Population pharmacokinetics of nefopam in elderly, with or without renal impairment, and its link to treatment response.

AIMS: Nefopam is a nonmorphinic central analgesic, for which no recommendation exists concerning adaptation of regimen in aged patients with or without renal impairment. The objective was to describe the pharmacology of nefopam in aged patients to obtain guidelines for practical use. METHODS: Elderly patients (n = 48), 65-99 years old, with severe or moderate renal impairment or with normal renal function, were recruited. Nefopam (20 mg) was administered as a 30 min infusion postoperatively. Simultaneously, a 1 min intravenous infusion of iohexol was performed, in order to calculate the glomerular filtration rate. Blood samples were drawn to determine nefopam, desmethyl-nefopam and iohexol plasma concentrations. Nefopam and desmethyl-nefopam concentrations were analysed using a nonlinear mixed-effects modelling approach with Monolix version 4.1.3. The association between pharmacokinetic parameters and treatment response was assessed using logistic regression. RESULTS: A two-compartment open model was selected to describe the pharmacokinetics of nefopam. The typical population estimates (between-subject variability) for clearance, volume of distribution, intercompartmental clearance and peripheral volume were, respectively, 17.3 l h(-1) (53.2%), 114 l (121%), 80.7 l h(-1) (79%) and 208 l (63.6%). Morphine requirement was related to exposure of nefopam. Tachycardia and postoperative nausea and vomiting were best associated with maximal concentration and the rate of increase in nefopam plasma concentration. CONCLUSIONS: We identified the nefopam pharmacokinetic predictors for morphine requirement and side-effects, such as tachycardia and postoperative nausea and vomiting. In order to maintain morphine sparing and decrease side-effects following a single dose of nefopam (20 mg), simulations suggest an infusion time of >45 min in elderly patients with or without renal impairment.

Validation of a fast method for quantitative analysis of elvitegravir, raltegravir, maraviroc, etravirine, tenofovir, boceprevir and 10 other antiretroviral agents in human plasma samples with a new UPLC-MS/MS technology.

Therapeutic drug monitoring (TDM) of antiretrovirals requires accurate and precise analysis of plasma drug concentrations. This work describes a simple, fast and sensitive UPLC-MS/MS method for determination of the commonly used protease inhibitors such as amprenavir, atazanavir, darunavir, indinavir, lopinavir, ritonavir, saquinavir and tipranavir, tenofovir a nucleoside reverse transcriptase inhibitor (NRTI), the non-NRTI such as efavirenz, nevirapine, etravirine, the CCR5 antagonist maraviroc as well as the more recent antiretrovirals, the integrase inhibitors such as raltegravir, elvitegravir and the new direct acting anti-HCV boceprevir. Adapted deuterated internal standard was added to plasma aliquots (100µl) prior to protein precipitation with methanol and acetonitrile. This method employed ultra-performance liquid chromatography coupled to tandem mass spectrometry with electrospray ionization mode. All compounds eluted within 4.2-min run time. Calibration curves were validated, with correlation coefficients (r(2)) higher than 0.997, for analysis of therapeutic concentrations reported in the literature. Inter- and intra-assay variations were <15%. Evaluation of accuracy shows a deviation <15% from target concentration at each quality control level. No significant matrix effect was observed for any of the antiretroviral studied. This new validated method fulfills all criteria for TDM of 15 antiretrovirals and boceprevir drugs and was successfully applied in routine TDM of antiretrovirals.

Determination of articaine in human plasma by liquid chromatography-mass spectrometry and its application in a preliminary pharmacokinetic study.

A specific liquid chromatography-mass spectrometric (LC-MS) method using an ion trap spectrometer was developed for the quantitation of articaine in human plasma. Articaine and the internal standard (trazodone) were extracted in a single step with diethyl-ether from 0.5 mL of alkalinized plasma. The mobile phase consisted of acetonitrile with 0.1% formic acid (40:60, v/v). It was delivered at a flow rate of 0.3 mL/min. The effluent was monitored by MS in positive-ion mode. Ionisation was performed using an electrospray ion source operating at 200 degrees C. Articaine was identified and quantified in SIM mode at m/z 185. Calibration curves were linear over the concentration range of 78.1-5000 ng/mL with determination coefficients>0.996. This method was fast (total run-time<3 min), accurate (bias<16%), and reproducible (intra-assay and inter-assay precision<14%) with a quantitation limit of 78.1 ng/mL. The good specificity and sensitivity achieved by this method allowed the determination of articaine plasma levels in patients following a submucosal infiltration injection of articaine in the patients undergoing a third molar surgery.

