Serotonergic neurotransmission mediates hypothermia induced by the N-phenylpiperazine antipsychotic prototypes LASSBio-579 and LASSBio-581

Previous studies have demonstrated that LASSBio-579 and LASSBio-581, two N-phenylpiperazine derivatives designed for the treatment of schizophrenia, are presynaptic dopamine D(2) receptor agonists that induce a hypothermic effect in mice that is not mediated by dopamine receptor activation. The aim of the present study was to investigate possible serotonergic mechanisms underlying hypothermia induced by LASSBio-579 and LASSBio-581 in CF1 mice. The reduction in core temperature was dose-dependent (15-60 mg/kg, i.p.) and occurred by the oral route (30 mg/kg). Pretreatment with haloperidol (4 mg/kg, i.p.) resulted in a synergistic hypothermic effect. Pretreatment with (+/-)DOI (0.25 mg/kg, i.p.), a serotonin 5-HT(2A/C) receptor agonist, reduced the hypothermic effect induced by LASSBio-579 and LASSBio-581 at 15 and 30 mg/kg, i.p. In contrast, (+/-)DOI enhanced the hypothermia induced by both compounds at 60 mg/kg, i.p. The serotonin 5-HT1A antagonist WAY 100635 (0.05 mg/kg, s.c.) abolished the hypothermia induced by LASSBio-579 and diminished the hypothermia induced by LASSBio-581. Pretreatment with LASSBio579 (30 and 60 mg/kg, i.p.) and LASSBio-581 (60 mg/kg, i.p.) reduced the number of head-twitches induced by (+/-)DOI (2.5 mg/kg, i.p.). The ear-scratch response induced by (+/-)DOI was inhibited by both LASSBio-579 and LASSBio-581 at 60 mg/kg, i.p. These results indicate that LASSBio-579 and LASSBio-581 have mechanisms of action through the serotonergic neurotransmitter system.     

Pharmacokinetics and tissue distribution of a new heterocyclic N-phenylpiperazine derivative (LASSBio-581) in rats.

This work investigated the pharmacokinetics of a new N-phenylpiperazine derivative (LASSBio-581), active on dopaminergic system. LASSBio-581 plasma concentrations were determined in rats after bolus administration of 10mg/kg, i.v., 30 and 60 mg/kg, i.p. and p.o., by HPLC. Individual profiles were evaluated by non-compartmental and compartmental analysis using WinNonlin. Protein binding by ultrafiltration showed free fraction of 29+/-4%. The compound showed linear pharmacokinetics for the extravascular doses investigated. The oral bioavailability ( approximately 25%) was approximately half of the intra-peritoneal one ( approximately 47%). The 60 mg/kg oral dose showed an unusual profile with two peaks (1 and 6h). A two-compartment model better described all plasma profiles. The Vd (0.8+/-0.4l/kg) and the t(1/2) (1.2+/-0.4h) were smaller for i.v. than for the other routes. The CL(tot) was statistically similar for all three administration routes investigated (0.6+/-0.2l/(hkg)) (alpha=0.05). The compound distribution into different organs, evaluated in tissue homogenates after i.v. administration, showed a higher penetration in lungs (51.0%), followed by the brain (39.2%), where the half-life was three times bigger than in the other tissues (1.9h). The compound brain profile agreed with the central nervous system activity determined.     

Validated HPLC method for determination of LASSBio-581, a new heterocyclic N-phenylpiperazine derivative, in rat plasma

A rapid, simple and accurate high performance liquid chromatography (HPLC) method was developed and validated for the determination of LASSBio-581 (1-[1-(4-chloro-phenyl)-1H-[1,2,3]triazol-4-ylmethyl]-4-phenyl-piperazine) in rat plasma using ketoconazole as internal standard. Plasma samples were deproteinized with methanol. A good chromatographic separation was achieved using a reversed phase C₁₈ column. Mobile phase consisting of sodium dihydrogen phosphate monohydrate (pH 4.5, 0.02 M) and methanol mixture (35:65, v/v) was used at a flow rate of 1.0 ml/min. The eluate was monitored using a UV detector at 248 nm. The retention times of LASSBio-581 and the internal standard were approximately 3.8 and 5.6 min, respectively. The calibration curves were linear over the concentration range of 0.25–8.0 μg/ml with correlation coefficients >0.99. The limit of quantitation was 0.25 μg/ml. The accuracy of the method was >90%. The intra-day relative standard deviation (R.S.D.) ranged from 6.15 to 10.52% at 0.4 μg/ml, 7.44 to 13.81% at 1.5 μg/ml and 6.10 to 13.94% at 6.0 μg/ml. The inter-day R.S.D. were 9.54, 8.42 and 8.25% at 0.4, 1.5 and 6.0 μg/ml, respectively. No interference from endogenous substances or metabolites were observed. The method has been used to measure plasma concentrations of LASSBio-581 in pharmacokinetic studies in rats.     

