticides in serum and whole blood by gas chromatography-mass-selective detection

This paper describes a rapid, specific and sensitive method for the determination of 29 organophosphorus pesticides in blood and serum, involving a rapid solid-phase extraction procedure using Oasis HLB cartridges and gas chromatography coupled to mass-selective detection. The ionization was performed by electron Impact and acquisition in the single ion monitoring mode followed three specific ions per analyte. Extraction recoveries were satisfactory and ranged between 40 and 108% in blood and serum. Limits of detection ranged from 5 to 25 ng/ml and limits of quantitation (LOQs) ranged from 10 to 50 ng/ml, in blood and serum. An excellent linearity was observed from these LOQs up to 1000 ng/ml. Intra- and inter-assay precision and accuracy were satisfactory for most of the pesticides analyzed.

[Functions of the 'Therapeutic Drug Monitoring (TDM)' Group of the French Society of Pharmacology]

Therapeutic Drug Monitoring consists of sampling organization, measurement and interpretation of the blood concentration or biological effect of a given xenobiotic, and sometimes using this result for pharmacokinetic computation, with the aim of individual dose adjustment. This branch of pharmacology is represented internationally by the International Association of Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT) and has been organized, in France, as a working group of the French Society of Pharmacology (SFP). This group takes part in the main French organizations dealing with or using TDM, as well as the scientific activities of SFP and organizes multi-centre clinical trials studying exposure-effect relationships or based on 'concentration-controlled' protocols. Finally, another aim of this TDM group is to promote the development and acknowledgement of this activity in hospitals.

Sensitive determination of vinorelbine and its metabolites in human serum using liquid chromatography-electrospray mass spectrometry

A liquid chromatography-electrospray mass spectrometry method was developed for the quantitation of vinorelbine (VNB) and two metabolites, vinorelbine N-oxide (VNO) and deacetyl vinorelbine (DAV) in human serum. The limits of quantitation (LOQ) reached 0.5 ng/ml for both VNB and VNO and 1 ng/ml for DAV. The method was proved linear in the range of LOQs up to 1000 ng/ml, and extraction recovery was 80% on average for the three compounds. It was applied to the pharmacokinetic monitoring of vinorelbine and, for the first time, to the detection of VNO in the serum of patients suffering from non-small-cell lung cancer.

A quantitative analysis of L-glutamate-regulated Na+ dynamics in mouse cortical astrocytes: implications for cellular bioenergetics

The mode of Na+ entry and the dynamics of intracellular Na+ concentration ([Na+]i) changes consecutive to the application of the neurotransmitter glutamate were investigated in mouse cortical astrocytes in primary culture by video fluorescence microscopy. An elevation of [Na+]i was evoked by glutamate, whose amplitude and initial rate were concentration dependent. The glutamate-evoked Na+ increase was primarily due to Na+-glutamate cotransport, as inhibition of non-NMDA ionotropic receptors by 6-cyano-7-nitroquinoxiline-2,3-dione (CNQX) only weakly diminished the response and D-aspartate, a substrate of the glutamate transporter, produced [Na+]i elevations similar to those evoked by glutamate. Non-NMDA receptor activation could nevertheless be demonstrated by preventing receptor desensitization using cyclothiazide. Thus, in normal conditions non-NMDA receptors do not contribute significantly to the glutamate-evoked Na+ response. The rate of Na+ influx decreased during glutamate application, with kinetics that correlate well with the increase in [Na+]i and which depend on the extracellular concentration of glutamate. A tight coupling between Na+ entry and Na+/K+ ATPase activity was revealed by the massive [Na+]i increase evoked by glutamate when pump activity was inhibited by ouabain. During prolonged glutamate application, [Na+]i remains elevated at a new steady-state where Na+ influx through the transporter matches Na+ extrusion through the Na+/K+ ATPase. A mathematical model of the dynamics of [Na+]i homeostasis is presented which precisely defines the critical role of Na+ influx kinetics in the establishment of the elevated steady state and its consequences on the cellular bioenergetics. Indeed, extracellular glutamate concentrations of 10 microM already markedly increase the energetic demands of the astrocytes.

High-performance liquid chromatographic determination of tianeptine in plasma applied to pharmacokinetic studies

An improved analytical method for the quantitative measurement of tianeptine and its main metabolite MC5 in human plasma was designed. Extraction involved ion-paired liquid-liquid extraction of the compounds from 1.0 ml of human plasma adjusted to pH 7.0. HPLC separation was performed using a Nucleosil C18, 5 microm column (150x4.6 mm I.D.) and a mixture of acetonitrile and pH 3, 2.7 g l(-1) solution of sodium heptanesulfonate in distilled water (40:60, v/v) as mobile phase. UV detection was performed using a diode array detector in the 200-400 nm passband, and quantification of the analytes was made at 220 nm. For both tianeptine and MC5 metabolite, the limit of quantitation was 5 microg l(-1) and the calibration curves were linear from 5 to 500 microg l(-1). Intra- and inter-assay precision and accuracy fulfilled the international requirements. The recovery of tianeptine and its metabolite from plasma was, respectively, 71.5 and 74.3% at 20 microg l(-1), 71.2 and 70.8% at 400 microg l(-1). The selectivity of the method was checked by verifying the absence of chromatographic interference from pure solutions of the most commonly associated therapeutic drugs. This method, validated according to the criteria established by the Journal of Chromatography B, was applied to the determination of tianeptine and MC5-metabolite in human plasma in pharmacokinetic studies.

