Pharmacokinetics of meperidine (pethidine) in rabbit oral fluid: correlation with plasma concentrations after controlled administration.

Oral fluid assays for quantifying drugs are useful in forensic toxicology and drug monitoring. Compared with blood and urine specimens, oral fluid collection is simple, non-invasive, and more difficult to adulterate. Therefore, we investigated whether meperidine and its metabolites could be detected in oral fluid and whether there was a predictable relationship between oral fluid and plasma concentrations. Male New Zealand white rabbits (n = 10) were administered meperidine hydrochloride (20 mg/kg, intravenous). Then, plasma and oral fluid were collected at various time points up to 10 h after administration. We developed a simple and sensitive gas chromatography-mass spectrometry method for the determination of meperidine and normeperidine in oral fluid and plasma. We estimated the apparent pharmacokinetic parameters for meperidine in oral fluid and plasma and determined the ratio and correlation between oral fluid and plasma concentrations. The results demonstrate that this method has excellent specificity, linearity, precision, and recovery. Meperidine and normeperidine were detected in both body fluids; meperidine was the most abundant analyte in oral fluid. The oral fluid-to-plasma drug concentration ratios did not differ significantly over time (p > 0.05). In addition, oral fluid and plasma levels of meperidine and normeperidine were significantly correlated over time (r = 0.713 and 0.725, respectively; p < 0.05). These results provide context for interpreting meperidine and metabolite concentrations in oral fluid and support the utility of oral fluid as an alternative matrix in clinical and forensic testing.

Homicide due to intravenous metallic mercury injection followed by sodium cyanide injection.

We report a case of homicide due to intravenous mercury injection followed by meperidine and sodium cyanide injection. A 35-year-old woman was found dead in bed at home by her husband. Reportedly, she had been sick for more than 5 months. Initial death investigation revealed no evidence of foul play. Her death was believed to be natural. Therefore, her body was buried without an autopsy. Two months after death, her family requested an autopsy because they suspected her physician husband killed her. Her body was exhumed, and an autopsy was performed. Postmortem examination revealed numerous metallic mercury globules in the pulmonary arteries. Toxicological analysis revealed a high concentration of mercury in the tissue samples of the lungs, liver, heart, and kidney. In addition, cyanide and meperidine were also found in the heart and liver. The detailed case history and postmortem examination findings are described.

Determination of stimulants and narcotics as well as their in vitro metabolites by online CE-ESI-MS.

A simple, rapid and sensitive CE-ESI-MS method for the simultaneous analysis of seven stimulants and narcotics (amphetamine, ephedrine, methadone, pethidine, tetracaine, codeine and heroin) was developed. The CE-ESI-MS experimental conditions were optimized as follows: 20 mmol/L ammonium acetate with pH 9.0 as running buffer, the separation voltage of 22 kV and the sheath liquid of isopropanol/water (1:1 v/v) containing 7.5 mmol/L acetic acid with 3.0 µL/min flow rate. Under the optimized conditions, the stimulants and narcotics were well separated within 4.6 min using a 70-cm length fused-silica capillary (50 µm id). The detection limits (S/N=3) of the CE-ESI-MS analysis were in the range of 0.40-1.0 ng/mL. Method repeatability of intra-day and inter-day was satisfactory. The recoveries obtained from the analysis of spiked urine samples were between 84.1 and 108%. The developed method was successfully applied for the simultaneous analysis of methadone, pethidine and codeine and their in vitro metabolites.

Determination of pethidine of abuse and relevant metabolite norpethidine in urine by ultra-performance liquid chromatography-tandem mass spectrometry.