Toxicological in vitro and subchronic evaluation of LASSBio-596

LASSBio-596, 2-[4-(1,4-tiazinan-4-ylsulfonyl) phenylcarbamoyl] benzoic acid, is an achiral compound containing a subunit carboxylic amide, was capable of preventing induced mechanical and morphological changes in the lungs that commonly caused the onset of asthma. Previous studies to determine the acute toxicity of oral LASSBio-596 at dose of 2000 mg/kg caused no deaths in any of the tested animals. To further evaluate the safety of LASSBio-596, in vitro and in vivo tests were carried out. Regarding to in vitro test were used renal, hepatic, pulmonary, cardiac, neurologic and intestinal cell lines. They were evaluated using neutral red (NR) and [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) assays. Micronuclei also was performed. Concerning to in vivo was performed subchronic on Wistar rats at doses of 10, 50, and 250 mg/kg and zebrafish test. The in vitro tests results showed the safety of LASSBio-596. However, subchronic toxicity study results revealed changes in the blood parameters of amylase, alanine aminotransferase (ALT), aspartate aminotransferase (AST), glucose and creatine kinase (CK) which is used for cardiotoxicity evaluation, although, did not identify any histopathological alterations. However, zebrafish test demonstrated cardiac damage. It was impossible to estimate the no-observed-adverse-effect-levels and lowest observed-adverse-effect level due to the presence of cardiotoxicity in all tested doses.     

Development and validation of a LC-MS/MS method with electrospray ionization for determination of LASSBio-579 in rat plasma

A simple and sensitive LC-MS/MS analytical method was developed and validated for the determination of LASSBio-579 in plasma rat, using fluconazole as internal standard. Analyses were performed on a Shimadzu HPLC system using a Shimadzu C18 column and isocratic elution with acetonitrile-water (80:20, v/v), containing 0.4mM ammonium hydroxide and 0.2 mM acetic acid at a flow rate of 1.0 ml/min (split ratio 1:5). A Micromass triple quadrupole mass spectrometer, equipped with an electrospray ionization interface, operated in the positive mode. Plasma samples were deproteinized with acetonitrile (1:2) and 50 microl of the supernatant were injected into the system. The retention times of LASSBio-579 and IS were approximately 4.7 and 2.4 min, respectively. Calibration curves in spiked plasma were linear over the concentration range of 30-2000 ng/ml with determination coefficient >0.98. The lower limit of quantification was 30 ng/ml. The accuracy of method was within 15%. Intra- and inter-day relative standard deviations were less or equal to 13.5% and 6.4%, respectively. The applicability of the LC-MS/MS method for pharmacokinetic studies was tested using plasma samples obtained after intraperitoneal administration of LASSBio-579 to male Wistar rats. No interference from endogenous substances was observed, showing the specificity of the method developed. The reported method can provide the necessary sensitivity, linearity, precision, accuracy, and specificity to allow the determination of LASSBio-579 in pre-clinical pharmacokinetic studies.     

Pharmacokinetic factors in the adverse cardiovascular effects of antipsychotic drugs

Antipsychotics may cause serious adverse cardiovascular effects, including prolonged QT interval and sudden death. This review considers antipsychotic-induced cardiovascular events from three perspectives: high-risk drugs, high-risk individuals and high-risk drug interactions. Pharmacokinetic drug interactions involving the cytochrome P450 (CYP) enzymatic pathway and pharmacodynamic interactions leading to direct cardiotoxic effects are discussed. Original reports on antipsychotic-induced drug interactions are reviewed, with consideration of management guidelines.The literature was reviewed from 1 January 1966 to 1 February 2002. The literature search revealed only 12 original articles published on antipsychotic drug interactions leading to cardiovascular adverse events. Only 4 of the 12 reports were prospective studies; the remainder were either retrospective or anecdotal.Although poor study designs preclude a definitive statement, it appears that pharmacokinetic interactions primarily involved the CYP2D6 and CYP3A4 enzymatic pathways. Those involving the CYP2D6 isozyme included interactions with tricyclic antidepressants, selective serotonergic reuptake inhibitors and beta-blockers. Among these drug interactions, tricyclic antidepressants were most likely to reach clinical significance because of their limited therapeutic index. Drug interactions related to the CYP3A4 pathway were generally less severe, and involved high-potency antipsychotics coadministered with inhibitors such as clarithromycin.Strategies are discussed for the management of adverse cardiovascular events related to antipsychotic drug interactions, including the use of an algorithm. Large, randomised, placebo-controlled studies with strict inclusion criteria are needed to determine the role that antipsychotics play in QT prolongation and sudden death.     