A non-fatal case of intoxication with foxglove, documented by means of liquid chromatography-electrospray-mass spectrometry

The non-fatal self-poisoning of a 36-year-old female patient, who ingested a concoction of foxglove (Digitalis Purpurea), is presented. On the admission, initial symptoms were nausea and vomiting, abdominal pain, and cardiovascular shock with sinus bradycardia. Blood and urine were assayed for 17 cardiotonic hetorosides, using a highly specific LC-MS procedure. Serum and urine specimens were collected over five days and analyzed by liquid chromatography-electrospray-mass spectrometry (LC-ES-MS). This accurate procedure allowed the determination of the digitalis glycosides and their metabolites in serum and urine. The serum concentrations of digitalis glycosides were maximum on the first day (gitoxin 13.1 ng/mL, digitoxin 112.6 ng/mL, digitoxigenin 3.3 ng/mL, and digitoxigenin mono-digitoxoside 8.9 ng/mL) and decreased over five days. We observed a peak gitaloxin level (112.6 ng/mL) on the fifth day only. After administration of atropine as well as dimeticone, alginic acid, and metoclopramide, health status improved. The peak urine concentrations were reached at hour 30 and were respectively 91.3 and 69.9 ng/mL for gitaloxin and digitoxin, while those of digitoxigenin, digitoxigenin mono-digoxoside and gitoxin were lower (respectively 0.7, 1, and 5.6 ng/mL). The patient was discharged on the fifth day when there were no residual symptoms.

Spatial filtering for zero-order and twin-image elimination in digital off-axis holography

Off-axis holograms recorded with a CCD camera are numerically reconstructed with a calculation of scalar diffraction in the Fresnel approximation. We show that the zero order of diffraction and the twin image can be digitally eliminated by means of filtering their associated spatial frequencies in the computed Fourier transform of the hologram. We show that this operation enhances the contrast of the reconstructed images and reduces the noise produced by parasitic reflections reaching the hologram plane with an incidence angle other than that of the object wave.

Methods for the determination of seven selective serotonin reuptake inhibitors and three active metabolites in human serum using high-performance liquid chromatography and gas chromatography

This paper describes a set of simple and sensitive multiresidue methods for the determination of the specific serotonin reuptake inhibitors (SSRIs) used as antidepressant drugs, and some of their respective active metabolites in human serum. It involves liquid-liquid extraction procedures followed by gas chromatography coupled to nitrogen phosphorus detection or isocratic reversed-phase high-performance liquid chromatography combined with fluorescence detection (HPLC-FL), depending on the analytes. Extraction recoveries were between 71 and 96% for the eight SSRIs and their metabolites analysed by GC and between 41 and 77% for the two of them analysed by HPLC. Limits of detection (LODs) and limits of quantitation (LOQs) ranged, respectively, from 2.5 to 5 microg/l and from 10 to 20 microg/l. Intra-assay and inter-assay precision was studied at three and four concentration levels, respectively, and was less than 19% for all compounds. Accuracy was also satisfactory for all. An excellent linearity was observed from the LOQs up to 1000 microg/l for milnacipram and paroxetine and from each LOQ up to 400 mg/l for the other compounds. The performance of the methods described thus allows the therapeutic drug monitoring of the currently commercialised SSRIs.

Adaptive control methods for the dose individualisation of anticancer agents

Numerous studies have found a clear relationship between systemic exposure and the toxicity or (more rarely) the efficacy of anticancer agents. Moreover, the clearance of most of these drugs differs widely between patients. These findings, combined with the narrow therapeutic index of anticancer drugs, suggest that patient outcome would be improved if doses were individualised to achieve a target systemic exposure. Bayesian maximum a posteriori probability (MAP) forecasting is an efficient and robust method for the optimisation of drug therapy, but its use for anticancer drugs is not yet extensive. The aim of this paper is to review the application of population pharmacokinetics and MAP to anticancer drugs and to evaluate whether and when MAP Bayesian estimation improves the clinical benefit of anticancer chemotherapy. For each drug, the relationships between pharmacokinetic variables [e.g. plasma concentration or the area under the concentration-time curve] and pharmacodynamic effects are described. Secondly, the methodologies employed are considered and, finally, the results are analysed in terms of predictive performance as well as, where possible, the impact on clinical end-points. Some studies were retrospective and intended only to evaluate individual pharmacokinetic parameter values using very few blood samples. Among the prospective trials, a few studied the pharmacokinetic/pharmacodynamic relationships which provided the basis for routine pharmacokinetic monitoring. Others were performed in clinical context where MAP Bayesian estimation was used to determine maximum tolerated systemic exposure (e.g. for carboplatin, topotecan, teniposide) or for pharmacokinetic monitoring (e.g. for methotrexate or platinum compounds). Indeed, its flexibility in blood sampling times makes this technique much more applicable than other limited sampling strategies. These examples demonstrate that individual dose adjustment helps manage toxicity. The performance of pharmacokinetic monitoring is linked to the methodology used at each step of its design and application. Moreover, a limitation to the use of pharmacokinetic monitoring for certain anticancer drugs has been the difficulty in obtaining pharmacokinetic or pharmacodynamic data. Recent progress in analytical methods, as well as the development of noninvasive methods (such as positron emission tomography) for evaluating the effects of chemotherapy, will help to define pharmacokinetic-pharmacodynamic relationships. Bayesian estimation is the strategy of choice for performing pharmacokinetic studies, as well as ensuring that a given patient benefits from the desired systemic exposure. Together, these methods could contribute to improving cancer chemotherapy in terms of patient outcome and survival.

