Simultaneous quantitation of meperidine, normeperidine, tramadol, propoxyphene and norpropoxyphene in human plasma using solid-phase extraction and gas chromatography/mass spectrometry: Method validation and application to cardiovascular safety of therapeutic doses.

RATIONALE: Several opioid analgesics have been related to the prolongation of cardiac repolarization, a condition which can be fatal. In order to establish a correct estimation of the risk/benefit balance of therapeutic doses of meperidine, normeperidine, tramadol, propoxyphene and norpropoxyphene, it was necessary to develop an analytical method to determinate plasma concentrations of these opioids. METHODS: Here we describe a method which incorporates strong alkaline treatment to obtain norpropoxyphene amide followed by a one-elution step solid-phase extraction, and without further derivatization. Separation and quantification were achieved by gas chromatography/electron ionization mass spectrometry (GC/EI-MS) in selected-ion monitoring mode. Quantification was performed with 500 µL of plasma by the addition of deuterated analogues as internal standards. RESULTS: The proposed method has been validated in the linearity range of 25-1000 ng/mL for all the analytes, with correlation coefficients higher than 0.990. The lower limit of quantification was 25 ng/mL. The intra- and inter-day precision, calculated in terms of relative standard deviation, were 2.0-12.0% and 6.0-15.0%, respectively. The accuracy, in terms of relative error, was within a ± 10% interval. The absolute recovery and extraction efficiency ranged from 81.0 to 111.0% and 81.0 to 105.0%, respectively. CONCLUSIONS: A GC/MS method for the rapid and simultaneous determination of meperidine, normeperidine, tramadol, propoxyphene and norpropoxyphene in human plasma was developed, optimized and validated. This procedure was shown to be sensitive and specific using small specimen amounts, suitable for application in routine analysis for forensic purposes and therapeutic monitoring. To our knowledge, this is the first full validation of the simultaneous determination of these opioids and their metabolites in plasma samples.

Urine drug testing of chronic pain patients. V. Prevalence of propoxyphene following its withdrawal from the United States market.

Propoxyphene is an opioid analgesic that was surrounded by controversy concerning its safety and efficacy during its lifespan in the US market. Propoxyphene was withdrawn in November of 2010 from the US market and is still being detected one year post-withdrawal in urine specimens from the pain management population. In this study, the prevalence of propoxyphene was determined in a total of 417,914 urine specimens collected from 630 clinics involved in pain management located in 24 states during the period of January 1, 2010, through December 31, 2011. Propoxyphene and norpropoxyphene were measured in urine by a validated liquid chromatography-tandem mass spectrometry procedure with a lower limit of quantitation of 50 ng/mL. The positivity rate for propoxyphene prevalence declined sharply between November and December of 2010 and further declined at a gradual rate, ending in a prevalence of 0.27% (one out of every 370 specimens, n = 25,658) for the month of December 2011. The presented data provide evidence of the dramatic decline in the use of propoxyphene products since their removal from the medical market, and may be beneficial to US urine drug testing programs determining the need for continual monitoring of propoxyphene levels.

Unstable propoxyphene metabolite excreted in human urine is detected by liquid chromatography-tandem mass spectrometry.

A "dilute and shoot" method for measuring norpropoxyphene in human urine using liquid chromatography-tandem mass spectrometry distinguishes two different metabolites of propoxyphene, norpropoxyphene (m/z 326) and a dehydrated rearrangement product (m/z 308). The metabolite formed from the rearrangement and dehydration of norpropoxyphene is excreted in human urine and also may be formed from the chemical degradation of norpropoxyphene. Previously, these two metabolites were indistinguishable by gas chromatography- mass spectrometry methods that use an alkaline extraction that converts norpropoxyphene into its rearrangement product. The degradation of norpropoxyphene presents a challenge for its analytical quantitation, and methods for circumventing these issues are presented.

Retrospective diagnosis of an adverse drug reaction in a breastfed neonate: liquid chromatography-tandem mass spectrometry quantification of dextropropoxyphene and norpropoxyphene in newborn and maternal hair.

