Simon A. Handley

LC-MS/MS of some atypical antipsychotics in human plasma, serum, oral fluid and haemolysed whole blood

Therapeutic drug monitoring (TDM) of atypical antipsychotics is common, but published methods often specify relatively complex sample preparation and analysis procedures. The aim of this work was to develop and validate a simple liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the analysis of amisulpride, aripiprazole and dehydroaripiprazole, clozapine and norclozapine, olanzapine, quetiapine, risperidone and 9-hydroxyrisperidone, and sulpiride in small (200 μL) volumes of plasma or serum for TDM purposes. The applicability of the method as developed to haemolysed whole blood and to oral fluid was also investigated. Analytes and internal standards were extracted into butyl acetate:butanol (9+1, v/v) and a portion of the extract analysed by LC-MS/MS (100 mm × 2.1 mm i.d. Waters Spherisorb S5SCX; eluent: 50 mmol/L methanolic ammonium acetate, pH* 6.0; flow-rate 0.5 mL/min; positive ion APCI-SRM, two transitions per analyte). Assay calibration (human plasma, oral fluid, and haemolysed whole blood calibration solutions) was performed by plotting the ratio of the peak area of the analyte to that of the appropriate internal standard. Assay validation was as per FDA guidelines. Assay calibration was linear across the concentration ranges studied. Inter- and intra-assay precision and accuracy were within 10% for all analytes in human plasma. Similar results were obtained for oral fluid and haemolysed whole blood, except that aripiprazole and dehydroaripiprazole were within 15% accuracy at low concentration (15 μg/L) in oral fluid, and olanzapine inter-assay precision could not be assessed in these matrices due to day-by-day degradation of this analyte. Recoveries varied between 16% (sulpiride) and 107% (clozapine), and were reproducible as well as comparable between human plasma, human serum, calf serum and haemolysed whole blood. For oral fluid, recoveries were reproducible, but differed slightly from those in plasma suggesting the need for calibration solutions to be prepared in this medium if oral fluid is to be analysed. LLOQs were 1-5 μg/L depending on the analyte. Neither ion suppression/enhancement, nor interference from some known metabolites of the antipsychotics studied has been encountered. The method has also been applied to the analysis of blood samples collected post-mortem after dilution (1+1, 1+3; v/v) in analyte-free calf serum.

Drugs and other chemicals involved in fatal poisoning in England and Wales during 2000–2011

Context. Fatal poisoning data can reveal trends in the poisons encountered, which can help guide prescribing practices and product safety and other legislation, and more recently has helped to monitor the use of emerging drugs of abuse (‘legal highs’). Methods. We searched Mortality Statistics – Injury and poisoning, Series DH4 (2000–2005), Mortality Statistics – Deaths registered in England and Wales, Series DR (2006–2011), and the Office for National Statistics drug poisoning database for information on fatal poisoning during 2000–2011. We also searched the Pubmed database for ‘fatal’ and ‘poisoning’ and ‘England’ and ‘Wales’: this search yielded seven papers that gave relevant information on deaths reported during 2000–2011 that were not superseded by later publications. Deaths from poisoning. The annual number of deaths from poisoning fell from 2000 (3092) to 2010 (2749), before increasing to 3341 in 2011. This increase was due in part to a change in the ICD coding relating to alcohol poisoning, suggesting that such deaths had been under-recorded previously. Although fatalities from dextropropoxyphene declined (287 in 2004 and 18 in 2011) following the withdrawal of co-proxamol (paracetamol [acetaminophen] and dextropropoxyphene [propoxyphene] mixture) during 2005–2007, deaths involving codeine and most notably tramadol (836 deaths during 2000–2011) increased. Deaths from paracetamol poisoning either alone, or with alcohol reached 89 in 2011, the lowest annual figure since 1974. However, in reality there has been no marked downward trend since 1999 despite reductions in pack size, continued publicity as to the dangers of paracetamol overdose, and improved liver failure treatment, including transplantation. The annual number of deaths from antidepressants remained relatively stable (median: 397, range: 335–469). Although the number of deaths from dosulepin [dothiepin] decreased (186 in 2000 and 49 in 2011), the number of deaths involving selective serotonin reuptake inhibitors increased (50 in 2000 and 127 in 2011). Although annual numbers of deaths involving diamorphine/morphine (88% unintentional) declined, deaths involving methadone (89% unintentional) increased and the total annual number of deaths from these drugs showed little change (2000: 1061, 2011: 995). Deaths involving amfetamine/metamfetamine remained relatively constant at about 50 annually, and whilst cocaine-related deaths fell by 48% during 2008–2011, and deaths involving MDMA and related compounds fell by 69% over this same period, deaths involving ‘legal highs’, notably γ-hydroxybutrate/γ-butyrolactone and ketamine, increased. Conclusions. Alterations in the availability of paracetamol and of prescription drugs such as dextropropoxyphene and dosulepin have not been accompanied by decreases in the number of deaths from poisoning. Despite intense media and other interest, the annual number of deaths (250–300) involving ‘recreational’ drugs remains small in relation to the 1000 or so deaths a year from diamorphine and/or methadone.