Simultaneous determination of four anthracyclines and three metabolites in human serum by liquid chromatography-electrospray mass spectrometry

A sensitive and very specific method, using liquid chromatography-electrospray mass spectrometry (LC-ES-MS), was developed for the determination of epirubicin, doxorubicin, daunorubicin, idarubicin and the respective active metabolites of the last three, namely doxorubicinol, daunorubicinol and idarubicinol in human serum, using aclarubicin as internal standard. Once thawed, 0.5-ml serum samples underwent an automated solid-phase extraction, using C18 Bond Elut cartridges (Varian) and a Zymark Rapid-Trace robot. After elution of the compounds with chloroform-2-propanol (4:1, v/v) and evaporation, the residue was reconstituted with a mixture of 5 mM ammonium formate buffer (pH 4.5)-acetonitrile (60:40, v/v). The chromatographic separation was performed using a Symmetry C18, 3.5 microm (150 x 1 mm I.D.) reversed-phase column, and a mixture of 5 mM ammonium formate buffer (pH 3)-acetonitrile (70:30, v/v) as mobile phase, delivered at 50 microl/min. The compounds were detected in the selected ion monitoring mode using, as quantitation ions, m/z 291 for idarubicin and idarubicinol, m/z 321 for daunorubicin and daunorubicinol, m/z 361 for epirubicin and doxorubicin, m/z 363 for doxorubicinol and m/z 812 for aclarubicin (I.S.). Extraction recovery was between 71 and 105% depending on compounds and concentration. The limit of detection was 0.5 ng/ml for daunorubicin and idarubicinol, 1 ng/ml for doxorubicin, epirubicin and idarubicin, 2 ng/ml for daunorubicinol and 2.5 ng/ml for doxorubicinol. The limit of quantitation (LOQ) was 2.5 ng/ml for doxorubicin, epirubicin and daunorubicinol, and 5 ng/ml for daunorubicin, idarubicin, doxorubicinol and idarubicinol. Linearity was verified from these LOQs up to 2000 ng/ml for the parent drugs (r > or = 0.992) and 200 ng/ml for the active metabolites (r > or = 0.985). Above LOQ, the within-day and between-day precision relative standard deviation values were all less than 15%. This assay was applied successfully to the analysis of human serum samples collected in patients administered doxorubicin or daunorubicin intravenously. This method is rapid, reliable, allows an easy sample preparation owing to the automated extraction and a high selectivity owing to MS detection.

Fatal intoxication following self-administration of a massive dose of buprenorphine

Several drug packages, including Subutex (high-dose buprenorphine, as sublingual tablets) boxes, were found near the corpse of a 25-year-old male drug addict, who apparently had committed suicide. The autopsy revealed a fatal respiratory depression. The toxicological investigations concluded that death resulted from massive burpienorphine intoxication. The determination of buprenorphine (BU) and norbuprenorphine (NBU) in all biological specimens was performed by liquid chromatography-electrospray mass spectrometry (LC-ES-MS) after hydrolysis (for solid tissues), deproteinization of the matrices, and solid-phase extraction of the compounds. Exceptionally high concentrations of BU and NBU were found in blood (3.3 and 0.4 mg/L, respectively), urine (3.4 and 0.6 mg/L), bile (2035 and 536 mg/L and brain (6.4 a nd 3.9 microg/g). The high concentration of BU (899 mg/L) and the absence of NBU in gastric liquid suggested oral intake. High concentrations of amino-7-flunitra/epam, the main metabolite of flunitra/epam, were also found in blood, urine and gastric liquid. This benzodiazepine may have been a co-factor in the toxic effects of BU.

Sensitive determination of irinotecan (CPT-11) and its active metabolite SN-38 in human serum using liquid chromatography-electrospray mass spectrometry

A couple of sensitive and accurate liquid chromatography-electrospray mass spectrometry (LC- S-MS) methods for the determination of the total forms of irinotecan and its active metabolite SN-38 in human serum, using the same chromatographic and detection conditions, is presented. Both used camptothecin as internal standard (I.S.). The sample pretreatment for irinotecan involved a simple protein precipitation with acetonitrile, whereas a liquid-liquid extraction was necessary for SN-38. A Symmetry C18, 3.5 microm (150 x 1 mm I.D.) reversed-phase column was used for the chromatographic separation, together with a gradient elution of acetonitrile in 5 mM ammonium formate buffer (pH 3) as mobile phase. After ionisation in the pneumatically-assisted electrospray source and in-source collision induced dissociation, acquisition was performed in the selected ion monitoring mode. Recoveries were 69 and 47% on average, detection limits 2.5 and 0.25 ng/ml and quantitation limits 10 and 0.5 ng/ml for irinotecan and SN-38, respectively. Reproducibility was good and the method was linear from limits of quantitation up to 10,000 ng/ml for irinotecan, and up to 100 ng/ml for SN-38. This sensitive and highly specific method is suitable both for pharmacokinetic studies and routine therapeutic drug monitoring.

Simultaneous amplitude-contrast and quantitative phase-contrast microscopy by numerical reconstruction of Fresnel off-axis holograms

We present a digital method for holographic microscopy involving a CCD camera as a recording device. Off-axis holograms recorded with a magnified image of microscopic objects are numerically reconstructed in amplitude and phase by calculation of scalar diffraction in the Fresnel approximation. For phase-contrast imaging the reconstruction method involves the computation of a digital replica of the reference wave. A digital method for the correction of the phase aberrations is presented. We present a detailed description of the reconstruction procedure and show that the transverse resolution is equal to the diffraction limit of the imaging system.

