The Effect of Body Weight Changes on Total Plasma Clozapine Concentrations Determined by Applying a Statistical Model to the Data From a Double-Blind Trial.

PURPOSE/BACKGROUND: Some therapeutic drug monitoring studies suggest that increased weight is associated with small increases in clozapine concentrations. The goal of this study was to reanalyze a US double-blind study using a sophisticated statistical model to test whether weight gains from baseline or increases in percentage of body fat from baseline, computed from a published equation, are associated with increased total plasma clozapine concentrations after controlling for the effects of smoking and sex. METHODS/PROCEDURES: Using data from a multidosage randomized double-blind US clozapine trial previously published, a random intercept linear model of steady-state total plasma clozapine concentrations was fitted to 424 concentrations from 47 patients. FINDINGS/RESULTS: After adjusting for sex and smoking, (1) a 1-kg gain in body weight during clozapine treatment was significantly associated with a 1.4% increase in total plasma clozapine concentrations (95% confidence interval = 0.55 to 2.3) and (2) a 1-point increase in percentage of body fat during clozapine treatment was significantly associated with a 5.4% increase in total clozapine concentration (2.5 to 8.3) in females and 1.4% (-1.1 to 4.0) in males. IMPLICATIONS/CONCLUSIONS: As hypothesized, weight increases during clozapine treatment, which probably reflect increases in fat tissue, were associated with increases in total plasma concentrations. Pending further replication in other samples, it seems likely that clozapine may deposit in body fat and that this may decrease clozapine clearance. This change may be small in most patients but may be clinically relevant in females with major gains in body fat.

Increased Prevalence of Rare Copy Number Variants in Treatment-Resistant Psychosis.

BACKGROUND: It remains unknown why ~30% of patients with psychotic disorders fail to respond to treatment. Previous genomic investigations of treatment-resistant psychosis have been inconclusive, but some evidence suggests a possible link between rare disease-associated copy number variants (CNVs) and worse clinical outcomes in schizophrenia. Here, we identified schizophrenia-associated CNVs in patients with treatment-resistant psychotic symptoms and then compared the prevalence of these CNVs to previously published schizophrenia cases not selected for treatment resistance. METHODS: CNVs were identified using chromosomal microarray (CMA) and whole exome sequencing (WES) in 509 patients with treatment-resistant psychosis (a lack of clinical response to ≥3 adequate antipsychotic medication trials over at least 5 years of psychiatric hospitalization). Prevalence of schizophrenia-associated CNVs in this sample was compared to that in a previously published large schizophrenia cohort study. RESULTS: Integrating CMA and WES data, we identified 47 cases (9.2%) with at least one CNV of known or possible neuropsychiatric risk. 4.7% (n = 24) carried a known neurodevelopmental risk CNV. The prevalence of well-replicated schizophrenia-associated CNVs was 4.1%, with duplications of the 16p11.2 and 15q11.2-q13.1 regions, and deletions of the 22q11.2 chromosomal region as the most frequent CNVs. Pairwise loci-based analysis identified duplications of 15q11.2-q13.1 to be independently associated with treatment resistance. CONCLUSIONS: These findings suggest that CNVs may uniquely impact clinical phenotypes beyond increasing risk for schizophrenia and may potentially serve as biological entry points for studying treatment resistance. Further investigation will be necessary to elucidate the spectrum of phenotypic characteristics observed in adult psychiatric patients with disease-associated CNVs.

Lixivaptan safely and effectively corrects serum sodium concentrations in hospitalized patients with euvolemic hyponatremia.