Pethidine is an opiate agonist used orally and parenterally. Pethidine-containing drugs abuse is frequently encountered on health workers and patients. The analysis methods used to determine the abuse of pethidine are important for forensic toxicology. Pethidine is metabolized to norpethidine by the liver. Therefore, the determination of pethidine and norpethidine in urine is one of the methods to determine the abuse of pethidine. In this study, we have developed a precise, simple and rapid ultra-performance liquid chromatography-tandem mass spectrometer method for the determination of pethidine and norpethidine simultaneously. The developed method was validated in terms of selectivity and linearity which was in the range of 9-1800 ng/mL for both pethidine and norpethidine. The intra-assay and inter-assay accuracy and precision were found within acceptable limits of the EMA guideline. Lower limits of quantitation were 9 ng/mL for both pethidine and norpethidine. The developed method was successfully applied for the determination of both analytes in the real samples.

Analysis of semivolatile pharmaceuticals and pollutants in organic micro extracts using hot cell membrane inlet mass spectrometry.

This paper presents the first membrane inlet method that can be used together with field portable mass spectrometers for the analysis of semivolatile pharmaceuticals (pethidine, benzophenone, and cocaine) and environmental pollutants (terbutryne and butylated hydroxyl toluene (BHT)) dissolved in organic micro extracts. A microliter of the organic extract is simply injected into a closed hot cell membrane inlet (hc-MIMS), and an electron ionization mass spectrum of the vaporized semivolatile sample molecules can be recorded shortly thereafter. Detection limits at low picomole quantities or low/sub ng/microL concentrations in the extract are demonstrated for solutes in methanol, ethanol, acetone, and toluene. A linear correlation between analyte concentration and signal was found in the range of 1-100 ng/microL, and the relative standard deviation (RSD) was approximately 10%. As a practical example we demonstrate the detection of cocaine in extracts from dried coca leaves. The analysis of organic micro extracts using hc-MIMS represents a considerable extension of the type and complexity of analytes that can be measured using a field portable MIMS system, since it does not require special and field tedious modifications to the standard MIMS system.

Method development for identification of ketobemidone metabolites in microdialysate samples by coupled-column capillary liquid chromatography-tandem mass spectrometry.

Methodologies for identification of ketobemidone metabolites in microdialysate samples utilizing coupled-column capillary liquid chromatography-electrospray quadrupole time-of-flight tandem mass spectrometry are presented. Two different methods were developed to efficiently analyze the metabolites norketobemidone, ketobemidone N-oxide and hydroxyketobemidone, respectively. Both methods include on-line desalting and trapping of the analytes on micro-solid-phase extraction columns with different retention mechanisms. Norketobemidone and ketobemidone N-oxide were trapped on a C18 column and then eluted by back-flush followed by isocratic separation on a fluorinated reversed-phase type silica gel column (Fluofix). Retention equations are proposed for the chromatographic observations made on the Fluofix column. Hydroxyketobemidone was trapped on a phenylboronic acid column by complex formation at basic pH and then eluted at acidic pH directly into to the mass spectrometer. Oxidation of hydroxyketobemidone to its corresponding quinone was also observed. The methods were successfully used to analyze synthetic ketobemidone metabolites in dilute low-volume microdialysis samples.

Simultaneous analysis of five antidepressant drugs using direct injection of biofluids in a capillary restricted-access media-liquid chromatography-tandem mass spectrometry system.

Direct analysis, with minimal sample pretreatment, of antidepressant drugs, fluoxetine, imipramine, desipramine, amitriptyline, and nortriptyline in biofluids was developed with a total run time of 8 min. The setup consists of two HPLC pumps, injection valve, capillary RAM-ADS-C18 pre-column and a capillary analytical C18 column connected by means of a six-port valve in backflush mode. Detection was performed with ESI-MS/MS and only 1 microm of sample was injected. Validation was adequately carried out using FLU-d(5) as internal standard. Calibration curves were constructed under a linear range of 1-250 ng mL(-1) in plasma, being the limit of quantification (LOQ), determined as 1 ng mL(-1), for all the analytes. With the described approach it was possible to reach a quantified mass sensitivity of 0.3 pg for each analyte (equivalent to 1.1-1.3 fmol), translating to a lower sample consumption (in the order of 10(3) less sample than using conventional methods).