Sensitive and specific determination of midazolam and 1-hydroxymidazolam in human serum by liquid chromatography-electrospray mass spectrometry

A liquid chromatographic-mass spectrometric technique was designed for the determination of the anaesthetic benzodiazepine midazolam (MID) and its active metabolite 1-hydroxymidazolam (1-OHM), with the aim of conducting pharmacokinetic/pharmacodynamic studies. MID and 1-OHM were extracted from alkalinised (pH 9.5) spiked and clinical serum samples using a single step, liquid-liquid extraction procedure with diethyl ether-2-propanol (98:2, v/v). The chromatographic separation was performed on a Nucleosil C18, 5 microm (150x1 mm I.D.) column, using a gradient of acetonitrile in 5 mM ammonium formate, pH 3.0 as the mobile phase, delivered at a flow-rate of 50 microl/min. The compounds were ionised in the ionspray source of an atmospheric pressure mass spectrometer, fragmented by in-source collisions and the pseudomolecular and fragment ions detected in the selected ion monitoring mode. The recovery was between 79 and 87% for MID, between 83 and 87% for 1-OHM and 81.5% for methylclonazepam. The limit of detection was 0.2 microg/l for MID and 0.5 microg/l for 1-OHM, the limit of quantitation (LOQ) was 0.5 microg/l for both. Linearity was verified from these LOQs up to 2000 microg/l and the method was found accurate and precise over this range. It was successfully applied to a preliminary study to establish the concentration versus time curve of MID and 1-OHM in a patient administered midazolam by continuous infusion.

Liquid chromatography-mass spectrometry: potential in forensic and clinical toxicology

A relatively limited number of papers concerning applications of liquid chromatography-mass spectrometry (LC-MS) to forensic or clinical toxicology, or analytical methods directly applicable to these topics have been published so far, but their number have greatly increased in the past two years, probably due to technical improvements and to a decrease in the price of such instruments. After a brief presentation and exemplary applications of the interfaces and/or sources proposed in the past for coupling HPLC to mass spectrometry (direct liquid inlet, moving belt, fast atom bombardment and thermospray interfaces), this paper describes electrospray-type and atmospheric pressure chemical ionisation interfaces and their most recent applications in forensic or clinical toxicology. In a third section, the different LC-MS solutions proposed for typical applications in human toxicology, such as the determination of morphine metabolites, LSD and its metabolites and corticosteroids in blood or urine, are reviewed in detail in order to highlight the strengths and weaknesses of each ionisation device and/or analytical method. The last section envisages the new analytical fields opened up by LC-MS in toxicology, regarding mainly peptides, proteins and large molecules, as well as the possible use of LC-MS as a complement to GC-MS for "general unknown" screenings; it also deals with the perspectives concerning technical improvements in ionisation interfaces/sources or mass spectrometers, as well as in sample preparation and liquid chromatography techniques applied to this type of coupling. Though LC-MS is still a relatively new technique in toxicology, on taking into consideration its success so far and owing to the simplification of instruments and concept handling thanks to user-friendly software, it is the authors' opinion that it will become a major success in analytical toxicology in the next few years.

In vivo local determination of tissue optical properties: applications to human brain

Local and superficial near-infrared (NIR) optical-property characterization of turbid biological tissues can be achieved by measurement of spatially resolved diffuse reflectance at small source-detector separations (<1.4 mm). However, in these conditions the inverse problem, i.e., calculation of localized absorption and the reduced scattering coefficients, is necessarily sensitive to the scattering phase function. This effect can be minimized if a new parameter of the phase function gamma, which depends on the first and the second moments of the phase function, is known. If gamma is unknown, an estimation of this parameter can be obtained by the measurement, but the uncertainty of the absorption coefficient is increased. A spatially resolved reflectance probe employing multiple detector fibers (0.3-1.4 mm from the source) is described. Monte Carlo simulations are used to determine gamma, the reduced scattering and absorption coefficients from reflectance data. Probe performance is assessed by measurements on phantoms, the optical properties of which were measured by other techniques [frequency domain photon migration (FDPM) and spatially resolved transmittance]. Our results show that changes in the absorption coefficient, the reduced scattering coefficient, and gamma can be measured to within +/-0.005 mm(-1), +/-0.05 mm(-1), and +/-0.2, respectively. In vivo measurements performed intraoperatively on a human skull and brain are reported for four NIR wavelengths (674, 811, 849, 956 nm) when the spatially resolved probe and FDPM are used. The spatially resolved probe shows optimum measurement sensitivity in the measurement volume immediately beneath the probe (typically 1 mm(3) in tissues), whereas FDPM typically samples larger regions of tissues. Optical-property values for human skull, white matter, scar tissue, optic nerve, and tumors are reported that show distinct absorption and scattering differences between structures and a dependence on the phase-function parameter gamma.

In vitro and in vivo study of the antithyroid side effects of trimeprazine

Trimeprazine (TMP), a phenothiazine used as antipsychotic drug, was previously shown to induce a decrease in thyroid hormone serum levels in rats. Different mechanisms might be involved, mainly (i) a central mechanism, involving a reduction of thyroid-stimulating hormone (TSH) secretion; (ii) a peripheral mechanism, acting upon the synthesis of thyroid hormones, by inhibition of thyroperoxidase (TPO) or trapping of molecular iodine present in the thyroid gland. These different hypotheses were investigated in the present study, using in vitro and in vivo experiments. In vitro studies concerned TMP and its three main metabolites: trimeprazine sulphoxide (TSO), N-desmethyl trimeprazine (NDT), and 3-hydroxy-trimeprazine (3-OHT). TMP and TSO expressed a high affinity for iodine in vitro, contrary to NDT, which did not complex iodine. Only 3-OHT inhibited TPO in vitro. Administration of 5 mg/kg TMP ip twice daily for 11 days to Wistar rats induced a decrease of free triiodothyronine and free thyroxine (fT(3) and fT(4)) and a trend toward an increase of TSH serum levels. Thyroid concentrations of TMP, NDT, and TSO were significantly higher than serum levels, while 3-OHT was never detected. An iodine-supplemented diet administered to a group of rats treated with TMP significantly increased the thyroid concentration of TMP and TSO, but not that of NDT, while it did not affect the concentrations observed in serum and other organs. The increase in plasma TSH is not consistent with the central mechanism hypothesis, and the absence of TPO inhibition by TMP, TSO, and NDT contradicts the TPO inhibition hypothesis. On the contrary, three findings support the hypothesis of iodine trapping through formation of a complex with TMP and TSO: these molecules complex iodine in vitro, they accumulate in the thyroid, and their thyroid concentration is increased when the rats are fed an iodine-supplemented diet.

