Development and validation of a sensitive UPLC-MS/MS method for the analysis of narcotic analgesics in urine and whole blood in forensic context.

Narcotic analgesics are widely (ab) used and sometimes only occur in low concentrations in biological samples. Therefore, a highly sensitive liquid chromatography tandem mass spectrometry method was developed for simultaneous analysis of 9 narcotic analgesics and metabolites (buprenorphine, O-desmethyltramadol, fentanyl, norbuprenorphine, norfentanyl, pethidine, piritramide, tilidine and tramadol) in urine and whole blood. Sample preparation was performed on a mixed-mode cation exchange solid phase extraction cartridge with an additional alkaline wash step to decrease matrix effects and thus increase sensitivity. Ionization with electrospray ionization was found to be more efficient than atmospheric pressure chemical ionization. The use of a mobile phase of high pH resulted in higher electrospray ionization signals than the conventional low pH mobile phases. In the final method, gradient elution with 10mM ammonium bicarbonate (pH 9) and methanol was performed on a small particle column (Acquity C18, 1.7 µm, 2.1 mm × 50 mm). Selectivity, matrix effects, recovery, linearity, sensitivity, precision, accuracy and stability were validated in urine and whole blood. All parameters were successfully evaluated and the method showed very high sensitivity, which was the major aim of this study. The applicability of the method was demonstrated by analysis of several forensic cases involving narcotic analgesics.

Quantitative determination of piritramide in human plasma and urine by off- and on-line solid-phase extraction liquid chromatography coupled to tandem mass spectrometry.

A method for the liquid chromatography/tandem mass spectrometric (LC/MS/MS) quantification of piritramide, a synthetic opioid, in plasma after conventional off-line solid-phase extraction (SPE) and in urine by on-line SPE-LC/MS/MS in positive electrospray mode was developed and validated. Applicability of the on-line approach for plasma samples was also tested. Deuterated piritramide served as internal standard. For the off-line SPE plasma method mixed cation-exchange SPE cartridges and a 150 x 2 mm C18 column with isocratic elution were used. For the on-line SPE method, a Waters Oasis HLB extraction column and the same C18 analytical column in a column-switching set-up with gradient elution were utilized. All assays were linear within a range of 0.5-100 ng/mL with a limit of detection of 0.05 ng/mL. The intra- and interday coefficients of variance ranged from 1.3 to 6.1% for plasma and 0.5 to 6.4% for urine, respectively. The extraction recovery for the off-line plasma assay was between 90.7 and 100.0%. Influence of matrix effects, and freeze/thaw and long-term stability were validated for both approaches; influence of urine pH additionally for quantification in urine.

Death during patient-controlled analgesia: piritramide overdose and tissue distribution of the drug.

We report about a fatality during patient-controlled analgesia (PCA). Piritramide peripheral blood concentration was measured with 0.1 mg/l and exceeded the normal therapeutic range. Therefore, a fatal overdose was considered as the cause of death with respiratory depression as the underlying pathophysiological mechanism. The tissue distribution was studied; highest concentrations of piritramide were measured in kidney, bile and urine. Due to a large volume of distribution a difference in the drug concentration found in heart and peripheral bloods the phenomenon of drug redistribution was observed. Confronted with toxicological results, investigations revealed, that the PCA pump had been changed during a previous servicing from displaying mg/h to ml/h, therefore, the anesthetist had entered "1.5" assuming mg/h, but actually applying 1.5 ml/h (which was therefore equivalent to 2.25 mg/h, given a concentration in the cartridge of 1.5 mg piritramide/ml). In total, 61.5 ml (instead of 61.5 mg) had been infused, equivalent to 92.25 mg piritramide. This case report is a further example that human errors can play a crucial role in the safety of medical equipment. Experts in anesthesia recommended human factors engineering design principles to improve the safety of medical devices.

The pharmacokinetics of piritramide after prolonged administration to intensive care patients.

BACKGROUND AND OBJECTIVE: The purpose of the present study was to determine the pharmacokinetics of the micro-agonist opioid pirinitramide (piritramide) after prolonged administration. METHODS: Nine patients requiring intensive care therapy and artificial ventilation for several days received piritramide with a median infusion rate of 5 mg h(-1) (range 4.8-10 mg h(-1)) for a median period of 69.9 h (range 49-89 h) for analgesia and sedation. After the end of the infusion, frequent arterial blood samples were withdrawn for 96 h and assayed for piritramide using a gas chromatographic method. Standard compartmental models were fitted to the individual concentration-time courses to characterize the elimination of piritramide after prolonged administration. RESULTS: The concentration-time course after the end of the infusion was adequately described with a three-compartment model in eight patients and a two-compartment model in one patient (standard two-stage geometric mean and 16-84% quantile: volumes of distribution V1 = 47.9 (26.8-85.8)L, V2 = 402 (241-672)L, V3 = 332 (124-885)L; clearances Cl1 = 66.5 (53.2-83.0)Lh(-1), Cl2 = 215 (125-369)Lh(-1), Cl3 = 18.4 (9.2-36.8) Lh(-1)). Both the steady-state volume of distribution (782 L) and the terminal elimination half-life (17.4 h) were larger than predicted from single bolus pharmacokinetic studies (412.5 L and 10.4 h, respectively), the context-sensitive half-time after more than 72 h of administration was 32% shorter than predicted (285 vs. 420 min). CONCLUSIONS: Despite increasing terminal elimination half-life and volume of distribution at steady state (increasing drug load for a given plasma concentration), the context-sensitive half-time of piritramide after 3 days of administration is lower than predicted from bolus kinetics, making the drug a suitable candidate for intensive care unit analgesia.