Determination of meperidine, tramadol and oxycodone in human oral fluid using solid phase extraction and gas chromatography-mass spectrometry.

Analytical procedures for the determination of meperidine, tramadol and oxycodone in oral fluid have been developed and validated using gas chromatography-mass spectrometry (GC/MS) following initial screening with enzyme linked immunosorbent assay (ELISA). The oral fluid samples were collected using the Quantisal device, and any drugs present were quantified using mixed mode solid-phase extraction and electron impact GC/MS. For confirmation, three ions were monitored and two ion ratios determined, which were within 20% of those of the known calibration standards. The limits of quantitation were 10 ng/mL; the intra-day precision of the assays (n=5) was 2.33%, 1.00% and 7.61%; inter-day precision 2.48%, 2.44% and 5.8% (n=10) for meperidine, tramadol and oxycodone, respectively. The percentage recovery of the drugs from the collection pads was 86.7%, 87.7% and 96.6%, respectively (n=6). The methods were applied to specimens obtained during research studies in the USA.

Potentiometric membrane sensor for the selective determination of pethidine in pharmaceutical preparations and biological fluids.

The construction and general performance characteristics of a novel potentiometric PVC membrane sensor based on pethidine-phosphomolybdate as electroactive material for the determination of pethidine are described. This sensor exhibits fast, stable and near-Nernstain response 55.24 +/- 0.1, over the concentration range 1.10(-2)-1.10(-5)M for pethidine-phosphomolybdate over pH 2-7. No interferences are caused by many organic, inorganic cations, alkaloids and amino acids. The sensor proved useful for determining pethidine in pure forms, pharmaceutical injections and monitoring the content uniformity assay of ampoules. The designed sensor also show good accuracy for the determination of pethidine in biological fluids.

LC-MS-MS Method for the Analysis of Miscellaneous Drugs in Wastewater During Football Games III.

Continuing our previous studies analyzing drugs of abuse in municipal wastewater, a method was developed for the analysis of miscellaneous drugs of abuse in wastewater samples using liquid chromatography coupled with tandem mass spectrometry (LC-MS-MS). Eight drugs and metabolites were analyzed including 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrolidine (EDDP), fentanyl, norfentanyl, meperidine, normeperidine, methadone, phencyclidine and tramadol. These drugs were chosen because of their widespread abuse. Wastewater samples were collected at both the Oxford Waste Water Treatment Plant in Oxford, Mississippi (MS) and the University Wastewater Treatment Plant in University, MS. These wastewater samples were collected on weekends in which the University of Mississippi football team (colloquially the "Ole Miss Rebels" football team) held home games (Vaught-Hemingway Stadium, University, MS 38677). The collected samples were analyzed using a validated method and found to contain tramadol in 25 samples at quantifiable levels. EDDP, meperidine, normeperidine and methadone were also detected but were under the limit of quantitation.

LC-MS determination of MPTP at sub-ppm level in pethidine hydrochloride.

An HPLC-MS with electrospray ionisation method for the determination of MPTP at sub-ppm level in pethidine hydrochloride has been developed and validated. Ionisation is performed by positive-ion electrospray and the quadrupole filter mass spectrometer is operated in the single ion recording mode. Chromatographic separation was achieved in gradient elution using a symmetry C18, 5 microm, 150 mm x 2.1 mm i.d. The mobile phase comprised water containing 0.1% formic acid (v/v) and acetonitrile containing 0.1% formic acid (v/v). The method showed to be linear in the range between 0.2 and 2.2 ng/ml, the estimated LOD was lower than 0.1 ng/ml and the LOQ was lower than 0.2 ng/ml.

Permeability of human chorion laeve to diazepam and meperidine.