Pharmacokinetic evaluation of roflumilast

INTRODUCTION: Roflumilast is a selective PDE4 inhibitor recently approved for oral, once-daily treatment of severe chronic obstructive pulmonary disease (COPD). Clinical trials have demonstrated the effect of roflumilast on reducing exacerbation frequency and improving lung function in COPD, while its mode of action may offer the potential to target the inflammatory processes underlying COPD. Roflumilast is, therefore, an important addition to current therapeutic options. It is catalyzed by cytochrome P450 (CYP) 1A2 and 3A4 to its active metabolite, roflumilast N-oxide, which accounts for > 90% of roflumilast total PDE4 inhibitory activity. AREAS COVERED: This article reviews the pharmacokinetics of roflumilast and considers the effects of co-administration with CYP inhibitors or inducers, and other medications commonly used in patients with COPD, on the pharmacokinetics of roflumilast and roflumilast N-oxide. EXPERT OPINION: Roflumilast has novel anti-inflammatory activity in COPD that provides the physician with a treatment option beyond bronchodilation. It can be co-administered with many medications commonly used by patients with COPD and its anti-inflammatory activity provides incremental benefits on top of existing therapies. Future research will further elucidate the impact of roflumilast on COPD and beyond, while alternative dosing regimens may offer a means to ameliorate transient tolerability issues.     

Pharmacokinetic evaluation of ambrisentan

INTRODUCTION: Pulmonary arterial hypertension (PAH) is a life-threatening and progressive disease characterized by increasing pulmonary vascular resistance leading to right ventricular failure and premature death. Current therapies target three major pathways involving endothelin, prostacyclin and NO. Ambrisentan is an oral, once daily, selective endothelin receptor antagonist. AREAS COVERED: This review focuses on, and critically appraises, the clinical efficacy and safety of ambrisentan as well as its pharmacokinetic and pharmacodynamic properties. The article also gives an expert perspective on the role of ambrisentan in the management of PAH. EXPERT OPINION: Ambrisentan is an effective and safe treatment which is, in the authors' opinion, a valuable addition to the armamentarium against PAH. Ambrisentan offers a relative lack of drug interactions, once daily dosing and reassuring liver safety, offering safety and convenience advantages over bosentan. Presently, there is a lack of comparative studies between PDE5 inhibitors and endothelin receptor antagonists and a lack of data comparing bosentan with ambrisentan. This is hindering data-based conclusions regarding relative efficacy and further studies are needed to define the role of ambrisentan in the management of PAH.     

Pharmacokinetic evaluation of levocetirizine

INTRODUCTION: There have recently been guidelines developed for the diagnosis and treatment of rhinitis and urticaria. For both conditions, second-generation antihistamines remain as the first-line therapy. AREAS COVERED: The article presents the current pharmacology, chemical properties, pharmacokinetics and metabolism of levocetirizine. The article also reviews the clinical efficacy of levocetirizine for seasonal allergic and perennial rhinitis, as well as chronic urticaria. The article is formed through the review of all the published literature in English retrieved from the PubMed/MEDLINE database between 1966 and March 2011 using the search terms: levocetirizine, allergic rhinitis, chronic urticaria and antihistamine. Furthermore, the article also reviews data provided by the manufacturer in addition to reports from governmental agencies. EXPERT OPINION: Levocetirizine has several pharmacokinetic properties that are desirable for an antihistamine providing a combination of both potency and safety. Its clinical advantages are derived from its rapid and extensive absorption, limited distribution and its very low degree of metabolism. Furthermore, levocetirizine scores very highly in terms of clinical efficacy as well as in patient/physician satisfaction studies. Given the lack of large multi-center studies that compare the treatment options for urticaria, clinicians must rely on potency studies when choosing treatment and levocetirizine does score very highly. However, other potent skin antihistamines, such as desloratadine or fexofenadine, should be preferred for patients who have a strict contraindication to the sedative effects of the drug.     

