Clinical pharmacokinetics of quetiapine: an atypical antipsychotic

Comparative Physicochemical and Pharmacokinetic Properties of Quetiapine and Its Active Metabolite Norquetiapine

Quetiapine (QTP) is an atypical antipsychotic drug commonly used to treat several psychiatric disorders and is metabolized into the active metabolite norquetiapine (NQTP). This study was designed to evaluate and compare the physicochemical properties, metabolic stability, brain distribution, and pharmacokinetics of QTP and NQTP. Compared to QTP, NQTP had a higher pK_a, solubility, and rat liver microsomal stability, optimal log D and similar log P values. For pharmacokinetic evaluation, QTP and NQTP were administered orally and intravenously to rats at various doses. The plasma QTP and NQTP concentrations in rats were determined by a fully-validated liquid-chromatography tandem mass spectrometry (LC-MS/MS). Over the investigated dosing range, both QTP and NQTP showed linear pharmacokinetics. Following oral administration of the same dose, the area under the concentration-time curve (AUC_0-∞) and maximum serum concentration (C_max) were larger after NQTP administration compared to QTP administration. In addition, NQTP had a greater absolute oral bioavailability compared to QTP (15.6% vs. 0.63%, respectively). The brain-to-plasma concentration ratio was greater after NQTP administration compared to the QTP and NQTP ratios after QTP administration. NQTP administration results in increased systemic exposure and brain distribution compared to QTP administration. Future studies are needed to evaluate the pharmacologic and toxicologic effects of increased NQTP exposures.

Acute Respiratory Failure with a Single Dose of Quetiapine Fumarate

Objective:

To report a case of acute respiratory failure after a single dose of quetiapine fumarate in an elderly patient with a history of chronic obstructive pulmonary disease (COPD).

Case Summary:

A 92-year-old woman with a history of COPD was admitted to the hospital with pneumonia. Her symptoms improved with antibiotics. Because of acute agitation and delirium, quetiapine 50 mg twice daily was started. After receiving the first dose, the woman developed acute respiratory failure and severe central nervous system depression. She required mechanical ventilation and supportive care in the intensive care unit (ICU). She had a full recovery within 24 hours.

Discussion:

Quetiapine is an atypical antipsychotic that has been used successfully for the treatment of schizophrenia and bipolar disorder for many years. Recently, it has also been used to treat delirium and agitation. It has proven to be very safe, even in the elderly. In previously reported cases, serious adverse effects were seen in patients who ingested very high doses of quetiapine. Those patients required intubation and supportive care in the ICU. To our knowledge, as of January 19, 2006, this is the first case report of acute respiratory failure of such severity with one dose of quetiapine. Using the Naranjo probability scale, we conclude that the acute respiratory failure observed in this patient was probably related to quetiapine.

Conclusions:

This case suggests that quetiapine can have significant adverse effects even with a single 50 mg dose. Elderly patients, especially those with significant underlying pulmonary pathology, should be monitored closely when started on this medication.

Agomelatine for the Treatment of Major Depressive Episodes in Schizophrenia-Spectrum Disorders: An Open-Prospective Proof-of-Concept Study

BACKGROUND

Depressive episodes in schizophrenia constitute a major clinical problem, and treatment success is often limited by treatment-emergent side effects. Agomelatine, an agonist at melatonergic MT1/MT2 receptors and 5-HT2C receptor antagonist, is a new antidepressant with a novel mode of action which constitutes a potential therapeutic option for depression in schizophrenia.

METHODS

Twenty-seven patients with lifetime diagnoses within the schizophrenia spectrum and comorbid depression were treated with agomelatine in addition to stable doses of antipsychotic agents. Severity of depression and other psychopathological domains (positive/negative symptoms, general psychopathology, psychosocial performance) was assessed regularly by means of standardized rating scales during a 6-week acute treatment phase as well as after a 6-week extension phase. Moreover, safety measures (electrocardiograms, laboratory counts, neurological and non-neurological side effects, sleep quality, sexual functioning) were monitored on a regular basis.

RESULTS

Depressive symptoms improved significantly during the 6-week acute treatment phase. In parallel, a significant improvement of negative symptoms, global psychopathology, and psychosocial performance was observed, whereas positive symptoms remained stable. Agomelatine was mostly well tolerated with predominantly mild and self-limiting side effects. However, pharmacokinetic interactions with antipsychotic agents were observed. Interestingly, the quality of sleep did not improve significantly, pointing toward mechanisms that do not depend on resynchronization of circadian rhythms.

CONCLUSIONS

Agomelatine appears to be safe and efficacious in treating depressive symptoms in patients with schizophrenia. The risk of pharmacokinetic interactions with antipsychotic agents warrants the need of therapeutic drug monitoring, and regular recording of vital signs seems necessary. Further randomized trials will have to confirm these findings.

Freeze Dried Quetiapine-Nicotinamide Binary Solid Dispersions: A New Strategy for Improving Physicochemical Properties and Ex Vivo Diffusion

Improving the physicochemical properties and oral bioavailability of quetiapine fumarate (QF) enabling enhanced antipsychotic attributes are the main aims of this research. The freeze dried solid dispersion strategy was adopted using nicotinamide (NIC) as highly soluble coformer. The prepared dispersions were characterized using scanning electron microscopy (SEM) differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Static disc intrinsic dissolution rate and ex vivo diffusion through intestinal tissues were conducted and compared to pure quetiapine fumarate. The results demonstrated a highly soluble coamorphous system formed between quetiapine fumarate and nicotinamide at 1 : 3 molar ratio through H-bonding interactions. The results showed >14-fold increase in solubility of QF from the prepared dispersions. Increased intrinsic dissolution rate (from 0.28 to 0.603 mg cm⁻² min⁻¹) and faster flux rate through duodenum (from 0.027 to 0.041 mg cm⁻² h⁻¹) and jejunum (0.027 to 0.036 mg cm⁻² h⁻¹) were obtained. The prepared coamorphous dispersion proved to be effective in improving the drug solubility and dissolution rate and ex vivo diffusion. Therefore, binary coamorphous dispersions could be a promising solution to modify the physicochemical properties, raise oral bioavailability, and change the biopharmaceutics classification (BCS) of some active pharmaceutical ingredients.

Safety Assessment of Liver Injury with Quetiapine Fumarate XR Management in Very Heavy Drinking Alcohol-Dependent Patients

BACKGROUND

Studies have reported liver injury as a consequence of antipsychotic treatment. Very heavy alcohol drinking (ten or more drinks/day for men and eight for women) also causes liver injury. This study aims to evaluate liver injury with quetiapine extended release (XR) in very heavy drinking alcohol-dependent (AD) patients.

