Pharmacogenetics of antipsychotics: useful for the clinician?

Therapeutic effect of adjunctive N-acetyl cysteine (NAC) on symptoms of chronic schizophrenia: A double-blind, randomized clinical trial

BACKGROUND

Schizophrenia is one of the most disabling psychiatric syndromes with the prevalence of 1% in the general population. Despite availability of various antipsychotics, negative symptoms and cognitive impairment are difficult to treat. In addition antipsychotic monotherapy is not effective in most of these patients. Current evidence indicates the roles of glutamatergic system in this disorder. N-acetyl cysteine (NAC) also increases extracellular glutamate. This study was conducted to evaluate the clinical effects of oral NAC as an add-on to maintenance medication for the treatment of chronic schizophrenia.

MATERIALS AND METHODS

This 12-week, double-blind, randomized, placebo-controlled, clinical trial was performed to determine the effectiveness of 1200mg N-acetyl cysteine as an adjunctive treatment with conventional antipsychotic medications in 84 patients with chronic schizophrenia. The subjects were evaluated with the Positive and Negative Syndrome Scale (PANSS), Mini-Mental State Examination (MMSE), and a standard neuropsychological screening test. Data were analyzed with SPSS-16 software.

RESULTS

NAC-treated patients showed significantly improvement in the positive (F=5.47, P=0.02) and negative (F=0.20, df=1) PANSS subscale. Also the general and total PANSS score of NAC group declined over times whilst it was increased for placebo group. Regarding cognitive functions, improvement was observed in some explored areas, such as attention, short-term and working memory, executive functioning and speed of processing. There was no significant difference between the 2 groups in the frequency of adverse effects.

CONCLUSION

The present study detected improvement in positive, negative, general and total psychopathology symptoms as well as cognitive performance with NAC treatment. It is also well-tolerated, safe and easy-to-use agent as an effective therapeutic strategy to improve outcome in schizophrenia treatment.

Rational Use of Second-Generation Antipsychotics for the Treatment of ICU Delirium

Delirium, described as an acute neuropsychiatric syndrome, occurs commonly in critically ill patients and leads to many negative outcomes including increased mortality and long-term cognitive deficits. Despite the lack of clinical data supporting the use of antipsychotics for the management of intensive care unit (ICU) delirium, pharmacological interventions are often needed to control acutely agitated patients. Given that the most current guidelines do not advocate the use of haloperidol for either the prevention or treatment of ICU delirium due to a lack of evidence, second-generation antipsychotics (SGAs) have been commonly used as alternatives to haloperidol for ICU patients with delirium. Nonetheless, the evidence supporting the use of SGAs to treat ICU delirium remains limited. This review is designed to assess the available clinical evidence and highlights the different neuropharmacological and safety properties of SGAs in order to guide the rational use of SGAs for the treatment of ICU delirium.

Histamine H3 receptor as a potential target for cognitive symptoms in neuropsychiatric diseases

The potential contributions of the brain histaminergic system in neurodegenerative diseases, and the possiblity of histamine-targeting treatments is attracting considerable interests. The histamine H3 receptor (H3R) is expressed mainly in the central nervous system, and is, consequently, an attractive pharmacological target. Although recently described clinical trials have been disappointing in attention deficit hyperactivity disorder (ADHD) and schizophrenia (SCH), numerous H3R antagonists, including pitolisant, demonstrate potential in the treatment of narcolepsy, excessive daytime sleepiness associated with cognitive impairment, epilepsy, and Alzheimer's disease (AD). This review focuses on the recent preclinical as well as clinical results that support the relevance of H3R antagonists for the treatment of cognitive symptoms in neuropsychiatric diseases, namely AD, epilepsy and SCH. The review summarizes the role of histaminergic neurotransmission with focus on these brain disorders, as well as the effects of numerous H3R antagonists on animal models and humans.

