Serum symmetric dimethylarginine in older dogs: Reference interval and comparison of a gold standard method with the ELISA.

BACKGROUND: Serum symmetric dimethylarginine (SDMA) is used to screen for renal dysfunction in dogs. The gold standard technique for measuring SDMA, liquid chromatography-tandem mass spectrometry (LC-MS/MS) is not widely available. Age-specific reference intervals for SDMA in older dogs are lacking. OBJECTIVES: Prospective study in older dogs to validate a commercially available LC-MS/MS method for SDMA, compare SDMA concentrations with concentrations measured using ELISA and obtain a reference interval (RI) for older dogs using both methods. ANIMALS: Client-owned older dogs undergoing health screening. METHODS: The LC-MS/MS method was analytically validated (limit of detection, precision, and linearity). Serum was sent cooled overnight for ELISA or was frozen at -80°C until batch analysis using LC-MS/MS. Results of LC-MS/MS and ELISA were compared and RIs for older dogs were calculated according to international guidelines. RESULTS: The LC-MS/MS method showed good linearity (r2 = .99) and precision (coefficient of variation <10%), with a laboratory RI between 8.0 and 14.0 µg/dL. Paired measurements were available from 118 different dogs. Median SDMA concentration were 9.4 (range, 5.0-21.2) using LC-MS/MS and 12.0 (range, 5.0-22.0) µg/dL using ELISA. Both methods significantly differed with a mean difference of 2.2 µg/dL. The RI for older dogs for LC-MS/MS was 4.4-15.0 µg/dL, and for ELISA was 6.4-17.4 µg/dL. CONCLUSIONS AND CLINICAL IMPORTANCE: The ELISA provided significantly higher SDMA concentrations compared to the validated LC-MS/MS method, indicating the need for device- or assay-specific RI. The obtained age-specific RI for SDMA is considerably higher in older dogs compared to the general laboratory RI.

Seroprevalence of IgG antibodies against SARS-CoV-2 - a serial prospective cross-sectional nationwide study of residual samples, Belgium, March to October 2020.

BackgroundTo control epidemic waves, it is important to know the susceptibility to SARS-CoV-2 and its evolution over time in relation to the control measures taken.AimTo assess the evolving SARS-CoV-2 seroprevalence and seroincidence related to the first national lockdown in Belgium, we performed a nationwide seroprevalence study, stratified by age, sex and region using 3,000-4,000 residual samples during seven periods between 30 March and 17 October 2020.MethodsWe analysed residual sera from ambulatory patients for IgG antibodies against the SARS-CoV-2 S1 protein with a semiquantitative commercial ELISA. Weighted seroprevalence (overall and by age category and sex) and seroincidence during seven consecutive periods were estimated for the Belgian population while accommodating test-specific sensitivity and specificity.ResultsThe weighted overall seroprevalence initially increased from 1.8% (95% credible interval (CrI): 1.0-2.6) to 5.3% (95% CrI: 4.2-6.4), implying a seroincidence of 3.4% (95% CrI: 2.4-4.6) between the first and second collection period over a period of 3 weeks during lockdown (start lockdown mid-March 2020). Thereafter, seroprevalence stabilised, however, significant decreases were observed when comparing the third with the fifth, sixth and seventh period, resulting in negative seroincidence estimates after lockdown was lifted. We estimated for the last collection period mid-October 2020 a weighted overall seroprevalence of 4.2% (95% CrI: 3.1-5.2).ConclusionDuring lockdown, an initially small but increasing fraction of the Belgian population showed serologically detectable signs of exposure to SARS-CoV-2, which did not further increase when confinement measures eased and full lockdown was lifted.

When clozapine appears at a dance event .