Thiodicarb and methomyl tissue distribution in a fatal multiple compounds poisoning.

Thiodicarb is a nonsystemic carbamate insecticide whose acetylcholinesterase activity is related to its main methomyl degradation product. A 40-year-old woman was found dead in her car. Empty packages of medicines and an open bottle of Larvin containing thiodicarb were found near her body. No signs of violence nor traumatic injuries were noticed upon autopsy, and police investigations strongly suggested a suicide. Systematic toxicological analysis performed on postmortem specimens revealed the presence of various sedatives, hypnotics, and antipsychotic drugs in blood, urine, and gastric content. Some of the compounds identified were determined at blood concentrations well above the known therapeutic concentrations: zolpidem (2.87 mg/L), bromazepam (2.39 mg/L), nordazepam (4.21 mg/L), and levopremazine (0.64 mg/L). Specific analysis of thiodicarb and of its methomyl metabolite was then performed on all fluids and tissues collected during autopsy by liquid chromatography ion trap tandem mass spectrometry (LC-MS-MS). The anticholinesterase capacity of blood, urine, and gastric content collected at autopsy was 83%, 82%, and 32%, respectively (normal value: 0%). The presence of thiodicarb in the bottle found near the body corroborates the hypothesis of an intake of that compound. Although thiodicarb was only detected in gastric content (24.3 mg/L), its methomyl metabolite was quantified in most postmortem tissues and fluids: gastric content (19.9 mg/L), peripheral blood (0.7 mg/L), urine (8.5 mg/L), bile (2.7 mg/L), liver (0.7 mg/kg), kidney (1.7 mg/kg), lung (1.5 mg/kg), brain (9.3 mg/kg), and heart (3.6 mg/kg).

Specific and sensitive analysis of nefopam and its main metabolite desmethyl-nefopam in human plasma by liquid chromatography-ion trap tandem mass spectrometry.

A specific and sensitive liquid chromatography-tandem mass spectrometric (LC-MS-MS) method using an ion trap spectrometer was developed for quantitation of nefopam and desmethyl-nefopam in human plasma. Nefopam, desmethyl-nefopam and the internal standard (ethyl loflazepate) were extracted in a single step with diethyl ether from 1 mL of alkalinized plasma. The mobile phase consisted of acetonitrile with 0.1% formic acid (50:50, v:v). It was delivered at a flow-rate of 0.3 mL/min. The effluent was monitored by MS-MS in positive-ion mode. Ionisation was performed using an electrospray ion source operating at 200 degrees C. Nefopam and desmethyl-nefopam were identified and quantified in full scan MS-MS mode using a homemade MS-MS library. Calibration curves were linear over the concentration range of 0.78-100 ng/mL with determination coefficients >0.996. This method was fast (total run time<6 min), accurate (bias<12.5%), and reproducible (intra- and inter-assay precision<17.5%) with a quantitation limit of 0.78 ng/mL. The high specificity and sensitivity achieved by this method allowed the determination of nefopam and desmethyl-nefopam plasma levels in patients following either intermittent or continuous intravenous administration of nefopam.

Identification and quantification of 8 sulfonylureas with clinical toxicology interest by liquid chromatography-ion-trap tandem mass spectrometry and library searching.