In vitro placental permeability to diazepam (Valium) and meperidine (Demerol) in excess of that measured for antipyrine, suggest that these compounds will diffuse across placental tissue in vivo at a maximal or perfusion-limited rate. Such findings correspond to the high fetal blood levels reported for these substances following maternal administration and indicate that these lipid-soluble analgesics cross this tissue by transcellular as well as extracellular pathways.

Behavioural effects of norpethidine, a metabolite of pethidine, in rats.

This study investigated behavioural effects of the toxic pethidine metabolite, norpethidine, in rats and its interactions with reserpine, apomorphine and physostigmine. Following intraperitoneal administration, brain concentrations of norpethidine reached a plateau after 20-40 min and remained elevated for 2 h. In the dose range 0.06-0.18 mmol/kg, norpethidine induced myoclonic jerks, a characteristic splayed posture, and episodes of exaggerated shivering. Forward locomotion, grooming, yawning and rearing were suppressed. Seizures and reverse locomotion occurred occasionally. Administration of reserpine 1 h prior to norpethidine, or of apomorphine or physostigmine 15 min after norpethidine, did not alter the norpethidine-induced behaviours; neither did norpethidine block the effects of apomorphine or physostigmine. The characteristic profile of behaviours induced by norpethidine make this toxicant readily amenable to animal studies. Our results indicate that its mechanism of action is unlikely to involve dopaminergic or cholinergic pathways.

Impurities in drugs II: meperidine and its formulations.

Three lots of meperidine hydrochloride, seven lots of meperidine tablets, and 41 lots of meperidine injectables were examined for impurities by TLC. Impurities found were ethyl 1-benzyl-4-phenyl-4-piperidinecarboxylate, methyl-4-piperidinecarboxylate, ethyl-4-phenyl-4-piperidinecarboxylate, and three unidentified compounds. Not all impurities were found in every lot of drug investigated, and none of the impurities exceeded a concentration of 1% of the meperidine present.

Quantitation of meperidine hydrochloride in pharmaceutical dosage forms by high-performance liquid chromatography.

A high-performance liquid chromatographic (HPLC) method for the quantitative determination of meperidine hydrochloride in pharmaceutical dosage forms was developed. The method is reproducible and precise with relative standard deviations (based on six readings) of 1.2% with hydroxyzine and 0.93% with hydroxyprogesterone caproate as the internal standards. A variety of other active and inactive ingredients which were mixed with meperidine hydrochloride did not interfere with the assay procedure. Among the ingredients tested were acetaminophen, atropine sulfate, disodium edetate, metacresol, phenol, promethazine, and sodium metabisulfite. This method appears to be stability-indicating since a hydrolyzed sample of meperidine showed zero potency and a new peak with a different retention time.

TLC identification adn GLC determination of meperidine and its metabolites in biological fluids.

Procedures were developed for TLC identification and GLC determination of meperidine and its metabolites, i.e., p-hydroxymeperidine, normeperidine, and meperidinic and normeperidinic acids. Meperidine, p-hydroxymeperidine, and normeperidine were extracted with ether from biological fluids at pH 10, whereas meperidinic and normeperidinic acids and conjugated metabolites remained in the aqueous phase. The residue, upon evaporation of the extract to dryness, was derivatized with trifluoroacetic anhydride and gas chromatographed. Total (free and conjugated) meperidinic and normeperidinic acids in the aqueous phase were converted and determined as meperidine and normeperidine, respectively. A preliminary result of urinary disposition of meperidine and its metabolites in the rat is presented. The identity of these metabolites was confirmed with GLC-mass spectrometry.

Determination of MPTP, a toxic impurity of pethidine.