Hyponatremia is a common electrolyte disorder associated with increased morbidity and mortality, particularly in the elderly. Lixivaptan, a new selective vasopressin V2-receptor antagonist, safely corrected serum sodium concentrations in phase II studies of patients with euvolemic hyponatremia. Here our multinational, double-blind, placebo-controlled, phase III study assessed the effect of lixivaptan on serum sodium concentrations in 106 initially hospitalized patients with euvolemic hyponatremia (serum sodium less than 130 mmol/l). Of them, 52 were randomized to receive placebo and 54 received 50 mg lixivaptan once daily and were then titrated to receive 25-100 mg once daily depending on serum sodium concentration. Fluid restriction was at the investigator's discretion. Initial titration occurred in a monitored inpatient setting; patients were then treated as outpatients for a total of 30 days. The primary end point was the change in serum sodium concentration from baseline to day 7. Lixivaptan significantly increased the serum sodium concentration from baseline to day 7 (the primary end point) by 6.7 mmol/l compared with placebo (4.5 mmol/l; P=0.034). Importantly, the serum sodium concentration was normalized safely and more rapidly in patients receiving lixivaptan than placebo (P=0.004) and was well tolerated. After drug discontinuation, serum sodium concentrations decreased to near-baseline levels within 7 days. Thus, lixivaptan safely and effectively corrects serum sodium concentrations in patients with euvolemic hyponatremia.

Oral lixivaptan effectively increases serum sodium concentrations in outpatients with euvolemic hyponatremia.

Hyponatremia is the most common electrolyte disorder in clinical practice. Its incidence increases with age and it is associated with increased morbidity and mortality. Recently, the vaptans, antagonists of the arginine vasopressin pathway, have shown promise for safe treatment of hyponatremia. Here we evaluated the efficacy, safety, and tolerability of oral lixivaptan, a selective vasopressin V2-receptor antagonist, for treatment of nonhospitalized individuals with euvolemic hyponatremia (sodium less than 135 mmol/l) in a multicenter, randomized, double-blind, placebo-controlled, phase III study. About half of the 206 patients were elderly in a chronic care setting. Of these patients, 52 were given a placebo and 154 were given 25-100 mg per day lixivaptan, titrated based on the daily serum sodium measurements. Compared with placebo (0.8 mmol/l), the serum sodium concentration significantly increased by 3.2 mmol/l from baseline to day 7 (primary efficacy endpoint) with lixivaptan treatment. A significantly greater proportion of patients that received lixivaptan achieved normal serum sodium (39.4%) by day 7 relative to placebo (12.2%). Overall, lixivaptan was considered safe and well-tolerated. Thus, oral lixivaptan can be safely initiated in the outpatient setting and effectively increases serum sodium concentrations in outpatients with euvolemic hyponatremia.

Treatment-resistant psychotic symptoms and early-onset dementia: A case report of the 3q29 deletion syndrome.

The 3q29 deletion is a rare copy number variant associated with neurodevelopmental and psychiatric disorders, including a >40-fold increased risk for schizophrenia. Current understanding of the clinical phenotype is derived primarily from published cases of patients in childhood or early adolescence. Symptoms include mild to moderate learning disability, developmental delay, facial dysmorphism, microcephaly, ocular disorders, and gastrointestinal abnormalities. There is, however, a lack of detailed longitudinal case studies describing 3q29 deletion syndrome in adults with psychosis. In this case report, we describe the lifetime clinical portrait of a 57-year-old woman with 3q29 deletion syndrome, treatment-resistant psychotic symptoms, multiple medical comorbidities, and a previously unreported co-occurrence of early-onset dementia.

Treatment-resistant psychotic symptoms and the 15q11.2 BP1-BP2 (Burnside-Butler) deletion syndrome: case report and review of the literature.

The 15q11.2 BP1-BP2 (Burnside-Butler) deletion is a rare copy number variant impacting four genes (NIPA1, NIPA2, CYFIP1, and TUBGCP5), and carries increased risks for developmental delay, intellectual disability, and neuropsychiatric disorders (attention-deficit/hyperactivity disorder, autism, and psychosis). In this case report (supported by extensive developmental information and medication history), we present the complex clinical portrait of a 44-year-old woman with 15q11.2 BP1-BP2 deletion syndrome and chronic, treatment-resistant psychotic symptoms who has resided nearly her entire adult life in a long-term state psychiatric institution. Diagnostic and treatment implications are discussed.

