Limited Sampling Strategy for Estimating Mycophenolic Acid Exposure on Day 7 Post-Transplant for Two Mycophenolate Mofetil Formulations Derived From 20 Chinese Renal Transplant Recipients

PURPOSE

To assess the pharmacokinetic properties of mycophenolate mofetil (MMF) dispersible tablets and capsules by the enzyme multiplied immunoassay technique (EMIT) in Chinese kidney transplant recipients in the early post-transplantation phase and to develop the equations to predict mycophenolic acid (MPA) area under the 12-hour concentration-time curve (AUC_0-12h) using a limited sampling strategy (LSS).

METHODS

Forty patients who underwent renal transplantation from brain-dead donors were randomly divided into dispersible tablets (Sai KE Ping; Hangzhou Zhongmei Huadong Pharma) and capsules (Cellcept; Roche Pharma, Why, NSW, Australia) groups, and treated with MMF combined with combination tacrolimus and prednisone as a basic immunosuppressive regimen. Blood samples were collected before treatment (0) and at 0.5,1, 1.5, 2, 4, 6, 8, 10, and 12 hours post-treatment and 7 days after renal transplantation. Plasma MPA concentrations were measured using EMIT. LSS equations were identified using multiple stepwise linear regression analysis.

RESULTS

The peak concentration (C_max) in the MMF dispersible tablets (MMFdt) group (7.0 ± 2.8) mg/L was reduced compared with that in the MMF capsules (MMFc) group (10.8 ± 6.2 mg/L; P = .012); time to peak concentration in the MMFdt group was 3.2 ± 2.3 hours, which was nonsignificantly elevated compared with that of the MMFc group (2.2 ± 1.7 hours). Three-point estimation formulas were generated by multiple linear regression for both groups: MPA-AUC_MMFdt = 3.542 + 3.332C_0.5h + 1.117C_1.5h + 3.946C_4h (adjusted r² = 0.90, P < .001); MPA-AUC_MMFc = 8.149 + 1.442C_2h + 1.056C_4h + 7.133C_6h (adjusted r² = 0.88, P < .001). Both predicted and measured AUCs showed good consistency.

CONCLUSIONS

After treatment with MMF dispersible tables or MMF capsules, the C_max of MPA for the MMFdt group was significantly lower than that of the MMFc group; there was no significant difference in other pharmacokinetic parameters. Three-time point equations can be used as a predictable measure of the AUC_0-12h of MPA.

False Elevation of the Blood Tacrolimus Concentration, as Assessed by an Affinity Column-mediated Immunoassay (ACMIA), Led to Acute T Cell-mediated Rejection after Kidney Transplantation

Tacrolimus is the most commonly used immunosuppressant. Because of its narrow therapeutic range, it is necessary to frequently monitor its concentration. We report the case of a 25-year-old man who underwent kidney transplantation whose tacrolimus concentrations, as measured by an affinity column-mediated immunoassay, were falsely elevated. As we reduced the dose of tacrolimus, the recipient developed T cell-mediated rejection. Using the same blood samples, an enzyme-multiplied immunoassay technique showed that the patient's levels of tacrolimus were extremely low. A further examination indicated that the false increase in the tacrolimus concentration was likely due to an unknown interfering substance. We administered methylprednisolone and antithymocyte-globulin. The patient's serum creatinine level decreased and remained stable after these treatments.

A non-specific biomarker of disease activity in HIV/AIDS patients from resource-limited environments

BACKGROUND

A general non-specific marker of disease activity that could alert the clinician and prompt further investigation would be of value in patients with HIV/AIDS, especially in resource limited environments.

OBJECTIVE

To investigate the potential of neopterin as non-specific biomarker in patients with advanced HIV/AIDS.

METHODS

Cross-sectional study in 105 HIV positive patients (75 on highly active antiretroviral treatment (HAART). Neopterin was assessed by enzyme linked immune-absorbent assay and cytokines by flow cytometry.

RESULTS

Neopterin levels were significantly higher (p<0.001) for the total patient than for the control group. Significant correlations between neopterin and plasma indicators of inflammation showed neopterin to be a good indicator of active inflammatory status and of the effect of HAART on the immune system. Neopterin was superior to C-reactive protein and to individual cytokines as indicator of immune deficiency. Increased neopterin levels were associated with a decline in albumin, haemoglobin and the albumin/globulin ratio, and with increases in red cell distribution width.

CONCLUSIONS

Plasma neopterin is a good non-specific biomarker of disease activity in HIV/AIDS patients. It is a good indicator of inflammatory activity, perpetuation of inflammation-associated co-morbidities, degree of immune deficiency and has predictive value for underlying disease, and for monitoring the HAART response.

Multiple immunoenzyme labeling using heat treatment combined with the polymer method: an analysis of the appropriate inactivation conditions of primary antibodies

Multiple immunoenzyme labeling is of considerable value to detect several antigens in the same specimen, although this technique is limited when the primary antibodies have been raised in the same animal species. Multiple immunoenzyme labeling using heat treatment is a simple, reliable and straightforward technique wherein the heat treatment prevents mixed labeling and cross-reaction. The present study determined the inactivation time for primary antibodies by heat treatment in order to apply this procedure to routine histopathological diagnosis and research, and found that the inactivation time differed among the primary antibodies. The secondary antibodies and the labeling enzyme were completely inactivated by heating for 10 min. Therefore, the inactivation of the primary antibodies is crucial to perform multiple immunoenzyme labeling using heat treatment. The sequential combination of the primary antibodies is also important; in the study presented here, an anti-thyroid transcription factor-1 (TTF-1) antibody should be used first and anti-cytokeratin AE1/AE3 antibody second, but not in the opposite sequence, to avoid a mixed-colour-labeling reaction. The present data provided the optimum combination of primary antibodies for multiple immunoenzyme labeling using heat treatment.

Reliability of mycophenolic acid monitoring by an enzyme multiplied immunoassay technique

BACKGROUND

For mycophenolic acid (MPA), substantial inter- and intra-individual variability and drug interactions have been observed and therapeutic drug monitoring is now recommended. In this study, a MPA commercial Enzyme Multiplied Immunoassay Technique (EMIT) was evaluated and compared with the HPLC-UV reference method which is easily practicable in a routine laboratory.

METHODS

Plasma samples (n = 117) were collected from adult renal graft patients treated by mycophenolate in combination with either cyclosporin A (CyA) (n = 32) or tacrolimus (n = 85).

RESULTS

Considering all samples, correlation was excellent (p < 0.0001). However, significant MPA overestimation was observed with EMIT in the early post-transplant period (30%, n = 32) or when combined with cyclosporin (45%).

CONCLUSIONS

In the early post-transplant period, or in cases where CyA is used in combination with MPA, the EMIT cannot be recommended. HPLC or LC/MS are here the method of choice.

Evaluation of ongoing oxycodone abuse among methadone-maintained patients

Prevalence of prescription opioid abuse has increased dramatically in recent years in the United States generally, and a similar pattern of increasing prescription opioid use has also been noted among patients seeking treatment for opioid dependence. This study presents results from an internal quality assurance project conducted by an outpatient methadone maintenance (MM) treatment clinic which sought to examine the extent of ongoing oxycodone abuse among patients that might be going undetected with current urinalysis-testing methods. One hundred five MM patients provided 437 urine samples over a 6-week period. Samples were analyzed using the clinic's usual enzyme multiplied immunoassay test (EMIT) opiate assay (300 ng/ml opiate cutpoint) and a supplemental oxycodone test strip (100 ng/ml oxycodone cutpoint). The EMIT assay identified only 6% (20/437) of samples as positive for oxycodone, whereas the oxycodone test strip indicated that 19% (83/437) tested positive for recent oxycodone use. Inspection of patient characteristics revealed that oxycodone users were more likely to report a prescription opioid as their primary drug at intake, be in MM treatment for a significantly shorter duration, and provide significantly more opioid- and cocaine-positive urine samples. Overall, these data illustrate the potential importance of monitoring for ongoing oxycodone use in MM clinics. Although future efforts should examine this question using more rigorous experimental methods, findings from this initial project have implications for clinical issues such as evaluating patient stability in treatment, making medication-dosing decisions, and determining patient eligibility for methadone take-home privileges.