Simple methodology for the therapeutic drug monitoring of the tyrosine kinase inhibitors dasatinib and imatinib.

A simple HPLC method has been developed to measure imatinib and N-desmethylimatinib (norimatinib) in plasma or serum at concentrations attained during therapy. Adaptation of this method to LC-MS/MS also allows dasatinib assay. A small sample volume (100 μL HPLC-UV, 50 μL LC-MS/MS) is required and analysis time is <5 min in each case. Detection was by UV (270 nm) or selective reaction monitoring (two transitions per analyte) tandem mass spectrometry. Assay calibration was linear (0.05-10 mg/L imatinib, 0.01-2.0 mg/L norimatinib and 1-200 µg/L dasatinib), with acceptable accuracy (86-114%) and precision (<14% RSD) for both methods. A comparison between whole blood and plasma confirmed that plasma is the preferred sample for imatinib and norimatinib assay. For dasatinib, although whole blood concentrations were slightly higher, plasma is still the preferred sample. Despite considerable variation in the (median, range) plasma imatinib and norimatinib concentrations in patient samples [1.66 (0.02-4.96) and 0.32 (0.01-0.99) mg/L, respectively, N = 104], plasma imatinib was >1 mg/L (suggested target for response) in all but one sample from patients achieving complete molecular response. As to dasatinib, the median (range) plasma dasatinib concentration was 13 (2-143) µg/L (N = 33). More observations are needed to properly assess the potential role of therapeutic drug monitoring in guiding treatment with dasatinib.

Stability of some atypical antipsychotics in human plasma, haemolysed whole blood, oral fluid, human serum and calf serum

Long-term stability data of atypical antipsychotics in different matrices are not widely available. The aim of this work was to assess the stability of amisulpride, aripiprazole and dehydroaripiprazole, clozapine and norclozapine, olanzapine, quetiapine, risperidone and 9-hydroxyrisperidone, and sulpiride in human EDTA plasma, heparinised haemolysed human whole blood, oral fluid, human serum, and newborn calf serum stored in tightly capped plastic containers under a range of conditions. Measurements were performed by LC-MS/MS. Analyte instability was defined as a deviation of 15% or greater from the expected concentration. All analytes were stable following 3 freeze-thaw cycles in human plasma, and were stable in this matrix for at least 5 days at ambient temperature (olanzapine, 3 days); 4 weeks at 2-8°C (olanzapine, 2 weeks), and 2 years at -20°C (except for dehydroaripiprazole, olanzapine, and quetiapine, 1 year). In human serum, aripiprazole, dehydroaripiprazole, norclozapine, olanzapine, quetiapine, risperidone, 9-hydroxyrisperidone, and sulpiride were unstable after 5 days at ambient temperature, 3 weeks at 2-8°C, and 9 months at -20°C. Olanzapine was unstable in whole blood and oral fluid under most conditions studied, although prior addition of ascorbic acid had a moderate stabilising effect. All other analytes were stable in whole blood and oral fluid for at least 2 days at ambient temperature, 1 week at 2-8°C, and 2 months at -20°C (clozapine and norclozapine, 1 month whole blood). These results confirm that plasma (EDTA anticoagulant) is the sample of choice for TDM of atypical antipsychotics. Delayed (more than 1 week) analysis of patient samples should be undertaken with caution, especially with serum and with haemolysed whole blood. With olanzapine, only plasma collected and stored appropriately is likely to give reliable quantitative results.