Frequencies of Functional Polymorphisms in Three Pharmacokinetic Genes of Clinical Interest within the Admixed Puerto Rican Population

OBJECTIVE

This cross-sectional study was aimed at determining the allele frequencies for the CYP2C19*2, CYP2C19*3, CYP2D6*10 and PON1 (rs662) polymorphisms in the Puerto Rican population. The CYP2C19, CYP2D6 and PON1 genes are known to be associated with functional changes in drug metabolism and activation. Individuals carrying the aforementioned polymorphisms are at a higher risk of suffering from drug-induced adverse events and/ or unresponsiveness from a variety of drugs that includes antidepressants, atypical antipsychotics and antiplatelet compounds. Information on the frequency of these polymorphisms is more commonly found on homogeneous populations, but is scarce in highly heterogeneous populations like Hispanics, as in the case of Puerto Ricans.

METHOD

Genotyping was carried out in 100 genomic DNA samples from dried blood spots supplied by the Puerto Rican Newborn Screening program using Taqman® Genotyping Assays.

RESULTS

The Minor Allele Frequencies (MAF) obtained were 9% for CYP2C19*2 and CYP2D6*10, 50% for PON1 (rs662), while the CYP2C19*3 variant was not detected in our study. Furthermore, Hardy Weinberg equilibrium analysis was assessed as well as a comparison between Puerto Rico and other reference populations using a Z-test for proportions.

CONCLUSION

The observed allele and genotype frequencies on these relevant pharmacogenes in Puerto Ricans were more closely related to those early reported in two other reference populations of Americans (Mexicans and Colombians).

Effect of Animal Condition and Fluvoxamine on the Result of [(18)F]N-3-Fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) Nortropane ([(18)F]FP-CIT) PET Study in Mice

PURPOSE

PET (positron emission tomography) is a noninvasive imaging technique, visualizing biological aspects in vivo. In animal models, the result of PET study can be affected more prominently than in humans by the animal conditions or drug pretreatment. We assessed the effects of anesthesia, body temperature, and pretreatment with selective serotonin reuptake inhibitor on the results of [(18)F]N-3-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) nortropane ([(18)F]FP-CIT) PET in mice.

METHODS

[(18)F]FP-CIT PET of C57BL/6 mice was performed in three different conditions: (1) anesthesia (isoflurane) with active warming (38°C) as a reference; (2) no anesthesia or warming; (3) anesthesia without warming at room temperature. Additional groups of mice pretreated with escalating doses of fluvoxamine (5, 20, 40, 80 mg/kg) were imaged in condition (1). The time activity curve and standardized uptake value of the striatum, cerebral cortex, and bone were compared among these conditions.

RESULTS

In all conditions, radioactivities of the striatum and cortex tended to form a plateau after rapid uptake and washout, but that of bone tended to increase gradually. When anesthetized without any warming, all the mice developed hypothermia and showed reduced bone uptake with slightly increased striatal and cortical uptakes compared to the reference condition. In conditions without anesthesia, striatal and cortical uptakes were reduced, whereas the bone uptake showed no change. Pretreatment with fluvoxamine increased the striatal uptake and striatal specific to cortical non-specific uptake ratio, whereas the bone uptake was reduced.

CONCLUSION

Anesthesia, body temperature, and fluvoxamine affect the result of [(18)F]FP-CIT PET in mice by altering striatal and bone uptakes.

Iloperidone: A new drug for the treatment of schizophrenia

PURPOSE

The pharmacology, pharmacokinetics, pharmacogenomics, clinical efficacy, and safety and tolerability profile of iloperidone for the treatment of schizophrenia are reviewed.

SUMMARY

Iloperidone is an atypical antipsychotic that recently received marketing approval from the Food and Drug Administration for the acute treatment of schizophrenia. Iloperidone is a pure antagonist and the first antipsychotic to have pharmacogenomic studies indicate predictive response based on six identified polymorphisms. Pharmacokinetic studies have determined that iloperidone is well absorbed orally, with a bioavailability of 96%. Phase II and III clinical trials have shown iloperidone to improve symptoms of schizophrenia, based on the Positive and Negative Symptom Scale, Brief Psychiatric Rating Scale, and Clinical Global Impressions-Severity scores (p < 0.05). Iloperidone has established tolerability at recommended dosages of up to 24 mg daily; however, the dosage must be slowly increased over seven days, and twice-daily administration is required to avoid orthostatic hypotension. The most common adverse effects associated with iloperidone were dizziness, dry mouth, fatigue, nasal congestion, orthostatic hypotension, somnolence, tachycardia, and weight gain. Safety studies have also found that iloperidone increases the risk of Q-Tc interval prolongation, similar to that seen with ziprasidone. Minimal changes in glucose and lipid abnormalities were seen in short-term (4- and 6-week) and long-term (52-week) studies, indicating a low chance of metabolic disturbance with iloperidone.