Risk factors for poor immune response to influenza vaccination in elderly people

Influenza vaccination of elderly people is efficacious and cost effective for the prevention of influenza and its complications. Some studies have pointed out low immunogenicity in this group. Health status has been poorly investigated as a risk factor that may influence the immune response to influenza vaccine. We established an immunization response study of a highly-matched elderly population in a nursing home. One-hundred-twenty subjects of Ashkenazian origin had their vaccine-induced antibody response assessed. Good response was obtained in 30.8% (37/120), and 31.7% (38/120) did not react. A lack of good response was found to be associated with dementia (P=0.016) in a multivariate analysis. In addition to dementia, malnutrition was frequently observed among poor responders, suggesting that these factors should be considered in vaccination studies. Chemoprophylaxis in addition to vaccination for elderly presenting dementia should be considered, particularly for those people living nursing homes.

Development and GC-MS Validation of a Highly Sensitive Recombinant G6PDH-Based Homogeneous Immunoassay for the Detection of Buprenorphine and Norbuprenorphine in Urine

Buprenorphine is now increasingly prescribed as an alternative to methadone for the treatment of heroin addiction. Because of its potency (dosage usages from 0.2 mg to 8 mg), the drug concentrations in body fluids are normally very low. Here, we report the first recombinant glucose-6-phosphate dehydrogenase (G6PDH)-based homogeneous immunoassay (EMIT-type assay) for free buprenorphine and free norbuprenorphine in urine. The antibody used in this assay cross-reacts nearly identically with buprenorphine and norbuprenorphine and, at the same time, has less than 1% cross-reactivity with a wide range of commonly prescribed opiates, particularly those structurally related compounds such as morphine, codeine, and dihydrocodeine. More importantly, this assay has a low detection limit of 1 ng/mL for buprenorphine or norbuprenorphine. Further evaluation of this technique using gas chromatography-mass spectrometry (GC-MS) of authentic urine samples demonstrated that the accuracy of the assay is greater than 95%. Because this assay is designed to measure the free drugs in urine, it resulted in simplification for GC-MS or liquid chromatography-MS confirmation methods that did not require urine hydrolysis before solid-phase or liquid-liquid extraction.

Development of homogeneous enzyme immunoassay for the organophosphorus insecticide fenthion

A rapid, convenient homogeneous competitive enzyme immunoassay for estimating the amount of fenthion is described. The assay utilizes glucose-6-phosphate dehydrogenase-hapten conjugates that are inhibited in solution by antibodies obtained from bovine serum albumin-hapten conjugates. In order to investigate the effects of bridging group recognition on the sensitivity of dose response characteristics, the bridging groups of varying alkyl chain length were attached at the phosphate position of fenthion. Among the antibodies used, the one obtained from the use of hapten (fenthion analog) with the same bridging group structure that was used in preparing the enzyme-fenthion conjugates showed maximum inhibition (up to 51.8%) in the absence of fenthion. In the presence of fenthion, the activity of the enzyme-hapten conjugate is regained in an amount proportional to the fenthion concentration. Under the optimized condition, the ED50 value for fenthion was 0.809 microg/ml. The assay developed in this study is a rapid effective screening method for fenthion prior to precise analysis.

Results of random drug testing in an adolescent substance abuse program

OBJECTIVE

The objective of this study was to estimate from a random urine drug-testing program for adolescents the proportion of drug tests that are susceptible to interpretation errors.

METHODS

This was a secondary analysis of a clinical database and chart review from an adolescent outpatient substance abuse program at a large children's hospital. We analyzed from 110 adolescent patients (13-21 years of age) all 710 urine drug test results that were collected between December 2002 and July 2005 and 85 original laboratory reports for tests that were collected between December 2002 and May 2006 and were confirmed positive for opioids. We calculated the percentage of tests that were too dilute to interpret (potential false-negatives) and the percentage of confirmed positive tests for oxycodone that did not result in a positive initial screen (potential false-negatives). We also reviewed clinical information to determine whether confirmed positive tests resulted from legitimate use of prescription or over-the-counter medication (potential false-positives).

RESULTS

Of 710 drug tests, 40 negative tests were too dilute to interpret properly, and 45 of 217 positive tests resulted from prescription medication use for a total of 85 tests that were susceptible to error. Of the 85 confirmatory laboratory reports reviewed, 43 were positive for oxycodone, but only 16 of these had produced a positive opiate screen.

CONCLUSIONS

Unless proper procedures are used in collecting, analyzing, and interpreting laboratory testing for drugs, there is a substantial risk for error.

Oligomerisation of Sarcoplasmic Reticulum Ca2+-ATPase Monomers from Skeletal Muscle

The fast-twitch SERCA1 isoform of the sarcoplasmic reticulum Ca(2+)-ATPase was purified to homogeneity and conjugated to peroxidase. The SERCA1 probe showed high affinity binding to the immobilized monomeric enzyme, but not crosslinker-stabilized oligomers. This suggests a preferential complex formation via homo-dimerization, rather than interactions with established oligomeric structures.

Reduced Interference by Phenothiazines in Amphetamine Drug of Abuse Immunoassays

Context.—Emergency department physicians frequently request urine drug screens, but many are unaware of their limitations, including the potential for false-positive results. Promethazine, a phenothiazine derivative, is used for the treatment of allergies, agitation, nausea, and vomiting. Many patients taking promethazine are subject to urine drug screens and any potential interferences are important to recognize.

Design.—During an 11-month period, all patients presenting to the Massachusetts General Hospital emergency department who had a finding of promethazine in their serum drug screen, and who also had a urine drug screen performed, were selected for inclusion in the study. The urine drug screen results (n = 22 patients/samples) were then studied.

Objective.—To determine if promethazine use can cause false-positive urine amphetamine results in widely used drug of abuse immunoassays.

Results.—Thirty-six percent of patients taking promethazine had false-positive test results for urine amphetamines using the EMIT II Plus Monoclonal Amphetamine/Methamphetamine Immunoassay. Sixty-four percent of patients showed cross-reactivity greater than 20% higher than the blank calibrator rate. In a separate, related study, no promethazine-induced false-positive results were seen with the EMIT II Plus, Triage, and TesTcard 9 amphetamine assays, or the Triage methamphetamine assay. Reduced chlorpromazine interference was also seen with these other assays.

Conclusions.—False-positive urine amphetamine results can be obtained in patients taking promethazine. Promethazine metabolite(s), and not the parent compound, are the likely cause of these urine false-positive results obtained with EMIT II Plus Monoclonal Amphetamine/Methamphetamine Immunoassay. Immunoassays from different manufacturers can have very different “interference” profiles, which the pathologist and laboratory scientist must understand and relay to clinicians.

Comparison of Urine and Oral Fluid as Matrices for Screening of Thirty-Three Benzodiazepines and Benzodiazepine-like Substances using Immunoassay and LC-MS(-MS)

Benzodiazepines are the most frequently detected medicinal drugs in drivers. The use of benzodiazepines is associated with an increased road accident risk. In this study, the presence of benzodiazepines detected by liquid chromatography-(tandem) mass spectrometry [LC-MS(-MS)] in oral fluid and urine samples obtained from drivers stopped during a roadside survey was compared. In addition, the sensitivity and selectivity of enzyme multiplied immunoassay technique (EMIT II Plus) relative to LC-MS(-MS) was determined for both matrices. A total number of 1,011 urine samples were collected and screened for benzodiazepines using immunoassay (IA) (EMIT II Plus; cutoff 300 ng/mL). In the IA-positive (n = 25) and a group of randomly selected negative urine samples (n = 79), the presence or absence of benzodiazepines was confirmed by LC-MS-MS after deglucuronidation. The corresponding oral fluid samples (n = 101, 3 samples omitted), were analyzed by LC-MS(-MS) and IA (EMIT II Plus; cutoff 10 ng/mL). The presence of benzodiazepines was demonstrated by LC-MS-(MS) in all IA-positive urine samples, but in only four corresponding oral fluid samples. Concentrations in oral fluid were, one substance excepted, lower than in urine. The sensitivity and specificity of EMIT II Plus were better by using urine as matrix for screening of benzodiazepines than by using oral fluid. The results show that benzodiazepines are detectable in oral fluid. More research has to be done to determine the pharmacokinetic profile of the different benzodiazepines in oral fluid and to study the relationship between dose, concentration (in oral fluid and blood), and impairment.