Dextropropoxyphene (DP) and norpropoxyphene (NP) are commonly used in the treatment of postpartum pain. The drug is widely prescribed in Europe and Canada and has been recently approved for use in the U.S. Its safety during breastfeeding, however, has not been fully established. Very few reports on its effects on neonates have been published. We report here the case of a mother treated with DP (6 capsules a day for 10 days) while she was breastfeeding. On day 7, her baby was lethargic and had difficulties with breastfeeding, which led to early weaning. The correlation between side effects observed in the infant and DP was made retrospectively by measuring DP and NP hair concentrations in the mother-infant pair with liquid chromatography-tandem mass spectrometry. Breastfeeding mothers taking DP expose their infants to high doses of DP and NP. In agreement with previously published reports, these data indicate that acetaminophen and nonsteroidal antiinflammatories are preferable for analgesia during breastfeeding. Breastfeeding should be encouraged under most circumstances, and if the mother takes any treatment for pain, a commonly prescribed drug with pharmacologic data available must be used.

Death from undiagnosed glioblastoma multiforme and toxic self-medication presenting with concurrent dysfunctional behavior.

We encountered a decedent with an unexpected glioblastoma multiforme. A 61-year-old retired African-American woman was found dead in her home, fully clothed in her bathtub, with a pillow under her head. At autopsy, the brain showed a glioblastoma multiforme. Toxicology showed elevated hydrocodone, propoxyphene, acetaminophen, and positive paroxetine. The presence of a brain tumor likely caused a severe headache. The use of her medications could have indicated a reaction to the escalating pain of the brain trauma, and overuse could be consistent with escalating pain or loss of rational thought processes. The present case is interesting in that it had evidence of behavioral dysfunction that could be related to the brain tumor, and death arising from the glioblastoma multiforme (cerebral hemorrhage and edema) with concurrent multiple drug intoxication.

Evaluation of the Triage PPY on-site testing device for the detection of dextropropoxyphene in urine.

A new point-of-care colloidal metal immunoassay urine drugs-of-abuse testing device, the BIOSITE TRIAGE Plus Propoxyphene (TPP), was evaluated for the rapid detection of dextropropoxyphene (PPY) and/or its primary metabolite, norpropoxyphene (NP), in urine at a total PPY/NP concentration of 300 ng/mL or greater. This assay has been added to the Triage device that tests for commonly abused drugs. Adding to drug-free urine PPY and NP established the linearity of the TPP assay at concentrations of 40%, 80%, 120%, and 160% of the cut-off concentration. No significant cross-reactivity was found at 1.0 g/L for 32 drugs commonly encountered in emergency department admissions. Significant cross-reactivity was observed only with diphenhydramine and tricyclic antidepressants. TPP results from 160 urine specimens screened for PPY and/or NP were compared to those obtained by testing with DRI enzyme immunoassay, Emit II plus immunoassay, Abuscreen Online immunoassay and gas chromatography-mass spectrometry (GC-MS). There was a 98.8% agreement of positive or negative results between TPP and both the DRI and OnLine assays. The two discordant TPP results were due to concentrations of NP below the TPP minimum cross-reactivity value of 400 ng/mL. These two specimens yielded GC-MS NP concentrations of 262 and 359 ng/mL. These NP concentrations were within +/- 20% of the cross-reactivity cut-off value for NP for TPP, DRI, and Online. There was only an 88% agreement of positive or negative results between TPP and the Emit assay. Twenty urine specimens yielding PPY positive results when tested by TPP were negative by Emit testing. The discordant TPP results were due to poor cross-reactivity of Emit to NP. A 98.8% agreement of positive PPY results was observed between TPP and GC-MS. Discordant urines were found to contain PPY concentrations below the cut-off value of the assay. TPP was found to be an accurate device for the detection of PPY and NP in urine.

CYP3A4 mediates dextropropoxyphene N-demethylation to nordextropropoxyphene: human in vitro and in vivo studies and lack of CYP2D6 involvement.