Objectives: The content of substances sold and consumed as party drugs is often unknown. They may contain inactive, contaminated or unexpected ingredients, and the dosage of the active components may vary considerably. Obviously, these phenomena increase the chances of a wrong or delayed therapy. To illustrate this point, we report 3 cases of clozapine intoxication at a dance event where most likely clozapine tablets were sold as party drugs.Methods: The three cases were part of a prospective toxicology study at a nocturnal indoor dance event.Results: One patient had to be intubated after obstructive breathing with desaturation and bradycardia, while the 2 other patients presented with syncope and altered mental status. All patients recovered after 20 minutes to 8 hours. Systematic toxicological analysis of the blood samples revealed the presence of clozapine (73-244 ng/ml) and its metabolite norclozapine (9-59 ng/ml). A pill, found in a pocket of one patient, was identified as Leponex® 100 mg (clozapine). This neuroleptic drug is mainly prescribed for treatment-resistant schizophrenia. In clozapine-naive subjects, orthostatic hypotension, bradycardia and syncope have been reported with a single 25 mg oral dose. Serum clozapine concentrations of the 3 cases were below the defined therapeutic range (350-600ng/ml) and the clozapine:norclozapine ratios were suggestive for recent drug intake.Conclusion: Routine drug screening may be unable to detect the toxic agent(s) involved. Whenever unusual symptoms are observed in an intoxicated patient, blood and urine samples should be sent to a reference toxicology laboratory.

Determination of Common Antipsychotics in Quantisal-Collected Oral Fluid by UHPLC-MS/MS: Method Validation and Applicability for Therapeutic Drug Monitoring.

BACKGROUND: Oral fluid (OF) is an interesting alternative for conventional blood testing in therapeutic drug monitoring. OF can be used for screening but its value for quantification has to be established. METHODS: To evaluate the value of OF for quantification of 11 commonly used antipsychotics (APs) and 5 metabolites, an ultra-high performance liquid chromatography-tandem mass spectrometric method was validated. OF was obtained from psychiatric patients using a Quantisal collection device. OF to serum concentration ratios were determined, taking into account the exact volume of collected OF. RESULTS: Linearity was evaluated at 7 or 8 calibration levels. Accuracy criteria were fulfilled, except for pipamperone (PIP) at quality control (QC) low. The intraday precision ranged 0.88%-14.73% and interday precision ranged 1.92%-16.17%. The mean recovery from the collection pad was 37.1% at QC low and 40.3% at QC high for 1 mL of collected OF; for 0.5 mL collected OF mean recovery was 35.0% at QC low and 37.3% at QC high. When 0.1 mL OF was collected, recovery data were unreliable. Mean absolute matrix effect was 101.1% (82.0%-120.0%). OF patient samples (n = 89) containing 269 APs and metabolites were acquired and the mean volume of collected OF was 0.562 mL (0.057-1.232 mL). The OF to serum ratios were above 1 for all APs (1.54-28.50), except for aripiprazole (0.21) and zuclopenthixol (0.66). A broad range of calculated ratios for all APs was obtained. CONCLUSIONS: This validated ultra-high performance liquid chromatography-tandem mass spectrometric method can be used to reliably quantify APs in OF, even when recovery is low. Because the correlation between OF and serum concentrations was low and in addition results were highly variable, it can only be concluded that OF is a potentially interesting matrix, particularly for screening for noncompliance.

Are capillary DBS applicable for therapeutic drug monitoring of common antipsychotics? A proof of concept.

AIM: DBS sampling has been proposed as an alternative for venous blood collection in therapeutic drug monitoring (TDM) of antipsychotics. For implementation in routine practice, a comparison between capillary and venous blood concentrations is mandatory. RESULTS: A DBS method for quantification of antipsychotics was clinically validated. First, whole blood therapeutic ranges were calculated using the blood:serum ratio. Calculation of DBS:blood ratios and Passing-Bablok regression analysis demonstrated that concentrations obtained by DBS analysis were highly comparable to those obtained by conventional whole blood analysis. Clinical interpretation of serum, whole blood and DBS concentrations were highly identical (sensitivity 91.6-97.6%). CONCLUSION: This is the first clinical study demonstrating the value of DBS sampling in TDM of antipsychotics.

