Mortality associated with clozapine: what is the evidence?

While clozapine has risks, relative risk of fatality is overestimated. The UK pharmacovigilance programme is efficient, but comparisons with other drugs can mislead because of reporting variations. Clozapine actually lowers mortality, partly by reducing schizophrenia-related suicides, but preventable deaths still occur. Clozapine should be used earlier and more widely, but there should be better monitoring and better management of toxicity.

Plasma Clozapine and N -Desmethylclozapine (Norclozapine) Concentrations and the Clozapine/Norclozapine Ratio : Effect of Dose, Sex, and Cigarette Smoking.

BACKGROUND: Smoking enhances plasma clozapine clearance, but the magnitude of the effect across the dose and age ranges is unclear. METHODS: We audited clozapine dose and predose plasma clozapine and N -desmethylclozapine (norclozapine) concentrations by sex and smoking habit in samples submitted for clozapine TDM, 1996-2017. RESULTS: There were 105,316/60,792 and 34,288/31,309 samples from male/female smokers/nonsmokers, respectively. There were distinct dose-median plasma concentration trajectories for male/female smokers/nonsmokers across the range <50 to >850 mg d -1 . For both sexes, the percentage difference in median plasma clozapine in nonsmokers versus smokers averaged 50% but was greatest for men (76%) and women (59%) in the 151 to 250 mg d -1 dose band. In men, the percentage difference declined steadily to 34% at doses of ≥850 mg d -1 . In women, the difference after falling initially remained relatively constant at 40% to 54%. The pattern in median plasma clozapine/norclozapine ratio by plasma clozapine concentration and dose groups was independent of sex and smoking habit, but increased with plasma clozapine concentration (higher ratio at higher concentrations) and also changed with dose. Median plasma clozapine concentration and median clozapine dose by sex and smoking habit were similar up to age 60 years. Proportional weight gain was similar over time in smokers and nonsmokers of either sex. IMPLICATIONS: These data explain the variations in the effect size of starting or stopping smoking on plasma clozapine concentration at constant dose reported in different studies. Changes in smoking habit in patients prescribed clozapine require prompt dose adjustment.

Effect of Coffee and Chocolate Ingestion on Clozapine Dose and on Plasma Clozapine and Norclozapine Concentrations in Clinical Practice.

BACKGROUND: Some reports point to dietary caffeine intake as a cause of increased plasma clozapine concentrations in certain patients. METHODS: We compared clozapine dose and plasma clozapine and N-desmethylclozapine (norclozapine) concentrations in male and female smokers and nonsmokers in relation to reported (i) coffee (caffeine) and (ii) chocolate (caffeine and theobromine) intake in samples submitted for clozapine therapeutic drug monitoring, 1993-2017. RESULTS: There was information on coffee ingestion for 16,558 samples (8833 patients) from males and 5886 samples (3433 patients) from females and on chocolate ingestion for 12,616 samples (7568 patients) from males and 4677 samples (2939 patients) from females. When smoking was considered, there was no discernible effect of either coffee or chocolate ingestion either on the median dose of clozapine or on the median plasma clozapine and norclozapine concentrations in men and in women. However, cigarette smoking was associated with higher coffee and chocolate consumption. Although male nonsmokers who reported drinking 3 or more cups of coffee daily had significantly higher median plasma clozapine and norclozapine concentrations than those who drank less coffee, they were also prescribed a significantly higher clozapine dose. There was no clear effect of coffee ingestion on plasma clozapine and norclozapine in female nonsmokers. IMPLICATIONS: Inhibition of clozapine metabolism by caffeine at the doses of caffeine normally encountered in those treated with clozapine is unlikely even in male nonsmokers. Measurement of plasma caffeine in an appropriate sample should be considered in any future investigation into a presumed clozapine-caffeine interaction.

A population pharmacokinetic model to guide clozapine dose selection, based on age, sex, ethnicity, body weight and smoking status.