METHODS

Two hundred and eighteen AD patients, 18-65 years of age, received 12 weeks of quetiapine XR or placebo treatment in a dose-escalated manner reaching the full dose of 400 mg/day during week 4. Blood chemistry and hematology were assessed at baseline (W0), post-titration at the end of week 3 (W4), week 8 (W8), and end of week 12 (W13). Patients were further grouped as GR.1 (no liver injury, ALT ≤40) and GR.2 (pre-existing liver injury, ALT >40) within each treatment. Drinking history, fasting blood glucose concentration (FBG), and lipid panel were used as covariates in the analyses.

RESULTS

Liver injury and total drinks and average drinking measures from the Timeline follow-back questionnaire (TLFB) were highly associated. No significant exacerbation in liver injury was observed in patients treated with quetiapine XR in GR.2. Liver injury as determined by elevated alanine aminotransaminase (ALT) was reported in a few patients in GR.1 who received quetiapine XR; however, the occurrence was low, and the level of liver injury was not significant. FBG and lipid measures showed some elevation, but did not show any significant association with liver injury.

CONCLUSION

Quetiapine XR did not show any significant exacerbation of liver injury in very heavy drinking alcohol-dependent patients with pre-existing liver injury. Frequency and severity of new liver injury cases in quetiapine XR-treated patients without any pre-existing liver injury was also low. Study findings support medical management of AD patients with heavy drinking profile using quetiapine XR formulation.

Experimental and in silico assessment of fate and effects of the antipsychotic drug quetiapine and its bio- and phototransformation products in aquatic environments

The antipsychotic drug quetiapine (QUT) has been frequently detected in sewage treatment plants. However, information on the fate of QUT in aquatic environments and its behavior during UV treatment is limited. In this study, QUT is shown not to be readily biodegradable in the Closed Bottle Test and the Manometric Respirometry Test according to OECD guidelines. The main biotransformation product (BTP) formed in the tests, a carboxylic acid derivative, was identified by means of high-resolution mass spectrometry. This BTP is presumably a human metabolite and showed higher detection rates than QUT in a river sampling campaign conducted in northern Germany. UV elimination kinetics of QUT at different initial concentrations (226.5, 45.3, 11.3, and 2.3 μmol L^-1) were faster at lower initial concentrations. All seven phototransformation products (PTPs) could be still identified at initial concentration of 11.3 μmol L^-1. The photolytic mixture generated after 128 min of photolysis of QUT was not better biodegradable than QUT. Initial UV treatment of QUT led to the formation of several additional BTPs. Four of them were identified. The bacterial cytotoxicity and genotoxicity before and after phototransformation of QUT in a modified luminescent bacteria test (LBT) and the umu-test (ISO/FDIS 13829) showed cytotoxic effects in the LBT for QUT. Furthermore, PTPs had similar cytotoxic effects on luminescent bacteria. The umu-test did not reveal any genotoxic activity for QUT or PTPs. In conclusion, the release of QUT into sewage treatment plants and aquatic environments could result in the formation of a main BTP. Additional UV treatment of QUT would lead to the formation of additional BTPs. Moreover, treatment did not result in lower toxicity to tested organisms. In conclusion, UV treatment of QUT should be considered critically as a potential treatment for QUT in aquatic systems.

Comparison of Capillary and Venous Drug Concentrations After Administration of a Single Dose of Risperidone, Paliperidone, Quetiapine, Olanzapine, or Aripiprazole

Risperidone, paliperidone, quetiapine, olanzapine, and aripiprazole are antipsychotic drugs approved for treating various psychiatric disorders, including schizophrenia. The objective of this randomized, parallel‐group, open‐label study was to compare finger‐stick‐based capillary with corresponding venous whole‐blood and plasma concentrations for these drugs after administration of a single dose to healthy volunteers. All whole‐blood and plasma drug concentrations were measured with validated liquid chromatography–tandem mass spectrometry methods. Capillary and venous concentrations (both in plasma and whole blood) were in close agreement, although a time‐dependent difference was observed, most obviously for olanzapine and paliperidone, with slightly higher capillary versus venous drug concentrations during the first hours after administering a single dose. The observed difference between capillary and venous plasma drug concentrations is expected not to be relevant in clinical practice, considering the wide window of therapeutic concentrations and the wide range of drug concentrations in the patient population for a given dose. Based on these results, finger‐stick‐based capillary drug concentrations have been shown to approximate venous drug concentrations.

Quetiapine Carboxylic Acid and Quetiapine Sulfoxide Prevalence in Patient Urine

Treatment adherence is often an issue with mental health patients. For those prescribed quetiapine (Seroquel^®), the low levels of parent drug and plasma metabolite(s) (e.g., 7-hydroxyquetiapine) typically used in urine drug monitoring can result in false negatives with concomitant unfavorable impacts on patient care. Literature review coupled with liquid chromatography/time-of-flight mass spectrometry analysis of patient positive urine samples indicated the presence of quetiapine carboxylic acid and quetiapine sulfoxide as significant urinary metabolites of quetiapine. Analysis of these two metabolites determined that they are abundant in the urine of quetiapine patients and can result in apparent adherence rates that are improved relative to those determined using only quetiapine and 7-hydroxyquetiapine. For example, analysis of a random set of 114 patients who were prescribed quetiapine exhibited an apparent adherence rate of 47% using the quetiapine carboxylic acid and quetiapine sulfoxide metabolites. Traditional metabolite testing with quetiapine and 7-hydroxyquetiapine yielded apparent adherence rates of ~31% while all four analytes resulted in apparent adherence of 48%. The prevalence of these metabolites suggests that quetiapine urine drug testing would be more consistent with prescriptions when they are included in the analysis.

The effect of second-generation antipsychotic drugs on sleep parameters in patients with unipolar or bipolar disorder

Sleep disturbances predominantly take the form of insomnia in patients with unipolar disorder, while patients with bipolar disorder show a decreased need for sleep. Sleep impairment in these patients is a risk factor for the development of a major depressive episode and suicidal behavior. Administration of second-generation antipsychotics (SGAs) olanzapine, quetiapine, and ziprasidone as augmentation therapy or monotherapy to unipolar and bipolar disorder patients, respectively, has been shown to improve sleep continuity and sleep architecture. Thus, their use by these patients could ameliorate their sleep disorder.