Photometric and Electrochemical Enzyme-Multiplied Assay Techniques Using β-Galactosidase as Reporter Enzyme

Beta-galactosidase (beta-gal) is shown to be a versatile new reporter enzyme in both photometric and electrochemical enzyme-multiplied assay techniques (EMATs). The well-known beta-gal substrate analog, o-nitrophenyl beta-d-galactopyranoside, yields the visibly colored, o-nitrophenol product upon hydrolysis, whereas the substrate, p-aminophenyl beta-D-galactopyranoside, gives rise to an electrooxidizable product, p-aminophenol. These beta-gal substrates made possible the demonstration of both photometric and electrochemical signal transduction schemes for beta-gal-based EMAT detection of estradiol (as the estradiol-bovine serum albumin (E-BSA) conjugate). The EMAT system is composed of the reporter enzyme, beta-gal, with covalently attached estradiol, and estrogen antibody, which inhibits enzyme activity of the beta-gal-estradiol conjugate up to approximately 75%. Reporter enzyme inhibition is relieved significantly by addition of < or =2 ng/mL of estradiol (as E-BSA), which competes for binding with the antibody. Thus, the presence of analyte (E-BSA) is reported by the enzyme (beta-gal), which amplifies the ligand-protein dissociation event by turning over its substrate repeatedly. The electrochemical version of EMAT, based on amperometric detection of p-aminophenol, is responsive to added estradiol within minutes. These results show that beta-gal may serve as a useful alternative to glucose-6-phosphate dehydrogenase, which currently is used as reporter enzyme in commercially available EMAT systems.

Determination of Mycophenolic Acid Plasma Levels in Renal Transplant Recipients Co-administered Sirolimus: Comparison of an Enzyme Multiplied Immunoassay Technique (EMIT) and Liquid Chromatography–Tandem Mass Spectrometry

This study was designed to compare the enzyme multiplied immunoassay technique (EMIT) and a specific ;liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of mycophenolic acid (MPA) concentrations in plasma samples collected from renal transplant patients receiving mycophenolate mofetil in association with sirolimus and corticosteroids. Ten-point blood concentration-time profiles, between pre-dose (C0) and 9-hour post-dose, were obtained on day 7, day 14, months 1, 2, and 3 posttransplantation in 8 patients. MPA plasma concentrations were measured simultaneously with both EMIT and LC-MS/MS. Higher concentrations were obtained with EMIT. The mean (+/-SD) absolute difference was +0.84 +/- 1.93 mg/L, which corresponds to a significant overestimation of 18.7 +/- 2 6.8% with EMIT, with variations depending on the time elapsed since transplantation. An EMIT overestimation of 16.7 +/- 22.5% also was obtained for the MPA areas under the curve calculated using the trapezoidal rule.

Drug screening and confirmation by GC–MS: Comparison of EMIT II and Online KIMS against 10 drugs between US and England laboratories

Drug screening through urinalysis is a widely accepted tool for rapid detection of potential drug use at a relatively low cost. It is, therefore, a potentially useful method for detecting and monitoring drug use in a variety of contexts such as the criminal justice system, pre-employment screening and a variety of treatment centers. This article explores the efficacy of two commercially available drug-screening assays: Online KIMS assay (Roche) and EMIT II assays. First, we evaluate the sensitivity and specificity of two immunoassays. A total of 738 urine samples were collected among adult arrestee populations from Chicago, New Orleans and Seattle through the Arrestee Drug Abuse Monitoring (ADAM) program. Partial samples were split within one laboratory and analyzed by both enzymes multiplied immunoassay technique (EMIT) II and kinetic interaction of microparticle in solution (KIMS) assays for a 10-drug panel (amphetamine, barbiturates, benzodiazepines, marijuana, cocaine, methadone, methaqualone, opiate, phencyclidine and propoxyphene). Gas chromatography-mass spectrometry (GC-MS) was used as a confirmation method for all positives from either EMIT II or KIMS for all experiments. Second, the paper examines whether using different testing laboratories plays a role in the final results. The same experiments were repeated at two different testing locations: one in California and one in London and England. Third, the paper studies whether drug testing results vary between two laboratories when each of them had used their own routine screening method: the Forensic Science Service (FSS) at Birmingham, United Kingdom with KIMS assay and Medscreen Limited at London, United Kingdom with EMIT II. In summary, both EMIT II and KIMS assays generate fairly consistent results. The concordance rate against each of the 10 drugs tested is relatively high (97.4-100%). The discrepancies, in most cases, occurred at drug concentrations near the cut-off levels. There were more discrepant results between two laboratories compared to when specimens were analyzed at the same laboratory using two different assays.

Increased serum formate in the diagnosis of methanol poisoning

Early diagnosis is essential for successful treatment in methanol poisoning. Methanol detection by gas chromatography is not available in most hospitals. Methanol increases the osmolal gap in serum and its metabolite formate increases the anion gap. The sensitivity of these indirect diagnostic methods is not good at low concentrations of methanol or formate. We therefore studied the usefulness of formate measurement in diagnosing methanol poisoning. In 15 patients poisoned with methanol, serum formate was measured enzymatically on a Cobas Mira analyzer using formate dehydrogenase and nicotinamid adenine dinucleotid. Day-to-day coefficient of variation was 5%, and the upper reference limit was 2 mg/dL (0.4 mmol/L). Methanol was detected in all 15 patients of whom 14 had elevated serum formate concentrations. Anion gap was increased in 11 of 11, and osmolal gap in 11 patients of 15 examined. Metabolic acidosis was present in 12 of 15 patients, but pH was below 7.30 in only 9 of them. Four patients with no symptoms had formate concentrations in the range 2-38 mg/dL (0.5-8.3 mmol/L), indicating that increased serum formate was a sensitive indicator of methanol poisoning. Our results proved formate analyzes to be a simple, sensitive, and specific way of diagnosing methanol poisoning. Confounders are patients admitted early, or concomitant ethanol ingestion, and therefore no acidosis. This problem may, however, be omitted by repeated formate analysis in patients developing metabolic acidosis.

Monitoramento de gestantes com toxoplasmose em serviços públicos de saúde

É discutido o monitoramento de 290 gestantes com suspeita de toxoplasmose aguda atendidas em serviços públicos. Em 69% um único teste (Elisa-IgM) conduziu ao tratamento. De 112 tratadas, o sistema não disponibilizou medicamento para 24%. Em 12,1% houve aumento progressivo de IgM e IgG. Em 48,2%, o tratamento foi iniciado trinta dias após o diagnóstico laboratorial.

Death of an infant involving benzocaine

This report describes the death of a four-month-old Hispanic male which may be related to benzocaine toxicity. A toxicological evaluation revealed benzocaine at a concentration of 3.48 mg/L, and postmortem methemoglobin of 36% (normal 0.4-1.5). Methemoglobinemia is a complication of benzocaine toxicity. In light of the toxicology findings, the coroner investigated the source of the benzocaine and discovered that the child was treated with Zenith Goldline Allergen Ear Drops containing 0.25% w/v benzocaine and 5.4% w/v antipyrine. There was an admission by a caregiver that on the day prior to the child's death, he had been treated with three times the prescribed dose. Blood benzocaine concentrations in nine other unrelated cases were determined and concentrations ranged from <0.05-5.3 mg/L (mean 1.48 mg/L). Seven of the nine cases were positive for drugs of abuse, and one additional case was described as a known drug user. Methemoglobin in these benzocaine positive cases ranged from 6-69%; however, methemoglobin concentrations in postmortem cases are frequently elevated and should be interpreted with caution. The unknown significance of the benzocaine, and the circumstances of the case raise questions about the ultimate attribution of this death to SIDS.