AIMS: Guidance on clozapine dosing in treatment-resistant schizophrenia is based largely on data from White young adult males. This study aimed to investigate the pharmacokinetic profiles of clozapine and N-desmethylclozapine (norclozapine) across the age range, accounting for sex, ethnicity, smoking status and body weight. METHODS: A population pharmacokinetic model, implemented in Monolix, that linked plasma clozapine and norclozapine via a metabolic rate constant, was used to analyse data from a clozapine therapeutic drug monitoring service, 1993-2017. RESULTS: There were 17 787 measurements from 5960 patients (4315 male) aged 18-86 years. The estimated clozapine plasma clearance was reduced from 20.2 to 12.0 L h-1 between 20 and 80 years. Model-based dose predictions to attain a predose plasma clozapine concentration of 0.35 mg L-1 was 275 (90% prediction interval 125, 625) mg day-1 in nonsmoking, White males weighing 70 kg and aged 40 years. The corresponding predicted dose was increased by 30% in smokers, decreased by 18% in females, and was 10% higher and 14% lower in otherwise analogous Afro-Caribbean and Asian patients, respectively. Overall, the predicted dose decreased by 56% between 20 and 80 years. CONCLUSION: The large sample size and wide age range of the patients studied allowed precise estimation of dose requirements to attain predose clozapine concentration of 0.35 mg L-1 . The analysis was, however, limited by the absence of data on clinical outcome and future studies are required to determine optimal predose concentrations specifically in those aged over 65 years.

Assessing Adherence to Clozapine: Practical Considerations.

BACKGROUND: The clinical assessment of adherence to clozapine may prove difficult. METHOD: We studied the incidence of nonadherence (plasma clozapine <0.01 mg L -1 ) in samples submitted to a clozapine therapeutic drug monitoring (TDM) service, 1993-2017. RESULTS: Clozapine was not detected in 2865 samples from men (2214 patients, 1.1% of all samples from men) and 1068 samples from women (822 patients, 1.0% of all samples from women). Information on the prescribed dose was supplied for 1623 of these samples from men and 492 of these samples from women. Prescribed doses ranged up to 1200 mg d -1 , although most were in the range 100 to 600 mg d -1 . Norclozapine was detected in 260 (9.1%) and 67 (6.3%) of the samples from men and from women, respectively, that did not contain clozapine. While an assay was requested to confirm either a patient history of nonadherence, or to establish that clozapine had been cleared from the circulation after overdosage, for example, in at least 38 instances, in the vast majority of cases the absence of clozapine from the sample was unexpected. IMPLICATIONS: While adherence to clozapine may be good in general, tolerance to its potentially fatal cardiovascular effects is easily lost. Moreover, in treatment-resistant schizophrenia, the risk of self-harm increases if the drug is not taken regularly. In addition to presently available TDM services, the advent of a clozapine immunoassay for laboratory use should make it easy to institute at least monthly clozapine TDM at minimal extra cost.

Effect of Cigarette Smoking on Clozapine Dose and on Plasma Clozapine and N-Desmethylclozapine (Norclozapine) Concentrations in Clinical Practice.

BACKGROUND: Cigarette smoking enhances plasma clozapine clearance and thus affects the clozapine dose requirement. METHODS: We compared clozapine daily dose and plasma clozapine and N-desmethylclozapine (norclozapine) concentrations in male and female smokers and nonsmokers in samples submitted for clozapine therapeutic drug monitoring (1996-2017). RESULTS: There were 105,316/60,792 and 34,290/31,309 samples with dose information from male and female smokers/nonsmokers, respectively. There was information on the number of cigarettes smoked daily for 12,842 samples (8409 patients) and 3948 samples (2753 patients) from men and women, respectively. Of these, 574 and 253 samples were from men and women, respectively, who reported smoking 1-9 cigarettes daily.In both sexes, the median clozapine doses in the nonsmokers were 75%-80% of those in the smokers, but the median plasma clozapine and norclozapine concentrations were 136% higher. The effect of smoking on the dose and on median plasma clozapine and norclozapine concentrations seemed maximal after 2-3, perhaps fewer, cigarettes daily in males. In females, the effect of smoking seemed to be near maximal after some 4-5 cigarettes per day. IMPLICATIONS: The optimum target range for predose plasma clozapine may be different in smokers (0.35-0.45 mg L-1) as opposed to nonsmokers (0.50-0.60 mg L-1). That changes in clozapine clearance are likely near maximal with cigarette smoking as low as 2-3 d-1 in males, perhaps slightly more in females, emphasizes that covert or passive smoking may be an important factor in seemingly random changes in plasma clozapine concentration at constant dose.