Long-Term Safety and Tolerability of Valbenazine (NBI-98854) in Subjects with Tardive Dyskinesia and a Diagnosis of Schizophrenia or Mood Disorder.

BACKGROUND: The short-term safety profile of once-daily valbenazine (NBI-98854) has been evaluated in several double-blind, placebo-controlled (DBPC) trials in adults with tardive dyskinesia (TD) who had a diagnosis of schizophrenia/schizoaffective (SCHZ) disorder or mood disorder. Studies with longer treatment duration (up to 48 weeks) were conducted to evaluate the long-term safety of this novel drug in subjects with TD. METHODS: The pooled long-term exposure (LTE) population included valbenazine-treated subjects from 3 studies: KINECT (NCT01688037: 6-week DBPC, 6-week open-label); KINECT 3 (NCT02274558: 6-week DBPC, 42-week blinded extension, 4-week drug-free follow-up); KINECT 4 (NCT02405091: 48-week open-label, 4-week drug-free follow-up). Safety assessments included adverse events (AEs), laboratory tests, vital signs, electrocardiograms (ECGs), and extrapyramidal symptom (EPS) scales. Psychiatric stability was monitored using the Positive and Negative Syndrome Scale (PANSS) and Calgary Depression Scale for Schizophrenia (CDSS) (SCHZ subgroup), as well as the Montgomery-Åsberg Depression Rating Scale (MADRS) and Young Mania Rating Scale (YMRS) (mood subgroup). All data were analyzed descriptively. RESULTS: The LTE population included 430 subjects (KINECT, n = 46; KINECT 3, n = 220; KINECT 4, n = 164), 71.7% with SCHZ and 28.3% with a mood disorder; 85.5% were taking an antipsychotic (atypical only, 69.8%; typical only or typical + atypical, 15.7%). In the LTE population, treatment-emergent AEs (TEAEs) and discontinuations due to AEs were reported in 66.5% and 14.7% of subjects, respectively. The TEAE incidence was lower in the SCHZ subgroup (64.4%) than in the mood subgroup (71.9%). The 3 most common TEAEs in the SCHZ subgroup were urinary tract infection (UTI, 6.1%), headache (5.8%), and somnolence (5.2%). The 3 most common TEAEs in the mood subgroup were headache (12.4%), UTI (10.7%), and somnolence (9.1%). Mean score changes from baseline to end of treatment (Week 48) indicated that psychiatric stability was maintained in the SCHZ subgroup (PANSS Total, -3.4; PANSS Positive, -1.1; PANSS Negative, -0.1; PANSS General Psychopathology, -2.2; CDSS total, -0.4) and the mood subgroup (MADRS Total, 0.0; YMRS Total, -1.2). These scores remained generally stable during the 4-week drug-free follow-up periods. In the LTE population, mean changes in laboratory parameters, vital signs, ECG, and EPS scales were generally minimal and not clinically significant. CONCLUSION: Valbenazine appeared to be well tolerated in adults with TD who received up to 48 weeks of treatment. In addition to long-term efficacy results (presented separately), these results suggest that valbenazine may be appropriate for the long-term management of TD regardless of underlying psychiatric diagnosis (SCHZ disorder or mood disorder).

Efficacy of Valbenazine (NBI-98854) in Treating Subjects with Tardive Dyskinesia and Mood Disorder.