Comparison of Cyclosporine Concentrations 2 Hours Post-Dose Determined Using 3 Different Methods and Trough Level in Pediatric Renal Transplantation

Immunosuppression has been one of the great challenges in pediatric recipients of kidney allografts. Cyclosporine (CsA) has evolved during the past 25 years of transplantation. It requires frequent blood level monitoring because of its narrow therapeutic window and interpatient and intrapatient variability. Neoral (Novartis) is no exception. Ideally, monitoring of blood levels should also include determination of the area under the time-concentration curve (AUC) to better target the therapeutic window, thus avoiding underdosing or overdosing, especially in pediatric patients. A single blood concentration measurement 2 hours after Neoral administration (C2) has been shown to be a more for accurate predictor of drug exposure than trough levels (C0). Therefore, its use may lead to reduction in the incidence and severity of cellular rejection and of CsA toxicity. Some studies have shown that the metabolites/CsA ratio is substantially lower using C2 than C0, however, the between-assay differences for C2 monitoring have not been considered. The purpose of this study was to evaluate CsA C0 and C2 levels, determined using monoclonal fluorescence polarization immunoassay (FPIA)/TDx and enzyme multiplied immunoassay (EMIT). CsA levels were determined using a radioimmunoassay (RIA) in 30 pediatric transplant recipients with stable renal function within 42.7 mean months follow-up. Mean age was 13.4 years; 15 children were girls; 23 patients were recipients of cadaveric kidneys. The mean CsA microemulsion dose was 5.7 mg/kg/d. The 3 methods showed a high correlation between C0 and C2 (r > or = 0.97). A linear regression slope was significantly higher for C0 than C2 (P < .001). The CsA concentrations both at C0 and C2 were significantly higher with FPIA than with RIA (P < .009) but no differences were found for EMITT (P = .2). The mean C0 level for FPIA was 22% and 26% higher than RIA and EMIT, respectively. The mean C2, for FPIA was 7% and 12% higher than RIA and EMIT, respectively. In conclusion, CsA levels determined using RIA or EMIT are better than using FPIA/Tx; also, C2 CsA levels are more accurate than C0 in pediatric transplantation patients.

Validation of a high-performance liquid chromatography method for the measurement of mycophenolic acid and its glucuronide metabolites in plasma

OBJECTIVES

The need for therapeutic drug monitoring of the immunosuppressant mycophenolic acid is becoming more evident. This paper describes a simple high-performance liquid chromatography procedure for the simultaneous quantitation of mycophenolic acid (MPA) and its glucuronide metabolites in plasma using protein precipitation followed by HPLC analysis with isocratic elution and UV detection.

DESIGN AND METHODS

The performance of this method is compared to the EMIT 2000 MPA immunoassay (Dade Behring Diagnostics Inc., Cupertino, California, USA).

RESULTS AND CONCLUSION

Intra-assay precision and accuracy of calibrators were determined for MPA at 0.5 and 20 mg/L, MPAGe at 5 and 200 mg/L, and MPAGa at 2.5 and 100 mg/L and showed coefficients of variation of less than 5.0% and biases of less than 14.0%. Inter-assay precision and accuracy of quality control samples were determined for MPA at 2 and 15 mg/L, MPAGe at 20 and 150 mg/L and showed CVs of less than 5.0% and biases of less than 14%. The lower limit of quantitation of the method was determined for MPA at 0.25 mg/L, MPAGe at 0.5 mg/L, and MPAGa at 0.25 mg/L and showed CVs of less than 19% and biases of less than 20%. This method, compared to the EMIT 2000 MPA immunoassay, showed a linear regression analysis relationship of EMIT = 0.973 HPLC + 0.55 (r(2) = 0.851), and was determined to be suitable for therapeutic drug monitoring and pharmacokinetic studies of MPA.

Diagnostic performance of Triage for benzodiazepines: urine analysis of the dose of therapeutic cases

We evaluated the diagnostic performance of Triage for benzodiazepines in 74 urine specimens from outpatients given therapeutic doses of benzodiazepines and compared the results of EMIT assays. Results obtained in all urine samples were confirmed using liquid chromatography-mass spectrometry (LC-MS). Overall agreement between results of Triage and EMIT assays was 73%. All of the Triage-positive samples were also positive by EMIT assays. Results of Triage and EMIT assays were different for 20 samples obtained from patients given thienodiazepines (etizolam, brotizolam, and clotiazepam) and nitrobenzodiazepines (nitrazepam, flunitrazepam, and clonazepam). LC-MS confirmed parent drugs in urine specimens, consistent with the prescriptions of drugs. The low agreement between Triage and EMIT results in this study might be due to low sensitivity of Triage for thienodiazepines. Thienodiazines are frequently prescribed benzodiazepines, and Triage panel is the most frequently used screening kit in Japan. It should be noted that negative results obtained by a Triage test might not mean the absence of thienodiazepines.

Quetiapine cross-reactivity with plasma tricyclic antidepressant immunoassays

BACKGROUND

Toxicology screens obtained on patients who have overdosed on drugs frequently include tricyclic antidepressants (TCAs) as part of the evaluation. Quetiapine is an antipsychotic agent with structural similarity to the TCAs.

OBJECTIVE

To determine whether quetiapine may cross-react with plasma TCA immunoassays in vitro using commonly available autoanalyzers.

METHODS

Quetiapine stock solution was added to 9 separate samples of pooled drug-free human plasma to produce concentrations ranging from 1 to 640 ng/mL that were verified by gas chromatography. No quetiapine metabolites were present. Each spiked plasma sample was tested in a blinded fashion using the Abbott Tricyclic Antidepressant TDx Assay on the TDxFLx autoanalyzer in 2 separate laboratories, the Syva Emit tox Serum Tricyclic Antidepressant Assay on the AU400 autoanalyzer and the S TAD Serum Tricyclic Antidepressant Screen on the ACA-Star 300 autoanalyzer. The TDx assay is quantitative, while Emit and S TAD are qualitative screening assays with a threshold of 300 ng/mL for TCA positivity. The outcome of interest was a positive TCA result.

RESULTS

The quantitative assay showed concentration-related TCA cross-reactivity beginning at quetiapine concentrations of 5 ng/mL. The 640-ng/mL spiked sample produced TCA results of 379 and 385 ng/mL in labs 1 and 2, respectively. The qualitative assays were screened as TCA positive at quetiapine concentrations of 160 and 320 ng/mL for the S TAD and Emit assays, respectively.

CONCLUSIONS

Quetiapine cross-reacts with quantitative and qualitative plasma TCA immunoassays in a concentration-dependent fashion. Therapeutic use or overdose of quetiapine may result in a false-positive TCA immunoassay result.

Higher exposure to mycophenolic acid with sirolimus than with cyclosporine cotreatment

INTRODUCTION

Therapeutic drug monitoring of mycophenolate mofetil is recommended because of the interindividual variability in the exposition to its active moiety, mycophenolic acid. However, most of the pharmacokinetic studies involved patients cotreated with cyclosporine (INN, ciclosporin).

METHODS

We analyzed the pharmacokinetics of mycophenolic acid in 13 renal graft recipients treated with sirolimus in an anticalcineurin-free regimen and compared it with that of 17 patients cotreated with cyclosporine. The area under the concentration versus time curve over a 12-hour period (AUC 0-12 ) of mycophenolic acid was estimated at 2 weeks, 1 month, 2 months, and 3 months after transplantation.

RESULTS

At the first 3 time points, patients cotreated with sirolimus had significantly higher mycophenolic acid AUC 0-12 values compared with patients cotreated with cyclosporine, as follows: 81 mg . h/L (SD, 39 mg . h/L) versus 43 mg . h/L (SD, 11 mg . h/L) (P < .001), 72 mg . h/L (SD, 17 mg . h/L) versus 48 mg . h/L (SD, 13 mg . h/L) (P < .001), and 70 mg . h/L (SD, 25 mg . h/L) versus 47 mg . h/L (SD, 17 mg . h/L) (P < .01) at week 2, month 1, and month 2, respectively. At all time points, patients cotreated with sirolimus had significantly higher dose-normalized mycophenolic acid AUC 0-12 values. At months 1 and 2, white blood cell counts were lower in the sirolimus group than in the cyclosporine group, as follows: 4.8 x 10(3)/mL (SD, 1.1 x 10(3)/mL) versus 6.5 x 10(3)/mL (SD, 2.2 x 10(3)/mL) (P < .01) at month 1 and 4.6 x 10(3)/mL (SD, 1.1 x 10(3)/mL) versus 5.9 x 10(3)/mL (SD, 2.0 x 10(3)/mL) (P < .05) at month 2.

CONCLUSION

These data show that exposure to mycophenolic acid is higher in patients cotreated with sirolimus than in those cotreated with cyclosporine.