Clozapine: Dose, Sex, Ethnicity, Smoking Habit, Age, Body Weight, and Plasma Clozapine and N -Desmethylclozapine (Norclozapine) Concentrations in Clinical Practice.

BACKGROUND: Guidance on clozapine dosing in treatment refractory schizophrenia is based largely on data from young adult male White patients. AIM: This study aimed to audit the plasma clozapine and N -desmethylclozapine (norclozapine) concentrations attained in male and female patients of different ethnicity and smoking habit. METHOD: The effect of dose, sex, ethnicity, age, body weight, and smoking habit on plasma clozapine and norclozapine concentrations were studied using data from a therapeutic drug monitoring service, 1993 to 2017. RESULTS: There were 371,610 samples (48,098 patients, 32,855 male). Ethnicity was recorded for 763 Afro-Caribbean, 536 Asian, and 7940 White patients. Males were prescribed significantly higher median doses than females but attained significantly lower median plasma clozapine and norclozapine concentrations. Asian and Afro-Caribbean males were prescribed significantly lower and higher median doses, respectively, than White males but attained significantly higher and lower median plasma clozapine and norclozapine concentrations, respectively. Data from 78,431 samples (23,516 patients) were analyzed using a linear mixed model. The predicted dose to attain a predose plasma clozapine concentration of 0.35 mg/L in a nonsmoking White male aged 40 years, with weight of 70 kg, and plasma clozapine-norclozapine ratio of 1.32 was 344 mg/d (95% confidence interval, 227-526 mg/d). The predicted dose was 33% higher and 20% lower in otherwise analogous Afro-Caribbean and Asian patients, respectively. In all cases, the predicted dose was increased by 36% in smokers and decreased by 22% in females. CONCLUSIONS: Research is needed to further investigate the complex relationships between dose, sex, ethnicity, plasma clozapine and norclozapine concentrations, and clinical outcome such as weight gain.

Plasma Clozapine and Norclozapine After Use of Either Crushed Tablets or Suspension Compared With Tablets.

BACKGROUND: With clozapine, either crushed tablets suspended in an aqueous medium or proprietary suspension is sometimes prescribed as an alternative to tablets, but bioequivalence data are scant. METHODS: We compared clozapine dose, and plasma clozapine and N -desmethylclozapine (norclozapine) concentrations after use of either tablets or crushed tablets/suspension in samples submitted for clozapine therapeutic drug monitoring, 1993 to 2017. RESULTS: There were 846 patients (1646 samples) given crushed tablets/suspension and 6065 patients (10,779 samples) given tablets. The median dose (mg d -1 ) was significantly higher in men (500 vs 450) and women (500 vs 400) given crushed tablets/suspension, but the median plasma clozapine and norclozapine concentrations (mg L -1 ) were significantly lower (men: 0.29 and 0.22 vs 0.39 and 0.28; women: 0.35 and 0.26 vs 0.50 and 0.32, respectively). A subgroup of 480 patients was prescribed either crushed tablets/suspension (1016 samples) or tablets (1259 samples) at different times. The median dose was again significantly higher in men (500 vs 500) and women (500 vs 450), but the median plasma clozapine and norclozapine concentrations were significantly lower (men: 0.29 and 0.22 vs 0.32 and 0.24; women: 0.30 and 0.24 vs 0.38 and 0.29, respectively). IMPLICATIONS: Poor adherence, sedimentation of suspension before use, and incomplete dosage are potential contributors to the lower median plasma clozapine and norclozapine concentrations observed after use of either crushed clozapine tablets or suspension as compared with tablets. Those administering crushed tablets/suspension should be aware of these factors.