CONCLUSION

Iloperidone may be a viable and safe option for the treatment of schizophrenia in adult patients, especially for patients who cannot tolerate other antipsychotic agents. However, iloperidone lacks a clear benefit over other antipsychotic agents.

Association of HTR2C, but not LEP or INSIG2, genes with antipsychotic-induced weight gain in a German sample

Background: Drug-induced bodyweight gain (BWG) is a serious concern in pharmacotherapy with second-generation antipsychotics. The interindividual variability is likely to be modulated by genetic factors. In the past, pharmacogenetic studies yielded conflicting results, and none of the identified genetic alterations exerts sufficient predictive value for this severe side effect of psychopharmacotherapy. Aim: We aimed to contribute to the replication and extension of prior association findings and investigated the genes encoding serotonin 2C receptor (HTR2C), insulin-induced gene 2 (INSIG2) and leptin (LEP). Patients & methods: We investigated the association of HTR2C, LEP and INSIG2 SNPs with antipsychotic-induced BWG in 128 German schizophrenic patients. Genotyping was performed for nine SNPs (HTR2C: rs498207, rs3813928, rs6318 and rs3813929; INSIG2: rs17587100, rs10490624, rs17047764 and rs7566605; LEP: rs7799039). Association analysis included logistic regression analysis and Pearson´s χ2 tests. Results: We report a significant association of three HTR2C SNPs (rs498207, rs3813928 and rs3813929) and of the respective haplotype with antipsychotic-induced BWG. Regarding the X-chromosomal SNP rs498207, individuals with AA/A genotype gained more weight than those with GG/G genotype. The association observed with the SNP rs498207 was also significant after correcting for multiple testing (p = 0.0196). No association was found for INSIG2 and LEP SNPs. Conclusion: The results contribute to the accumulating evidence for an association of the X-chromosomal HTR2C gene with antipsychotic-induced BWG. The proposed underlying mechanisms include decreased HTR2C gene expression with reduced 5-HT-modulated activation of hypothalamic proopiomelanocortin-neurons, and inverse 5-HT2C agonism in the presence of D2 receptor antagonism.

New atypical antipsychotics for schizophrenia: iloperidone

The optimal treatment of schizophrenia poses a challenge to develop more effective treatments and safer drugs, to overcome poor compliance, discontinuation and frequent switching with available antipsychotics. Iloperidone is a new dopamine type 2/serotonin type 2A (D(2)/5-HT(2A)) antagonist structurally related to risperidone, expected to give better efficacy with less extrapyramidal symptoms than D(2) receptor antagonist antipsychotics. In double-blind phase III trials iloperidone reduced the symptoms of schizophrenia at oral doses from 12 to 24 mg. It was more effective than placebo in reducing positive and negative syndrome total score and Brief Psychiatric Rating scale scores; it was as effective as haloperidol and risperidone in post-hoc analysis. Its long-term efficacy was equivalent to that of haloperidol. The most common adverse events were dizziness, dry mouth, dyspepsia and somnolence, with few extrapyramidal symptoms and metabolic changes in short- and long-term studies in adults. Akathisia was rare, but prolongation of the corrected QT (QTc) interval was comparable to haloperidol and ziprasidone, which is of particular concern. Further comparative studies are needed to clarify the benefit/risk profile of iloperidone and its role in the treatment of schizophrenia.