Comparison of the Sensitivity and Specificity of Six Immunoassays for the Detection of Amphetamines in Urine

We analyzed 225 urine samples with FPIA (Abbott Amphetamine/Methamphetamine II on ADx and AxSYM), EMIT (Emit II Plus Monoclonal Amphetamine/Metamphetamine assay and EMIT II Plus Amphetamines assay, EMIT N), and KIMS (standard protocol and MDMA protocol, KIMS and KIMS X, respectively) immunoassays and compared their sensitivity and specificity. All assays were calibrated and used semi-quantitatively. All samples that screened positive by any amphetamine screening method and 15% of the negative samples were confirmed by liquid chromatography-tandem mass spectrometry (LC-MS-MS). A sample was considered positive for amphetamines if amphetamine, methamphetamine, methylenedioxymethamphetamine, methylenedio-xyethylamphetamine, or methylenedioxyamphetamine was present at 250 ng/mL. Ninety (40%) of the samples were positive by LC-MS-MS. The areas under the receiver operating characteristic curve varied between 0.972 (KIMS X) and 1.000 (ADx). The optimal cut-off concentrations varied between 271 ng/mL (EMIT N) and 723 ng/mL (AxSYM). The sensitivity was 100% for ADx and between 93 and 95% for the other assays. The specificity varied between 88% (KIMS) and 100% (EMIT N). Use of a 500 ng/mL screening cut-off would have resulted in identical or very similar results for ADx and KIMS X and large increases in the false positives for AxSYM and EMIT and the false negatives for EMIT N and KIMS.

Papain: A Novel Urine Adulterant*

The estimated number of employees in the United Stated screened annually for illicit drugs is approximately 20 million, with marijuana being the most frequently abused drug. Urine adulterants provide an opportunity for illicit drug users to obtain a false-negative result on commonly used primary drug screening methods such as the enzyme multiplied immunoassay technique and the fluorescence polarized immunoassay technique (FPIA). Typical chemical adulterants such as nitrites are easily detected or render the urine specimen invalid as defined in the proposed SAMHSA guidelines for specimen validity testing based on creatinine, specific gravity, and pH. Papain is a cysteine protease with intrinsic ester hydrolysis capability. The primary metabolite of the psychoactive chemical in marijuana, 11-norcarboxy-Delta9-tetrahydrocannibinol (THC-COOH), was assayed by FPIA in concentrations ranging from 25 to 500 ng/mL, at pH values ranging from 4.5 to 8, over the course of 3 days with papain concentrations ranging from 0 to 10 mg/mL. FPIA analysis of other frequently abused drugs: amphetamines, barbiturates, benzodiazepines, cocaine, opiates, and phencyclidine, along with gas chromatography-mass spectrometry (GC-MS) of THC-COOH and high-pressure liquid chromatography-ultraviolet detection (HPLC-UV) of nordiazepam was performed in order to determine if the mechanism of urine adulteration by papain was analyte specific. Control and adulterated urine specimens (n = 30) were assayed for creatinine, specific gravity, and pH to determine if papain rendered the specimens invalid based on the proposed SAMHSA guidelines. There was a direct pH, temperature, and time-dependent correlate between the increase in papain concentration and the decrease in THC-COOH concentration from the untreated control groups (p < 0.01). The average 72-h THC-COOH concentration decrease at pH 6.2 with a papain concentration of 10 mg/mL was 50%. Papain did not significantly decrease the concentration of the other drugs analyzed with the exception of nordiazepam. GC-MS of THC-COOH and HPLC-UV of nordiazepam revealed a 66% and 24% decrease in concentration of the respective analyte with 10 mg/mL papain after 24 h at room temperature (approximately 23 degrees C). No adulterated specimens were rendered invalid based on the SAMHSA guidelines. Immediate FPIA analysis is suggested to minimize the interfering effects of papain with regards to primary drug screening.

[Drug analytics in oral fluid using immunoassay]

Drug analytics in oral fluid can be of relevance for various clinical and forensic questions, for example when testing for driving ability. To date few studies have been conducted concerning validity of different methods. The reliability of drug analytics in oral fluid was studied using cedia test and emit test (for cannabinoids). CUT-offs for different substances were defined after evaluation of ROC curves following various prestudies. 97 saliva and 103 urins probes from 31 opioid dependent patients were tested. Only for methadone, the results in oral fluid were comparable to those in urine. For most other drugs including opioids and barbiturates, results were less favourable. For cannabinoids and benzodiazepines, results were unsatisfactory. To date drug testing in oral fluid does not seem to be as accurate as urine analytics. Urine testing using immunoassays or gas chromatography is still the most reliable non-invasive test method. Drug testing in oral fluid may be of relevance as an additional method in substitution treatment and as an experimental tool in epidemiological road surveys.

Effects of some hematological parameters on whole blood tacrolimus concentration measured by two immunoassay-based analytical methods

OBJECTIVES

Tacrolimus (FK506) is a potent immunosuppressive drug used for prevention of rejection following transplantation. Several methods including immunoassays have been used for monitoring tacrolimus levels. The purpose of the present study was to compare the effects of various hematological parameters on whole blood tacrolimus concentrations which were measured with two different analytical methods, namely the microparticle enzyme immunoassay (MEIA II) and enzyme multiplied immunoassay technique (EMIT).

DESIGN AND METHODS

The effects of hematological variables, namely hematocrit (Htc), hemoglobin (Hb), red blood cell (RBC), mean cell volume (MCV), mean cell hemoglobin (MCH), mean cell hemoglobin concentration (MCHC), red cell distribution width (RDW) and platelet (PLT) counts on tacrolimus concentrations (n = 2430 measurements) measured with EMIT (n = 1171) and MEIA II (n = 1259) methods in whole blood samples from kidney or liver or combined kidney-pancreas transplant patients (n = 162) during a 2-year post-transplantation period were compared.

RESULTS

The whole blood tacrolimus concentrations measured with MEIA II method were affected much more significantly by hematological parameters than those measured with EMIT method. In MEIA II method, RDW (r = 0.479, P < 0.01) showed a stronger correlation with tacrolimus concentration than Htc (r = -0.239, P < 0.01) in all patients. A negative significant correlation (r = -0.468, P < 0.01) was also observed between the Htc and tacrolimus concentration in patients with Htc values < or =25% in MEIA II method.

CONCLUSIONS

The results of the present study suggest that EMIT method might be preferred to MEIA II in determination of whole blood tacrolimus concentrations in anemic transplant patients. For better therapeutic drug monitoring, physicians should be aware of these assay differences. Evaluation of hematologic factors that affect the whole blood concentrations of tacrolimus may be helpful in deciding the dosage of this drug.

Determination of creatinine in urine by tandem mass spectrometry

BACKGROUND

Electrospray tandem mass spectrometry (TMS) is a very powerful tool that enables one to perform high sample throughput analysis. This paper describes a method to determine creatinine in urine by tandem mass spectrometry with direct sample infusion into an ion source.

METHODS

Samples (50 microl) were diluted with internal standard (IS) (450 microl of 0.667 mmol/l deuterated creatinine). Diluted samples were introduced into mass spectrometer with no prior pretreatment and after purification on ion-exchange 96-column cartridge. Tandem mass spectrometry analyses were performed in selected reaction monitoring mode. Creatinine and creatinine-d(3) were monitored using precursor and product ion settings (m/z 114 to 86 and m/z 117 to 89, respectively). The time of an analysis was 3.015 min. Both TMS methods were compared mutually and with the results obtained by enzymatic and Jaffe method.

RESULTS

Linearity was obtained in the range 0.06-60 mmol/l. Detection limit was 0.2 mumol/l and recoveries were in the range 95.1-98.3% for both the assays with and without ion-exchange column. Results of both assays are in good agreement with those obtained by enzymatic and Jaffe method based on log-transformed Bland-Altman plots. Electrospray tandem mass spectrometry method utilizing both approaches with and without ion-exchange column is acceptable according to CLIA criteria.

CONCLUSION

Tandem mass spectrometry allows rapid, sensitive and selective determination of creatinine in untreated urine.

Evaluation of the new heterogeneous ACMIA immunoassay for the determination of whole-blood cyclosporine concentrations in bone marrow, kidney, heart, and liver transplant recipients

Cyclosporine (CyA) has a narrow therapeutic index. Determination of CyA concentrations correlate with rejection or adverse effects like nephropathy. Cyclosporine is assayed based on either chromatographic or many different immunoenzymologic techniques. The investigators evaluated a new heterogeneous immunoassay of CyA on RxL Dimension. The pretreatment step is automatically performed in the apparatus. Linearity, intra- and interday precision, limit of quantification, dilutions, and stability of the equipment were compared with the EMIT method for patient determinations. The heterogeneous immunoassay showed a good linearity between 0 and 500 ng/mL, and intra- and inter-day precision with a coefficient of variation below 9.2%. The investigators observed reproducible and accurate dilutions of high concentrations (500 to 2000 ng/mL). The correlation with the EMIT technique was valid: ACMIA = 0.964 EMIT + 0.156 (r = .96) for different types of transplant (n = 116). Finally, this new system improves the determination of CyA concentrations.