BACKGROUND: Identification of sulfonylureas in blood may be useful in the evaluation of hypoglycemic crises of unknown origin. The aim of the present study was to develop a highly selective liquid chromatography-electrospray tandem mass spectrometry (MS-MS) method using an ion-trap detector for rapid screening, identification, and quantification of sulfonylureas in human plasma. METHODS: After standard liquid-liquid extraction with glisoxepide as an internal standard, 8 sulfonylureas (glibenclamide, glipizide, gliclazide, glibornuride, glimepiride, carbutamide, chlorpropamide, and tolbutamide) were eluted from a C18 column within 10 min with an isocratic mobile phase. Drugs were identified and quantified in full-scan MS-MS mode by use of a homemade MS-MS library. We used the assay in 134 cases of hypoglycemic crises of unknown origin. RESULTS: No ion suppression effect was noted for the analytes at their specific retention-time windows. For all drugs, assay validation showed good linearity (r2>0.990) and acceptable imprecision and recovery based on commonly used criteria of acceptance. The mean extraction recoveries were 63%-87% for 5 sulfonylureas but <45% for 3 (carbutamide, chlorpropamide, and tolbutamide). Nevertheless, the high sensitivity of the MS instrument made possible detection and quantification of all 8 drugs at subtherapeutic to toxic concentrations with good precision. Sulfonylureas were found in 9 hypoglycemic patients. CONCLUSION: The described assay method allows accurate, rapid identification and quantification of 8 sulfonylureas in human plasma and can be used for specific diagnosis of factitious hypoglycemia caused by ingestion of these drugs.

Sensitive bioassay of bupivacaine in human plasma by liquid-chromatography-ion trap mass spectrometry.

A sensitive high-performance liquid chromatography-tandem mass spectrometric (HPLC-MS-MS) method, using an ion trap spectrometer, was developed for quantitation of bupivacaine in human plasma. Bupivacaine and an internal standard (ropivacaine) were extracted in a single step from 100 microL of alkalinized plasma with diethyl-ether. The mobile phase consisted of acetonitrile with 0.1% formic acid (50:50, v/v), and was delivered at a flow rate of 0.3 mL/min. The effluent was detected by MS-MS in positive ion mode. Ionisation was performed, using an electrospray ion source, operating at 200 degrees C. The selected reaction monitoring transitions m/z 289-->m/z 140 and m/z 275-->m/z 126 were chosen for bupivacaine and ropivacaine, respectively. Calibration curves were linear over the concentration range of 3.90-500 microg/L with determination coefficients >0.996. The method is accurate (bias <10%) and reproducible (intra-assay and inter-assay precision <15%), with a quantitation limit of 3.90 microg/L, using only 100 microL of plasma. The high specificity and sensitivity, achieved by this fast method (total run-time <3 min), allowed the determination of bupivacaine plasma levels in pediatric patients, following epidural administration of bupivacaine.

An unusual case of methyl bromide poisoning.

A nonlethal poisoning case by methyl bromide in a young woman due to leakage of old fire extinguishers is described. The patient developed major action and intention myoclonus the day following exposure. Inorganic bromide concentrations in plasma were determined by inductively coupled plasma mass spectrometry. The initial plasma bromide level was 202 mg/L, 40-fold in excess than the commonly accepted tolerance limit, and decreased slowly to normal levels within 2 months. Although plasma inorganic bromide concentration is known not to be directly correlated to the severity of organic bromide poisoning, its determination was, in the present case, particularly useful to confirm the diagnosis. One year post-exposure, the patient showed no sign of central nervous system toxicity. While such a case of poisoning is particularly rare today, it illustrates, however, that the danger still exists in France although the destruction

Simultaneous determination of amoxicillin and clavulanic acid in human plasma by HPLC with UV detection.

A simple and accurate high-performance liquid chromatographic method with ultraviolet detection at 220 nm has been validated for the simultaneous determination of amoxicillin and clavulanic acid in human plasma. Plasma samples were pretreated by direct deproteinization with methanol. A good chromatographic separation between both compounds was achieved using a reversed phase C8 column and a mobile phase, consisting of acetonitrile-phosphate solution-tetramethyl ammonium chloride solution. The calibration curves were linear over the concentration range of 0.625-20 mg l(-1) for amoxicillin and 0.3125-10 mg l(-1) for clavulanic acid with determination coefficients > 0.998. The method is accurate (bias < 7%) and reproducible (intra- and inter-day R.S.D. < 15%), with a quantitation limit of 0.625 and 0.3125 mg l(-1) for amoxicillin and clavulanic acid, respectively. Analytical recoveries from human plasma ranged from 91 to 102% for both components. This fully validated method, which allows the simultaneous measurement of amoxicillin and clavulanic acid in biological samples, is rapid (total run time < 10 min) and requires only a 100 microl sample. This assay is suitable for biomedical applications and was successfully applied to a pilot pharmacokinetics study in healthy volunteers after a single-oral administration of amoxicillin/clavulanic acid combination (500/125 mg).