Pethidine, predominantly a mu-receptor agonist, is a phenyl-piperidinic synthetic drug. It is used in the management of moderate to several pain. A possible hydrolytic degradation of an ester group can generate a very toxic compound, the N-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP) which contaminates the drug. Because of the toxicity of MPTP a suitable method for its determination must be selective and sensitive. Afterwards we propose simple methods to determine pethidine and MPTP by capillary electrophoresis (CE), MECK and RP-high performance liquid chromatography (HPLC) looking at the limit of detection obtained using these three techniques. CE was carried out using as running buffer ammonium acetate (pH 8.3). MECK was performed with a borate buffer (pH 8.3) containing sodium dodecylsulphate and trimethyl-beta-cyclodextrins. RP-HPLC was carried out on a RP18 stationary phase, using as mobile phase a mixture of phosphate buffer (pH 7) containing acetonitrile and 1% of diethylamine.

The stability of tetramine, morphine and meperidine in formalin solution.

The stability of tetramine, morphine and meperidine in formalin solution is an important factor for drug analysis in forensic investigation. In this paper, the tissues (liver, kidney, lung and heart) from poisoned rabbits were immersed in 50 ml 10% formalin solutions for 4 months before examination. We compared the levels of tetramine, morphine, meperidine and the main metabolite normeperidine, measured by GC/NPD or GC-MS, in frozen rabbit tissues, formalin-fixed rabbit tissues, and formalin solution. There was a decrease in the levels of tetramine, morphine, meperidine in formalin-preserved tissues compared with the levels of these drugs in the frozen tissues. It is suggested that the formalin-fixed tissues and formalin solution should be analyzed at the same time to assure the accurate results.

A forensic toxicological dilemma: the interpretation of post-mortem concentrations of central acting analgesics.

Dora V., a 88-year-old pensioner suffering from a hiatus hernia, died at the home of an orthopaedist and his wife, an anaesthetist, immediately after she had received a dose of 300 mg pethidine via intravenous infusion in a timeframe of about 90 min. One day before her death a befriended notary of the couple visited Dora V. and obtained a blank signature. After her death, a will was forged using this signature, rendering the couple sole heirs of Dora V.'s estate with a value of several million euros. Post-mortem toxicology was performed in three different institutes of legal medicine. The concentrations of pethidine in peripheral venous blood were between 6.1 and 6.5mg/l and 9.5 and 17.2mg/kg in brain. Pharmacokinetic calculation confirms the given dose. There was no doubt that the cause of death was acute pethidine intoxication. The accused couple claimed that this dose of pethidine was indicated to relief pain, and as the pathologists said in their expert opinions that the hiatus hernia could explain her death, the court had to acquit the accused. This very special case demonstrates that preconceived murder of a sick person with suitable analgesics cannot be proven--at least not with the methods available to forensic toxicology and pathology. This has to be taken into consideration if euthanasia will be legalised under special circumstances.

The simultaneous determination of pethidine and norpethidine in biofluids by nitrogen selective gas chromatography.

A rapid sensitive and selective gas chromatographic method has been developed for the simultaneous determination of pethidine and its major basic metabolite, norpethidine, using a nitrogen selective detector. The procedure involved a preliminary ethereal extraction of the drug, its metabolite and internal marker (lignocaine) from the alkalinised biological fluids (plasma or urine). The extract, after concentration, was analysed by a GC system (3 per cent OV 17 on Gas Chrom Q, 80-100 mesh) linked to a nitrogen selective detector. The calibration graphs (relating peak height ratios of the drug to internal marker and concentration) of pethidine and norepethidine were linear and reproducible over the ranges of 5 ng/ml to 100 ng/ml for plasma samples and 50 ng/ml to 1000 ng/ml for urine samples. The recovery of the drug and metabolite from plasma samples at 5 ng/ml and 100 ng/ml is 100 per cent and 84.9 per cent respectively for pethidine, and 100 per cent and 90.9 per cent respectively for norpethidine. Similar recovery from urine samples of pethidine and norpethidine is also achieved at 50 ng/ml and 1000 ng/ml levels. The reproducibility of the assay procedure for pethidine and norpethidine is 100 +/- 0.02 per cent and 100 +/- 0.04 per cent at 100 ng/ml level, and 100 +/- 0.15 per cent and 100 +/- 0.12 per cent at 5 ng/ml level.