Differences in binding affinities of MDA, MDMA, MDEA, Amphetamine, Methamphetamine, and their deuterated analogues to solid-phase extraction cartridges.

This study evaluated the potential for partial separation of drugs from their deuterated internal standards using Cerex(®) Polycrom™ CLIN II solid-phase extraction (SPE) cartridges. After elution from the column and derivatization, gas chromatography-mass spectrometry results showed that the target compound eluted from the SPE cartridge prior to its deuterated form. This elution separation effect was greater for 3,4-methylenedioxymethamphetamine (MDMA) and methamphetamine (MAMP) than for the other drugs studied. When the drugs were eluted in 0.5 mL increments from a 50 mg sorbent bed, no drug appeared in the first fraction. The drug to internal standard ratios (expected value 1.00) for subsequent fractions collected were 1.30, 1.07, and 0.83 for MDA/MDA-d(5); 1.65, 1.18, 0.67, and 0.56 for MDMA/MDMAd(5); and 1.37, 1.18, and 0.95 for MDEA/MDEA-d(6). For d-AMP and d-MAMP, the expected ratio was 0.40. The subsequent ratios were 0.63, 0.46, 0.35, and 0.34 for d-AMP/d-AMP-d(11); and 1.00, 0.59, 0.25, and 0.18 for d-MAMP/d-MAMP-d(14). The affinity of d-MAMPd(14) was shown to be greater than that of d-MAMP-d(5), and deuteration at the propyl end of the molecule was shown to increase binding more than deuteration on the phenyl group.

Mechanism-based PK/PD modeling of the respiratory depressant effect of buprenorphine and fentanyl in healthy volunteers.

The objective of this study was to characterize the pharmacokinetic/pharmacodynamic (PK/PD) relationship of buprenorphine and fentanyl for the respiratory depressant effect in healthy volunteers. Data on the time course of the ventilatory response at a fixed P(ET)CO(2) of 50 mm Hg and P(ET)O(2) of 110 mm Hg following intravenous administration of buprenorphine and fentanyl were obtained from two phase I studies (50 volunteers received buprenorphine: 0.05-0.6 mg/70 kg and 24 volunteers received fentanyl: 0.075-0.5 mg/70 kg). The PK/PD correlations were analyzed using nonlinear mixed effects modeling. A two- and three-compartment pharmacokinetic model characterized the time course of fentanyl and buprenorphine concentration, respectively. Three structurally different PK/PD models were evaluated for their appropriateness to describe the time course of respiratory depression: (1) a biophase distribution model with a fractional sigmoid E(max) pharmacodynamic model, (2) a receptor association/dissociation model with a linear transduction function, and (3) a combined biophase distribution-receptor association/dissociation model with a linear transduction function. The results show that for fentanyl hysteresis is entirely determined by the biophase distribution kinetics, whereas for buprenorphine hysteresis is caused by a combination of biophase distribution kinetics and receptor association/dissociation kinetics. The half-time values of biophase equilibration (t(1/2, k(eo))) were 16.4 and 75.3 min for fentanyl and buprenorphine, respectively. In addition, for buprenorphine, the value of k(on) was 0.246 ml/ng/min and the value of k(off) was 0.0102 min(-1). The concentration-effect relationship of buprenorphine was characterized by a ceiling effect at higher concentrations (intrinsic activity alpha=0.56, 95% confidence interval (CI): 0.50-0.62), whereas fentanyl displayed full respiratory depressant effect (alpha=0.91, 95% CI: 0.19-1.62).

Buprenorphine induces ceiling in respiratory depression but not in analgesia.