The individual cytochrome P450 isoforms in dextropropoxyphene N-demethylation to nordextropropoxyphene were determined and the pharmacokinetics of dextropropoxyphene and nordextropropoxyphene in cytochrome P4502D6 (CYP2D6) extensive (EM) and poor (PM) subjects were characterized. Microsomes from six CYP2D6 extensive metabolizers and one CYP2D6 poor metabolizer were used with isoform specific chemical and antibody inhibitors and expressed recombinant CYP enzymes. Groups of three CYP2D6 EM and PM subjects received a single 65-mg oral dose of dextropropoxyphene, and blood and urine were collected for 168 and 96 h, respectively. Nordextropropoxyphene formation in vitro was not different between the CYP2D6 extensive metabolizers (Km = 179 +/- 74 microM, Cl(int) = 0.41 +/- 0.26 ml mg(-1)h(-1)) and the PM subject (K = 225 microM, Cl(int) = 0.19 ml mg(-1) h(-1)) and was catalysed predominantly by CYP3A4. There was no apparent difference in the pharmacokinetics of dextropropoxyphene and nordextropropoxyphene in CYP2D6 EM and PM subjects. CYP3A4 is the major CYP enzyme catalysing the major metabolic pathway of dextropropoxyphene metabolism. Hence variability in the pharmacodynamic effects of dextropropoxyphene are likely due to intersubject variability in hepatic CYP3A4 expression and/or drug-drug interactions. Reported CYP2D6 phenocopying is not due to dextropropoxyphene being a CYP2D6 substrate.

Determination of dextropropoxyphene and nordextropropoxyphene in urine by liquid chromatography-electrospray ionization mass spectrometry.

Dextropropoxyphene and nordextropropoxyphene were extracted from urine samples with mixed mode solid-phase extraction cartridges. After elution and evaporation to dryness, the eluate was dissolved in mobile phase and each sample was injected in a LC-ESI-MS system. Quantification was carried out in the selected ion monitoring mode. This article shows the possibility to analyse drugs of abuse substances in urine with a single quadrupole mass spectrometer if only a thorough work-up procedure and a sufficient chromatographic separation is accomplished. In order to enhance the fragmentation of the analytes, in-source fragmentation was carried out. One fragment and the pseudomolecular ion per analyte together with chromatographic retention times were sufficient to verify that the sought compound was found in the samples. In- and between day variation was lower than 10% and the recovery was well above 90%. The analytes were quantified in the range 100-10000 ng/ml urine.

Drug- and mutagenesis-induced changes in the selectivity filter of a cardiac two-pore background K+ channel.

OBJECTIVE: As compared with voltage-gated K(+) channels (Kv-type), our knowledge of the structure-function and pharmacology of two-pore background K(+) channels is still very limited. Here we have used a drug- and mutagenesis-based approach to study the effect of the antidepressant fluoxetine (FL) and analgesic D-norpropoxyphene (NORP) on the cardiac two-pore background K(+) channel. METHODS: Whole-cell currents of the cTBAK-1 channel expressed in Xenopus laevis oocytes were investigated using conventional two-microelectrode voltage-clamp recording method combined with functional mutagenesis of the channel protein. RESULTS: Both drugs inhibit cTBAK-1 current: FL proved to be a voltage-dependent pore-blocker, while NORP induced a change in the selectivity of cTBAK-1 giving rise to a shift in the reversal potential (E(rev)) toward more positive voltages due to an increased Na(+) permeability. Mutations were introduced into the selectivity filter of the first (Y105F) and the second (F211Y) pore to mimic the P-region of HERG (GFGN) and Kv1.1 (GYGD) channels. Point mutations in the channel resulted in two distinct phenotypes of cTBAK-1: the mutant Y105F channel lost its selectivity and was unaffected by NORP, in contrast to the F211Y mutant. CONCLUSION: FL and NORP block the current of cTBAK-1 channels differently, the latter modified the selectivity of the channel pore. Our mutagenesis study revealed that NORP interacts with the selectivity filter of cTBAK-1. The significant role of the GYGD motif in this type of K(+) channels is emphasized.

Açäo do napsilato de propoxifeno sobre o fígado e rins maternos e fetais de ratas albinas, durante toda a prenhez: aspectos morfológicos / Hepatic and renal effects of propoxyphene napsylate on pregnancy rats