The use of dried blood spots for quantification of 15 antipsychotics and 7 metabolites with ultra-high performance liquid chromatography - tandem mass spectrometry.

Therapeutic drug monitoring of antipsychotics is important in optimizing individual therapy. In psychiatric populations, classical venous blood sampling is experienced as frightening. Interest in alternative techniques, like dried blood spots (DBS), has consequently increased. A fast and easy to perform DBS method for quantification of 16 antipsychotics (amisulpride, aripiprazole, asenapine, bromperidol, clozapine, haloperidol, iloperidone, levosulpiride, lurasidone, olanzapine, paliperidone, pipamperone, quetiapine, risperidone, sertindole and zuclopenthixol) and 8 metabolites was developed. DBS were prepared using 25 µL of whole blood and extraction of complete spots was performed using methanol: methyl-t-butyl-ether (4:1). After evaporation, the extract was reconstituted in the mobile phase and 10 µL were injected on an ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Separation using a C18 column and gradient elution with a flow rate of 0.5 mL/min resulted in a 6-min run-time. Ionization was performed in positive mode and a dynamic MRM method was applied. Median recovery was 66.4 % (range 28.7-84.5%). Accuracy was within the acceptance criteria, except for pipamperone (LLOQ and low concentration) and lurasidone (low concentration). Imprecision was only aberrant for lurasidone at low and medium concentration. All compounds were stable during 1 month at room temperature, 4 °C and -18 °C. Lurasidone was unstable when the extract was stored for 12 h on the autosampler. Absolute matrix effects (ME) (median 66.1%) were compensated by the use of deuterated IS (median 98.8%). The DBS method was successfully applied on 25-µL capillary DBS from patients and proved to be a reliable alternative for quantification of all antipsychotics except for olanzapine and N-desmethylolanzapine.

Advances in detection of antipsychotics in biological matrices.

Measuring antipsychotic concentrations in human matrices is important for both therapeutic drug monitoring and forensic toxicology. This review provides a critical overview of the analytical methods for detection and quantification of antipsychotics published in the last four years. Focus lies on advances in sample preparation, analytical techniques and alternative matrices. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is used most often for quantification of antipsychotics. This sensitive technique makes it possible to determine low concentrations not only in serum, plasma or whole blood, but also in alternative matrices like oral fluid, dried blood spots, hair, nails and other body tissues. Current literature on analytical techniques for alternative matrices is still limited and often requires a more thorough validation including a comparison between conventional and alternative results to determine their actual value. Ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) makes it possible to quantify a high amount of compounds within a shorter run time. This technique is widely used for multi-analyte methods. Only recently, high-resolution mass spectrometry has gained importance when a combination of screening of (un)known metabolites, and quantification is required.

Retrospective evaluation of therapeutic drug monitoring of clozapine and norclozapine in Belgium using a multidrug UHPLC-MS/MS method.

OBJECTIVE: Clozapine is an atypical antipsychotic with a narrow therapeutic range and serious toxic side effects. According to AGNP-TDM consensus guidelines, therapeutic drug monitoring (TDM) of clozapine and its metabolite norclozapine is strongly recommended. 330 serum samples, sent to the toxicological laboratory of Ziekenhuis Netwerk Antwerpen for monitoring of clozapine, were tested with a new ultra-high performance liquid chromatography-tandem mass spectrometric method (UHPLC-MS/MS). The aim of this research was to evaluate this method for TDM of clozapine and norclozapine, but also to determine other antipsychotics present in these serum samples. DESIGN AND METHODS: Serum samples were taken just prior to the morning dose of the antipsychotic (trough concentration). All samples were, after a simple liquid-liquid extraction with methyl t-butylether, analyzed using a fully validated UHPLC-MS/MS method which is able to quantitate 16 different antipsychotics and 8 of their major metabolites. Serum concentrations were compared with the therapeutic ranges as defined by the AGNP-TDM guidelines. RESULTS: For clozapine, only 22.3% of the serum concentrations were within the therapeutic range of 350-600 ng/mL, while 67.9% of the concentrations were below 350 ng/mL. For norclozapine, 68.2% of the serum samples were within the therapeutic range of 100-600 ng/mL. The mean clozapine:norclozapine ratio was 1.7 (SD 0.8). 218 of the 330 serum samples contained other antipsychotics than clozapine. Only 52.5% of these concentrations were within the proposed range. CONCLUSION: This retrospective study highlights the importance of TDM for clozapine and other APs, since many patients show suboptimal serum concentrations.