Alpha-particle emitting atomic generator (Actinium-225)-labeled trastuzumab (herceptin) targeting of breast cancer spheroids: efficacy versus HER2/neu expression

PURPOSE

The humanized monoclonal antibody, trastuzumab (Herceptin), directed against HER2/neu, has been effective in the treatment of breast cancer malignancies. However, clinical activity has depended on HER2/neu expression. Radiolabeled trastuzumab has been considered previously as a potential agent for radioimmunotherapy. The objective of this study was to investigate the efficacy of trastuzumab labeled with the alpha-particle emitting atomic generator, actinium-225 ((225)Ac), against breast cancer spheroids with different HER2/neu expression levels. (225)Ac has a 10-day half-life and a decay scheme yielding four alpha-particles.

EXPERIMENTAL DESIGN

The breast carcinoma cell lines MCF7, MDA-MB-361 (MDA), and BT-474 (BT) with relative HER2/neu expression (by flow cytometry) of 1:4:18 were used. Spheroids of these cell lines were incubated with different concentrations of (225)Ac-trastuzumab, and spheroid growth was measured by light microscopy over a 50-day period.

RESULTS

The activity concentration required to yield a 50% reduction in spheroid volume at day 35 was 18.1, 1.9, and 0.6 kBq/ml (490, 52, 14 nCi/ml) for MCF7, MDA, and BT spheroids, respectively. MCF7 spheroids continued growing but with a 20-30 day growth delay at 18.5 kBq/ml. MDA spheroid growth was delayed by 30-40 days at 3.7 kBq/ml; at 18.5 kBq/ml, 12 of 12 spheroids disaggregated after 70, days and cells remaining from each spheroid failed to form colonies within 2 weeks of being transferred to adherent dishes. Eight of 10 BT spheroids failed to regrow at 1.85 kBq/ml. All of the BT spheroids at activity concentrations 3.7 kBq/ml failed to regrow and to form colonies. The radiosensitivity of these three lines as spheroids was evaluated as the activity concentration required to reduce the treated to untreated spheroid volume ratio to 0.37, denoted DVR(37). An external beam radiosensitivity of 2 Gy was found for spheroids of all three of the cell lines. After alpha-particle irradiation a DVR(37) of 1.5, 3.0, and 2.0 kBq/ml was determined for MCF7, MDA, and BT, respectively.

CONCLUSION

These studies suggest that (225)Ac-labeled trastuzumab may be a potent therapeutic agent against metastatic breast cancer cells exhibiting intermediate to high HER2/neu expression.

The V-Twin system (Dade Behring Laboratories): A useful tool for immunosuppressive drug monitoring

The predose trough cyclosporine (CsA) level (C0) was widely used to assess the possibility of drug nephrotoxicity. Owing to its potential limitation as an indicator of total drug exposure, 2-hour postdose (C2) monitoring has been considered to be a more accurate marker. The V-Twin analyzer (Vital SC, Netherlands) conceived for EMIT technologies (Dade Behring Laboratories) is proposed herein to determine CsA levels using a specific calibrator without any dilution, as well as tacrolimus (FK) and mycophenolate mofetil (MMF) levels. Both CsA (C0: n = 133 and C2: n = 55) and FK (n = 121) EMIT assays were compared to the RIA CsA assay (DiaSorin Laboratory) and to the MEIA tacrolimus assay (Abbott Laboratory), respectively. In addition, the feasibility of MMF EMIT assay was evaluated. Overall, 309 transplant patients were included in this study. For all parameters tested, total imprecision studies were lower than 10%, and the coefficient of linearity was r(2) > .99. For the CsA kit, the range of linearity was between 25 and 500 ng/mL for the C0 and 400 and 2000 ng/mL for the C2 assay. The values obtained were highly correlated with the RIA for the C0 levels (EMIT = 0.9 RIA+3.66; r = .97) and for the C2 levels (EMIT = 0.89 RIA-14.2; r = .956). Similar results were obtained with the EK EMIT kit, with a linearity range between 3 and 30 ng/mL, and a high concordance with the MEIA test (EMIT = 0.98 RIA+1.09; r = .96). Preliminary MMF results in 59 sera, containing from 0.1 to 30 microg/mL, showed that this examination could be included as a routine. The V-twin system is a useful tool for routine monitoring with a single method for C0 and C2 cyclosporine, tacrolimus, and mycophenolate levels.

False positive acetaminophen levels associated with hyperbilirubinemia

Serum acetaminophen determination is frequently necessary in patients with hepatic failure. We observed two patients (#1, #2) with elevated serum total bilirubin levels (26.5 mg/dL and 40.1 mg/dL) who had multiple false positive acetaminophen levels using the kinetic method of the GDS Diagnostics enzymatic acetaminophen assay (GDS Diagnostics, Elkhart, IN). We investigated the magnitude, threshold, and linearity of this effect using the GDS Diagnostics assay and an EMIT acetaminophen assay on two other hyperbilirubinemic patients (#3, #4) and a commercial solubilized bilirubin standard. Samples were diluted using fresh frozen plasma, and acetaminophen levels were analyzed twice using the kinetic method of the GDS Diagnostic acetaminophen assay and twice with the EMIT assay. The absence of acetaminophen in all samples was verified by gas chromatography/mass spectroscopy (GC/MS). The kinetic GDS assay resulted in a positive acetaminophen assay (cutoff for a positive result= 10 mg/L) with patient #3, patient #4, and in the bilirubin standard when the total bilirubin levels were 28.2 mg/dL, 22.5 mg/dL, and 18.3 mg/dL, respectively. One sample was interpolated to give a positive acetaminophen reading when diluted to a total bilirubin concentration of 15 mg/L. None of the samples tested with GC/MS or the EMIT assay resulted in any detectable acetaminophen. In conclusion, caution must be taken utilizing the GDS Diagnostic assay for the quantification of acetaminophen with concomitant hyperbilirubinemia. Alternatives such as EMIT or GC/MS should be employed to assess acetaminophen levels in such patients.

Drug abuse among workers in Brazilian regions

OBJECTIVE: Many business organizations in Brazil have adopted drug testing programs in the workplace since 1992. Rehabilitation, rather than layoff and disciplinary measures, has been offered as part of the Brazilian employee assistance programs. The purpose study is to profile drug abuse among company workers of different Brazilian geographical regions. METHODS: Urine samples of 12,700 workers from five geographical regions were tested for the most common illicit drugs of abuse in the country: marijuana, cocaine, and amphetamine. Enzyme multiplied immunoassay technique (EMIT) and gas chromatography coupled with mass spectrometry (GC/MS) were the techniques utilized for urine testing. The distribution of collected urine samples according to geographical regions was: 72.0% southeast, 13.8% northeast, 7.9% south, 5.7% central west and 0.6% north. RESULTS: Of all samples analyzed, 1.8% was found to be positive for drugs: 0.5% from the south region, 1.1% from northeast, 1.2% from central west, 1.3% from north, and 2.2% from southeast. Of these, 59.9% was marijuana, 17.7% cocaine, 14.6% amphetamine, and 7.7% associated drugs. CONCLUSIONS: The distribution of drugs found in the samples shows a regional variation. Marijuana, however, was found in all regions. Cocaine was seen only in central west and southeast regions. Amphetamine was found in northeast, central west, and southeast regions.

A new trend in drugs-of-abuse; the 2C-series of phenethylamine designer drugs

OBJECTIVE

To collect data related to phenethylamine drugs-of-abuse of the 2C-series, to review possible health risks of their use and to discuss legal counter actions of authorities in the European Union (EU).

SETTINGS

Dutch smartshops.

METHODS

In the period of 1994-2002, all products that were claimed to contain synthetic drugs and sold in the smartshops, were purchased. The contents were analysed using analytical chemical technologies such as gas chromatography/mass spectrometry and nuclear magnetic resonance. Additionally, using computerised searches in relevant databases and checking cross-references, literature and documents were screened for scientific based information.