O uso do napsilato de propoxifeno (NP), um fármaco analgésico opióide e depressor do Sistema Nervoso Central, está envolvido com risco potencial de abuso e suas conseqüências, particularmente durante a gravidez. Como na literatura há dados indicando a possibilidade de sérios efeitos colaterais do NP sobre o fígado, o objetivo deste trabalho foi examinar os efeitos do NP em ratas prenhes e seus fetos. Ratas prenhas foram tratadas durante toda a gravidez (desde o dia zero ao 200 dia) com 5, 15 e 45 mglkg de peso corporal/dia de NP, uma vez ao dia, por gavage. Grupos controles receberam o veículo (solução de Acácia). Ao término, amostras de fígados e rins foram retiradas das matrizes e de seus conceptos, submetidos a exames de microscopia de luz e eletrônica. Nenhuma alteração morfológica foi detectada nos fígados maternos e fetais com qualquer dose do NP empregado, na microscopia óptica; porém, nos rins, tanto nas matrizes quanto nos conceptos mostraram sinais de toxicidade, particularmente com as doses máximas do fármaco, e especialmente nas células dos túbulos contorcidos proximais. Nossos resultados sugerem que, na rata, as alterações fisiológicas próprias da gravidez parecem atingir o órgão alvo de toxicidade do napsilato de propoxifeno, ou seja, os efeitos passam a exercer alterações sobre os rins e não sobre o fígado. Os mecanismos envolvidos ainda não são conhecidos

Norpropoxyphene-induced cardiotoxicity is associated with changes in ion-selectivity and gating of HERG currents.

OBJECTIVE: Norpropoxyphene (NP) is a major metabolite of propoxyphene (P), a relatively weak mu-opioid receptor agonist. Toxic blood concentrations ranging from 3 to 180 mumol/l have been reported and the accumulation of NP in cardiac tissue leads to naloxone-insensitive cardiotoxicity. Since several lines of evidence suggest that not only block of INa but also IK block may contribute to the non-opioid cardiotoxic effects of P and NP, we investigated the effects of P and NP on HERG channels. HERG presumably encodes IKr, the rapidly-activating delayed rectifier K+ current, which is known to have an important role in initiating repolarization of action potentials in cardiac myocytes. METHODS: Using the 2-microelectrode voltage clamp technique we investigated the interaction of P and NP with HERG channels, expressed in Xenopus oocytes. RESULTS: Our experiments show that low drug concentrations (5 mumol/l) facilitate HERG currents, while higher drug concentrations block HERG currents (IC50-values of approx. 40 mumol/l) and dramatically shift the reversal potential to a more positive value because of a 30-fold increased Na(+)-permeability. P and NP also alter gating of HERG channels by slowing down channel activation and accelerating channel deactivation kinetics. The mutant S631C nullifies the effect of P and NP on the channel's K(+)-selectivity. CONCLUSION: P and NP show a complex and unique drug-channel interaction, which includes altering ion-selectivity and gating. Site-directed mutagenesis suggests that an interaction with S631 contributes to the drug-induced disruption of K(+)-selectivity. No specific role of the minK subunit in the HERG block mechanism could be determined.

Gas chromatographic-mass spectrometric quantitation of dextropropoxyphene and norpropoxyphene in hair and whole blood after automated on-line solid-phase extraction. Application in twelve fatalities.

After conversion of norpropoxyphene (NP) to its corresponding amide, dextropropoxyphene (DP) and NP are extracted from 1 ml of blood or 50 mg of powdered hair, on C18 cartridges and eluted using methanol containing 0.5% acetic acid. Automated extraction is conducted on-line with automated device, starting from buffered and centrifuged sample. After extraction, the dried residue is reconstituted with 40 microl of methanol, and then injected in a gas chromatograph at 250 degrees C. Quantitation is carried out by gas chromatography-mass spectrometry in the selected-ion monitoring mode, lidocaine being the internal standard. The method gave relative standard deviations lower than 6.2% in whole blood, and 6.0% in hair for the entire range of calibration from 0.5 to 10 microg/ml in blood and from 1 to 20 ng/mg in hair of both compounds. Limits of detection in blood and hair for DP are, respectively, 0.07 microg/ml and 0.05 ng/mg, whereas the respective limits of detection in whole blood and hair for NP are 0.09 microg/ml and 0.04 ng/mg. The present method was used for one year in our laboratory. Postmortem concentrations of DP in blood ranged from 1.6 to 44.0 microg/ml (mean=9.8microg/ml, n = 12) and are comparable to those found in the literature. Out of 30 hair samples from people who died from heroin overdose, 13 were positive both for DP and NP with concentrations ranging from 0.2 to 27.4 ng/mg (mean 8.7 ng/mg) for DP and 0.3 to 68.9 ng/mg (mean 24.1 ng/mg) for NP.