The influence of the body mass index (BMI) on the volume of distribution of ethanol.

The volume of distribution of ethanol was already established in 1930s by Widmark. However, since then the average body composition has changed considerably. The effect of the body mass index (BMI) on the volume of distribution of ethanol was evaluated in this study. Fifty healthy volunteers (23 men and 27 women), with BMI-values between 16.0 and 36.0kg/m(2), were asked to drink a dose of 0.4g ethanol per kilogram body weight after an overnight fast. The ethanol content was measured by a fully validated headspace-GC-FID method. The volume of distribution of ethanol varied between 0.40 and 0.68L/kg for women, and between 0.43 and 0.73L/kg for men. For both sexes, the volume of distribution decreased with increasing BMI. Regression analysis resulted in the following equations: volume of distribution=0.8202-0.0090×BMI for men (r=0.66), and 0.7772-0.0099×BMI for women (r=0.78). Population probability prediction interval limits were also calculated. In view of the current study, fixed values for the volume of distribution of 0.7L/kg and 0.6L/kg for men and women, respectively, often applied in legal blood alcohol calculations, are mainly suited to judge underweight or normal weight people, but not obese persons.

High throughput identification and quantification of 16 antipsychotics and 8 major metabolites in serum using ultra-high performance liquid chromatography-tandem mass spectrometry.

BACKGROUND: Therapeutic drug monitoring of antipsychotics is important for optimizing therapy, explaining adverse effects, non-response or poor compliance. We developed a UHPLC-MS/MS method for quantification of 16 commonly used and recently marketed antipsychotics and 8 metabolites in serum. METHODS: After liquid-liquid extraction using methyl tert-butyl ether, analysis was performed on an Agilent Technologies 1290 Infinity LC system coupled with an Agilent Technologies 6460 Triple Quadrupole MS. Separation with a C18 column and gradient elution at 0.5 mL/min resulted in a 6-min run-time. Detection was performed in dynamic MRM, monitoring 3 ion transitions per compound. Isotope labeled internal standards were used for every compound, except for bromperidol and levosulpiride. RESULTS: Mean recovery was 86.8%. Matrix effects were -18.4 to +9.1%. Accuracy ranged between 91.3 and 107.0% at low, medium and high concentrations and between 76.2 and 113.9% at LLOQ. Within-run precision was <15% (CV), except for asenapine and hydroxy-iloperidone. Between-run precision was aberrant only for 7-hydroxy-N-desalkylquetiapine, asenapine and reduced haloperidol. No interferences were found. No problems of instability were observed, even for olanzapine. The method was successfully applied on patient samples. CONCLUSIONS: The liquid-liquid extraction and UHPLC-MS/MS technique allows robust target screening and quantification of 23 antipsychotics and metabolites.

Bupropion for the treatment of seasonal affective disorder.

INTRODUCTION: Seasonal affective disorder (SAD) is a psychiatric illness with recurring depressive episodes during particular seasons, mostly winter. Bupropion is effective in the preventive treatment of SAD and is probably also effective in the acute treatment of SAD. AREAS COVERED: This review covers the pharmacokinetics and pharmacodynamics of bupropion. The authors also evaluate bupropion's clinical efficacy as well as its safety and tolerability. EXPERT OPINION: Bupropion is available in an immediate release formulation, as well as a sustained release formulation and an extended release (XR) formulation. The XR formulation is recommended for SAD due to its ease of use and is the only formulation currently used as a therapy. Due to the predictable nature of SAD, the use of bupropion XR is considered a relevant treatment option. Bupropion's efficacy is shown in three trials that started in autumn at a time when SAD symptoms were not yet present although treatment effects were relatively small compared with a placebo. Bupropion was also shown to have efficacy in an open-label study. That being said, in order to reach definitive conclusions about its efficacy with acute treatment of SAD, more placebo-controlled trials are needed.