Pharmacokinetic Investigation of Quetiapine Transport across Blood-Brain Barrier Mediated by Lipid Core Nanocapsules Using Brain Microdialysis in Rats

Lipid-core nanocapsules (LCNs) have been proposed as drug carriers to improve brain delivery by modulating drug pharmacokinetics (PK). However, it is not clear whether the LCNs carry the drug through the blood-brain barrier or increase free drug penetration due to changes in the barrier permeability. Quetiapine (QTP) penetration to the brain is mediated by influx transporters and therefore might be reduced by drug transporters inhibitiors as probenecid. The goal of this work was to investigate the role of type-III LCNs on brain penetration of QTP using microdialysis in the presence probenecid. QTP-loaded LCN (QLNC) was successfully obtained with a small particle size (143 ± 6 nm), low polydispersity index (PI < 0.1), and high encapsulation efficiency (95.4 ± 1.82%.). Total and free drug concentration in plasma and free drug concentration in brain were analyzed following i.v. bolus dosing of nonencapsulated drug (FQ) and QLNC formulations alone and in association with probenecid to male Wistar rats. QTP free plasma fraction right after administration of QLNC was smaller than the fraction observed after FQ dosing; however, it increased over time until similar free drug levels were attained, suggesting that type-III LNCs produce a short in vivo sustained release of the drug. The inhibition of influx transporters by PB led to a reduction of free QTP brain penetration, as observed by the reduction of penetration factor from 1.55 ± 0.17 to a value closer to unit (0.94 ± 0.15). However, when the drug was nanoencapsulated, the inhibition of influx transporters had no effect on the brain penetration factor (0.88 ± 0.21 to 0.92 ± 0.13) probably because QTP is loaded into LNC and not available to interact with transporters. Taken together, these results suggest that LNC type-III carried QTP in the bloodstream and delivered the drug to the brain.

On-Line Organic Solvent Field Enhanced Sample Injection in Capillary Zone Electrophoresis for Analysis of Quetiapine in Beagle Dog Plasma

A rapid and sensitive capillary zone electrophoresis (CZE) method with field enhanced sample injection (FESI) was developed and validated for the determination of quetiapine fumarate in beagle dog plasma, with a sample pretreatment by LLE in 96-well deep format plate. The optimum separation was carried out in an uncoated 31.2 cm × 75 μm fused-silica capillary with an applied voltage of 13 kV. The electrophoretic analysis was performed by 50 mM phosphate at pH 2.5. The detection wavelength was 210 nm. Under these optimized conditions, FESI with acetonitrile enhanced the sensitivity of quetiapine about 40-50 folds in total. The method was suitably validated with respect to stability, specificity, linearity, lower limit of quantitation, accuracy, precision and extraction recovery. Using mirtazapine as an internal standard (100 ng/mL), the response of quetiapine was linear over the range of 1-1000 ng/mL. The lower limit of quantification was 1 ng/mL. The intra- and inter-day precisions for the assay were within 4.8% and 12.7%, respectively. The method represents the first application of FESI-CZE to the analysis of quetiapine fumarate in beagle dog plasma after oral administration.

Quetiapine monotherapy in acute treatment of generalized anxiety disorder: a systematic review and meta-analysis of randomized controlled trials

Background

Some studies have indicated the efficacy of quetiapine in the treatment of generalized anxiety disorder (GAD).

Objective

The purpose of this study was to systematically review the efficacy, acceptability, and tolerability of quetiapine in adult patients with GAD.

Methods

The SCOPUS, MEDLINE, CINAHL, Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov databases were searched in April 2015. All randomized controlled trials (RCTs) of GAD were considered to be included in this meta-analysis. All RCTs of quetiapine in GAD patients providing endpoint outcomes relevant to severity of anxiety, response rate, remission rate, overall discontinuation rate, or discontinuation rate due to adverse events were included. The version reports from suitable clinical studies were explored, and the important data were extracted. Measurement for efficacy outcomes consisted of the mean-changed scores of the rating scales for anxiety, and response rate.

Results

A total of 2,248 randomized participants in three RCTs were included. The pooled mean-changed score of the quetiapine-treated group was greater than that of the placebo-treated group and comparable to selective serotonin reuptake inhibitors (SSRIs). Unfortunately, the response and the remission rates in only 50 and 150 mg/day of quetiapine-XR (extended-release) were better than those of the placebo. Their response and remission rates were comparable to SSRIs. The rates of pooled overall discontinuation and discontinuation due to adverse events of quetiapine-XR were greater than placebo. Only the overall discontinuation rate of quetiapine-XR at 50 and 150 mg/day and the discontinuation rate due to adverse events of quetiapine-XR at 50 mg/day were comparable to SSRIs.

Conclusion

Based on this meta-analysis, quetiapine-XR is efficacious in the treatment of GAD in adult patients. Despite its low acceptability and tolerability, the use of 50–150 mg/day quetiapine-XR for adult GAD patients may be considered as an alternative treatment. Further well-defined studies should be conducted to warrant these outcomes.

Impact of genetic variability in CYP2D6, CYP3A5, and ABCB1 on serum concentrations of quetiapine and N-desalkylquetiapine in psychiatric patients

BACKGROUND

To investigate the impact of genetic variability in CYP2D6, CYP3A5, and ABCB1 on steady-state serum concentrations of quetiapine and the active metabolite, N-desalkylquetiapine, in psychiatric patients.

METHODS

Measured serum concentrations of quetiapine and N-desalkylquetiapine from patients with biobanked DNA samples were included retrospectively from a routine therapeutic drug monitoring database. The impact of CYP2D6, CYP3A5, and ABCB1 (345C>T) genotypes on dose-adjusted serum concentrations (C/D ratios) of quetiapine and N-desalkylquetiapine was investigated by multivariate mixed model analysis.

RESULTS

In total, 289 patients with 633 serum measurements were included. In the multivariate analysis, mean C/D ratio of N-desalkylquetiapine was estimated to be 33% and 22% higher in inherent CYP2D6 poor metabolizers (P = 0.03) and heterozygous extensive metabolizers (P < 0.001), respectively, compared with inherent extensive metabolizers. The ABCB1 3435C>T polymorphism and CYP3A5 genotype had no significant influence on either of the substances in the present material.

CONCLUSIONS

Genetic variability in CYP2D6 contributes to the interindividual variability in steady-state serum concentrations of N-desalkylquetiapine. Although the metabolite exhibits relevant pharmacological activity, the quantitative effect of CYP2D6 genotype on serum concentration of N-desalkylquetiapine is probably of limited clinical relevance for quetiapine treatment.