Association of the NPAS3 gene and five other loci with response to the antipsychotic iloperidone identified in a whole genome association study

A whole genome association study was performed in a phase 3 clinical trial conducted to evaluate a novel antipsychotic, iloperidone, administered to treat patients with schizophrenia. Genotypes of 407 patients were analyzed for 334,563 single nucleotide polymorphisms (SNPs). SNPs associated with iloperidone efficacy were identified within the neuronal PAS domain protein 3 gene (NPAS3), close to a translocation breakpoint site previously observed in a family with schizophrenia. Five other loci were identified that include the XK, Kell blood group complex subunit-related family, member 4 gene (XKR4), the tenascin-R gene (TNR), the glutamate receptor, inotropic, AMPA 4 gene (GRIA4), the glial cell line-derived neurotrophic factor receptor-alpha2 gene (GFRA2), and the NUDT9P1 pseudogene located in the chromosomal region of the serotonin receptor 7 gene (HTR7). The study of these polymorphisms and genes may lead to a better understanding of the etiology of schizophrenia and of its treatment. These results provide new insight into response to iloperidone, developed with the ultimate goal of directing therapy to patients with the highest benefit-to-risk ratio.

Azoles and antidepressants: a mini-review of the tolerability of co-administration

Depression is a common condition in chronically ill immunosuppressed patients on long-term antifungal therapy with azoles. As both azoles and more recent antifungals are metabolised by the P450 enzymatic system in the liver, here we review the potential of clinically meaningful interactions between antidepressants and azoles. Selective serotonin reuptake inhibitors are safer compared to tricycle antidepressants when co-administered with azoles. More pharmacovigilance is needed.

Antipsychotics for the treatment of schizophrenia: likelihood to be helped or harmed, understanding proximal and distal benefits and risks

Benefit-risk decisions are the central part of the philosophy of evidence-based medicine. Although number needed to treat (NNT) and number needed to harm (NNH) can quantify differences between two antipsychotics in terms of benefits and risks for the treatment of schizophrenia, these benefits and risks can take on greatly differing degrees of importance or relevance depending on the subjective point of view of the patient and clinician, baseline risks, severity of the underlying illness, as well as the time horizon when these effects emerge. The metric of likelihood to be helped or harmed, the ratio NNH to NNT, can be helpful in quantifying the benefit:risk ratio, provided that the outcomes are carefully matched in terms of both importance to the clinician and the patient and whether they are proximal or distal. The examples provided are extensions to the initially published NNT and NNH analyses conducted by the first author.

Potential utility of histamine H3 receptor antagonist pharmacophore in antipsychotics

Histamine H3 receptor (H3R) antagonists have some antipsychotic properties although the clear molecular mechanism is still unknown. As actually the most effective and less side effective antipsychotics are drugs with multiple targets we have designed typical and atypical neuroleptics with an additional histamine H3 pharmacophore. The 4-(3-piperidinopropoxy)phenyl pharmacophore moiety has been linked to amitriptyline, maprotiline, chlorpromazine, chlorprothixene, fluphenazine, and clozapine. Amide, amine and ester elements have been used generally to maintain or slightly shift affinity at dopamine D(2)-like receptors (D2 and D3), to decrease affinity at histamine H(1) receptors, and to obtain H3R ligands with low nanomolar or subnanomolar affinity. Change of effects at D(1)-like receptors (D1) and (D5) were heterogeneous. With these newly profiled compounds different antipsychotic properties might be achieved.

Should we be 'pushing meds'? The implications of pharmacogenomics

Medication continues to be the most widely prescribed treatment in the NHS for mental health problems. It has been known for many years that individuals differ in the way they respond to a given pharmaceutical therapy, and one reason for this lies in the genetic variation between individuals. This paper recognizes the impact that pharmacogenomics and pharmacogenetics are having in the field of mental health. Variants in genes that code for the drug metabolizing enzymes in the liver have been found to influence the way in which these enzymes handle psychotropic medication. Individuals can be classified as poor, moderate or extensive metabolizers when standard regimes are used, and this can lead to huge differences in therapeutic effect and toxicity. There are now genotyping tests available which provide information on the individual's ability to metabolize psychotropic medication. One author provides an account of the effects of medication on her son's physical and psychological well-being. Genotyping provided evidence for his poor metabolism of psychotropic medication, and his life is now changing as he is being very gradually weaned off this medication. This emerging field of work has implications for the way in which practitioners consider medication adherence.