BACKGROUND: We measured the effect of two weight adjusted i.v. doses (0.2 mg per 70 kg and 0.4 mg per 70 kg) of the potent opioid buprenorphine on analgesia and respiratory depression in healthy volunteers. The aim of the study was to compare buprenorphine's behaviour with respect to the occurrence of ceiling (or apparent maximum) in these typical micro-opioid protein-(MOP) receptor effects. METHODS: Ten subjects (5 males) received 0.2 mg per 70 kg, 10 others (5 males) 0.4 mg per 70 kg i.v. buprenorphine. Steady-state inspired minute ventilation at a fixed end-tidal Pco(2) of 7 kPa was measured before drug infusion and at regular intervals after drug infusion. Experimental pain was induced using transcutaneous electrical stimulation and a gradually increasing current. Pain tolerance was measured at regular intervals before and after drug infusion. The studies lasted 8 h. RESULTS: After infusion of the drug ventilation showed a rapid decline and reached peak depression between 150 and 180 min after drug administration. This effect was dose-independent with respect to timing and magnitude. At peak respiratory depression minute ventilation was 13.1 (sd 1.8) litre min(-1) in the 0.2 mg group vs 12.0 (sd 1.3) litre min(-1) in the 0.4 mg group (n.s.). At buprenorphine 0.2 mg a small short-lived analgesic effect was observed with a maximum increase in pain tolerance current of 6.7 (sd 2.8) mA occurring at 75 min after drug administration. Peak analgesic effect was 29% above baseline current. In contrast, buprenorphine 0.4 mg caused a large and long-lived analgesic effect with a maximum increase in pain tolerance current of 23.8 (sd 7.4) mA occurring at 130 min after drug administration. Peak analgesic effect was 160% above baseline current (0.4 vs 0.2 mg, P<0.01). CONCLUSIONS: While buprenorphine's analgesic effect increased significantly, respiratory depression was similar in magnitude and timing for the two doses tested. We conclude that over the dose range tested buprenorphine displays ceiling in respiratory effect but none in analgesic effect.

Melanocortin-1 receptor gene variants affect pain and mu-opioid analgesia in mice and humans.

BACKGROUND: A recent genetic study in mice and humans revealed the modulatory effect of MC1R (melanocortin-1 receptor) gene variants on kappa-opioid receptor mediated analgesia. It is unclear whether this gene affects basal pain sensitivity or the efficacy of analgesics acting at the more clinically relevant mu-opioid receptor. OBJECTIVE: To characterise sensitivity to pain and mu-opioid analgesia in mice and humans with non-functional melanocortin-1 receptors. METHODS: Comparisons of spontaneous mutant C57BL/6-Mc1r(e/e) mice to C57BL/6 wildtype mice, followed by a gene dosage study of pain and morphine-6-glucuronide (M6G) analgesia in humans with MC1R variants. RESULTS: C57BL/6-Mc1r(e/e) mutant mice and human redheads--both with non-functional MC1Rs--display reduced sensitivity to noxious stimuli and increased analgesic responsiveness to the mu-opioid selective morphine metabolite, M6G. In both species the differential analgesia is likely due to pharmacodynamic factors, as plasma levels of M6G are similar across genotype. CONCLUSIONS: Genotype at MC1R similarly affects pain sensitivity and M6G analgesia in mice and humans. These findings confirm the utility of cross species translational strategies in pharmacogenetics.

Comparison of the respiratory effects of intravenous buprenorphine and fentanyl in humans and rats.

BACKGROUND: There is evidence from animal studies suggesting the existence of a ceiling effect for buprenorphine-induced respiratory depression. To study whether an apparent ceiling effect exists for respiratory depression induced by buprenorphine, we compared the respiratory effects of buprenorphine and fentanyl in humans and rats. METHODS: In healthy volunteers, the opioids were infused i.v. over 90 s and measurements of minute ventilation at a fixed end-tidal PCO2 of 7 kPa were obtained for 7 h. Buprenorphine doses were 0.7, 1.4, 4.3 and 8.6 microg kg(-1) (n=20 subjects) and fentanyl doses 1.1, 2.1, 2.9, 4.3 and 7.1 microg kg(-1) (n=21). Seven subjects received placebo. In rats, both opioids were infused i.v. over 20 min, and arterial PCO2 was measured 5, 10, 15 and 20 min after the start of fentanyl infusion and 30, 150, 270 and 390 min after the start of buprenorphine infusion. Doses tested were buprenorphine 0, 100, 300, 1000 and 3000 microg kg(-1) and fentanyl 0, 50, 68 and 90 microg kg(-1). RESULTS: In humans, fentanyl produced a dose-dependent depression of minute ventilation with apnoea at doses > or = 2.9 microg kg(-1); buprenorphine caused depression of minute ventilation which levelled off at doses > or = 3.0 microg kg(-1) to about 50% of baseline. In rats, the relationship of arterial PCO2 and fentanyl dose was linear, with maximum respiratory depression at 20 min (maximum PaCO2 8.0 kPa). Irrespective of the time at which measurements were obtained, buprenorphine showed a non-linear effect on PaCO2, with a ceiling effect at doses > 1.4 microg kg(-1). The effect on PaCO2 was modest (maximum value measured, 5.5 kPa). CONCLUSIONS: Our data confirm a ceiling effect of buprenorphine but not fentanyl with respect to respiratory depression.