Evaluation of the Safety of Quetiapine in Treating Delirium in Critically Ill Children: A Retrospective Review

OBJECTIVE

Quetiapine is an atypical antipsychotic that has been used off-label for the treatment of intensive care unit (ICU) delirium in the adult population, with studies demonstrating both efficacy and a favorable safety profile. Although there is a potential role for quetiapine in the treatment of pediatric ICU delirium, there has been no systematic reporting to date of safety in this patient population.

METHODS

Pharmacy records were used to identify 55 consecutive pediatric ICU patients who were diagnosed with delirium and received quetiapine. A comprehensive retrospective medical chart review was performed to collect data on demographics, dosing, and side effects.

RESULTS

Fifty patients treated between January 2013 and November 2014 were included, and five patients were excluded from the study. Subjects ranged in age from 2 months to 20 years. Median daily dose was 1.3 mg/kg/day, and median duration of treatment was 12 days. There were three episodes of QTc prolongation that were clinically nonsignificant with no associated dysrhythmia: Two resolved over time without intervention, and one resolved with decrease in quetiapine dosage. There were no episodes of extrapyramidal symptoms or neuroleptic malignant syndrome.

CONCLUSIONS

In this population of critically ill youth, short-term use of quetiapine as treatment for delirium appears to be safe, without serious adverse events. Further research is required to assess efficacy and evaluate for long-term effects. A prospective, randomized, placebo-controlled study of quetiapine in managing pediatric delirium is necessary.

Population pharmacokinetic modeling of quetiapine after administration of seroquel and seroquel XR formulations to Western and Chinese patients with schizophrenia, schizoaffective disorder, or bipolar disorder

A population model describing quetiapine pharmacokinetics (PK) in Western and Chinese patients following oral administration of immediate-release (IR) and extended-release (XR) formulations was developed using plasma concentrations in 127 patients from 5 studies with quetiapine IR and/or XR in Western patients and 1 study with quetiapine XR in Chinese patients. A 1-compartmental model with first-order absorption and first-order elimination adequately described the quetiapine PK. The typical apparent volume of distribution and elimination rate constant of quetiapine were 574 L and 0.12 h(-) (1) , respectively. The estimated population absorption rate constants were 1.46 and 0.10 h(-1) for quetiapine IR and XR, respectively. Covariate analysis revealed that race was not a significant covariate influencing the PK of quetiapine. Simulation conducted with the final quetiapine population PK model predicted that the administration of a 200-mg twice-daily dose of quetiapine IR in Chinese patients would achieve a steady-state AUC (AUCss ) ± standard deviation of 3087 ± 1480 ng · h/mL, which is in close agreement with the reported value (3538 ± 1728 ng · h/mL). The model also predicted that once-daily administration of 300 mg quetiapine IR or XR would achieve similar exposure in terms of AUCss in Chinese patients.

Cardiac effects of sertindole and quetiapine: analysis of ECGs from a randomized double-blind study in patients with schizophrenia

The QT interval is the most widely used surrogate marker for predicting TdP; however, several alternative surrogate markers, such as Tpeak-Tend (TpTe) and a quantitative T-wave morphology combination score (MCS) have emerged. This study investigated the cardiac effects of sertindole and quetiapine using the QTc interval and newer surrogate markers. Data were derived from a 12 week randomized double-blind study comparing flexible dosage of sertindole 12-20mg and quetiapine 400-600mg in patients with schizophrenia. ECGs were recorded digitally at baseline and after 3, 6 and 12 weeks. Between group effects were compared by using a mixed effect model, whereas assessment within group was compared by using a paired t-test. Treatment with sertindole was associated with QTcF and QTcB interval prolongation and an increase in MCS, T-wave asymmetry, T-wave flatness and TpTe. The mean increase in QTcF from baseline to last observation was 12.1ms for sertindole (p<0.001) and -0.5ms for quetiapine (p=0.8). Quetiapine caused no increase in MCS, T-wave asymmetry, T-wave flatness or TpTe compared to baseline. In the categorical analysis, there were 11 patients (9.6%) receiving quetiapine who experienced more than 20ms QTcF prolongation compared with 36 patients (33.3%) in the sertindole group. Sertindole (12-20mg) was associated with moderate QTc prolongation and worsening of T-wave morphology in a study population of patients with schizophrenia. Although, quetiapine (400-600mg) did not show worsening of repolarization measures some individual patients did experience significant worsening of repolarization. Clinical Trials NCT00654706.

Coma After Quetiapine Fumarate Intentional Overdose in a 71-year-old Man: A Case Report

A 71-year-old man developed coma with severe respiratory failure, hypotension, and tachycardia induced by the intentional ingestion of quetiapine fumarate extended release (XR) 20 g. At the time, he had been treated for bipolar depression with venlafaxine 75 mg/day, lamotrigine 100 mg/day, pregabalin 75 mg/day, and quetiapine XR 400 mg/day for approximately 1 year. Comorbidities were hypertension treated with metoprolol, diabetes mellitus type 2 treated with metformin, and benign prostatic hyperplasia treated with silodosin. In the emergency room, about 4 h after ingestion of quetiapine fumarate XR, the presenting symptomatology was characterized by coma (Glasgow Coma Scale score 3), hypotension (blood pressure [BP] 90/60 mmHg), tachycardia (electrocardiogram [ECG] showed sinus tachycardia with heart rate 120 beats per minute and a QTc of 499 ms). A gastric lavage was performed and activated charcoal 50 g and magnesium sulfate 30 g was administered. About 6 h after ingestion, he developed marked desaturation and underwent mechanical ventilation; 13 h after ingestion, a severe hypotensive episode followed (BP 70/40), which was treated with an infusion of ringer lactate 500 cc. On the 3rd day after intentional overdose, an episode of agitation occurred; 4 days after ingestion, the quetiapine plasma level was found to be 42 ng/ml (within therapeutic range). At 5 days after ingestion, the patient developed septicemia caused by staphylococci (probably originating from the central vein catheter), which was treated with antibiotic therapy. On days 10 and 18 after the suicide attempt, two episodes of paroxysmal supraventricular tachycardia (PSVT) occurred and were successfully treated with intravenous adenosine triphosphate. The patient recovered completely without residual symptoms. In line with literature data, in this case report, symptoms of quetiapine overdose were tachycardia, agitation, hypotension, QT interval prolongation, and coma. A causal relationship between PSVT and quetiapine intoxication seems quite unlikely due to the drug level.