BACKGROUND: Valbenazine (VBZ, NBI-98854) is a novel vesicular monoamine transporter 2 (VMAT2) inhibitor approved for the treatment of tardive dyskinesia (TD). The KINECT 3 study (NCT02274558) evaluated the effects of VBZ on TD in subjects with mood disorder or schizophrenia/schizoaffective disorder (SCHZ, presented separately) who received up to 48 weeks of treatment. METHODS: KINECT 3 included: 6-week, double-blind, placebo (PBO)-controlled (DBPC) period (205 completers); 42-week VBZ extension (VE) period (124 completers); 4-week washout period (121 completers). Subjects entering the DBPC were randomized 1:1:1 to once-daily VBZ 80 mg, VBZ 40 mg, or PBO; stable concomitant antipsychotic medication regimens were allowed. Subjects completing the DBPC and entering the VE period were re-randomized (blinded) from PBO to VBZ (80 or 40 mg) or continued VBZ treatment at the same dose. Efficacy assessments included: mean changes from baseline in Abnormal Involuntary Movement Scale (AIMS) total score (items 1-7); mean Clinical Global Impression of Change (CGI-TD) scores; AIMS responders (subjects with ≥50% score reduction from baseline); and CGI-TD responders (subjects with score ≤2 ["much improved" or "very much improved"]). Treatment effect sizes (Cohen's d) and numbers needed to treat (NNTs) were analyzed for DBPC outcomes. RESULTS: Efficacy analyses were conducted in 77 subjects (DBPC) and 73 subjects (VE) with a mood disorder. At Week 6 (end of DBPC), AIMS mean score improvements were greater in the VBZ groups (in a dose-related pattern) than in the PBO group (80 mg, -3.6, d = 0.94; 40 mg, -2.4, d = 0.55; PBO, -0.7). AIMS mean score changes at Week 48 (end of VE) showed continued TD improvement during long-term VBZ treatment (80 mg, -5.8; 40 mg, -4.2). By Week 52 (end of washout), AIMS mean scores in both dose groups were returning toward baseline levels, indicating re-emergence of TD. CGI-TD scores showed a similar pattern: Week 6 (80 mg, 2.7, d = 0.64; 40 mg, 2.9, d = 0.39; PBO, 3.2), Week 48 (80 mg, 2.0; 40 mg, 2.2), Week 52 (80 mg, 3.6; 40 mg, 2.8). AIMS responder rates (≥50% score reduction) were greater with VBZ vs PBO at Week 6 (80 mg, 38.5%, NNT = 4; 40 mg, 19.0%, NNT = 9; PBO, 7.7%), were increased at Week 48 (80 mg, 56.0%; 40 mg, 33.3%), and lower after VBZ washout (Week 52 80 mg, 16.7%; 40 mg, 27.8%). CGI-TD responder rates followed a similar pattern: Week 6 (80 mg, 34.6%, NNT = 6; 40 mg, 28.6%, NNT = 8; PBO, 15.4%), Week 48 (80 mg, 80.0%; 40 mg, 61.1%), Week 52 (80 mg, 25.0%; 40 mg, 44.4%). CONCLUSION: Sustained TD improvements were found in subjects with a mood disorder who received up to 48 weeks of VBZ, with TD reverting toward baseline severity when assessed 4 weeks after treatment withdrawal. Together with results from SCHZ subjects and the long-term safety profile (presented separately), these results indicate that long-term VBZ can be beneficial for managing TD regardless of psychiatric diagnosis.

Successful Treatment of Severe Tardive Dyskinesia with Valbenazine, Including a Patient's Perspective.

BACKGROUND Tardive dyskinesia (TD) is a chronic involuntary movement disorder frequently induced by dopamine receptor blockers, particularly first-generation antipsychotics. Until recently, management of TD was restricted to lowering the dose of the current medication, switching to another medication, or using off-label treatments with insufficient evidence of efficacy. Valbenazine, a vesicular monoamine transporter-2 (VMAT2) inhibitor, became the first drug to be approved by the FDA specifically for the treatment of TD. CASE REPORT We describe the case of a 49-year-old African-American woman who was diagnosed with bipolar disorder at the age of 34 and treated with lithium carbonate (900 mg daily) and citalopram (10 mg daily). She also received low doses of second-generation antipsychotics for weeks at a time, but these were always discontinued due to severe sedation. Over a decade later, at the age of 45, she experienced rapid onset of severe TD symptoms. She enrolled in a phase III double-blind clinical trial and received valbenazine 80 mg, with encouraging results. CONCLUSIONS Once-daily dosing of valbenazine (80 mg) was effective and safe over a long period, even in this atypical case of severe and rapid-onset TD.