Antipsychotic-Related Fatal Poisoning, England and Wales, 1993-2019: The Impact of Second-Generation Antipsychotics.

BACKGROUND: Deaths from antipsychotic (AP) poisoning have increased in England and Wales despite restriction of the use of thioridazine in 2000. METHODS: We analyzed data from the Office for National Statistics drug-related death database, England and Wales, 1993-2019, to investigate fatal AP poisoning. RESULTS: There were 2286 deaths (62% male patients). Annual numbers of intentional AP-related fatal poisonings (suicides) were relatively stable (1993, 35; 2019, 44; median, 44; range, 30-60). Intentional overdose deaths involving clozapine (96 male, 25 female) increased from 1 in 1994 to 5 in 2003 and have since remained relatively constant (median, 6; range, 3-10 per annum). Unintentional second-generation AP-related fatal poisonings have increased steadily since 1998, featuring in 828 (74%) of all unintentional, AP-related fatal poisonings in the period studied (2019, 89%). There were 181 unintentional clozapine-related deaths, (107 [59%] alone without other drugs ± alcohol) as compared with 291 quetiapine-related deaths (86 [30%] alone without other drugs ± alcohol) and 314 unintentional olanzapine-related deaths (77 [25%] alone without other drugs ± alcohol). Some 75% of all unintentional clozapine- and olanzapine-related deaths were of male patients (78% and 73%, respectively) as compared with 58% of unintentional quetiapine-related fatal poisonings. Clozapine now features prominently in intentional and in unintentional AP-related fatal poisoning in England and Wales. Deaths of male patients predominate in both categories. There were also 77 and 86 deaths attributed to unintentional poisoning with olanzapine and with quetiapine, respectively, in the absence of other drugs. CONCLUSIONS: More effort is needed to prevent unintentional deaths not only from clozapine but also from olanzapine and quetiapine.

Detecting Nuclear Materials in Urban Environments Using Mobile Sensor Networks.

Radiation detectors installed at major ports of entry are a key component of the overall strategy to protect countries from nuclear terrorism. While the goal of deploying these systems is to intercept special nuclear material as it enters the country, no detector system is foolproof. Mobile, distributed sensors have been proposed to detect nuclear materials in transit should portal monitors fail to prevent their entry in the first place. In large metropolitan areas, a mobile distributed sensor network could be deployed using vehicle platforms such as taxis, Ubers, and Lyfts, which are already connected to communications infrastructure. However, performance and coverage that could be achieved using a network of sensors mounted on commercial passenger vehicles has not been established. Here, we evaluate how a mobile sensor network could perform in New York City using a combination of radiation transport and geographic information systems. The geographic information system is used in conjunction with OpenStreetMap data to isolate roads and construct a grid over the streets. Vehicle paths are built using pickup and drop off data from Uber, and from the New York State Department of Transportation. The results show that the time to first detection increases with source velocity, decreases with the number of mobile detectors, and reaches a plateau that depends on the strength of the source.

The Use of Granulocyte Colony-Stimulating Factor in Clozapine Rechallenge: A Systematic Review.