Effects of green tea extracts on the pharmacokinetics of quetiapine in rats

Quetiapine is an atypical antipsychotic, used clinically in the treatment of schizophrenia, acute mania in bipolar disorders, and bipolar depression in adults. In this study, the effect of green tea extracts (GTE) on the pharmacokinetics of quetiapine (substrate of CYP3A4) was investigated in rats. Male Wistar albino rats received GTE (175 mg/kg) or saline (control) by oral gavage for 7 days before a single intragastric administration of 25 mg/kg quetiapine. Plasma concentrations of quetiapine were measured up to 12 h after its administration by a validated ultraperformance liquid chromatography-tandem mass spectroscopy. Pretreatment with GTE produced significant reductions in the maximum plasma concentration and area under the curve of quetiapine by 45% and 35%, respectively, compared to quetiapine alone. However, GTE did not produce significant change in elimination half-life and oral clearance of quetiapine. This study concluded that GTE may decrease the bioavailability of quetiapine when coadministered.

Quetiapine and clarithromycin-induced neuroleptic malignant syndrome

We report a case of neuroleptic malignant syndrome possibly caused by the combined administration of quetiapine and clarithromycin in a 75-year-old male patient. He was receiving quetiapine regularly. Two days before his admission to the hospital, he had been feverish and started receiving clarithromycin without consulting a doctor. Clarithromycin administration was interrupted 3 days after his admission because it was ineffective and because his clinical state was deteriorating. The patient presented altered level of consciousness and excessive muscular rigidity on his limbs, while he remained feverish (38.7 °C). Laboratory abnormalities included elevated serum creatine phosphokinase level (5.387 U/L), leukocytosis, and low serum iron. The patient was diagnosed with neuroleptic malignant syndrome, and quetiapine was immediately discontinued. After the following days, his muscle rigidity and mental status ameliorated, his fever withdrew, and his laboratory findings improved. The various features of the case are discussed in view of the fact that the concomitant administration of cytochrome 3A4 inhibitors, such as clarithromycin, is suggested to cause an increase of plasma concentrations of quetiapine. Thus, physicians should have a high index of suspicion of the interactions of commonly administered medications.

Development of physiologically based pharmacokinetic model to evaluate the relative systemic exposure to quetiapine after administration of IR and XR formulations to adults, children and adolescents

Quetiapine is an atypical antipsychotic drug with a high permeability, moderate solubility and defined as a Biopharmaceutics Classification System class ll compound. The pharmacokinetics (PK) of the quetiapine immediate-release (IR) formulation has been studied in both adults and children, but the quetiapine extended-release (XR) formulation has only been conducted in adults. The purpose of the current study was to use physiologically based pharmacokinetic modeling (PBPK) quantitatively to predict the PK of the XR formulation in children and adolescents. Using a 'learn and confirm' approach, PBPK models were developed employing in vitro ADME and physicochemical data, clinical PK data of quetiapine IR/XR in adults and clinical PK data of quetiapine IR in children. These models can predict well the effects of CYP3A4 inhibition and induction on the PK of quetiapine, the PK profile of quetiapine IR in children and adults, and the PK profile of quetiapine XR in adults. The AUC and Cmax ratios (children vs adults) for the different age groups were in reasonable agreement with the observed ratios. In addition, the PBPK model predicted that children and adolescents are likely to achieve a similar exposure following administration of either the XR formulation once daily or the IR formulation twice daily at similar total daily doses. The results from the study can help inform dosing regimens in pediatrics using the quetiapine XR formulation.

The influence of the CYP3A4*22 polymorphism on serum concentration of quetiapine in psychiatric patients

BACKGROUND

Besides dietary, hormonal, or pathological factors, mutations in cytochrome P450 enzymes are thought to be responsible for the interindividual differences in serum concentrations of cytochrome P450 (CYP450)-dependent drugs. Cytochrome P450 3A4 (CYP3A4) is involved in the metabolism of greater than 50% of the prescribed drugs. Recently, a new single-nucleotide polymorphism (SNP) was found (CYP3A4*22), which results in a decreased enzyme activity, in contrast to the other known SNPs in CYP3A4. We investigated to which degree the CYP3A4*22 SNP affects serum concentrations of patients receiving quetiapine, a drug exclusively metabolized by CYP3A4.

METHODS

Two hundred thirty-eight adult patients receiving quetiapine were included in this study, based on availability of DNA, serum quetiapine levels, and information on dose. Patients were genotyped for CYP3A4*22 using allele-specific polymerase chain reaction, and, as a control, restriction fragment length polymorphism analysis.

RESULTS

Carriers of the CYP3A4*22 allele (*1/*22 and *22/*22, n = 31) had 2.5-fold higher serum levels of quetiapine than did wild-type patients (n = 207; P = 0.03) when using a comparable dose (median, 300 mg/d for both wild-type and carriers; P = 0.67). The dose-corrected serum concentration (C/D) was 67% higher in carriers than in wild-type patients (P = 0.01). The number of patients who achieved serum levels above the therapeutic range (>500 µg/L) was also higher in *22-allele carriers (16.1% vs 2.9%; P = 0.007).

CONCLUSION

Being a carrier of the CYP3A4*22 allele increases the serum concentration of quetiapine at comparable doses.

The integration of allometry and virtual populations to predict clearance and clearance variability in pediatric populations over the age of 6 years

BACKGROUND AND OBJECTIVES

Pharmacokinetics play an integral role in the pediatric drug development process. The determination of pharmacokinetic parameters, particularly clearance, in different age groups directly informs dosing strategies for subsequent efficacy trials. Allometric scaling for prediction of pediatric clearance from the observed clearance in adults has been used in this effort. Clinical trial simulation, a powerful tool used to inform clinical trial design, requires both an estimate of clearance along with an estimate of the expected pharmacokinetic variability. The standard deviations (SD) of individual clearance values for adults are typically used and may lead to inaccurate predictions by not taking into account the more widespread distribution of factors such as body weight in the pediatric population. The objective of this study was to assess the accuracy of allometric prediction of drug clearance as well as methods for predicting clearance variability in children 6 years of age and older.