Comparison of morphine-6-glucuronide and morphine on respiratory depressant and antinociceptive responses in wild type and mu-opioid receptor deficient mice.

BACKGROUND: Morphine-6-glucuronide (M6G) is a metabolite of morphine with potent analgesic properties. The influence of M6G on respiratory and antinociceptive responses was investigated in mice lacking the micro -opioid receptor (MOR) and compared with morphine. METHODS: Experiments were performed in mice lacking exon 2 of the MOR (n=18) and their wild type (WT) littermates (n=20). The influence of M6G and morphine on respiration was measured using whole body plethysmography during three elevations of inspired carbon dioxide. Antinociception was assessed using tail flick and hotplate tests. RESULTS: In WT but not null mutant mice, a dose-dependent depression of the slope of the ventilatory carbon dioxide response was observed after M6G and morphine. Similarly, both opioids were devoid of antinociceptive effects in null mutant mice, but showed potent dose-dependent analgesia in WT animals. Potency differences between M6G and morphine in WT mice were of the same order of magnitude for analgesia and respiration. CONCLUSIONS: The data indicate that the desired (antinociceptive) and undesired (respiratory depression) effects of M6G and morphine are linked to the same gene product; that is the MOR. Other opioid- and non-opioid-receptor systems may play a minor role in the actions of M6Gs and morphine. The clinical implications of our findings are that any agent acting at the MOR will invariably cause (potent) analgesia in combination with (variable) respiratory depression.

[The effect of anesthetics on control of respiration]. / Einfluss von Anästhetika auf die Atemkontrolle.

Ventilatory control in humans depends on complex mechanisms which aim to maintain a cellular CO2-, O2- and H(+)-homeostasis under physiological conditions. This regulation is based on chemical control which predominantly acts via peripheral chemoreceptors in the carotid bodies and central chemoreceptors in the ventral medulla of the brainstem on the one hand, and behavioural control on the other, by which it is possible to adapt respiration to conditions of daily living. The influence of anaesthesia and related conditions may depress respiration and have a sustained effect on ventilatory control. Perioperative respiratory depression remains a serious clinical problem in perioperative medicine. This review will give an overview of ventilatory control and discuss the most relevant responses, describe the effects of pain, anaesthetics and opioids on ventilatory control and their interaction. The current body of knowledge is put into perspective to identify patients at risk for perioperative respiratory depression.

Response surface modeling of alfentanil-sevoflurane interaction on cardiorespiratory control and bispectral index.