Intramuscular aripiprazole for the treatment of acute agitation in patients with schizophrenia or schizoaffective disorder: a double-blind, placebo-controlled comparison with intramuscular haloperidol.

INTRODUCTION: This double-blind, placebo-controlled study investigated the efficacy and safety of intramuscular (IM) aripiprazole and IM haloperidol for the treatment of acute agitation in patients with schizophrenia or schizoaffective disorder. MATERIALS AND METHODS: Four-hundred and forty-eight patients were randomized (2:2:1 ratio) to IM aripiprazole 9.75 mg, IM haloperidol 6.5 mg, or IM placebo. Patients could receive up to three injections over the first 24 h, with second and third injections administered > or =2 and > or =4 h, respectively, after the first if deemed clinically necessary. Primary efficacy measure was mean change in Positive and Negative Syndrome Scale Excited Component (PEC) score from baseline to 2 h. RESULTS: Mean improvement in PEC at 2 h was significantly greater for IM aripiprazole (-7.27) vs placebo (-4.78; p<0.001); IM aripiprazole was noninferior to IM haloperidol (-7.75) on PEC. All secondary efficacy measures showed significantly greater improvements at 2 h for IM aripiprazole and IM haloperidol over placebo. Mean number of injections/patient and percentage of patients requiring benzodiazepines were significantly lower for IM aripiprazole vs placebo (p<0.01). IM aripiprazole was well tolerated. Extrapyramidal symptom-related adverse events were similar for aripiprazole (1.7%) and placebo (2.3%) and lower than with haloperidol (12.6%). CONCLUSION: These results show that IM aripiprazole is an effective treatment, comparable to IM haloperidol, and well-tolerated for acute agitation in patients with schizophrenia.

Clozapine augmented with risperidone in the treatment of schizophrenia: a randomized, double-blind, placebo-controlled trial.

OBJECTIVE: The authors evaluated the efficacy and safety of augmenting clozapine with risperidone in patients with treatment-resistant schizophrenia. METHOD: In a randomized, double-blind, placebo-controlled 12-week trial, 40 patients unresponsive or partially responsive to clozapine monotherapy received a steady dose of clozapine combined with either placebo (N=20) or up to 6 mg/day of risperidone (N=20). Patient psychopathology was assessed at 2-week intervals with the Brief Psychiatric Rating Scale (BPRS) and the Scale for the Assessment of Negative Symptoms (SANS), among other measures. Movement disorders were assessed with the Simpson-Angus Rating Scale. RESULTS: From baseline to week 6 and week 12, mean BPRS total and positive symptom subscale scores were reduced significantly in both groups, but the reductions were significantly greater with clozapine/risperidone treatment. Reductions in SANS scores were also significantly greater with clozapine/risperidone treatment than with clozapine/placebo. The adverse event profile for clozapine/risperidone treatment was similar to that for clozapine/placebo. Simpson-Angus Rating Scale scores were lower with clozapine/risperidone treatment throughout the trial but increased to approach those of clozapine/placebo treatment at week 12. Clozapine/risperidone treatment did not induce additional weight gain, agranulocytosis, or seizures compared with clozapine/placebo treatment. CONCLUSIONS: In patients with a suboptimal response to clozapine, the addition of risperidone improved overall symptoms and positive and negative symptoms of schizophrenia. The combination appears to be safe and well tolerated. Augmentation of clozapine with risperidone may provide additional clinical benefit for patients who are nonresponsive or only partially responsive to clozapine alone.

Plasma clozapine concentration coefficients of variation in a long-term study.