METHODS

US Food and Drug Administration (FDA) clinical pharmacology reviews of pediatric studies conducted from 2002 onwards were reviewed to collate adult and pediatric clearance and clearance variability for studies including children 6 years of age and older. A set of 1,000 virtual adults {A} and a set of 5,000 virtual children (aged 2-17) {P} were generated on the basis of the White American NHANES database. Pediatric clearances were predicted in method 1 by using the geometric mean adult clearance from the in vivo study and calculating pediatric clearance for each virtual child within a subset {P'} of {P} that contained only those children that were within the age range of the in vivo pediatric study. In method 2, adult clearance values were randomly generated from the geometric mean adult clearance and standard deviation and assigned to each virtual adult in {A}. For each adult, allometric clearance scaling was completed with each virtual child within {P'}. The prediction error for the predicted and observed clearance and the clearance variability metric, coefficient of variation (CV), was calculated. The prediction accuracy as a function of the lowest age range (2 years and older) included in the study was also assessed.

RESULTS

Thirty-nine unique drugs were included in the study. For both method 1 and method 2, 100 % of predicted pediatric mean clearances were within 2-fold of the observed values and approximately 82 % were within a 30 % prediction error. There was a significant increase in the prediction accuracy of CV using method 2 vs. method 1. There was a major bias towards underprediction of pediatric CV in method 1 whereas method 2 was precise and not biased. Clearance and CV prediction accuracy were not a function of the age range included in the in vivo studies. The observed CV between the adult and pediatric study groups was not significantly different although, on average, the observed pediatric CV was 32 % greater than that from adult studies.

CONCLUSIONS

Allometric scaling may be a useful tool during pediatric drug development to predict drug clearance and dosing requirements in children 6 years of age and older. A novel methodology is reported that employs virtual adult and pediatric populations and adult pharmacokinetic data to accurately predict clearance variability in specific pediatric subpopulations. This approach has important implications for both clinical trial simulations and sample size determination for pediatric pharmacokinetic studies.

Release characteristics of quetiapine fumarate extended release tablets under biorelevant stress test conditions

The aim of the present work was the investigation of robustness and reliability of drug release from 50 to 400 mg quetiapine extended release HPMC matrix tablets towards mechanical stresses of biorelevant intensity. The tests were performed under standard conditions (USP apparatus II) as well as under simulated gastrointestinal stress conditions. Mechanical stresses including pressure and agitation were applied by using the biorelevant dissolution stress test apparatus as it has been introduced recently. Test algorithms already established in previous studies were applied to simulate fasting gastrointestinal conditions. The dissolution experiments demonstrated striking differences in the product performance among standard and stress test conditions as well as dose strengths. In USP apparatus II, dissolution profiles were affected mainly by media pH. The dissolution experiments performed in biorelevant dissolution stress test device demonstrated that stress events of biorelevant intensity provoked accelerated drug release from the tablets.

Interactions between valproic acid and quetiapine/olanzapine in the treatment of bipolar disorder and the role of therapeutic drug monitoring

OBJECTIVES

The anticonvulsant valproic acid and the atypical antipsychotics olanzapine and quetiapine provide synergistic mood-stabilising, antidepressant and antipsychotic activities in the treatment of bipolar and schizoaffective disorders. Existing literature shows that pharmacokinetic and pharmacodynamics drug-drug interactions (DDIs) possibly occur with the use of such a combination. Clinical reports of a possible interaction between the drugs leading to an increased risk of adverse drug reactions have also emerged. The main objective of this paper is to review the incidence of DDIs between the anticonvulsant and the antipsychotics, to postulate the possible mechanisms of the interaction and to establish whether certain target populations are at an increased susceptibility to such interactions. The usefulness of therapeutic drug monitoring (TDM) of the antipsychotics to monitor for an interaction was also assessed. A systematic database search was carried out using the search engine provided by PubMed using the following key words: olanzapine, quetiapine, valproic acid, pharmacokinetic drug-drug interaction, bipolar disorder, therapeutic drug monitoring.

KEY FINDINGS

Evidence of a possible clinically relevant DDI between valproic acid and both antipsychotics has been uncovered. A possible mechanism for the interactions has been postulated, and the importance of TDM has been discussed.

SUMMARY

Further research is required to determine whether DDIs occur with the concurrent use of valproic acid and olanzapine or quetiapine, and to investigate the potential of TDM as a clinical tool in improving pharmacotherapy and preventing toxicity.

Clinically significant drug interactions with atypical antipsychotics

Atypical antipsychotics [also known as second-generation antipsychotics (SGAs)] have become a mainstay therapeutic treatment intervention for patients with schizophrenia, bipolar disorders and other psychotic conditions. These agents are commonly used with other medications--most notably, antidepressants and antiepileptic drugs. Drug interactions can take place by various pharmacokinetic, pharmacodynamic and pharmaceutical mechanisms. The pharmacokinetic profile of each SGA, especially with phase I and phase II metabolism, can allow for potentially significant drug interactions. Pharmacodynamic interactions arise when agents have comparable receptor site activity, which can lead to additive or competitive effects without alterations in measured plasma drug concentrations. Additionally, the role of drug transporters in drug interactions continues to evolve and may effect both pharmacokinetic and pharmacodynamic interactions. Pharmaceutical interactions occur when physical incompatibilities take place between agents prior to drug absorption. Approximate therapeutic plasma concentration ranges have been suggested for a number of SGAs. Drug interactions that markedly increase or decrease the concentrations of these agents beyond their ranges can lead to adverse events or diminished clinical efficacy. Most clinically significant drug interactions with SGAs occur via the cytochrome P450 (CYP) system. Many but not all drug interactions with SGAs are identified during drug discovery and pre-clinical development by employing a series of standardized in vitro and in vivo studies with known CYP inducers and inhibitors. Later therapeutic drug monitoring programmes, clinical studies and case reports offer methods to identify additional clinically significant drug interactions. Some commonly co-administered drugs with a significant potential for drug-drug interactions with selected SGAs include some SSRIs. Antiepileptic mood stabilizers such as carbamazepine and valproate, as well as other antiepileptic drugs such as phenobarbital and phenytoin, may decrease plasma SGA concentrations. Some anti-infective agents such as protease inhibitors and fluoroquinolones are of concern as well. Two additional important factors that influence drug interactions with SGAs are dose and time dependence. Smoking is very common among psychiatric patients and can induce CYP1A2 enzymes, thereby lowering expected plasma levels of certain SGAs. It is recommended that ziprasidone and lurasidone are taken with food to promote drug absorption, otherwise their bioavailability can be reduced. Clinicians must be aware of the variety of factors that can increase the likelihood of clinically significant drug interactions with SGAs, and must carefully monitor patients to maximize treatment efficacy while minimizing adverse events.