Dexamethasone in resting and exercising men. II. Effects on adrenocortical hormones

This study presents the reactions of adrenocorticosteroids (cortisol and aldosterone) and sex steroids [testosterone, androstenedione, and dehydroepiandrosterone and its sulfate (DHAS)] 1) to a dexamethasone (Dex) treatment, which is expected to lower steroid levels via the ACTH blockade, and 2) to an exercise bout at maximal O(2) consumption, which is expected to increase steroid production via ACTH stimulation. Consistent with the decrease in ACTH, all steroids except testosterone reacted negatively to Dex, independently of the dose (0.5 and 1.5 mg administered twice daily for 4.5 days). After exercise, plasma ACTH rose to 600% of basal value, resulting in a significant increase in aldosterone and adrenal androgens, but cortisol and DHAS were unaffected. This apparently surprising result can be explained by differences in peripheral metabolism: a theoretical calculation predicted that after 15 min the increase in hormone concentration may only reach 12% for cortisol and 2% for DHAS. For cortisol and adrenal androgens, assays were carried out using plasma and saliva. The consistent results obtained from the two matrices allow us to consider salivary assays as a useful tool for steroid abuse detection.

Dexamethasone in resting and exercising men. I. Effects on bioenergetics, minerals, and related hormones

A placebo and a low and a high dose of dexamethasone (Dex) were administered for 4.5 days, at 3-wk intervals, to 24 healthy men, following a double-blind, random-order, crossover procedure. After the last dose the subjects performed a maximal cycling exercise, during which respiratory exchanges, electrocardiogram, and blood pressures were monitored. Blood was sampled just before and after each exercise bout. Dex showed no significant effect on fitness, sleep, exhaustion during exercise, maximal O(2) consumption, ventilatory threshold, maximal blood lactate, or rest and exercise blood pressures. On the contrary, both doses of Dex significantly decreased heart rate at rest and during maximal exercise. Blood glucose at rest was higher after both doses of Dex than after placebo; the opposite was found during exercise. Blood levels of ACTH, beta-endorphin, cortisol, and cortisol-binding globulin were lowered by Dex at rest and after exercise. Dex stimulated the increase in atrial natriuretic factor during exercise and lowered rest and postexercise aldosterone. Finally, no difference between "fit or trained" and "less fit or untrained" subjects could be found with respect to Dex effects.

[Therapeutic monitoring: analytic, pharmacokinetic and clinical aspects]

This paper gives an overview of present aspects and future prospects of therapeutic drug monitoring (TDM). The main aims of TDM are to avoid therapeutic failures due to bad compliance or too low dose of a given drug, as well as adverse or toxic effects due to an excessive dose. The therapeutic drugs frequently monitored depend on the country, but are generally few. For some of these drugs or for others, only patients at risk or belonging to particular sub-populations for a given drug, need TDM. A pre-analytical management is necessary, comprising a correct information of the physician, concerning the nature of the sample to collect and the clinical data necessary to the interpretation, as well as their recording; the control of the sample routing and storing conditions. Nowadays, drug analyses are essentially performed using immunochemical techniques, rapid and easy to operate but limited to a small number of drugs, and chromatographic methods, more specific and adaptable to almost any therapeutic drug and financially and technically more and more accessible. The interpretation of analytical results is a most important part of TDM, which requires knowledge of clinical data, precise collection time, co-administered treatments, and to dispose of a previously defined therapeutic range or target concentration, adapted to the population to which the patient belongs; the limitations of the analytical technique used must also be considered. Clinical pharmacokinetics is a further step in the use of analytical results, allowing the prediction of an efficient dose and administration schedule in one step, using a limited number of blood samples and generally a Bayesian estimation algorithm, readily available through commercial software dedicated to a few drugs in different reference populations. The pharmacokinetic characteristics of different populations and the validation of bayesian estimation have also been published for a number of drugs, sometimes by pharmaceutical companies following phase I and II clinical trials, even taking into account various physiopathological co-variables, but mostly by independent researchers using smaller populations. The efficiency and cost of routine TDM are questionable when it is prescribed with no clinical information or even no indication of administration and sampling times. On the contrary, several studies reported that clinical pharmacokinetics significantly improved patient outcome and were cost-saving, particularly in terms of duration of hospitalisation. The author's opinion is that TDM, in the near future, will be mainly dedicated to drugs used to treat life-threatening diseases, such as anti-HIV, anticancer and immunosuppressive drugs, and maybe also biotechnological peptides or proteins, because of cost considerations. TDM will probably also be used preferentially in target populations, characterised by higher risk or pharmacokinetic variability. Very sensitive, specific and partly automated separative techniques, such as liquid chromatography-tandem mass spectrometry, might become more common than immunochemical methods, owing to a higher flexibility and improved sample throughout. Clinical pharmacokinetics may spread to a larger number of drugs and patients, due to larger reference populations available, taking into account a number of co-variables, computerised data collection and simplified modelisation. Therefore, TDM will mainly be performed in hospitals, with an essentially clinical role for the pharmacists or pharmacologists involved and routine use of recent and efficient technologies for the TDM laboratory technical staff.

