A selected ion monitoring method for the determination of pethidine and norpethidine in plasma. Comparison with a gas chromatographic method using electron capture detection

An analytical approach to determining pethidine: An investigation of 18 patients' urine

Pethidine (PET) is an opioid pain-relief medicine with high addiction potential, especially among health professionals. Pethidine is commonly prescribed in Turkey as a pain-relieving medication for operative purposes. Due to its accessibility, low cost, user-friendliness, and effectiveness, PET is often misused by both healthcare professionals and patients. For this reason, analytical determination methods for PET abuse are essential in terms of forensic toxicology. In this study, a fast, reliable, and accurate gas chromatography-mass spectrometry method was developed for the first time in Turkey for the simultaneous detection of PET and its main urinary metabolite norpethidine (NPET). The method was validated in terms of selectivity, linearity, the limit of detection (LOD), the limit of quantification (LOQ), trueness, and precision according to the Scientific Working Group for Forensic Toxicology guidelines. The linear range was between 0.125-25.00 μg/mL for PET and 1.00-20.00 μg/mL for NPET. The LOD values for PET and NPET were 0.05 µg/mL and 0.49 µg/mL, while the LOQ values were 0.125 µg/mL and 1.00 µg/mL, respectively. Extraction efficiencies were calculated as 113% for PET and 104% for NPET. The intra-assay and inter-assay precision results were within acceptable limits. In the presented study, the validated method was applied to the urine of 18 patients collected at the 1st and 3rd hours after receiving PET. All samples in the study were collected under patients' consent and in line with ethical guidelines.

Sensitive determination of pethidine in body fluids by gas chromatography-tandem mass spectrometry

We have presented a simple and sensitive method for determining pethidine, a narcotic analgesic drug in body fluids by gas chromatography-tandem mass spectrometry (GC-MS/MS). Pethidine and 4'-piperidinoacetophenone (internal standard) were extracted from body fluids with Bond Elut C(18) columns; the recoveries were above 85% for both compounds. The calibration curves for blood and urine showed good linearities in the range of 1.25-40 ng/ml. Its detection limits (signal-to-noise ratio=3) were estimated to be approximately 0.5 ng/ml of whole blood and urine.

Sensitive determination of pethidine in body fluids by surface ionization organic mass spectrometry

We have presented a simple and sensitive method for determining pethidine, a narcotic analgesic drug in body fluids by gas chromatography (GC)/surface ionization organic mass spectrometry (SIOMS). Good linearity was obtained in the range of 0.625-25 ng/ml of whole blood and urine by mass chromatography, and in the range of 0.05-2 ng/ml of whole blood by selected ion monitoring (SIM). Pethidine and diphenylpyraline (internal standard) were extracted from body fluids with Bond Elut Certify cartridges; their recoveries were above 95%. The detection limits (signal-to-noise ratio=3) were estimated to be 0.2 ng/ml of whole blood or urine by mass chromatography, 0.02 ng/ml of whole blood by SIM.

Stability of meperidine in an implantable infusion pump using capillary gas chromatography-mass spectrometry and a deuterated internal standard

A capillary gas chromatographic-mass spectrometric (GC MS) method is described for the analysis of meperidine using 3,3,5,5-[2H4]-meperidine as an internal standard. Chromatography was performed on a (5% phenyl) methylpolysiloxane column (30 m x 0.32 mm I.D., 0.25 microm film thickness) operated at 195 degrees C; helium carrier gas-50 cm/s(-1), tR = 2.3 min. Ionization was by electron impact (EI) and detection by selected ion monitoring of the molecular ions. The method provided high response linearity (mean r = 0.9982) and precision (< 6.5% C.V.). Application of this method to a pilot study of aqueous meperidine x HCl (10 mg/ml(-1)) stability in a surgically implantable infusion pump at 37 degrees C for 90 days revealed no demonstrable drug degradation.

CSF and plasma pharmacokinetics of pethidine and norpethidine in man after epidural and intrathecal administration of pethidine

The disposition of pethidine and its main metabolite, norpethidine, in cerebrospinal fluid (CSF) and plasma was studied in 11 thoracic surgery patients after lumbar epidural (100 mg; n = 6) or lumbar intrathecal (25 mg; n = 5) administration of pethidine. Pethidine appeared more slowly in plasma after intrathecal than after epidural administration (tmax 2.3 h and 14 min, respectively), but systemic bioavailability was similar. The CSF concentrations of pethidine were higher than those in plasma after both routes of administration. The maximal CSF/plasma concentration ratio was 6000 to 45,000 after intrathecal administration but was only 26 to 97 after the epidural route. Pethidine was rapidly distributed in CSF; nine to ten h after the intrathecal and epidural injections the CSF/plasma concentration ratios were 12 to 89 and 2 to 33, respectively. The calculated bioavailability in CSF of epidural pethidine was 10.3%. The terminal elimination half-life of pethidine was 6.0 h (CSF) and 5.4 h (plasma) after intrathecal administration and 8.6 h (CSF) and 8.8 h (plasma) after epidural injection. The volume of distribution of unchanged pethidine in the subarachnoid space was 13 ml.kg-1 and clearance from the CSF was 15 microliters.kg-1.min-1. In all patients receiving intrathecal pethidine and in some patients after epidural pethidine, CSF norpethidine concentrations were higher than those in plasma; the maximum CSF norpethidine was 102 to 1211 ng.ml-1 and 14 to 210 ng.ml-1 and the maximum CSF/plasma norpethidine concentration ratios were 21 to 652 and 0.6 to 14 times after intrathecal and epidural administration, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Gas chromatographic analysis of meperidine and normeperidine: determination in blood after a single dose of meperidine