PURPOSE/BACKGROUND: Clozapine is associated with hematological abnormalities, with neutropenia and agranulocytosis of most concern. Granulocyte colony-stimulating factor (G-CSF) has been used to support clozapine rechallenge after neutropenia with the aim of maintaining the neutrophil count. This study aims to explore the practice, use, safety, and efficacy of G-CSF in this context. METHODS/PROCEDURES: We conducted a systematic review to identify all studies investigating or describing G-CSF as a prophylaxis to enable continued clozapine treatment during a rechallenge. FINDINGS/RESULTS: We identified 32 reports of patients who received G-CSF either regularly (n = 23) or as required (n = 9) to support clozapine rechallenge after an episode of neutropenia necessitating discontinuation of clozapine. Seventy-five percent (n = 24) of published cases remained on clozapine with the use of continual prophylactic G-CSF or after single G-CSF administrations (n = 8). Seventy percent (n = 16) of patients in receipt of continual prophylactic G-CSF were successfully maintained on clozapine. However, 1 of the 3 episodes of rechallenge in those with a history of severe agranulocytosis (absolute neutrophil count <0.1 × 10/L) had a recurrence of agranulocytosis at week 9. IMPLICATIONS/CONCLUSIONS: Our findings suggest that G-CSF can sometimes be safely used to support the maintenance of normal neutrophil counts and clozapine use after neutropenia. Publication bias is an important limitation, however. Also, few reports clearly documented the presence or absence of an independent nonclozapine cause of the index neutropenia, which may have increased success rates. Furthermore, adverse events were not systematically recorded. Prospective studies are needed to determine safety because if agranulocytosis occurs on clozapine while supported by G-CSF, there is no obvious alternate rescue therapy to promote granulopoiesis. From the available data, it is not possible to recommend this course of action for someone with a true clozapine agranulocytosis.

Clozapine-Associated Agranulocytosis Treatment With Granulocyte Colony-Stimulating Factor/Granulocyte-Macrophage Colony-Stimulating Factor: A Systematic Review.

PURPOSE/BACKGROUND: Clozapine is associated with hematological abnormalities, notably neutropenia, which may progress to agranulocytosis. Granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) have been used to reduce the frequency and duration of clozapine-associated neutropenia. This review aims to explore the use, efficacy, and tolerability of these cytokines in the treatment of clozapine-associated agranulocytosis. METHODS/PROCEDURES: We conducted a systematic review of published interventional and observational studies, case series, and case reports where G-CSF/GM-CSF was used to treat clozapine-associated agranulocytosis. FINDINGS/RESULTS: We identified 29 reports (40 patients). The median duration of neutrophil recovery time after stopping clozapine and starting cytokine treatment was 7 days (range, 2-13 days) for those with agranulocytosis (absolute neutrophil count < 0.5 × 10 cells/L). Ninety-four percent (n = 29) had no serious adverse reactions, and no deaths occurred. IMPLICATIONS/CONCLUSIONS: Our findings indicate that G-CSF/GM-CSF use is well tolerated and suggest that G-CSF can sometimes be safely used to reduce the duration of neutropenia associated with clozapine use. However, the interpretation of this outcome is difficult, given the likely publication bias for positive outcomes in case reports.

An assessment of the variation in the concentration of acetylcysteine in infusions for the treatment of paracetamol overdose.

BACKGROUND: Intravenous acetylcysteine is the treatment of choice for paracetamol poisoning. A previous UK study in 2001 found that 39% of measured acetylcysteine infusion concentrations differed by >20% from anticipated concentrations. In 2012, the UK Commission on Human Medicines made recommendations for the management of paracetamol overdose, including provision of weight-based acetylcysteine dosing tables. The aim of this study was to assess variation in acetylcysteine concentrations in administered infusions following the introduction of this guidance. METHODS: A 6-month single-centre prospective study was undertaken at a UK teaching hospital. After preparation, 5-ml samples were taken from the first, second and third/any subsequent acetylcysteine infusions. Acetylcysteine was measured in diluted (1:50) samples by high-performance liquid chromatography. Comparisons between measured and expected concentrations based on prescribed weight-based dose and volume were made for each infusion. RESULTS: Ninety samples were collected. There was a variation of ≤10% in measured compared to expected concentration for 45 (50%) infusions, of 10-20% for 27 (30%) infusions, 20.1-50% for 14 (16%) infusions and >50% for four (4%) infusions. There was a median (interquartile range) variation in measured compared to expected concentration of -3.6 mg ml-1 (-6.7 to -2.3) for the first infusion, +0.2 mg ml-1 (-0.9 to +0.4) for the second infusion and -0.3 mg ml-1 (-0.6 to +0.2) for third and fourth infusions. CONCLUSION: There has been a moderate improvement in the variation in acetylcysteine dose administered by infusion. Further work is required to understand the continuing variation and consideration should be given to simplification of acetylcysteine regimes to decrease the risk of administration errors.