RESULTS

All purchased products proved to be tablets, of which most of them contained one of the phenethylamine designer drugs 2C-B, 2C-T-2 or 2C-T-7. The different drugs were introduced on the Dutch smartshop market within time intervals of approximately three years. The information that was supplied on leaflets and accompanied the products sometimes appeared to be extensive, but was partly misleading and incorrect. Besides that, scientific based information in respect to health risks of drugs of the 2C-series and the detection of their abuse was scarce. Until now no intoxications have been reported in the EU and no centralised legal actions have been taken to prevent possible intoxications.

CONCLUSIONS

The lack of observed intoxications may justify the absence of legal actions in the EU against phenethylamine designer drugs-of-abuse of the 2C-series. However, this may also be explained by either the inability of toxicologists to detect the abuse of substances of the 2C-series or the unawareness of the phenomenon of these drugs. Therefore, EU authorities should promote the availability of relevant standards, validated assays and scientific knowledge regarding these drugs.

Compliance with methadone-based substitutive treatment: a proposed model based on immunoassay urinary sample screening

Methadone (MTD) maintenance treatment is a recognized method to reduce illicit opiate abuse. Because of the difficulties of collecting 24-hour urines routinely, the monitoring of MTD compliance is currently done with random urinary screening. However, monitoring of MTD compliance by random urinary screening lacks accuracy because of its highly variable pharmacokinetics, leading to false positive or negative results. This study's objective was to identify factors influencing the reliability of urinary screening of methadone for MTD compliance monitoring in a field setting involving usual care for opiate-dependent patients. In a cross-sectional population-based study, 1981 urine samples obtained from 68 patients in parallel with drug dose, gender, and weight were analyzed by MTD enzyme immunoassay (EMIT). Urinary pH was measured, and positive threshold was determined experimentally by box-plot analysis. Multivariate determinants of MTD excretion were established with stepwise multiple regression analysis. On this basis, adjusted values for MTD excretion were proposed and verified with an (S)-2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) assay from independent urine samples that were negative or doubtful by the MTD assay. MTD excretion was higher in men, decreased with increased urinary pH, and increased with daily dosage of MTD; these factors explain 32% of the total variance of urinary MTD. Adjustment on these 3 variables (urinary pH, sex, daily dosage) improved the prediction of compliance to MTD treatment. Threshold was stable across pH values and in agreement with EDDP results. The influence of simple variables such as gender, urinary pH, and daily dosage on urinary MTD excretion could be put in evidence and accounted for. Adjusted values of urinary MTD are more reliable than the raw values for monitoring compliance to MTD treatment.

Monitoring trough plasma concentrations of mycophenolate mofetil in patients with uveitis

BACKGROUND

Mycophenolate mofetil (MMF) has been used successfully in patients with various forms of uveitis not responsive to other immunosuppressants. Nevertheless, for these patients neither recommendations for optimal dosage of MMF nor data concerning drug exposure of MMF are available.

OBJECTIVE

To describe the results of the therapeutic drug monitoring (TDM) of MMF trough concentrations in a cohort of patients with uveitis, with the aim of optimizing the dosage of this drug, by maintaining a target concentration to achieve adequate immunosuppression with a minimal risk of therapeutic failure or toxicity.

PATIENTS AND METHODS

This study describes the results of monitoring trough plasma concentrations of MMF in 12 patients with uveitis during a mean period of 21.4 months. Patients included one with Stevens-Johnson syndrome, one with Graves-Basedow's disease, one with Behcet's disease, one with idiopathic thrombocytopenic purpura and the rest with idiopathic uveitis. All patients were treated with steroids and additional therapy prior to treatment with MMF.

RESULTS

Pharmacokinetic monitoring of mycophenolic acid (MPA) was performed with 108 trough plasma samples using an EMIT assay. Mean daily MMF dose was 24.5 +/- 6.3 mg/kg and mean trough MPA concentration was 2.9 +/- 1.9 microg/mL. Therapy was effective in 10 patients (83%). There were few side-effects: diarrhoea, excitement, agitation and cough that disappeared with daily dose reduction of MMF.

CONCLUSIONS

MMF was effective in the majority of patients with uveitis with an acceptable profile of side-effects. TDM of MMF in patients with uveitis is clinically practicable and may help to optimize individual immunosuppressive therapy. We estimated that MMF dosages in the range of 0.5-1.5 g/day might be sufficient for treating uveitis and we recommend an initial target range of 2-4 microg/mL, which included 50% of our results. Randomized controlled trials are essential to confirm the efficacy of MMF in uveitis.

Analytical Performance of the CEDIA(R) Cyclosporine PLUS Whole Blood Immunoassay

Cyclosporine A (CsA) is a potent immunosuppressive agent used in solid organ and bone marrow transplantation. Because of the narrow therapeutic range and variable pharmacokinetics, blood levels of CsA are routinely monitored. The performance of the CEDIA CsA PLUS whole blood immunoassay was evaluated on the Olympus AU400 trade mark, and results were compared to those obtained by high-performance liquid chromatography (HPLC), enzyme-multiplied immunoassay technique (EMIT), and fluorescence polarization immunoassay (FPIA). A total of 592 whole blood samples from patients receiving CsA were tested by each of the assays. CEDIA was linear from 25 to 2000 micro g/L. Total imprecision ranged from 2.7% to 8.7% at CsA values between 48 and 1502 micro g/L. Recovery of added CsA was within 10% of assigned values and was unaffected by bilirubin and lipemia. Metabolite cross-reactivity at 500 micro g/L was 8.1% for AM1, 21.7% for AM4n, and 32.5% for AM9. Regression analysis revealed the following: HPLC = 0.93. CEDIA - 21.2 (r = 0.975), EMIT = 1.08. CEDIA - 25.2 (r = 0.982), and FPIA = 1.14. CEDIA + 13.4 (r = 0.984). CEDIA has acceptable analytical performance for routine CsA monitoring. Advantages are the absence of an extraction step and an extended measuring range. The disadvantage is the high metabolite cross-reactivity; however, results were similar to EMIT

Comparison of automated ACMIA and EMIT immunoassays for whole blood cyclosporin monitoring

OBJECTIVE

Evaluation of a new fully automated antibody conjugated magnetic immunoassay (ACMIA) for whole blood cyclosporin (CsA) monitoring.

METHOD

Evaluation of the analytical performance of the ACMIA method and comparison to the Enzyme Multiplied Immunoassay (EMIT) method.

RESULTS

The analytical performance of the ACMIA and the EMIT methods was comparable. Without the need of a pretreatment step of the sample, the ACMIA method is faster than the EMIT method.

CONCLUSION

The ACMIA method for CsA monitoring is a good alternative to the EMIT method.

Evaluation of the new EMIT tacrolimus assay in kidney and liver transplant recipients

Tacrolimus (FK506) is a potent macrolide immunosuppressant used for prevention of organ transplant rejection following transplantation. Monitoring of blood tacrolimus concentrations is essential to assess organ rejection and toxicity, because of the agent's narrow therapeutic range, wide inter- and intraindividual pharmacokinetic variability as well as drug interactions mediated by alteration in cytochrome P450. Several methods have been developed to monitor tacrolimus; immunoassays, bioassays, and HPLC/MS. The purpose of this study was to compare two analytical methods: the well-established MEIA II tacrolimus immunoassay using the IMx analyzer and the new EMIT 2000 tacrolimus immunoassay on the Cobas Integra 400 system. Tacrolimus results obtained using the two methods have been compared on 180 whole blood samples from kidney and liver transplant patients. The analytical sensitivities of both methods were defined as 1.2 ng/mL for EMIT and 1.5 ng/mL for MEIA II. The within-run CVs (n = 15) obtained with four-level controls were 9.08%, 9.41%, 5.23% and 4.4% for EMIT 2000. The comparison showed the following relationship between two methods: MEIA = 1.08.EMIT + 0.20 (r =.893). In conclusion, the EMIT 2000 tacrolimus immunoassay is a reliable alternative for the MEIA II method to monitor tacrolimus in organ transplant recipients. It provides a valid quantitative measurement of tacrolimus with comparable % CVs in quality-control as well as patient blood samples. Additionally, the EMIT 2000 method provides a rapid analysis of a large number of samples in one run with a low turnaround time and possibilities to reanalyze critical samples.

Enzymatic amplification staining for single cell analysis: applied to in situ hybridization

Single cell analysis by flow cytometry is a powerful modality for analyzing the expression of a set of molecules. Nevertheless, the most significant deficiency of this technology has been the poor sensitivity of flow cytometry compared to other techniques such as immunoblotting. In order to address this deficiency, we have developed an enzymatic amplification system for flow cytometry that enhances the specific signal by 10-100-fold. Using enzymatic amplification staining (EAS), we and others have been able to assess the expression of molecules that could not be detected otherwise. In this review, we show the capability of this new technology to detect specific RNA expression.