Synthesis of new d-propoxyphene derivatives and the development of a microparticle-based immunoassay for the detection of propoxyphene and norpropoxyphene.

The synthesis of [S-(R,S)]-4-[[methyl[2-methyl-3-(1-oxopropoxy)-3, 4-diphenylbutyl]amino]-1-oxobutoxy]-2,5-pyrrolidinedione+ ++ (propoxyphene active ester, 2) is described. This was used as an intermediate to prepare a propoxyphene immunogen, [S-(R,S)]-4-[methyl][2-methyl-3-(1-oxopropoxy)-3,4-diphenylbuty l]-amino]- 1-oxobutyl-Bovine Thyroglobulin (3). This immunogen was then used to generate antibodies which demonstrate good cross-reactivity to d-propoxyphene, d-norpropoxyphene, and other propoxyphene metabolites. In addition, these antibodies were shown to have very low cross-reactivity to methadone, a structurally related compound. The introduction of an aminomethyl benzoate spacer into the propoxyphene active ester (2), followed by the activation of the carboxylic acid, provided for a more stable active ester (5). This stable active ester, together with the antibodies generated from the propoxyphene immunogen, has led to the development of an immunoassay based on the Kinetic Interaction of Microparticles in Solution (KIMS).

Gas chromatographic quantitation of dextropropoxyphene and norpropoxyphene in urine after solid-phase extraction.

A gas chromatographic technique with flame ionization detection, which is based on a solid-phase extraction (SPE) procedure using mixed-mode SPE columns, for the simultaneous quantitation of dextropropoxyphene and norpropoxyphene in urine is presented. Urine is treated with sodium hydroxide in order to rearrange, by base catalysis, norpropoxyphene to norpropoxyphene amide, which is then extracted with these columns and chromatographed. The method is specific, linear over the range 0-2000 ng/mL, sensitive, and reproducible. The extracts are cleaner than those obtained with traditional liquid-liquid extraction procedure, which is an important feature in view of further mass spectrometric confirmation of narcotics and other drugs.

Evaluation of the online immunoassay for propoxyphene: comparison to EMIT II and GC-MS.

A study was conducted to compare the clinical sensitivity of the OnLine and EMIT II assays for propoxyphene (PPX) use in human urine. A total of 5138 random clinical samples were evaluated by both OnLine and EMIT II. Samples that were positive for each immunoassay were confirmed for PPX and norpropoxyphene (NPPX) by gas chromatography-mass spectrometry (GC-MS). There were 14 samples that were identified positive by both immunoassays and confirmed positive by GC-MS. An additional six samples were positive by OnLine, negative by EMIT II, and confirmed positive by GC-MS. There was one unconfirmed positive sample identified by each immunoassay, and 5116 samples were identified as negative by both immunoassays. The increased sensitivity by OnLine can be attributed to the cross reactivity of the OnLine antibody, which is higher than the cross reactivity of the EMIT II antibody for NPPX (77% versus 7%, respectively). The high concentrations of NPPX, relative to those of PPX, found in all of the clinical samples suggest that laboratories that currently confirm for PPX should confirm for NPPX in order to obtain a better correlation between immunoassay results and GC-MS confirmations.

Extraction of selected drugs from serum using microwave irradiation.

Microwave irradiation is used as an alternative heating method for extraction over more conventional hot plate methods. We describe a fast, efficient method for the determination of selected drugs in human blood/serum using microwave extraction. The microwave extraction of organic substances requires special instrumentation and the results have been compared with the results from classical liquid/liquid extraction. The present microwave extractions were performed in an 'atmospheric pressure' system. Before irradiation with microwaves, an appropriate solvent mixture was added to the buffered specimen. Lidocaine, methadone, diazepam, nordiazepam, propoxyphene and norpropoxyphene were tested as model substances. The quantitation was performed by GC/NPD. The procedure has been applied successfully to a number of forensic cases. The use of microwaves decreases the time of extraction and the solvent consumption.

Methadone block of K+ current in squid giant fiber lobe neurons.