Pharmacokinetic evaluation of axitinib

INTRODUCTION: The role of angiogenic inhibitors is clearly established in the treatment of diverse malignancies. The field of antiangiogenesis is expanding rapidly, with an increasing number of agents currently approved by the FDA. Axitinib is a vascular endothelial growth factor receptor (VEGFR)-specific inhibitor currently being developed for the treatment of various malignancies. The pharmacokinetic (PK) properties of axitinib may provide a selective treatment effect while minimizing adverse reactions and enhancing safety. It is paramount that health-care providers understand the properties and nuances of each agent inclusive of PK variability in the patient population as well as current safety and tolerability data. AREAS COVERED: This article provides a comprehensive and critical review of the PK properties of axitinib as they relate to safety and tolerability, as well as potential pharmacodynamic and efficacy parameters. EXPERT OPINION: Axitinib is a unique VEGFR tyrosine kinase inhibitor (TKI), which acts through greater receptor specificity compared with many other VEGFR TKIs. An understanding of axitinib's PK characteristics and common adverse events may allow for a tailored dosing approach in patients with cancer, in an attempt to maximize efficacy while minimizing toxicity.     

Pharmacokinetic evaluation of frovatriptan

INTRODUCTION: Migraine is the most common painful neurological disorder, affecting 13% of the general population. Triptans represent a powerful pharmacological tool in acute migraine treatment, however, a significant portion of treated patients cannot have access to this class due to possible adverse affects. Today, a total of seven triptan molecules are available, representing a commonly prescribed migraine treatment. Although there is a need of extensive use of triptans, only 25% of migraine patients are using triptans. AREAS COVERED: This review includes triptans and evidence for the use of frovatriptan. A systematic approach is used to discuss the pharmacodynamic and pharmacokinetic aspects of frovatriptan, considering the emerging data on the clinical efficacy of frovatriptan in the treatment of migraine and cluster headaches. The data were obtained by searching the following key words in MEDLINE: pharmacokinetic, pharmacodynamic, triptans, frovatriptan, migraine, menstrual migraine, relatively to the period 1988 - 2011. EXPERT OPINION: Frovatriptan has been developed in order to improve safety and efficacy of triptans. It shows a favorable tolerability and efficacy profile, limited to 24/48-h headache recurrence, when compared with other triptans. Preclinical data suggest that the pharmacokinetic profile of frovatriptan may differ from other available triptans. In fact, among triptans, frovatriptan showed the highest potency at the 5-HT1B receptor (8.2) and the longer half-life (26 h). These parameters determine the clinical properties of frovatriptan; in particular the lowest rate of headache recurrence in comparison with other triptans.     

Pharmacokinetic evaluation of pramipexole

INTRODUCTION: Immediate-release (IR) pramipexole dihydrochloride is indicated for the treatment of signs and symptoms of idiopathic Parkinson's disease (PD). It is administered alone (without levodopa) or in combination with levodopa, during the entire progress of the disease, up to an advanced stage. Currently, it is also indicated for the treatment of moderate-to-severe primary restless legs syndrome (RLS). An extended-release (ER) formulation of pramipexole has been developed to allow a once-daily administration and to provide more stable dopaminergic stimulation in PD patients. AREAS COVERED: This review summarizes the overall pharmacokinetic profile of pramipexole for both the IR and ER formulations. Also discussed are the clinically relevant determinants of pramipexole peripheral pharmacokinetics and the potential role of genetic and clinical determinants in drug efficacy. EXPERT OPINION: Pramipexole is a non-ergot agonist with selective affinity for dopamine receptors of the D2 subfamily, in particular D3. Pramipexole has a very low affinity for serotoninergic 5-HT2A and 5-HT2B receptors, as well as D1-type receptors. Furthermore, it does not carry the risk to induce valvular heart disease or pulmonary and retroperitoneal fibrosis, seen with long-term use of the ergot-derived dopamine agonists. The recent introduction of a once-daily formulation poses significant advantages for patients, reflected by relatively stable plasma levels. The most obvious benefit is convenience of use and better adherence to treatment schedule. Additional advantages could include the opportunity to provide more continuous drug delivery in a fashion that could help minimize dyskinesia risk, if the drug is used early in the disease course.     

Pharmacokinetic evaluation of losartan

INTRODUCTION: Blockade of the renin-angiotensin system is one of the major therapeutic strategies in the management of patients with essential hypertension, congestive heart failure and diabetic as well as non-diabetic renal diseases. As the first angiotensin II receptor blocker (ARB) on the market, losartan belongs to the most frequently prescribed ARB. AREA COVERED : The present review examines the pharmacokinetics of losartan with a special discussion on the dose of losartan that should be used in clinical practice to obtain the maximal benefits of the drug. Readers are provided with arguments suggesting that the dose of 50 mg losartan is probably too low and that losartan should preferably be prescribed at the dose of 100 mg/day or higher. EXPERT OPINION : Losartan is an effective antagonist of angiotensin II AT(1) receptors which has been shown to provide important clinical benefits in patients with hypertension, congestive heart failure and renal diseases. Losartan should be prescribed at the dose of 100 mg/day and the use of higher doses should be reconsidered in future studies to improve its clinical efficacy.     