BACKGROUND: Respiratory depression is a serious side effect of anesthetics and opioids. The authors examined the influence of the combined administration of sevoflurane and alfentanil on ventilatory control, heart rate (HR), and Bispectral Index (BIS) in healthy volunteers. METHODS: Step decreases in end-tidal partial pressure of oxygen from normoxia into hypoxia (approximately 50 mmHg) at constant end-tidal partial pressure of carbon dioxide (approximately 48 mmHg) were performed in nine male volunteers at various concentrations of alfentanil and sevoflurane, ranging from 0 to 50 ng/ml for alfentanil and from 0 to 0.4 end-tidal concentration (ET%) for sevoflurane, and with various combinations of alfentanil and sevoflurane. The alfentanil-sevoflurane interactions on normoxic resting (hypercapnic) ventilation (Vi), HR, hypoxic Vi, and HR responses and BIS were assessed by construction of response surfaces that related alfentanil and sevoflurane to effect using a population analysis. RESULTS: Concentration-effect relations were linear for alfentanil and sevoflurane. Synergistic interactions were observed for resting Vi and resting HR. Depression of Vi by 25% occurred at 38 +/- 11 ng/ml alfentanil (population mean +/- SE) and at 0.7 +/- 0.4 ET% sevoflurane. One possibility for 25% reduction when alfentanil and sevoflurane are combined is 13.4 ng/ml alfentanil plus 0.12 ET% sevoflurane. Additive interactions were observed for hypoxic Vi and HR responses and BIS. Depression of the hypoxic Vi response by 25% occurred at 16 +/- 1 ng/ml alfentanil and 0.14 +/- 0.05 ET% sevoflurane. The effect of sevoflurane on the BIS (25% reduction of BIS occurred at 0.45 +/- 0.08 ET%) was independent of the alfentanil concentration. CONCLUSIONS: Response surface modeling was used successfully to analyze the effect of interactions between two drugs on respiration. The combination of alfentanil and sevoflurane causes more depression of Vi and HR than does the summed effect of each drug administered separately. The effects of combining alfentanil and sevoflurane on hypoxic Vi and HR responses and BIS could be predicted from the separate dose-response curves. Over the dose range tested, the hypoxic response is more sensitive to the effects of anesthetics and opioids relative to resting ventilation.

Sex differences in morphine analgesia: an experimental study in healthy volunteers.

BACKGROUND: Animal and human studies indicate the existence of important sex-related differences in opioid-mediated behavior. In this study the authors examined the influence of morphine on experimentally induced pain in healthy male and female volunteers. METHODS: Young healthy men and women (10 of each sex) received intravenous morphine (bolus 0.1-mg/kg dose followed by an infusion of 0.030 mg. kg-1. h-1 for 1 h). Pain threshold and pain tolerance in response to a gradual increase in transcutaneous electrical stimulation, as well as plasma concentrations of morphine and its major metabolites (morphine-6-glucuronide and morphine-3-glucuronide) were determined at regular intervals up to 7 h after the start of morphine infusion. A population pharmacodynamic model was used to analyze the morphine-induced changes in stimulus intensity. The improvement of the model fits by inclusion of covariates (sex, age, weight, lean body mass) was tested for significance. The model is characterized by baseline current, a rate constant for equilibrium between plasma and effect-site morphine concentrations (ke0), and analgesic potency (AC50, or the morphine concentration causing a 100% increase in stimulus intensity for response). RESULTS: The inclusion of the covariates age, weight, and lean body mass did not improve the model fits for any of the model parameters. For both pain threshold and tolerance, a significant dependency on sex was observed for the parameters ke0 (pain threshold: 0.0070 +/- 0.0013 (+/- SE) min-1 in men vs. 0.0030 +/- 0. 0005 min-1 in women; pain tolerance: 0.0073 +/- 0.0012 min-1 in men vs. 0.0024 +/- 0.0005 min-1 in women) and AC50 (pain threshold: 71.2 +/- 10.5 nm in men vs. 41.7 +/- 8.4 nm in women; pain tolerance: 76. 5 +/- 7.4 nm in men vs. 32.9 +/- 7.9 nm in women). Baseline currents were similar for both sexes: 21.4 +/- 1.6 mA for pain threshold and 39.1 +/- 2.3 mA for pain tolerance. Concentrations of morphine, morphine-3-glucuronide, and morphine-6-glucuronide did not differ between men and women. CONCLUSIONS: These data show sex differences in morphine analgesia, with greater morphine potency but slower speed of onset and offset in women. The data are in agreement with observations of sex differences in morphine-induced respiratory depression and may explain higher postoperative opioid consumption in men relative to women.

Atom-selective bond breaking in a chemisorbed homonuclear molecule induced by core excitation: N2/Ru(001)

We observe photochemical selectivity for N 1s to pi(*) excitations of chemisorbed N2. By narrow bandwidth synchrotron radiation we selectively excite one of the two atoms of the molecule. Photon stimulated desorption of neutral N atoms predominates for excitations of the N atom close to the surface, whereas excitation of the outer atom ejects predominantly N02 and small amounts of N+, demonstrating the predominant breaking of the inner or outer bond, respectively, of the N2 adsorbate. Analysis on the basis of previously obtained decay electron spectra after atom-selective excitation can explain the mechanism of localized bond breaking.