Therapeutic drug monitoring of common antipsychotics.

The aim of this review is to provide information for interpreting outcome results from monitoring of antipsychotics in biological samples. A brief overview of the working mechanisms, pharmacological effects, drug interactions, and analytical methods of classical and atypical antipsychotics is given. Nineteen antipsychotics were selected based on their importance in the worldwide market as follows: amisulpride, aripiprazole, asenapine, bromperidol, clozapine, flupenthixol, haloperidol, iloperidone, lurasidone, olanzapine, paliperidone, perphenazine, pimozide, pipamperone, quetiapine, risperidone, sertindole, sulpiride, and zuclopenthixol. A straightforward relationship between administered dose, plasma or serum concentration, clinical outcome, or adverse effects is often lacking. Nowadays, focus lies on therapeutic drug monitoring and individualized therapy to find adequate treatment, to explain treatment failure or nonresponse, and to check patient compliance. However, extensive research in this field is still mandatory.

Pharmacokinetic evaluation of armodafinil for the treatment of bipolar depression.

INTRODUCTION: Bipolar disorder is a psychiatric illness with recurring episodes of mania and depression. Armodafinil , the R-enantiomer of modafinil, approved for treating excessive sleepiness associated with narcolepsy, obstructive sleep apnea and shift work disorder, is possibly effective as an adjunctive treatment for bipolar depression. AREAS COVERED: This review covers the pharmacokinetics of armodafinil, with an emphasis on its use in bipolar depression. Its clinical efficacy in the treatment of bipolar depression is evaluated, along with current data regarding its safety and tolerability. EXPERT OPINION: One placebo-controlled trial is available, in which armodafinil was efficacious as an adjunctive treatment in bipolar depression. Armodafinil shows a linear pharmacokinetic profile over a broad dose range of 50 - 400 mg (maximal plasma concentration and area under concentration-time curve). Compared with modafinil, an equivalent dose of armodafinil attains higher blood concentrations 4 - 6 h post-dose. The possibility of drug interactions is generally low, although interactions have been shown with some drugs used in bipolar disorder, through mild CYP3A4-induction and CYP2C19-inhibition. Armodafinil is well tolerated and presents a possible new treatment option for bipolar depression. However, further investigation is still needed in order to confirm its efficacy and to clarify its role in the treatment of bipolar depression.

Laboratory detection of macro-aspartate aminotransferase: case report and evaluation of the PEG-precipitation method.

BACKGROUND: Chronic elevated AST without other signs of liver disease, cardiac or skeletal abnormalities, is suggestive for macro-AST. Laboratory detection can be performed by gel filtration chromatography, ultrafiltration or precipitation with polyethylene glycol (PEG). PATIENT AND METHODS: A healthy 27 year-old female was referred because of chronic elevated AST (116-704U/L) without other abnormalities. Macro-AST positivity was suspected since AST was no longer measurable in the supernatant of a serum sample (<3U/L) after PEG precipitation. Optimization of this method included analysis of proteins and lipids precipitated, testing the effect of different PEG concentrations and centrifugation times. 25% (m/v) PEG solution gave the most reliable results. No significant difference was seen between 10 and 30 min centrifugation time. A reference range was obtained by analysis of 31 normal patient samples (mean % PEG precipitation activity 35.1% with 95% confidence limits of 14.5-62.5%). Retrospective analysis of 1371 patient samples with elevated AST revealed one other positive patient sample. CONCLUSION: Early recognition of macro-AST, proven by simple PEG precipitation, can avoid time-consuming and invasive investigations.