Kurz et al. conducted the first study of the intra-individual variability of clozapine plasma concentrations but did not take into account the effect of smoking and co-medication. As patients were receiving varying doses, Kurz et al. standardized plasma levels by using a plasma level/dose/kg ratio. In 15 patients, the mean coefficient of variation (CV) was 53% (S.D. = 21). In this new study, plasma clozapine and norclozapine concentrations were measured every 2 weeks in 47 patients randomized to 100, 300, or 600 mg/day for 16-week double-blind clozapine trials under controlled conditions (stable smoking, limited co-medication and absence of caffeinated beverages). For 100, 300 and 600 mg/day, the respective mean CVs for plasma clozapine concentrations were 23% (S.D. = 14), 19% (S.D.= 11) and 18% (S.D. = 8). For the combined concentrations of clozapine and norclozapine, the respective mean CVs were 20% (S.D. = 13), 16% (S.D. = 9) and 15% (S.D. = 7). Under 100 mg/day, the mean CV for clozapine concentrations was significantly higher for heavy smokers than non-heavy smokers (32%, S.D. = 3 vs. 19%, S.D. = 8) (p = 0.03). Studies of CVs in other environments are needed. Clozapine CVs may be important in order to understand the importance of variations around the therapeutic range and to interpret drug interactions above the usual noise of measuring plasma concentrations.

Does clozapine decrease smoking?

McEvoy et al.'s study in 1999, which used cotinine levels but had limited power, suggested that clozapine treatment may be associated with a mild smoking decrease (particularly when plasma clozapine levels are > 150 ng/ml). Some naturalistic studies also suggest that clozapine treatment may be associated with a mild smoking decrease. The present study included 38 schizophrenic daily smokers from a double-blind clozapine trial. Five analyses were tested for significant decreases in plasma cotinine levels from a haloperidol baseline to: (1) the end of clozapine trials regarding clozapine doses (100, 300 or 600 mg/day), (2) the end of the clozapine trial where the highest plasma clozapine level was achieved, (3) the end of the clozapine trial where a clozapine level in the 150-450 ng/ml range was achieved, (4) the end of the first clozapine trial regardless of clozapine dose, and (5) the end of the last clozapine trial in the study. The first and straightforward analysis by dose showed no clozapine effects on smoking. The second and the third analyses (an attempt to mimic the design by McEvoy et al. [McEvoy, J.P., Freudenreich, O., Wilson, W.H., 1999. Smoking and therapeutic response to clozapine in patients with schizophrenia. Biol. Psychiat. 46, 125-129.]) also indicated that there was not a significant effect of clozapine on smoking. The fourth and five analyses were also negative. None of the five analyses in our clozapine trial demonstrated that clozapine had major effects on smoking. This study cannot rule out that in some subjects, clozapine treatment may be associated with a small decrease in smoking. New prospective longitudinal studies using repeated cotinine and clozapine levels are needed to explore whether clozapine may reduce smoking in some patients.

Effects of elevated serum prolactin on bone mineral density and bone metabolism in female patients with schizophrenia: a prospective study.

OBJECTIVE: This study was designed to prospectively examine differential effects of sustained "high" and "low" serum prolactin levels on bone mineral density and peripheral markers of bone metabolism. METHOD: A dual-energy X-ray absorptiometer was used to measure bone mineral density. Peripheral markers of bone formation and resorption were used to measure bone metabolism in 14 Caucasian female patients with schizophrenia treated with risperidone or olanzapine monotherapy over 12 months. RESULTS: Analyses of variance failed to show an association between elevated prolactin and bone mineral loss over time. However, higher rates of bone formation and resorption were seen in those with high prolactin levels. CONCLUSIONS: The results failed to show that elevated prolactin accelerates bone mineral density loss. However, sustained hyperprolactinemia did have an impact on the rate of bone metabolism. Perhaps higher prolactin levels over longer time periods are necessary before the metabolic processes become uncoupled, leading to bone mineral density loss.

Prevalence of hyperprolactinemia in schizophrenia: association with typical and atypical antipsychotic treatment.