Methamphetamine and amphetamine derived from the metabolism of selegiline.

Routine methamphetamine testing identified a urine specimen with inconsistent screening and confirmation results. The methamphetamine RIA screening test (Diagnostic Products Corporation) indicated a borderline positive specimen, while the achiral confirmatory GC/MS result showed 4690 ng/mL of methamphetamine and 1895 ng/mL of amphetamine. Analysis of the specimen after derivatization with S(-)-N-trifluoroacetylprolyl chloride showed only the presence of 1-amphetamine and 1-methamphetamine. It was later learned that the individual providing the specimen had been taking Selegiline. Selegiline, (-) propynylmethamphetamine, is a monoamine oxidase inhibitor used for the treatment of Parkinson's disease. It is sold under the trade name Eldepryl. Its major metabolites are 1-methamphetamine, 1-amphetamine and N-desmethylselegiline. Urine specimens from other Selegiline users were obtained and analyzed. A characteristic metabolic pattern was noted, exemplified by a ratio of 1-methamphetamine to 1-amphetamine of about 2.8. This is in contrast to what is observed in the urine of individuals who ingest pure 1-methamphetamine, such as with Vicks Inhaler, where the 1-methamphetamine to 1-amphetamine ratio in the urine is usually greater than 8. Caution is advised when interpreting methamphetamine results without using a chiral identification technique.

Comparison of the hydrolysis rates of morphine-3-glucuronide and morphine-6-glucuronide with acid and beta-glucuronidase.

The acid and enzymatic hydrolysis rates for two morphine metabolites, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G), were compared. Urine fortified with M3G or M6G was hydrolyzed in a boiling water bath or with beta-glucuronidases. Optimal temperatures for beta-glucuronidases were 60 degrees C for Helix pomatia and abalone and 50 degrees C for Escherichia coli. A 3-h incubation with 1,000-1,500 Fishman units of enzyme gave complete hydrolysis of M3G. The enzymatic hydrolysis rate of M6G was approximately 25% of the hydrolysis rate of M3G and required 24 h for completion. The acid hydrolysis rate of M6G was slower than M3G and required a 0.5-h incubation with a 1:1 mixture of concentrated HCl in a boiling water bath for completion. For comparison, the acid hydrolysis rate of codeine conjugates was found to be similar to the rate of M6G, but the enzymatic rate of codeine conjugates appeared slower than the rate of M6G.

Reanalysis of forensic urine specimens containing benzoylecgonine and THC-COOH.

Drug testing laboratories are often requested to retest specimens that have tested positive. The reproducibility of analytical retest data for delta-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) and benzoylecgonine in specimens that had previously been analyzed and then frozen by the Navy Drug Screening Laboratory, Great Lakes is examined in this study. All specimens were tested by gas chromatography/mass spectrometry (GC/MS). Retest values generally showed a decrease in concentration but exhibited considerable variability. Eighty-five THC-COOH positive urine specimens stored frozen for 1 to 10 months (average 2.3 months) declined an average of 25% (range, +30% to -80%) and 61 benzoylecgonine positive urine specimens stored for 1 to 8 months (average 2.3 months) declined an average of 19% (ranged +20% to -100%) from initial GC/MS test results. Drugs were found to partition into strata when frozen in urine because of the thermodynamics of the freezing process. To assure a homogenous solution for repeat testing, specimens that have been frozen and thawed were gently mixed before analysis.

Effect of pre-enlistment testing on the confirmed drug-positive rate for Navy recruits.

In June 1988, the armed forces of the United States began testing prospective candidates for military service for alcohol, marijuana metabolite (THC-COOH), and cocaine metabolite (benzoylecgonine) through the Military Entrance Processing Station (MEPS) program. Comparison of the confirmed positive drug rates for pre-inductees into the Navy during the MEPS program testing period with the confirmed drug-positive rates for 5 years before and 1 year after MEPS testing showed a decrease in the confirmed positive rate for THC-COOH and an apparent initial decrease for cocaine metabolite as a result of MEPS testing. The overall results for cocaine seem to be overshadowed by other demographic factors operating in the population tested.