[Therapeutic drug monitoring of mycophenolate mofetil, sirolimus and cyclosporine at C2]

The evolutions in treatments and clinical practices in organ transplantations led to modifications in the therapeutic drug monitoring (TDM) of immunosuppressive drugs. A focus is made regarding the C2 sampling of cyclosporin, as well as the TDM of mycophenolate mofetil and sirolimus. A review of literature about the evolution of drug monitoring, technical methods and sampling strategies is described. Arguments in favour of TDM are thus a decrease in the frequency of both graft rejection and adverse drug reactions, however, new strategies or new targets are needed in new associations or indications.

Performance of immunoassays in screening for opiates, cannabinoids and amphetamines in post-mortem blood

Several immunoassay methods for screening of abused drugs in whole blood were evaluated in post-mortem forensic toxicology. Blood samples known to be positive or negative for opiates, cannabinoids or amphetamines by gas chromatography-mass spectrometry (GC-MS) were analysed by EMIT II Plus and EMIT d.a.u., Syva RapidTest and Triage 8 after acetone precipitation. In these experiments, the EMIT immunoassay method was modified by using the Dade Behring VIVA analyser to detect substances more sensitively. Low concentrations of abused drugs were detected in blood samples. The sensitivities of the modified EMIT method for opiates, cannabinoids and amphetamines were 100, 86 and 98%, respectively, whereas the values were below 86% with the other methods. The specificities of all immunoassay methods for opiates and cannabinoids were 83% or above but 51-85% for amphetamines. Sample rejection occurred in a few cases with the EMIT amphetamine assays. The modified EMIT immunoassay system presented here seems to be useful for screening of drugs of abuse in post-mortem blood samples, especially when urine is not available.

Simultaneous and rapid analysis of cyclosporin A and creatinine in finger prick blood samples using liquid chromatography tandem mass spectrometry and its application in C2 monitoring

A simple and rapid liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the simultaneous analysis of cyclosporin A (CsA) and creatinine using capillary blood has been developed. Venous and capillary blood samples were taken predose and at C2 from 65 heart and lung transplant recipients (65 x 4 samples). For comparisons, serum creatinine and blood CsA concentrations were measured by the Jaffe and EMIT methods, respectively, using an Olympus AU600 analyzer. For the LC-MS/MS assay, samples were prepared in a 96 x 700-microL well block by adding 10 microL of blood (or serum) to 40 microL of 0.1 mol/L zinc sulphate solution containing deuterated creatinine internal standard. Proteins were precipitated by adding 100 microL acetonitrile containing ascomycin internal standard. After vigorous mixing and centrifugation, 5 microL of the supernatant was injected into the LC-MS/MS system. A Waters 2795 high-performance liquid chromatography (HPLC) system was used to elute a C18 cartridge (3 mm x 4 mm) at 0.6 mL/min with a step gradient of 50-100% methanol containing 2 mmol/L ammonium acetate and 0.1% (v/v) formic acid. The column was maintained at 55 degrees C, and the retention times were creatinine, 0.4 minutes; ascomycin, 0.98 minutes; and CsA, 1.2 minutes. Cycle time was 2.5 minutes, injection to injection. The analytes were monitored using a Quattro microtandem mass spectrometer operated in multiple reaction monitoring mode using the following transitions: creatinine, m/z 114>44; d3-creatinine (IS), m/z 117>47; ascomycin (IS), m/z 809>756; and CsA, m/z 1,220>1,203. Assay characteristics were CsA intraassay CV, 3.6-3.0% (33-1,500 microg/L); CsA interassay CV, 6.7-2.5% (10-5,000 microg/L); LC-MS/MS capillary [CsA] = 0.99 x LC-MS/MS venous [CsA] - 4.2, R = 0.98; and LC-MS/MS venous [CsA] = 0.93 x EMIT venous [CsA] + 2.9, R = 0.98. Creatinine intraassay CV, 6.6-2.5% (20-720 micromol/L); interassay CV, 5.7-3.3% (80-590 micromol/L); LC-MS/MS capillary [creatinine] = 0.99 Jaffe plasma [creatinine] -42.6, R = 0.87. Total time for the preparation and analysis of 30 samples was approximately 2 hours. This assay will provide a flexible, robust, and cost-effective solution for the monitoring of CsA and creatinine in transplant recipients with potential applications in pediatric medicine and pharmacokinetic studies, in which frequent sampling is required.

Monitoring urinary excretion of cannabinoids by fluorescence-polarization immunoassay: a cannabinoid-to-creatinine ratio study

Drug testing in substance abuse treatment programs is focused on urine analysis of parent drugs and major metabolites. Huestis reported that serial monitoring of the major urinary cannabinoid metabolite (delta9-THC-COOH)-to-creatinine ratios in paired urine specimens (collected at least 24 hours apart) could differentiate new marijuana or hashish use from residual cannabinoid metabolite excretion in urine after previous drug use. Subjects with a history of chronic marijuana use were screened for cannabinoids in urine over several months by an enzyme immunoassay (EMIT) with a cut-off value of 50 ng/mL. Presumptive positive specimens were confirmed by gas chromatography-mass spectrometry (GC-MS) for delta9-THC-COOH with a cut-off value of 15 ng/mL. The objective of this study was to determine whether a semiquantitative cannabinoids immunoassay (corrected for creatinine concentration) could differentiate new marijuana use from residual cannabinoid excretion in chronic users of marijuana or hashish compared with GC-MS. The criterion for new marijuana use was a cannabinoid-to-creatinine ratio > or =0.5 (dividing the immunoassay quantitative result to creatinine ratio of specimen 2 by the specimen 1 ratio, specimen 3 by the specimen 2 ratio, etc.). Urine specimens were analyzed by fluorescence-polarization immunoassay (FPIA) on an Abbott TDxFLx analyzer after analysis by GC-MS. In 90 urine specimens (group A) with delta9-THC-COOH values determined by GC-MS, the mean delta9-THC-COOH concentration was 44.4 ng/mL (range, 16-100), and the mean FPIA total cannabinoids value was 91.7 ng/mL (range, 21-204 ng/mL) with a correlation coefficient of 0.993 (group A). In 111 specimens (group B), the mean delta9-THC-COOH concentration was 361 ng/mL (range, 101-960 ng/mL). The mean FPIA value was 657 ng/mL (range, 211-1,270 ng/mL), and the correlation coefficient of the B series was 0.975. Percent cross-reactivity for delta9-THC-COOH standards prepared in drug-free urine by FPIA was 82% at 25 ng/mL, 45% at 50 ng/mL, and 50% at 100 ng/mL. Overall, there was 89% agreement (132 of 148 specimens) between FPIA and GC-MS. In 16 of 148 specimens, however, the FPIA and GC-MS paired urine data did not agree. The sensitivity of the FPIA assay was 95.3%, and the specificity was 44.4%. The authors conclude that FPIA cannabinoid analysis should be further evaluated as an alternative to GC-MS quantitation to help distinguish new marijuana use from residual marijuana metabolite excretion in clinical drug treatment programs.

Drug-herb interactions: unexpected suppression of free Danshen concentrations by salicylate

The general population of the U.S. uses over-the-counter herbal medicines. Danshen is a Chinese herbal product used for the treatment of cardiovascular disease. In a previous study we showed that Danshen has significant digoxin-like immunoreactivity, and we used this parameter to monitor total and free Danshen activities in sera (10). In this report we demonstrated strong protein binding of Danshen (50-70%), and we also identified albumin as the major serum protein that binds Danshen. Because salicylate, which is also strongly bound to albumin, is a widely used over-the-counter medicine in the U.S., we studied Danshen-salicylate interaction in vitro. We observed no significant change in free Danshen concentrations as measured by free-digoxin-like activity when salicylate concentrations were subtherapeutic (< or = 100 microg/mL). With therapeutic concentrations of salicylate (> or = 150 microg/mL), the free Danshen concentrations significantly decreased from the control. On the other hand, Danshen can displace salicylate from protein binding, thereby increasing the free salicylate concentration. We conclude that salicylate in therapeutic concentration can significantly decrease free Danshen concentrations, and Danshen can displace salicylate.