Measurement of Clozapine, Norclozapine, and Amisulpride in Plasma and in Oral Fluid Obtained Using 2 Different Sampling Systems.

BACKGROUND: There is a poor correlation between total concentrations of proton-accepting compounds (most basic drugs) in unstimulated oral fluid and in plasma. The aim of this study was to compare clozapine, norclozapine, and amisulpride concentrations in plasma and in oral fluid collected using commercially available collection devices [Thermo Fisher Scientific Oral-Eze and Greiner Bio-One (GBO)]. METHODS: Oral-Eze and GBO samples and plasma were collected in that order from patients prescribed clozapine. Analyte concentrations were measured by liquid chromatography-tandem mass spectrometry. RESULTS: There were 112 participants [96 men, aged (median, range) 47 (21-65) years and 16 women, aged 44 (21-65) years]: 74 participants provided 2 sets of samples and 7 provided 3 sets (overall 2 GBO samples not collected). Twenty-three patients were co-prescribed amisulpride, of whom 17 provided 2 sets of samples and 1 provided 3 sets. The median (range) oral fluid within the GBO samples was 52 (13%-86%). Nonadherence to clozapine was identified in all 3 samples in one instance. After correction for oral fluid content, analyte concentrations in the GBO and Oral-Eze samples were poorly correlated with plasma clozapine and norclozapine (R = 0.57-0.63) and plasma amisulpride (R = 0.65-0.72). Analyte concentrations in the 2 sets of oral fluid samples were likewise poorly correlated (R = 0.68-0.84). Mean (SD) plasma clozapine and norclozapine were 0.60 (0.46) and 0.25 (0.21) mg/L, respectively. Mean clozapine and norclozapine concentrations in the 2 sets of oral fluid samples were similar to those in plasma (0.9-1.8 times higher), that is, approximately 2- to 3-fold higher than those in unstimulated oral fluid. The mean (±SD) amisulpride concentrations (microgram per liter) in plasma (446 ± 297) and in the Oral-Eze samples (501 ± 461) were comparable and much higher than those in the GBO samples (233 ± 318). CONCLUSIONS: Oral fluid collected using either the GBO system or the Oral-Eze system cannot be used for quantitative clozapine and/or amisulpride therapeutic drug monitoring.

Women Administered Standard Dose Imatinib for Chronic Myeloid Leukemia Have Higher Dose-Adjusted Plasma Imatinib and Norimatinib Concentrations Than Men.