[A specific dosage method for the analysis of 24 antidepressants using gas chromatography-mass spectrometry (GC/SM)]

A specific and sensitive method for the analysis of 24 antidepressants in human serum was developed using gas chromatography-mass spectrometry (GC/MS). This method allowed the simultaneous determination of antidepressants belonging to different classes: tricyclic antidepressants (TADs), selective serotonin reuptake inhibitors (SSRIs) and selective inhibitors of monoamine oxidase A (IMAOs). Antidepressants were submitted to liquid-liquid extraction at pH 9.5 using a mixture of heptane/isoamyl alcohol (98.5/1.5; v/v) without derivatization. Cyproheptadine was used as the internal standard (IS). Separation was obtained with a nonpolar PTE5 capillary column (30 m x 0.32 mm; film thickness 0.25 micron). Mass spectrometry consisted of electron impact ionisation (70 eV), and full scan acquisition. Extraction recoveries were over 60% for 22 antidepressants and between 35 and 95% for moclobemide and viloxazine. Limits of quantitation ranged from 20 to 100 ng/ml for most of the antidepressants, except for moclobemide and viloxazine for which it was 500 ng/ml. Intra-assay standard deviation was satisfactory. An excellent linearity was observed from the respective LOQs up to 1000 ng/ml for 22 antidepressants and up to 4000 ng/ml for moclobemide and viloxazine.

Liquid chromatography-electrospray mass spectrometry multi-residue determination of pesticides in apples and pears

This paper describes a rapid, specific and sensitive multi-residue method for the routine quantitative analysis of pesticides of several classes used for the treatment of apples and pears, down to their respective maximum residue limits (MRLs). It involves a rapid extraction procedure and liquid chromatography coupled to electrospray mass selective detection. Seven pesticides were extracted at pH 4.5 with a mixture of acetone-dichloromethane-hexane (50:20:30, v/v/v). Ionization was performed at atmospheric pressure in an electrospray-type source and detection was carried out using the selected ion monitoring (SIM) mode. Extraction recoveries were between 55 and 98% except for methylthiophanate (< 20%). Limits of detection (LODs) and limits of quantitation (LOQs) ranged, respectively, from 0.01 to 0.02 mg/kg and from 0.02 to 0.05 mg/kg, with relative standard deviation (R.S.D.) less than 19%. An excellent linearity was observed for LOQs up to 5 mg/kg. Intermediate ("inter-assay") precision and accuracy were satisfactory. The method was applied to many fruit samples intended for commercialization.

Decrease of serum paraoxonase activity in chronic renal failure

Paraoxonase is an esterase that hydrolyzes organophosphate compounds. The enzyme is associated with HDL and could protect LDL against peroxidation, which suggests a possible involvement of paraoxonase in the antiatherogenic properties of HDL. Paraoxonase activity has been shown to be low in patients with myocardial infarction, diabetes mellitus, or familial hypercholesterolemia. Because cardiovascular disease is the main cause of death in chronic renal failure, serum paraoxonase activity was measured by spectrophotometry using three synthetic substrates (phenyl acetate, paraoxon, and 4-nitrophenyl acetate) in 305 patients with kidney disease, including 47 patients with non-end-stage chronic renal failure, 104 patients treated with hemodialysis, 22 patients treated with peritoneal dialysis, and 132 renal transplant patients. Patients were compared with two groups of aged-matched control subjects (total number = 195). Especially with 4-nitrophenyl acetate, paraoxonase activity was lower in patients with some degree of renal insufficiency (chronic renal failure [P < 0.05], chronic hemodialysis [P < 10(-4)], chronic peritoneal dialysis [P < 10(-4)]) than in control subjects. In transplant patients, paraoxonase activity was not found to be different from that in control subjects. The decrease of paraoxonase activity and thus the reduction of its antiatherogenic properties in renal failure could be an essential factor of premature vascular aging, especially when dialysis is used. Renal transplantation seems to restore paraoxonase activity.

Thyroid accumulation and adverse effects of imipramine and desipramine in rats after long-term administration

The respective adverse effects of imipramine and desipramine on serum thyroid hormone levels and their accumulation in thyroid were investigated in male Wistar rats. Two groups of 30 rats were gavaged for 4 weeks with 30 mg/kg/day imipramine hydrochloride (IMI) or desipramine hydrochloride (DESI), while the control group (12 rats) received the arabic gum vehicle only. In the IMI-treated group, the serum thyroxine (T4) level significantly decreased (by 13%) and IMI and its metabolite DESI were accumulated in the thyroid, as pointed out by mean thyroid-to-serum concentration ratios close to 12 and 8, respectively. In the DESI-treated group, the mean thyroid-to-serum concentration ratio of the drug was close to 14, and significant decreases in both serum T4 (-20%) and triiodothyronine serum levels (-14%) were found. The accumulation of antidepressant drugs in the thyroid was more pronounced and the thyroid serum levels were even lower after DESI administration than after IMI administration. These results are in favour of an antithyroid action of IMI and DESI due to the formation of a complex in the thyroid between molecular iodine and the drugs or metabolites.

Is there an optimal time to administer methotrexate in the treatment of rheumatoid arthritis?