Risperidone and Total 9-Hydroxyrisperidone in Relation to Prescribed Dose and Other Factors: Data From a Therapeutic Drug Monitoring Service, 2002-2010

Background: Information on the plasma risperidone and total 9-hydroxyrisperidone concentrations (‘total risperidone’) attained in clinical practice is scant. The aim of this work was to gather such information to better inform the interpretation of results. Method: This involved the audit of plasma total risperidone data from a risperidone therapeutic drug monitoring service 2002–2010. Results: There were 586 samples from 411 patients [289 (70%) males aged at the time of the first sample (median, range) 37 (7–83) years and 121 females aged 42 (10–91) years]. In patients aged 18 years and over, the mode of risperidone administration was oral: 242 samples (163 patients), risperidone long-acting injection (RLAI): 42 samples (39 patients), both oral and RLAI: 18 samples (12 patients), no information: 266 samples (211 patients). No risperidone/9-hydroxyrisperidone was detected in 10% of the samples, including 5 samples from patients prescribed RLAI. In the remainder, the mean (SD) total plasma total risperidone was all samples 35 (36), oral only 33 (29), RLAI only 23 (16), oral and RLAI 50 (21) &mgr;g/L. Overall, only 45% of the samples had plasma total risperidone within the range 20–59 mcg/L. Multiple linear regression analysis (95 samples) revealed that sex, smoking habit, and dose explained 21% of the variation in plasma total risperidone after oral dosage (dose alone only explained 11% of the variation). There was no discernable influence of age, body weight, and the plasma risperidone:total 9-hydroxyrisperidone ratio on plasma total risperidone. Conclusions: Risperidone therapeutic drug monitoring can help assess adherence and guide dosage even after RLAI.

Measurement of quetiapine and four quetiapine metabolites in human plasma by LC‐MS/MS

There is interest in monitoring plasma concentrations of N-desalkylquetiapine in relation to antidepressant effect. A simple LC-MS/MS method for quetiapine and four metabolites in human plasma (50 μL) has been developed to measure concentrations of these compounds attained during therapy. Analytes and internal standard (quetiapine-d8) were extracted into butyl acetate-butanol (10:1, v/v) and a portion of the extract analysed by LC-MS/MS (100 × 2.1 mm i.d. Waters Spherisorb S5SCX; eluent: 50 mmol/L methanolic ammonium acetate, pH* 6.0; flow-rate 0.5 mL/min; positive ion APCI-SRM, two transitions per analyte). Assay calibration (human plasma calibrators) was linear across the ranges studied (quetiapine and N-desalkylquetiapine 5-800, quetiapine sulfoxide 100-15,000, others 2-100 µg/L). Assay validation was as per FDA guidelines. Quetiapine sulfone was found to be unstable and to degrade to quetiapine sulfoxide. In 47 plasma samples from patients prescribed quetiapine (prescribed dose 200-950 mg/day), the (median, range) concentrations found (µg/L) were: quetiapine 83 (7-748), N-desalkylquetiapine, 127 (7-329), O-desalkylquetiapine 12 (2-37), 7-hydroxyquetiapine 3 (<1-48), and quetiapine sulfoxide 3,379 (343-21,704). The analyte concentrations found were comparable to those reported by others except that the concentrations of the sulfoxide were markedly higher. The reason for this discrepancy in unclear.

Plasma concentrations of quetiapine, N-desalkylquetiapine, o-desalkylquetiapine, 7-hydroxyquetiapine, and quetiapine sulfoxide in relation to quetiapine dose, formulation, and other factors.