Quantitative determination of piritramide in human serum applying liquid chromatography-two-stage mass spectrometry.

A method for the determination of the synthetic narcotic analgesic piritramide in human serum utilizing high-performance liquid chromatography with atmospheric pressure chemical ionization two-stage mass spectrometry (HPLC-APCI-MS-MS) is presented. Pipamperone is used as the internal standard. Serum samples are prepared by liquid-liquid extraction under basic conditions with 1-chlorobutane. The chromatographic separation is achieved on an RP-18 stationary phase applying gradient elution with methanol-0.02% trifluoroacetic acid in water. Detection is carried out in the MS-MS single reaction monitoring mode of the ion-trap mass spectrometer. The limit of detection is 0.3 ng/ml and the calibration covers the range of 1-80 ng/ml. The intra-day RSDs are 6.1 to 7.3% over the calibration range, whereas the inter-day RSDs are 9.6 to 12.8%.

Population pharmacokinetics of piritramide in surgical patients.

BACKGROUND: Piritramide is a synthetic opioid used for postoperative analgesia in several European countries. The authors present a mixed-effects model of its population pharmacokinetics in patients undergoing surgery. METHODS: After institutional approval and informed patient consent was obtained, 29 patients who were classified as American Society of Anesthesiologists physical status I or II and aged 21-82 yr were enrolled in the study. They received 0.2 mg/kg piritramide as an intravenous bolus before anesthesia was induced. Central venous blood samples were drawn for as long as 48 h after administration of the drug. The plasma concentration of piritramide was determined by gas chromatography. The concentration-time data were analyzed by mixed-effects modeling. Target-controlled infusions and intermittent bolus regimens were simulated to identify a regimen suitable for patient-controlled analgesia based on population pharmacokinetics and published pharmacodynamic data. RESULTS: The pharmacokinetics of piritramide were described adequately by a linear three-compartment model. Patient age and weight were significant covariates. The values of the pharmacokinetic parameters are: V1 = 50.5 [1], V2 = 150 x (1 + 9.32 x 10(-3) x (age - 47 yr)) [l], V3 = 212 x (1 + 6.37 x 10(-3) x (age - 47 yr)) [l], Cl1 = 0.56 x (1 - 6.14 x 10(-3) x (age - 47 yr)) [l/min], Cl2 = 8.25 x (1 + 2.02 x 10(-2) x (Wt - 74 kg)) [l/min], Cl3 = 0.80 [l/min]. The age of 47 yr and the weight of 74 kg refer to the median values for these factors in the patients studied. Rapid distribution, slow distribution, and elimination half-lives for the median patient are 0.05, 1.34, and 10.43 h, respectively. The context-sensitive half-time after a 24-h infusion is predicted at 10.5 h in a 75-yr-old patient compared with 7 h for the median patient. CONCLUSIONS: Piritramide is distributed extensively and eliminated slowly. The pharmacokinetic profile of the drug allows for intermittent bolus administration even when constant effect compartment concentrations are desirable, e.g., for PLA.

Sensitive determination of piritramide in human plasma by gas chromatography.

A selective and sensitive method for the determination of piritramide in human plasma is described. A 1-ml aliquot of plasma was extracted with 10 ml of hexane-isoamyl alcohol (99.5:0.5, v/v) (extraction efficiency 86%) after addition of 50 microliters of 2 M ammonia and 20 microliters of aqueous strychnine solution (100 ng per 10 microliters) as internal standard. Gas chromatography was performed with J&W DB-1, 30 m x 0.53 mm I.D. separation column, film thickness 1.5 microns, using an nitrogen-phosphorus-sensitive detector. The assay was linear in the concentration range 3.75-2250 ng/ml (r = 0.999), with a lower limit of detection of 1-2 ng/ml. The precision was determined using spiked plasma samples (10 and 50 ng/ml), with coefficients of variation of 3.5 and 3.1% (intra-day; n = 5) and 4.6 and 4.1% (inter-day; n = 4). In the range 3.75-150 ng/ml, the accuracy of the assay was 3.36%. The method was used for the determination of piritramide plasma concentrations in patients receiving intra- or post-operative analgesia.

[Determination of piritramid in plasma using high pressure liquid chromatography methods]. / Oznaczanie pirytramidu w osoczu metoda wysokosprawnej chromatografii cieczowej.

After alkalization piritramid and codeine (internal standard) were extracted from plasma thrice with ether, solvent was removed, the residue dissolved in a mobile phase (methanol-phosphate buffer pH 4.5. 7:3) and injected on the column (packing Lichrosorb RP-18). The amount (0.5-2.5 micrograms) of piritramid was determined, average recovery was 88%.

[Identification of pentazocine, piritramide and methadone in blood using thin layer chromatography]. / Identyfikacja pentazocyny, pirytramidu i metadonu we krwi metoda chromatografii cienkowarstwowej.

Pentazocine, piritramide and methadone, when extracted from blood or plasma with ether at pH ca. 12, were separated by TLC method on alumina or silica gel by ascending technique on 5 x 20 cm and 2.5 x 7.5 cm plates and also by horizontal development, using suitable mobile phases. The substances were identified by reaction with potassium iodoplatinate or 20% Na2CO3 solution (up to the amount 2 micrograms pentazocine, 0.5 microgram piritramide and 1.5 micrograms methadone.