OBJECTIVE: To evaluate the prevalence and severity of hyperprolactinemia among a large sample of patients with schizophrenia and related psychotic disorders treated with typical and atypical antipsychotic medications. METHOD: Three electronic databases (general medical, psychiatric, and pharmacologic) containing the census data from November 2002 through March 2003 for a state-funded, inpatient hospital serving the chronically mentally ill were merged (N = 470). This database was purged of patient names, while the unique hospital identification number and demographic variables in each record were retained. These records were then screened to exclude patients with medications (except neuroleptics) or medical conditions known to elevate or suppress prolactin, leaving an overall sample (N = 422) in which to evaluate the prevalence of hyperprolactinemia. The sample was composed of patients with DSM-IV schizophrenia (N = 213), other related psychotic disorders (N = 131), mood disorders (N = 44), and other disorders (N = 34). RESULTS: For the overall sample (N = 422), which combined men and women, the mean serum prolactin level was 41.5 ng/mL; 290 of 422 patients were above the normal range. For women (N = 133), the mean serum prolactin level was 57.9 ng/mL, and 67% had levels above normal. For men (N = 289), the mean level was 33.9 ng/mL, with a 70% prevalence of hyperprolactinemia. While age did not influence the prevalence of elevated prolactin among men, age (reflecting reproductive status) was a significant variable in women; older age was associated with lower prolactin levels. For the study sample, a highly significant correlation was observed between neuroleptic dose (chlorpromazine equivalent) and serum prolactin level; however, this relationship was not determined on a medication-by-medication basis. Medications known to elevate prolactin were associated with higher prevalence rates of hyperprolactinemia, and "prolactin-sparing" medications had lower prevalence rates. However, when they were used in combination, the prolactin-elevating medication overwhelmed the effects of prolactin-sparing medication. CONCLUSIONS: This study suggested that neuroleptic treatment of schizophrenia is strongly associated with hyperprolactinemia and showed important differences between prolactin-sparing and prolactin-elevating medications.

Clozapine-induced agranulocytosis is associated with rare HLA-DQB1 and HLA-B alleles.

Clozapine is a particularly effective antipsychotic medication but its use is curtailed by the risk of clozapine-induced agranulocytosis/granulocytopenia (CIAG), a severe adverse drug reaction occurring in up to 1% of treated individuals. Identifying genetic risk factors for CIAG could enable safer and more widespread use of clozapine. Here we perform the largest and most comprehensive genetic study of CIAG to date by interrogating 163 cases using genome-wide genotyping and whole-exome sequencing. We find that two loci in the major histocompatibility complex are independently associated with CIAG: a single amino acid in HLA-DQB1 (126Q) (P=4.7 × 10(-14), odds ratio (OR)=0.19, 95% confidence interval (CI)=0.12-0.29) and an amino acid change in the extracellular binding pocket of HLA-B (158T) (P=6.4 × 10(-10), OR=3.3, 95% CI=2.3-4.9). These associations dovetail with the roles of these genes in immunogenetic phenotypes and adverse drug responses for other medications, and provide insight into the pathophysiology of CIAG.

Motor deficits associated with mild, chronic hyponatremia: a factor analytic study.

Chronic hyponatremia (CHN) has traditionally been considered asymptomatic. If symptoms are observed, they are often mistakenly attributed to the underlying disorder. However, in recent studies neuropsychological deficits have been associated with CHN. The authors sought to determine the association between CHN and motor deficits. They used previously collected data, and 41 subjects with hyponatremia were included. An exploratory factor analysis with principal component analysis (PCA) was performed (eigenvalues >1.0). Factor scores were generated for each subject based on the resultant PCA factor structure. Finally, partial correlations were computed to measure the degree of association between baseline serum sodium concentration [Na+] and individual neuropsychological factor scores with the effect of age removed. All significance tests were performed using 2-tailed comparisons with alpha level of p ≤ .05. A 3-factor model emerged accounting for 70.17% of the total variance, including 1 factor that loaded primarily with motor speed and reaction time. A significant correlation was observed between this motor factor and serum [Na+] (r = -.477, p = .002). These findings add to previous observations suggesting that CHN is associated with subtle yet harmful motor deficits.