Voltage-dependent ionic currents were recorded from squid giant fiber lobe neurons using the whole-cell patch-clamp technique. When applied to the bathing solution, methadone was found to block IK, I Na and I Ca. Both I Na and I Ca were reduced without apparent change in kinetics and exhibited IC(50)'s of 50-100 and 250-500 mu M, respectively, at +10 mV. In contrast, IK was reduced in a time-dependent manner that is well fit by a simple model of open channel block (K(D)= 32+/- or 2 mu M, +60 mV, 10 degrees Celsius). The mechanism of I(K) block was examined in detail and involves a direct action of methadone, a tertiary amine, on K channels rather than an opioid receptor-mediated pathway. The kinetics of I(K) block resemble those reported for internally applied long chain quaternary ammonium (QA) compounds; and recovery from I(K) block is QA-like in its slow time course and strong dependence on holding potential. A quaternary derivative of methadone (N-methyl-methadone) only reproduced the effects of methadone on I(K) when included in the pipette solution; this compound was without effect when applied externally. I(K) block thus appears to involve diffusion of methadone into the cytoplasm and occlusion of the open K channel at the internal QA blocking site by the protonated form of the drug. This proposed mode of action is supported by the pH and voltage dependence of block as well as by the observation that high external K+ speeds the rate of drug dissociation. In addition, the effect of methadone on I(K) evoked during prolonged (300 ms) depolarizations suggests that methadone block may interfere with endogenous K+ channel inactivation. The effects of temperature, methadone stereoisomers, and the methadone-like drugs propoxyphene and nor-propoxyphene on IK block were examined. Methadone was also found to block I(K) in GH3 cells and in chick myoblasts.

D-propoxyphene and norpropoxyphene kinetics after the oral administration of D-propoxyphene: a new approach to liver function?

In an attempt to design a liver function test which takes into account both portal-systemic shunting and hepatocellular dysfunction, we investigated a group of patients with cirrhosis with or without surgical porta-caval shunt for d-propoxyphene and its major metabolite, norpropoxyphene kinetics. A small dose of d-propoxyphene (0.7 mg/kg body weight) was given orally to seven normal subjects, 15 patients with cirrhosis and seven patients with cirrhosis and surgical portacaval shunt. D-propoxyphene and norpropoxyphene areas under the plasma concentration-time from 0 to 4-h (AUC) were determined by the trapezoidal method. As d-propoxyphene is a high extraction drug and since the production of norpropoxyphene should reflect the amount of d-propoxyphene available to the hepatocytes, we tested the hypothesis that norpropoxyphene/d-propoxyphene AUC ratios should reflect both the degree of portal-systemic shunting and the severity of hepatocyte dysfunction. Norpropoxyphene/d-propoxyphene AUC ratios were significantly lower in patients with cirrhosis (mean +/- S.D.: 0.92 +/- 0.59) than in controls (2.51 +/- 0.45) and also significantly lower in patients with cirrhosis and a surgical shunt (0.53 +/- 0.23) than in patients with cirrhosis but without surgical shunt (1.10 +/- 0.63). Moreover, there was an overall statistically significant correlation between norpropoxyphene/d-propoxyphene AUC ratios and branched to aromatic amino acids ratios (rs = 0.91) and fasting venous NH4 (rs = -0.63). On the other hand, there was only a weak correlation between norpropoxyphene/d-propoxyphene AUC ratios and the 14C-aminopyrine breath test (rs = 0.43). These data suggest that the norpropoxyphene/d-propoxyphene AUC ratio reflects both shunting and reduced hepatocellular function.(ABSTRACT TRUNCATED AT 250 WORDS)

Propoxyphene and norpropoxyphene quantitation in the same solid-phase extraction using Toxi-Lab Spec VC MP3 system.

We have found that in using the Toxi-Lab Spec VC MP3 column we were able to easily identify and quantitate both propoxyphene and the major metabolite, norpropoxyphene, in a single extraction using urine as a matrix. Samples were screened using the Syva EMIT d.a.u. 1.0 assay for propoxyphene on the Olympus 5131, and all presumptive positives were prepared for confirmation by gas chromatography-mass spectrometry on Hewlett-Packard instruments. Urine (1.0 mL) was extracted and treated with a strong base (pH 11.0) in order to rearrange, by base catalysis, norpropoxyphene to norpropoxyphene amide, which chromatographs well on these columns.