Background: N-Desalkylquetiapine may be a pharmacologically active quetiapine metabolite. However, information on plasma concentrations of N-desalkylquetiapine and other quetiapine metabolites attained during quetiapine therapy is scant. The aim of this study was to investigate plasma concentrations of quetiapine, N-desalkylquetiapine, O-desalkylquetiapine, 7-hydroxyquetiapine, and quetiapine sulfoxide attained during therapy and analyze the data with respect to prescribed dose and other variables. Method: Quetiapine and its metabolites were measured in plasma samples submitted for quetiapine therapeutic drug monitoring (2009–2011). Concentration, metabolic ratio, and concentration corrected for dose (C/D) were investigated against quetiapine dose, age, sex, and formulation. Sample results were excluded if nonadherence with therapy was queried. Results: There were 99 samples from 59 patients. N-Desalkylquetiapine plasma concentrations showed the strongest correlation with dose of all analytes, but O-desalkylquetiapine and quetiapine sulfoxide were strongly correlated to plasma quetiapine concentrations. There was no significant difference in C/D for any analyte between males and females and no correlation to age. Quetiapine and quetiapine sulfoxide C/D were significantly different (P < 0.01) between patients prescribed immediate- and extended-release formulations. Quetiapine, 7-hydroxyquetiapine and quetiapine sulfoxide C/D showed significant variation (P < 0.02) between those samples taken 10–14 hours postdose as compared with that of 16–24 hours postdose, but there was no significant effect as regards N-desalkylquetiapine. Conclusions: Plasma quetiapine, O-desalkylquetiapine, 7-hydroxyquetiapine, and quetiapine sulfoxide concentrations were significantly affected by formulation and/or time since last dose. Plasma N-desalkylquetiapine concentrations were not affected by either factor therefore may be a better marker for quetiapine exposure than plasma quetiapine concentrations.

Plasma clozapine and norclozapine in relation to prescribed dose and other factors in patients aged <18 years: data from a therapeutic drug monitoring service, 1994–2010

Clozapine is used in children and adolescents to treat early onset schizophrenia, but data on efficacy and on the plasma clozapine concentrations attained are limited.

Measurement of hepcidin isoforms in human serum by liquid chromatography with high resolution mass spectrometry

AIM Hepcidin-25 is the master regulator of iron homeostasis. N-truncated isoforms of hepcidin-25 have been identified (hepcidin-20, -22, -24), although data on the concentrations of these isoforms are sparse. MATERIALS & METHODS Serum was mixed with aqueous formic acid, and the supernatant loaded onto a 96-well-SPE-plate. Eluted analytes were analyzed using LC-HR-MS. Forty-seven paired dipotassium-EDTA human plasma and serum samples were analyzed. RESULTS The LLOQ was 1 μg/l (all analytes). Accuracy and precision were acceptable. There was a good correlation (R2 >0.90, all analytes) between matrices. The median (range) serum hepcidin-20, -22, -24 and -25 concentrations measured were 4 (1-40), 8 (2-20), 8 (1-50) and 39 (1-334) μg/l, respectively. CONCLUSION LC-HR-MS is widely applicable to the measurement of hepcidin-25, and truncated isoforms.

Measurement of serum lanthanum in patients treated with lanthanum carbonate by inductively coupled plasma-mass spectrometry

Background Lanthanum carbonate is used as a phosphate binder in patients with stage V chronic kidney disease (CKD). While well tolerated in clinical trials, with no toxicity reported as regards bone and liver metabolism, and cognitive function, concerns remain over possible toxicity. Published methods for the measurement of lanthanum ion in biological samples include aggressive and complicated sample preparation steps that are unsuitable for routine use. A simple method has been developed and validated for the measurement of serum lanthanum. Method A ThermoFisher Scientific XSERIES-II inductively coupled plasma-mass spectrometer was used to monitor 139La. Validation was undertaken using internal quality control solutions containing lanthanum ion (0.20, 0.70 and 4.00 μg/L). Lanthanum was measured in patients (number = 20) with CKD prescribed lanthanum carbonate (500–1500 mg/d) and patients undergoing haemodialysis not prescribed lanthanum carbonate (number = 20). Results Accuracy and imprecision were >95% and <5%, respectively. Calibration was linear (range 0.1–5 μg/L, R 2 = 0.99). The lower limit of quantification (LLoQ) was 0.1 μg/L lanthanum ion. In patients with CKD not prescribed lanthanum carbonate, serum lanthanum was below the LLoQ. Out of 20 CKD patients prescribed lanthanum carbonate, serum lanthanum was measurable in only 12 (range 0.11–0.60 μg/L lanthanum ion). There was no apparent relationship between dose and serum lanthanum in these patients. Conclusions A lack of relationship between the dose of lanthanum carbonate and the serum lanthanum concentration may have been due to poor adherence to the treatment regimen. However the concentrations measured were close to the LLoQ.