Factors influencing confirmed drug positives for Navy and Marine Corps recruits.

Confirmed use of marijuana and cocaine in Navy and Marine Corps recruit populations was examined in terms of age, month of enlistment, recruit class size, education level, and Armed Forces Qualifications Test (AFQT) scores. Between 1982 and 1989, confirmed use of the drugs showed a seasonal variation, with the highest levels in the fall and winter. The rate for marijuana and cocaine was inversely related to the size of the recruit class (r = -0.80) and completion of high school (r = -0.82). The recruit class is larger and younger in the summer. AFQT scores were directly related to age. Education level appears to be one major determinant in addressing drug use.

Limits of linearity and detection for some drugs of abuse.

The limits of linearity (LOL) and detection (LOD) are important factors in establishing the reliability of an analytical procedure for accurately assaying drug concentrations in urine specimens. Multiple analyses of analyte over an extended range of concentrations provide a measure of the ability of the analytical procedure to correctly identify known quantities of drug in a biofluid matrix. Each of the seven drugs of abuse gives linear analytical responses from concentrations at or near their LOD to concentrations several-fold higher than those generally encountered in the drug screening laboratory. The upper LOL exceeds the Department of Navy (DON) cutoff values by factors of approximately 2 to 160. The LOD varies from 0.4 to 5.0% of the DON cutoff value for each drug. The limit of quantitation (LOQ) is calculated as the LOD + 7 SD. The range for LOL is greater for drugs analyzed with deuterated internal standards compared with those using conventional internal standards. For THC acid, cocaine, PCP, and morphine, LOLs are 8 to 160-fold greater than the defined cutoff concentrations. For the other drugs, the LOL's are only 2 to 4-fold greater than the defined cutoff concentrations.

Extraction of 6-monoacetylmorphine from urine.

An efficient and improved procedure for the extraction of 6-monoacetylmorphine (6-MAM) from urine is described. The procedure uses a 10% isobutanol in methylene chloride solution for initial extraction of 6-MAM, back extraction with acidic sodium acetate, and then another alkaline extraction into 10% isobutanol in methylene chloride. Compared to solid-phase extraction, this method provided significant improvement in 6-MAM recovery, along with the elimination of extraneous peaks when analyzed by GC/MS.

Comparison of drug abuse in different military populations.

Quantitative analytical data, generated at the Navy Drug Screening Laboratory, Great Lakes, Illinois, expressed as percent confirmed positives for four drugs of abuse (marijuana metabolite, cocaine metabolite, amphetamines, and opiates) are summarized and compared according to their population of origin. The four populations of interest included U.S. Navy and Marine Corps recruits and service school members. Conformed positive urines for marijuana showed a small but significant decline (p less than 0.001) from about 1.2% confirmed positive among U.S. Navy recruits entering service school commands in 1984 to 0.9% among Navy service school members in 1988 and from 2.0% among U.S. Marine Corps recruits entering service schools in 1984 to 0.8% among Marine Corps service school members in 1988. Navy and Marine Corps recruits showed a significantly higher (p less than 0.001) confirmed positive use rate (6.1 and 3.3%, respectively) compared to service school members, perhaps reflecting their recent civilian use pattern. The relatively high confirmed positive cocaine rate among all groups may have reflected an increasing trend in all populations, confirming a similar trend in high school and other civilian populations. Generally, the frequency of confirmed positive urines with amphetamines and opiates, based upon the findings at the Navy Drug Screening Laboratory at Great Lakes, has been static except for an apparent recent increase in amphetamine use in 1988. The decline in confirmed positive drug urinalyses among service school members from both the Navy and Marine Corps indicated that perhaps education and maturity had a positive effect upon their behavior.

Performance appraisal, 1: Risks and rewards.

Employers must make sure that performance-appraisal systems meet a series of critical standards designed to avoid bias while enhancing accuracy as well as equity.