Pharmacokinetic evaluation of eltoprazine

INTRODUCTION: Approvals and availability of drugs and delivery systems to treat attention-deficit/hyperactivity disorder (ADHD) have increased steadily in the last decade. The development of new pharmacological agents to treat ADHD symptoms in adults allows for both single and combination therapy for optimal efficacy. Eltoprazine hydrochloride, a serotonergic agent currently under development, is the focus of the current paper. AREAS COVERED: This paper provides an overview of the pharmacokinetics (PK) of the non-stimulant medication eltoprazine. The PK profile of eltoprazine, based on standard PK sampling accompanied by safety monitoring, is described. A literature search and review of the studies published on eltoprazine were carried out using the PubMed database up to November 2010. EXPERT OPINION: Although clinical studies of eltoprazine did not conclusively demonstrate its efficacy in treating pathological aggression in humans, eltoprazine has shown to be a well-tolerated drug in both healthy volunteers and patients across several indications studied thus far. More recently, the role of eltoprazine in reducing symptoms of ADHD in adults has been explored in a clinical trial. Future research may provide endophenotypical characteristics to help identify specific subgroups of patients with ADHD, who can benefit from the development of eltoprazine, to maximize efficacy while minimizing adverse reactions.     

Determination of the cardioactive prototype LASSBio-294 and its metabolites in dog plasma by LC-MS/MS: application for a pharmacokinetic study

In this work we describe the evaluation of the pharmacokinetics of a novel cardioactive compound of the N-acylhydrazone class, LASSBio-294, using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) in dog plasma for the first time. Separation was achieved on a ZORBAX Rapid Resolution High Definition (RRHD) SB-C18 (50mm×2.1mm, 1.8μm) reversed-phase column at 20°C with methanol-10mM ammonium acetate solution (65:35, v/v) at a flow rate of 1.0mL/min. Detection was performed using an electrospray ionization (ESI) operating in positive ion multiple reaction monitoring (MRM) mode by monitoring the ion transitions from m/z 275.2→149.1 (LASSBio-294) and m/z 152.0→110.0 (acetaminophen, internal standard). The calibration curve of LASSBio-294 in plasma showed good linearity over the concentration range of 1.25-800ng/mL. The validated method was successfully applied to a pre-clinical pharmacokinetic study of the cardioactive prototype LASSBio-294 in beagles after oral administration. The main pharmacokinetic parameters t(1/2), C(max) and AUC(0-24) were (5.74±0.55)h, (547.66±35.12)ng/mL and (1621.77±41.66)ngh/mL, respectively.     

Neurotensin: an endogenous antipsychotic?

Despite evidence from a variety of experimental approaches implicating the neuropeptide neurotensin in both the mechanism of action of antipsychotic drugs and the pathophysiology of schizophrenia, there has been some debate as to whether a peripherally administered neurotensin receptor agonist represents a sound strategy for the development of a novel class of antipsychotic drugs.     

Clozapine: an atypical antipsychotic agent

The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, dosage, and cost of the atypical antipsychotic drug clozapine are reviewed. Clozapine is a dibenzazepine compound chemically similar to loxapine but with a distinct pharmacologic profile. Unlike currently available medications, clozapine has a low potential for causing extrapyramidal symptoms and does not induce dopamine type 2 receptor hypersensitivity. It shows affinity in vitro not only for dopamine type 1 and 2 receptors but also for histamine type 1, alpha-adrenergic type 1 and 2, serotonin type 2, and muscarinic receptors. Clozapine given orally is nearly completely absorbed and readily metabolized. Urinary excretion is the major route of metabolite elimination. Clozapine has been used to treat schizophrenia, nonschizophrenic psychotic states, depression, neuroses, and behavioral disorders. Double-blind comparative studies have shown clozapine to be superior to haloperidol, chlorpromazine, and placebo in treating the symptoms of schizophrenia, as measured with validated psychiatric rating scales. Adverse effects include orthostatic hypotension, tachycardia, benign hyperthermia, hypertension, seizures, and sedation. Many of these effects are transient. Because of the risk of agranulocytosis, a comprehensive case-management system has been developed. In treating acute psychosis, the optimum dosage of clozapine is 300-450 mg/day given orally in divided doses. The high cost of clozapine may be offset by improved patient response and reduced hospital costs. Clozapine may be superior to other agents in the treatment of refractory schizophrenia and is associated with a negligible incidence of extrapyramidal symptoms.