A method is described for the determination of meperidine and its pharmacologically active metabolite, normeperidine, in blood, plasma, and urine using gas chromatography with nitrogen-phosphorus detection. Structural analogs of both meperidine and normeperidine were used as internal standards. Unlike previously reported assays, this procedure was sensitive and convenient enough for use in pharmacokinetic studies of both meperidine and normeperidine following single doses of meperidine. The assay was sensitive to 5 ng of meperidine/ml and 2.5 ng of normeperidine/ml extracted from a 1-ml biological sample. The between-assay coefficients of variation at these concentrations were 9.4 and 10.4%, respectively.

Analysis of mepivacaine, bupivacaine, etidocaine, lidocaine, and tetracaine

A GLC method, employing a nitrogen-phosphorus-sensitive detector, is described for the analysis of mepivacaine, bupivacaine, etidocaine, lidocaine, and tetracaine in biological fluids. The method is simple, reliable, and sensitive, with a practical limit of sensitivity of approximately 2.5 ng/ml, well below therapeutic plasma levels. Extensive start-up procedures and sample preparation are not required.

Investigation of the Urinary excretion of pethidine and five of its metabolites in man using selected ion monitoring

The urinary excretion in man of pethidine and five of its metabolites (norpethidine, pethidinic acid, norpethidinic acid, p-hydroxypethidine and pethidine N-oxide) after a single intramuscular dose has been investigated using analytical procedures based on selected ion monitoring. New methods for the determination of p-hydroxypethidine and pethidine N-oxide have been developed, and the selectivity and sensitivity of the procedures are discussed. Only some 5% of the administered dose was excreted as unchanged pethidine. The mean urinary excretion of norpethidine was 16.4%. Pethidinic acid and norpethidinic acid constituted the major fraction of the dose excreted in urine. The total excretion of pethidinic acid and norpethidinic acid was 41.7 and 23.2%, respectively. Pethidine N-oxide constituted less than 0.5% of the excreted amount, and p-hydroxypethidine could only be detected in the urine of two of the patients. A mean total recovery of about 90% of the dose was found in urine as pethidine and the five metabolites.

The determination of meperidine, noremeperidine and deuterated analogs in blood and plasma by gas chromatography mass spectrometry selected ion monitoring

A gas chromatographic mass spectrometric assay using selected ion monitoring for meperidine and normeperidine in blood and plasma is described. Both unlabeled and [3H]-phenyl ring labeled drugs may be determined simultaneously using [2H10] analogs as internal standards. Calibration curves are linear over the range 5--100 ng ml-1, the results reproducible (coefficient of variation < 5%), the sensitivity limit is about 5 ng using a 1 ml sample and no interference is present in blank blood or plasma, or by isotope inpurity. The method is shown to be applicable to measuring the concentration of meperidine and its metabolite, normeperidine, in blood, following simultaneous administration by the intravenous and oral routes of 25 mg each of unlabeled and [2H5] labeled drug, respectively.

Patient controlled analgesic therapy in the early postoperative period

Fourteen patients with postoperative pain were allowed to self-administer preset doses of pethidine intravenously via a logic-controlled motor syringe. Plasma samples were collected during anaesthesia and the postoperative self-administration period, and the concentrations of pethidine and nor-pethidine were determined. Separate single-dose studies in eight patients yielded pharmacokinetic parameters which made possible computer simulations of continuous plasma concentration curves for the anaesthesia and postoperative self-administration period. The consumption of pethidine showed great interindividual variations with a mean consumption for the entire group of 26 mg per hour. The patients established steady-state plasma concentrations with far less than the maximum amount of pethidine allowed. The mean measured plasma concentration of pethidine which provided adequate analgesia was 738 +/- 149 ng/ml. Simulated and measured plasma concentrations were in close agreement. The individual mean drug consumption per hour during self-administration correlated closely with the individual elimination rate of pethidine. No serious side effects were observed. Thus, patient-controlled analgesic therapy offers an individualized analgesic supply to meet an analgesic demand which is governed by each patient's appreciation of pain.