Norepinephrine transporter occupancy in the human brain after oral administration of quetiapine XR

Quetiapine, originally developed as an antipsychotic, demonstrates efficacy in clinical studies of schizophrenia, bipolar mania and depression, major depressive disorder and generalized anxiety disorder. This broad spectrum of efficacy was not predicted from the preclinical pharmacology of quetiapine. Binding studies in vitro show that quetiapine and its major active human metabolite, norquetiapine, have moderate to high affinity for dopamine D2 and serotonin 5-HT2A receptors, while norquetiapine alone has high affinity for the norepinephrine transporter (NET). This positron emission tomography (PET) study measured NET occupancy in human subjects treated with extended-release quetiapine (quetiapine XR) at doses relevant in the treatment of depression. PET measurements using the specific NET radioligand (S,S)-[(18)F]FMeNER-D2 were performed before and after quetiapine XR treatment at 150 and 300 mg/d for 6-8 d in nine healthy males (aged 21-33 yr). Regions of interest were defined for the thalamus, using the caudate as reference region. NET occupancy was calculated using a target:reference region ratio method. Plasma concentrations of quetiapine and norquetiapine were monitored during PET measurements. Following quetiapine XR treatment, the mean NET occupancy in the thalamus was 19 and 35%, respectively, at quetiapine XR doses of 150 and 300 mg/d. The estimated plasma concentration of norquetiapine corresponding to 50% NET occupancy was 161 ng/ml. This is the first demonstration of NET occupancy by an antipsychotic in the human brain. NET inhibition is accepted as a mechanism of antidepressant activity. NET occupancy may therefore contribute to the broad spectrum of efficacy of quetiapine.

Use of high doses of quetiapine in bipolar disorder episodes are not linked to high activity of cytochrome P4503A4 and/or cytochrome P4502D6

The use of quetiapine for treatment of bipolar disorders at a higher dosage than the licensed range is not unusual in clinical practice. Quetiapine is predominantly metabolised by cytochrome P450 3A4 (CYP3A4) and to a lesser extent by CYP2D6. The large interindividual variability of those isozyme activities could contribute to the variability observed in quetiapine dosage. The aim of the present study is to evaluate if the use of high dosages of quetiapine in some patients, as compared to patients treated with a dosage in the licensed range (up to 800 mg/day), could be explained by a high activity of CYP3A4 and/or of CYP2D6. CYP3A4 activities were determined using the midazolam metabolic ratio in 21 bipolar and schizoaffective bipolar patients genotyped for CYP2D6. 9 patients were treated with a high quetiapine dosage (mean ± SD, median; range: 1467 ± 625, 1200; 1000-3000 mg/day) and 11 with a normal quetiapine dosage (433 ± 274, 350; 100-800 mg/day). One patient in the high dose and one patient in the normal dose groups were genotyped as CYP2D6 ultrarapid metabolizers. CYP3A4 activities were not significantly different between the two groups (midazolam metabolic ratio: 9.4 ± 8.2; 6.2; 1.7-26.8 vs 3.9 ± 2.3; 3.8; 1.5-7.6, in the normal dose group as compared to the high dose group, respectively, NS). The use of high quetiapine dosage for the patients included in the present study cannot be explained by variations in pharmacokinetics parameters such as a high activity of CYP3A4 and/or of CYP2D6.

Effect of food on the pharmacokinetics of lurasidone: results of two randomized, open-label, crossover studies

OBJECTIVE

This study aimed to investigate the effect of prandial status and caloric and fat composition of meals on the pharmacokinetics of lurasidone.

METHODS

Two randomized, open-label, crossover studies were conducted in clinically stable adults with schizophrenia or schizoaffective disorder. Study 1 (n = 16) evaluated the effect of fasting and three meal types (100 kcal/medium fat, 200 kcal/medium fat, and 800-1000 kcal/high fat), and Study 2 (n = 26) evaluated the effect of fasting and five meal types (350 kcal/high fat, 500 kcal/low fat, 500 kcal/high fat, 800-1000 kcal/low fat, and 800-1000 kcal/high fat) on the bioavailability of lurasidone. Subjects received lurasidone 120 mg once daily. Maximum serum concentration (Cmax ) and area under the serum concentration-time curve over the dosing interval (AUC0-tau ) were determined on Day 5 for each meal type.

RESULTS

In Study 1, the geometric mean Cmax in the fasted state was 56.7 ng/mL compared with 123.0 ng/mL for the 800- to 1000-kcal meal; mean AUC0-tau was 360.0 versus 752.4 ng·h/mL (both p < 0.001). Lurasidone exposure following meals containing 100 and 200 kcal was substantially lower than with meals containing 800-1000 kcal. In Study 2, the geometric mean Cmax was 52.9 ng/mL in the fasted state, 161 ng/mL for the 350-kcal/high-fat meal, 135 ng/mL for the 500-kcal/high-fat meal, and 131 ng/mL for the 800- to 1000-kcal/high-fat meal; mean AUC0-tau was 390, 743, 727, and 769 ng·h/mL, respectively. For all comparisons, the 90% confidence interval of the fed to fasted ratios indicated nonequivalence. Lurasidone exposure was similar following meals containing 350-1000 kcal and was independent of fat content.

CONCLUSION

Lurasidone should be administered with food-at least 350 kcal-to ensure maximum exposure.

Pharmacokinetic profile of the extended-release formulation of quetiapine fumarate (quetiapine XR): clinical implications

OBJECTIVES

A series of studies were conducted to guide the development and characterise the pharmacokinetics of extended-release quetiapine fumarate (quetiapine XR), a once-daily formulation to control the release of the drug.

METHODS

Data from these studies are described and discussed herein.

RESULTS

Once-daily quetiapine XR produced a similar area under the plasma concentration-time curve (AUC), minimum plasma concentration (Cmin) and a slightly lower maximum plasma concentration (Cmax) than the equivalent dose of immediate-release quetiapine (quetiapine IR) given twice daily. In a crossover, head-to-head study, total daily exposure, measured by AUC at steady state, was less variable with quetiapine XR versus quetiapine IR (percent coefficient of variation 39.2% versus 51.2%, respectively). Compared with fasting, a high-fat meal increased the AUC and Cmax for quetiapine XR, whereas a light meal had no significant effect on these parameters. Quetiapine XR exhibits a less pronounced D2 receptor occupancy peak and receptor occupancy levels remain higher for longer compared with quetiapine IR. Quetiapine XR was generally well tolerated with a safety profile similar to quetiapine IR, although the intensity of sedation in the first hours of treatment was significantly lower (p < 0.01) with quetiapine XR versus IR.