OBJECTIVE

To determine the optimal time to administer methotrexate (MTX) in rheumatoid arthritis (RA).

METHODS

In a crossover study 23 patients were administered MTX intramuscularly at either 10 AM or 6 PM. A 2 week interval separated the 2 injections. MTX concentrations were measured using a fluorescence polarization immunoassay. Pharmacokinetic variables were estimated using a Bayesian approach. The morning and evening schedules were compared using analysis of variance to determine the optimal time of injection.

RESULTS

No statistical difference was found in the pharmacokinetics of MTX according to hour of injection. A difference in the creatinine clearance, however, was observed in the samples obtained at noon and 8 PM, but clearance of MTX was unchanged.

CONCLUSION

Pharmacokinetic variables suggest that MTX can be administered either in the morning (10 AM) or evening (6 PM) in the treatment of RA.

Prevalence of drugs of abuse in urine of drivers involved in road accidents in France: a collaborative study

The collaborative, anonymous, case-control study was intended to determine the prevalence of opiates, cocaine metabolites, cannabinoids and amphetamines in the urine of drivers injured in road accidents and to compare these values with those of non-accident subjects ("patients") in France. Recruitment was performed nationwide in the emergency departments of five hospitals and comprised 296 "drivers" aged 18 to 35 and 278 non-traumatic "patients" in the same age range. Females represented 28.4% of "drivers" and 44.2% of "patients." Screening for drugs in urine was performed by fluorescence polarization immunoassays in each center. Each positive result was verified using gas chromatography-mass spectrometry (GC-MS), in a single laboratory. Statistical analysis comprised single-step logistic regression and simultaneously took account of confounding factors and the final differences in prevalence values between the two populations or different subgroups. Cannabinoids were found in 13.9% of drivers (16.0% of males and 8.3% of females, p < 0.05) and 7.5% of patients (12.3% of males, 1.6% of females, p < 0.0001); only in females was this prevalence higher in injured drivers than in patients (p < 0.05). Opiates were present in 10.5% of drivers' and 10.4% of patients' urine samples (NS), and were more frequent in urine samples positive for cannabinoids, in drivers (p < 0.01) as well as in patients (p < 0.001). The prevalence of cocaine metabolites in drivers and patients was 1.0 and 1.1% and that of amphetamines 1.4 and 2.5%, respectively. No causal relationship between drugs and accidents should be inferred from this retrospective study. Nevertheless, the high prevalence of cannabis and opiate (licit or illicit) use in young people, whether injured drivers or patients, has potential implications for road traffic safety in France. Cocaine and amphetamines did not appear to be a major problem, unlike the experience in other countries.

Multiresidue determination of pesticides in apples and pears by gas chromatography-mass spectrometry

This paper describes a rapid, specific and sensitive multiresidue method for the routine analysis of several classes of pesticides used for the treatment of apples and pears, involving a rapid extraction procedure at pH 4.5 with a mixture of acetone-dichloromethane-hexane (50:20:30, v/v/v) and gas chromatography coupled to mass-selective detection, in order to achieve quantitative analysis down to their respective maximum residue limit. Extraction recoveries were between 55 and 98%. Limits of detection and limits of quantitation ranged respectively, from 0.01 to 0.05 mg/kg and from 0.02 to 0.1 mg/kg. Intra-assay relative standard deviation was less than 19% for all compounds. An excellent linearity was observed from these LOQs up to 500 mg/kg. Intermediate (inter-assay) precision and accuracy were satisfactory. The method has been applied to many fruit samples intended for commercialisation.

Bayesian pharmacokinetic estimation of vinorelbine in non-small-cell lung cancer patients

OBJECTIVE

To develop a population pharmacokinetics of vinorelbine in a population of non-small-cell lung cancer (NSCLC) patients using a Bayesian estimation in order to calculate for any further patient, individual pharmacokinetic parameters from few blood samples.

METHODS

Vinorelbine was given by a 15-min infusion (30 mg x m(-2)) to eight patients with NSCLC. Its serum concentration was determined by HPLC and its pharmacokinetics was described by a three-compartment open model with elimination from the central compartment. Volume of the central compartment (V1) and rate constants (k10, k12, k21, k13, k31) were selected as population pharmacokinetic parameters and computed by non-linear regression (two-step approach) from 14 to 18 concentration measurements per course. Subsequently, these parameters were used by the Bayesian estimator to calculate individual pharmacokinetics from only 2 or 3 measured concentrations.

RESULTS

The population mean values (CV%) of V1, k10, k12, k21, k13, k31, CL, t1/2gamma were respectively 21 l (55%), 3.2 h(-1) (29%), 7.7 h(-1) (74%), 1.3 h(-1) (67%), 4.7 h(-1) (53%), 0.04 h(-1) (20%), 57 l x h(-1) (31%) and 43 h (36%). The comparison of results obtained from the Bayesian estimator and from the three-compartment model showed that CL and t1/2gamma were well predicted (relative deviation: +/- 12 to 22%) by the Bayesian method using only two blood samples.

CONCLUSION

We demonstrated that Bayesian estimation allows, at minimal cost and minimal disturbance for the patient, the determination of several vinorelbine pharmacokinetic parameters and therefore dose adaptation from as few as two drug concentrations, measured at 6 h and 24 h after infusion.