BACKGROUND: The standard dose of imatinib for the treatment of chronic-phase chronic myeloid leukemia (CML) is 400 mg·d. A predose plasma imatinib concentration of >1 mg·L is associated with improved clinical response. This study aimed to assess the plasma imatinib and norimatinib concentrations attained in patients with chronic myeloid leukemia administered standard doses of imatinib adjusted for dose, age, sex, body weight, and response. METHODS: We evaluated data from a cohort of patients treated between 2008 and 2014 with respect to dose, age, sex, body weight, and response. RESULTS: The study comprised 438 samples from 93 patients (54 male, 39 female). The median imatinib dose was 400 mg·d in men and in women. The plasma imatinib concentration ranged 0.1-5.0 mg·L and was below 1 mg·L in 20% and 16% of samples from men and women, respectively. The mean dose normalized plasma imatinib and norimatinib concentrations were significantly higher in women in comparison with men. This was partially related to body weight. Mixed effects ordinal logistic regression showed no evidence of an association between sex and plasma imatinib (P = 0.13). However, there was evidence of an association between sex and plasma norimatinib, with higher norimatinib concentrations more likely in women than in men (P = 0.02). CONCLUSIONS: Imatinib therapeutic drug monitoring only provides information on dosage adequacy and on short-term adherence; longer-term adherence cannot be assessed. However, this analysis revealed that approximately 1 in 5 samples had a plasma imatinib concentration <1 mg·L, which was suggestive of inadequate dosage and/or poor adherence and posed a risk of treatment failure. Higher imatinib exposure in women may be a factor in the increased rate of long-term, stable, deep molecular response (undetectable breakpoint cluster-Abelson (BCR-ABL) transcript levels with a PCR sensitivity of 4.5 log, MR4.5) reported in women.

Triazole antifungals used for prophylaxis and treatment of invasive fungal disease in adult haematology patients: Trough serum concentrations in relation to outcome.

Triazole antifungal drugs are widely used for the prophylaxis and treatment of invasive fungal disease (IFD). Efficacy may depend on attaining minimum effective plasma concentrations. The aim of this study was to ascertain the proportion of samples in which the recommended concentrations were achieved in patients given these drugs in relation to outcome. In-patients prescribed standard doses of fluconazole, itraconazole solution, posaconazole suspension, or oral voriconazole for at least one week were studied. Pre-dose serum triazole concentrations were measured using validated methods. There were 359 samples from 90 patients. The median (range) number of samples per patient was 3 (1-13), and the median (range) fluconazole, itraconazole, posaconazole (prophylaxis), posaconazole (treatment), and voriconazole serum concentrations were 5.64 (0.11-18), 0.57 (0-5.3), 0.31 (0.02-2.5), 0.65 (0.02-2.5), and 0.95 (0.10-5.4) mg/l, respectively. The number of samples in which the recommended pre-dose concentrations were achieved was 98 (54%), 9 (20%), 2 (18%), and 29 (49%) for itraconazole, posaconazole (>0.7 mg/l prophylaxis), posaconazole (treatment), and voriconazole, respectively. No significant differences were detected in the median triazole trough concentrations between patients with proven/probable IFD compared to those with no evidence of IFD. However, itraconazole was not detected in 10 samples (7 patients). The small number of patients who achieved the recommended trough posaconazole concentrations may explain the high rate of break-through IFD observed in patients prescribed this drug. Except for fluconazole, the number of patients prescribed standard doses of triazoles who achieved recommended trough triazole concentrations was low. The prospective use of serum triazole measurements assay may have improved outcomes with itraconazole, posaconazole, and with voriconazole.

Automated Analysis of Clozapine and Norclozapine in Human Plasma Using Novel Extraction Plate Technology and Flow-Injection Tandem Mass Spectrometry.