CONCLUSION

At steady state, quetiapine XR provided a similar AUC and Cmin and a slightly lower Cmax relative to an equivalent dose of quetiapine IR administered twice daily. Quetiapine XR exhibited linear pharmacokinetics in the dose range tested and no food effect was observed with a light meal. Once-daily dosing and simpler dose titration makes using quetiapine XR convenient for clinicians and patients. Quetiapine XR has predictable pharmacokinetics and was generally well tolerated, with significantly lower intensity of sedation after the first hours of administration compared with quetiapine IR. With once-daily quetiapine XR, the impact of daytime sedation may be mitigated by evening dosing.

Safety and pharmacokinetics of atypical antipsychotics in children and adolescents

Pediatric behavioral and affective disorders often require antipsychotic therapy, in combination with psychotherapeutic interventions, for their treatment and stabilization. Although pharmacotherapy can include either typical or atypical antipsychotics, the latter are generally preferred because of their apparently lower risk of adverse effects. Recent controlled trials have demonstrated the efficacy of some of these agents (including aripiprazole, clozapine, olanzapine, paliperidone, quetiapine, risperidone, ziprasidone) in adolescent schizophrenia and children or adolescent bipolar mania, or to treat severe aggression and self-injury in the context of autism in children and adolescents. Although few studies have systematically monitored their short- and, more importantly, long-term safety, current evidence indicates that sedation, hyperprolactinemia, and metabolic abnormalities such as excess weight gain, diabetes, and related cardiovascular effects were clinically relevant adverse effects in young patients, with the individual agents differing in their propensity to induce these effects. When prescribing antipsychotics for children and adolescents, physicians should therefore be aware of the specific adverse effect profiles and patients should be closely monitored for the short- and long-term development of adverse events. In pediatric patients, the starting dose, titration plan, and maintenance dose of antipsychotics must be based on their pharmacokinetics and metabolism, as in adults. Because there are significant individual differences in drug and active metabolite(s) pharmacokinetics and metabolism, which may be further affected by a number of confounding factors (including demographic variables, phenotype and drug interactions), therapeutic drug monitoring may be a valid tool for individualizing dosage, but its interpretation should also take account of changes in pharmacodynamic sensitivity with the development during childhood and adolescence.

Plasma quetiapine in relation to prescribed dose and other factors: data from a therapeutic drug monitoring service, 2000-2011

OBJECTIVE

Suggested predose plasma quetiapine target ranges for effective therapy in schizophrenia lie between 50 and 500 µg/l. We aimed to examine data from a quetiapine therapeutic drug monitoring (TDM) service to assess the plasma quetiapine concentrations attained at specified doses in clinical practice.

METHOD

We studied TDM data from patients given immediate-release quetiapine in the period 2000-2011.

RESULTS

There were 946 samples from 487 patients (257 males, age at time of first sample, median [range] 34 [14-87] years, and 230 females, age at time of first sample, median [range] 38 [10-92] years). The plasma quetiapine concentration was <50 and <100 µg/l in 30% and 50% of samples, respectively (no quetiapine detected in 9% of samples). The relationship between dose and plasma quetiapine was poor. The mean (95% confidence interval [CI]) quetiapine dose was higher (t = 3.6, df = 446, p <0.01) in males versus females (641 [600-1240] and 548 [600-943] mg/day, respectively), although there was no difference in median dose (600 mg/day) or in the mean (95% CI) plasma quetiapine concentrations attained. Smoking habit had no discernible effect on plasma quetiapine concentration.

CONCLUSIONS

There was a poor relationship between dose and plasma quetiapine concentration in this study, as found by others. This is probably because of the short plasma half-life of the drug, at least in part. Nevertheless, quetiapine TDM can help assess adherence and measurement of quetiapine metabolites, notably N-desalkylquetiapine, as well as quetiapine itself may enhance the value of quetiapine TDM in future.

Development and validation of a sensitive and robust LC-MS/MS with electrospray ionization method for simultaneous quantitation of quetiapine and its active metabolite norquetiapine in human plasma

BACKGROUND

Quetiapine is an atypical antipsychotic agent for the treatment of schizophrenia, acute mania, and acute bipolar depression. The antidepressive response is considered to be mediated by the metabolite norquetiapine (N-desalkylquetiapine), and the aim of this study was to develop an LC-MS/MS method to measure concentrations of these compounds in human plasma.

METHODS

Following one step liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a Sunfire C18 column (50mm×2.1mm, 5μm). The retention times were 2.12, 2.24, 2.12 and 2.19min for quetiapine, norquetiapine and their respective stable labeled internal standards, respectively. Cycle time was 4min. Selected reaction monitoring (SRM) in positive ion mode was used for quantitation.

RESULTS

The present method exhibited a linear dynamic range of 0.5-500ng/ml for quetiapine and 0.6-600ng/ml for norquetiapine. The applicable range was extended by dilution up to 5-fold with blank matrix. The accuracy and precision for quetiapine were <103.0% and 8.8%, for norquetiapine were <108.8% and 11.1%, respectively.

CONCLUSIONS

A rapid, sensitive, and robust LC-MS/MS method for quantifying quetiapine and its metabolite norquetiapine levels in human plasma was validated and successfully applied to samples from schizophrenic patients in clinical pharmacokinetics studies.

Pharmacokinetics, Tolerability, and Safety of ACP-103 Following Single or Multiple Oral Dose Administration in Healthy Volunteers

The pharmacokinetics, safety, and tolerability of ACP-103, a selective serotonin 5-HT(2A) receptor inverse agonist, were evaluated in 2 double-blind, placebo-controlled, dose escalation studies in healthy male volunteers. Pharmacokinetic sampling was measured up to 216 hours after single oral/nasogastric doses of ACP-103 and after the last dose of once-daily oral administration of ACP-103 for 14 days. Single doses of ACP-103 (20-300 mg) resulted in dose-proportionate mean C(max) values (9-152 ng/mL) and AUC(0-infinity) (706-10 798 h x ng/mL), and multiple doses (50-150 mg) resulted in dose-proportionate mean C(max,ss) (93-248 ng/mL) and AUC(0-infinity,ss) (1839-4680 h x ng/mL). The half-life of ACP-103 was approximately 55 hours, with a t(max) at 6 hours. ACP-103 was well tolerated at single doses up to and including 300 mg and multiple doses up to 100 mg once daily for 14 days.