Relationship between psychotropic drugs and thyroid function: a review

Some widely used psychoactive drugs, such as tricyclic antidepressants and antipsychotic phenothiazines exhibit iatrogenic effects on the thyroid. These side effects may arise from interactions at different steps of thyroid hormone biosynthesis. These drugs can induce a change in iodine capture by thyroid cells or can complex iodine, making it unavailable for thyroid hormone synthesis and thus decreasing thyroid hormone blood levels; they can also inhibit thyroid peroxidase activity and thus T3 and T4 synthesis or enhance deiodination of T4 to T3 or to Rt3 by stimulation of deiodinase activity. Moreover, tricyclic antidepressants interfere with the hypothalamic-pituitary-thyroid axis via the noradrenergic or serotonergic systems and might therefore decrease T4 or T3 blood levels, respectively. Phenothiazines can induce autoimmune hypothyroidism, as shown by an increase in the expression of the major histocompatibility complex antigen and by a production of antithyroglobulin or antithyroperoxidase antibodies. However, all these mechanisms are only speculative in humans, as they have only been demonstrated in vitro or in animal experiments. Clinically, thyroid function and affective disorders are closely linked. On one hand, the therapeutic response to antidepressants could be influenced by the thyroid status; on the other hand, the larger the thyroxin decrease induced by antidepressants, the better the therapeutic effect might be. Moreover, cotreatment with thyroid hormones and antidepressant drugs could allow either a decrease in the rate of treatment failure or a faster recovery from depression. As antipsychotic or antidepressant treatments are administered over long periods in humans, their thyroid toxic effects must be taken seriously.

Influence of biological variables upon pharmacokinetic parameters of intramuscular methotrexate in rheumatoid arthritis

The pharmacokinetics of methotrexate were studied in 22 patients receiving 5-15 mg per week in a single i.m. administration for rheumatoid arthritis. The data consisted of 3 plasma levels per patient, taken at 2, 6, and 12 hours after the administration. The concentration of methotrexate was determined by fluorescence polarization immunoassay. The pharmacokinetic parameters of a 2-compartment model were determined by Bayesian estimation using the population values of Bressolle et al. [1996]. The fitted parameters were: total plasma clearance of methotrexate (CL), first-order absorption constant (ka), volume of central compartment (V1), and transfer constants between the 2 compartments (k12 and k21). Additional parameters were derived from the fitted ones: maximal concentration (Cmax), time to maximum (tmax), volume of distribution at steady-state (Vss), and terminal half-life (t1/2). Twenty-one biological covariates were considered to explain the interpatient variability. The relationships between these covariates and the pharmacokinetic parameters were investigated by principal component analysis and multiple regression analysis. About 90% of the variability of CL were explained by 4 variables (sex, age, height and serum creatinine). About 50%-70% of the variability of the other pharmacokinetic parameters were explained by a set of covariates including age, height, creatinine, creatinine clearance, and dose. The effect of dose was noticed mainly on k12, Vss, and t1/2, thus suggesting that the transfer of the drug from plasma to tissues may be nonlinear. The possibility of predicting CL with a good precision would facilitate the computation of dosage regimens in these patients.

[Acute poisoning during substitution therapy based on high-dosage buprenorphine. 29 clinical cases--20 fatal cases]

OBJECTIVES

Buprenorphine has been an important advance in care for drug abusers, but the toxic risk may be fatal. We report here two original series of buprenorphine poisoning in opiate abusers on substitution therapy.

PATIENTS

The first series included 20 males and 9 females, aged 20-35 years (mean = 27.5) with non-fatal poisoning. The second series included 20 subjects (19 males, 1 female) aged 14-48 years (mean = 26.6) with a fatal outcome. All subjects were opiate addicts taking high-dosage sublingual buprenorphine formulation as substitution therapy.

RESULTS

Blood concentrations of buprenorphine were found in all cases to remain at a low level (1.0-2.3 ng/ml, m = 1.4 ng/ml, and 1.1-29.0 ng/ml, m = 8.4 ng/ml in non-fatal and fatal cases respectively). Almost all cases involved concomitant intake of psychotropic medications, especially benzodiazepines (18 non-fatal and 17 fatal cases).

DISCUSSION

These observations confirm previously reported data on the danger of buprenorphine-benzodiazepine combinations. Intravenous injection of crushed tablets also appears to be a risk factor (8 deaths and 10 non-fatal poisonings). This series highlights the need for improvement in the recently developed French program for substitution therapy with high-dosage buprenorphine in heroin addicts.

Screening procedure for 21 amphetamine-related compounds in urine using solid-phase microextraction and gas chromatography-mass spectrometry

A specific, sensitive, and rapid procedure for the screening of 21 amphetamine-related compounds in urine is developed using solid-phase microextraction (SPME) and gas chromatography-mass spectrometry. Very clean extracts are obtained in one step with SPME using silica fibers coated with a 100-micron polydimethylsiloxane stationary phase. Temperature, time, pH, and salt saturation are optimized to obtain consistent extraction. An excellent chromatographic separation of the underivatized analytes is obtained with a specially treated nonpolar capillary column (Supelco PTA-5, 30 m x 0.32-mm i.d., 0.5-micron film thickness) dedicated to amino compounds. Selected ion monitoring of three fragments per analyte and one for each of the three deuterated internal standards elicits a high selectivity and detection limits between 1 and 50 ng/mL (i.e., low enough to verify positive results obtained with immunochemical assays). The method is linear in a narrow range (from the detection limit up to 500 ng/mL) when all the amphetamines are assayed together but shows a good linearity up to 2000 ng/mL when the molecules are determined individually. Repeatability is not satisfactory for all compounds but could probably be improved by strictly controlling the extraction time (e.g., by automating the whole procedure using an autosampler). The use of SPME reduces the interference due to urinary low-volatility organic compounds and avoids the risks related to the use of organic solvents. To our knowledge, this technique is the first one allowing the sensitive determination of such a number of amphetamine analogs.