Co-occurrence of ADHD and autism spectrum disorders: phenomenology and treatment

The Diagnostic and Statistical Manual of Mental Disorders (4th Edition) prohibits the co-diagnosis of attention-deficit/hyperactivity disorder (ADHD) and an autism spectrum disorder (ASD). However, recent studies indicate that co-occurrence of clinically significant ADHD and autistic symptoms is common, and that some genes may influence both disorders. Children with the combination of ADHD and motor coordination problems are particularly likely to have an ASD. These co-occurrences of symptoms are important since children with ASD in addition to ADHD symptoms may respond poorly to standard ADHD treatments or have increased side effects. Such children may benefit from additional classes of pharmacologic agents (i.e., alpha-agonists, selective serotonin reuptake inhibitors and neuroleptics). They may also benefit from social skills therapy, individual and family psychotherapy, behavioral therapy and other nonpharmacologic interventions.

Predicting antipsychotic drug response - replication and extension to six weeks in an international olanzapine study

OBJECTIVE

To use the degree of response after 2 weeks of treatment to predict non-response at 4 to 6 weeks.

METHOD

Post-hoc re-analysis of a large multi-centered double-blind trial including 1996 patients with schizophrenia using receiver-operator curves and logistic regression analyses to predict non-response at 4 weeks and at 4-6 weeks from the percentage BPRS change at weeks 1 and 2. The primary non-response criterion was a less than 25% BPRS reduction from baseline.

RESULTS

A 0% BPRS reduction at 2 weeks predicted non-response at 4 weeks with a positive predictive value of 77.1%; and sustained non-response at weeks 4, 5 and 6 with a positive predictive value of 75.8%. In a secondary last-observation-carried forward-analysis a less stringent cutoff of < or =15% BPRS reduction was associated with an acceptable positive predictive value (75%), with even higher sensitivity (76%).

CONCLUSIONS

Those patients who showed little to no reduction of symptoms at week 2 were unlikely to show even minimal response at weeks 4 to 6. There is increasing evidence that such patients may benefit from a change in treatment.

DRD4 48 bp VNTR but not 5-HT 2C Cys23Ser receptor polymorphism is related to antipsychotic-induced weight gain

Weight gain is a major side effect of antipsychotic treatment. The antidopaminergic and antiserotonergic effect of antipsychotics may contribute to antipsychotic-induced weight gain. We, therefore conducted a prospective clinical study, to investigate whether the D4 receptor (DRD4) 48 bp (base pair) variable number of tandem repeat (VNTR) polymorphism and the 5-hydroxytryptamine 2C receptor (HT(2C)) cysteine for serine substitution at position 23 (Cys23Ser) polymorphism may influence weight gain during antipsychotic treatment in a naturalistic setting of 102 Caucasian psychiatric in-patients. Patients suffering from psychotic disorders and treated according to local clinical practice were classified as either homozygous for the shorter alleles of the DRD4 48 bp VNTR polymorphism (<7-fold repeat, group 1) or heterozygous/homozygous for the long allele (7-fold repeat or higher, group 2). HT(2C) Cys23Ser polymorphism male patients were grouped hemizygous G (Cys) or C (Ser), while female patients were GG, GC or CC and both sexes were evaluated separately. Concerning the DRD4 48 bp VNTR polymorphism the increase in body mass index was significantly less in group 1 (0.38 kg m(-2); s.d.=1.04) than in group 2 (0.89 kg m(-2); s.d.=1.23; P=0.003). The difference between the genotype groups remained significant in male patients but not in female patients. In contrast, no influence on antipsychotic-induced increase in body weight was observed for the HT(2C) Cys23Ser polymorphism. These results support the hypothesis that the DRD4 48 bp VNTR polymorphism influences antipsychotic-induced weight gain. Male patients may be more affected than female patients. Due to the limitations of the study (heterogeneity of treatment, pretreatment and concomitant therapy) further studies are required before diagnostic genotyping of the DRD4 48 bp VNTR polymorphism may be useful for individualizing therapy.