BACKGROUND: Analysis of plasma clozapine and N-desmethylclozapine (norclozapine) for therapeutic drug monitoring purposes is well established. To minimize analysis times and facilitate rapid reporting of results, we have fully automated sample preparation using novel AC Extraction Plates and a Tecan Freedom EVO 100 liquid handling platform, and minimized extract analysis times using flow-injection tandem mass spectrometry (FIA-MS/MS). METHODS: Analytes and deuterium-labeled internal standards were extracted from plasma (100 µL) at pH 10.6 and extracts analyzed directly using tandem mass spectrometry [20 µL injection, 0.7 mL/min methanol carrier flow, analysis time (injection-to-injection) approximately 60 seconds]. RESULTS: Validation data showed excellent intraplate and interplate accuracy (95%-104% nominal concentrations). Interbatch precision (% RSD) at the limit of quantitation (0.01 mg/L) was 3.5% and 5.5% for clozapine and norclozapine, respectively. Matrix effects were observed for both clozapine and norclozapine, but were compensated for by the internal standards. Overall process efficiency was 56%-70% and 66%-77% for clozapine and norclozapine, respectively. Mean relative process efficiency was 98% and 99% for clozapine and norclozapine, respectively. Comparison of results from patient samples (n = 81) analyzed using (1) manual liquid-liquid extraction with liquid chromatography-tandem mass spectrometry (LC-MS/MS) and (2) automated extraction with FIA-MS/MS gave y = 1.01x - 0.002, R(2) = 0.9943 and y = 1.01x + 0.009, R(2) = 0.9957 for clozapine and norclozapine, respectively. Bland-Altman plots revealed a [mean (95% limits of agreement) bias of 0.0074 (-0.04 to 0.06) mg/L and of 0.015 (-0.02 to 0.05) mg/L for clozapine and norclozapine, respectively]. CONCLUSIONS: FIA-MS/MS used with automated extraction offers a rapid, simple, cost-effective alternative to manual liquid-liquid extraction and conventional LC analysis for clozapine therapeutic drug monitoring.

Prevalence and Predictors of Clozapine-Associated Constipation: A Systematic Review and Meta-Analysis.

Constipation is a frequently overlooked side effect of clozapine treatment that can prove fatal. We conducted a systematic review and meta-analysis to estimate the prevalence and risk factors for clozapine-associated constipation. Two authors performed a systematic search of major electronic databases from January 1990 to March 2016 for articles reporting the prevalence of constipation in adults treated with clozapine. A random effects meta-analysis was conducted. A total of 32 studies were meta-analyzed, establishing a pooled prevalence of clozapine-associated constipation of 31.2% (95% CI: 25.6-37.4) (n = 2013). People taking clozapine were significantly more likely to be constipated versus other antipsychotics (OR 3.02 (CI: 1.91-4.77), p < 0.001, n = 11 studies). Meta-regression identified two significant study-level factors associated with constipation prevalence: significantly higher (p = 0.02) rates of constipation were observed for those treated in inpatient versus outpatient or mixed settings and for those studies in which constipation was a primary or secondary outcome measure (36.9%) compared to studies in which constipation was not a specified outcome measure (24.8%, p = 0.048). Clozapine-associated constipation is common and approximately three times more likely than with other antipsychotics. Screening and preventative strategies should be established and appropriate symptomatic treatment applied when required.

Tyrosine kinase inhibitors impair B-cell immune responses in CML through off-target inhibition of kinases important for cell signaling.

Tyrosine kinase inhibitors (TKIs) have significant off-target multikinase inhibitory effects. We aimed to study the impact of TKIs on the in vivo B-cell response to vaccination. Cellular and humoral responses to influenza and pneumococcal vaccines were evaluated in 51 chronic phase chronic myeloid leukemia (CML) patients on imatinib, or second-line dasatinib and nilotinib, and 24 controls. Following vaccination, CML patients on TKI had significant impairment of IgM humoral response to pneumococcus compared with controls (IgM titer 79.0 vs 200 U/mL, P = .0006), associated with significantly lower frequencies of peripheral blood IgM memory B cells. To elucidate whether CML itself or treatment with TKI was responsible for the impaired humoral response, we assessed memory B-cell subsets in paired samples collected before and after imatinib therapy. Treatment with imatinib was associated with significant reductions in IgM memory B cells. In vitro coincubation of B cells with plasma from CML patients on TKI or with imatinib, dasatinib, or nilotinib induced significant and dose-dependent inhibition of Bruton's tyrosine kinase and indirectly its downstream substrate, phospholipase-C-γ2, both important in B-cell signaling and survival. These data indicate that TKIs, through off-target inhibition of kinases important in B-cell signaling, reduce memory B-cell frequencies and induce significant impairment of B-cell responses in CML.