4-(1,3-Dimethoxyprop-2-ylamine)-2,7-dimethyl-8-(2,4-dichlorophenyl)-pyrazolo[1,5-a]-1,3,5-triazine (DMP696) is a highly selective and potent, nonpeptide corticotropin-releasing factor 1 (CRF 1 ) antagonist. In this study, we measured in vivo CRF 1 receptor occupancy of DMP696 by using ex vivo ligand binding and quantitative autoradiography and explored the relationship of receptor occupancy with plasma and brain exposure and behavioral efficacy. In vitro affinity (IC 50 ) of DMP696 to brain CRF 1 receptors measured using the brain section binding autoradiography in this study is similar to that assessed using homogenized cell membrane assays previously. The ex vivo binding assay was validated by demonstrating that potential underestimation of receptor occupancy with this procedure could be minimized by identifying an appropriate in vitro incubation time (40 min) based upon the dissociation kinetics of DMP696. Orally administrated DMP696 dose dependently occupied CRF 1 receptors in the brain, with ϳ60% occupancy at 3 mg/kg. In the defensive withdrawal test of anxiety, this dose of DMP696 produced approximately 50% reduction in the exit latency. The time course of plasma and brain drug levels paralleled that of receptor occupancy, with peak exposure at 90 min after dosing. The plasma-free concentration of DMP696 corresponding to 50% CRF 1 receptor occupancy (in vivo IC 50 , 1.22 nM) was similar to the in vitro IC 50 (ϳ1.0 nM). Brain concentrations of DMP696 were over 150-fold higher than the plasma-free levels. In conclusion, doses of DMP696 occupying over 50% brain CRF 1 receptors are consistent with doses producing anxiolytic efficacy in the defense withdrawal test of anxiety, and the IC 50 value estimated in vivo based on plasmafree drug concentrations is consistent with the in vitro IC 50 value.Corticotropin releasing factor (CRF), a 41-amino acid peptide, plays a pivotal role in the behavioral, endocrine, immune, and autonomic responses of the body to stress (Owens and Nemeroff, 1991). In addition to the hypothalamic paraventricular nucleus where it was originally identified, CRF is also widely distributed across brain regions (Chalmers et al., 1996;Heinrichs and De Souza, 1999;Gilligan et al., 2000a). The physiological functions of CRF are mediated by at least two G-protein coupled receptors, CRF 1 and CRF 2 (including splice variants CRF 2␣ , CRF 2␤ , CRF 2␥ ), both of which are linked to adenylyl cyclase activation but have distinct brain distributions. CRF 1 receptors are widespread in the cortex, limbic system, cerebellum, and pituitary, whereas CRF 2 receptors are dominant in subcortical areas including the lateral septum (CRF 2␣ ), ventromedial hypothalamus (CRF 2␣ ), and choroid plexus (CRF 2␤ ) (De Souza, 1987;Chalmers et al., 1995;Primus et al., 1997;Rominger et al., 1998).Increasing evidence suggests that the CRF system is involved in pathophysiology of anxiety disorders (Heinrichs and De Souza, 1999;Gilligan et al., 2000a). Intracerebroventricular administration of CRF induces stress beha...

Aims To investigate a possible association of sibutramine with QT interval prolongation. Methods Post‐marketing surveillance using prescription event monitoring in the New Zealand Intensive Medicines Monitoring Programme (IMMP) identified a case of QT prolongation and associated cardiac arrest in a patient taking sibutramine for 25 days. This patient was further investigated, including genotyping for long QT syndrome. Other IMMP case reports suggesting arrhythmias associated with sibutramine were assessed and further reports were obtained from the World Health Organisation (WHO) adverse drug reactions database. Results The index case displayed a novel mutation in a cardiac potassium channel subunit gene, KCNQ1, which is likely to prolong cardiac membrane depolarization and increase susceptibility to long QT intervals. Assessment of further IMMP reports identified five additional patients who experienced palpitations associated with syncope or presyncopal symptoms, one of whom had a QTc at the upper limit of normal. Assessment of reports from the WHO database identified three reports of QT prolongation and one fatal case of torsade de pointes in a patient also taking cisapride. Conclusions This case series suggests that sibutramine may be associated with QT prolongation and related dysrhythmias. Further studies are required, but in the meantime we would recommend that sibutramine should be avoided in patients with long QT syndrome and in patients taking other medicines that may prolong the QT interval.

Several compounds, such as epibatidine, A-85380, and their analogs, have been identified recently as nAChR ligands whose affinities lie in the low picomolar range. Accurate measurement of such high affinities is fraught with certain technical difficulties, which may account for the inconsistency of previously reported affinities of epibatidine, ranging from 4 to 60 pM. Here, we demonstrate that (+/-)-[3H]epibatidine (1-500 pM) binds to a single population of sites in rat brain with KD of 8 +/- 2 pM. This affinity was confirmed in both kinetic experiments and competition assays with (+/-)-[3H]epibatidine and (-)-[3H]cytisine, which were performed under experimental conditions developed specifically for ligands with subnanomolar affinities. Variations from these conditions decreased the observed affinities.

Radiotracers suitable for positron emission tomography studies often serve as preclinical tools for in vivo receptor occupancy. The serotonin 1B receptor (5-HT 1B ) subtype is a pharmacological target used to discover treatments for various psychiatric and neurological disorders. In psychiatry, 5-HT 1B antagonists may provide novel therapeutics for depression and anxiety. We report on the in vitro and in vivo evaluation of tritiated 5-methyl-8-(4-methyl-piperazin-1-yl)-4-oxo-4H-chromene-2-carboxylicacid (4-morpholin-4-yl-phenyl)-amide ([N-methyl- (Hoyer et al., 2002). The serotonin 1B receptor (5-HT 1B ) subtype has been implicated in normal physiological functions and behavior and in neurological and psychiatric disorders, such as diseases of locomotion, migraine, drug abuse, aggressive behavior, anxiety, and depression [Moret and Briley, 2000;Svenningsson et al., 2006; for review, see Sari (2004)]. 5-HT 1B receptors modulate synaptic release of sero-M.D., M.E.Po., Q.J., and G.H. contributed equally to this work. Article, publication date, and citation information can be found at

BackgroundPharmacovigilance signal detection largely relies on individual case reports, but longitudinal health data are being explored as complementary information sources. Research to date has focused on the ability of epidemiological methods to distinguish established adverse drug reactions (ADRs) from unrelated adverse events.ObjectiveThe aim of this study was to evaluate a process for structured clinical and epidemiological assessment of temporally associated drugs and medical events in electronic medical records.MethodsPairs of drugs and medical events were selected for review on the basis of their temporal association according to a calibrated self-controlled cohort analysis in The Health Improvement Network. Six assessors trained in pharmacovigilance and/or epidemiology evaluated seven drugs each, with up to 20 medical events per drug. A pre-specified questionnaire considered aspects related to the nature of the temporal pattern, demographic features of the cohort, concomitant medicines, earlier signs and symptoms, and possible confounding by underlying disease. This informed a classification of drug–event pairs as known ADRs, meriting further evaluation, or dismissed.ResultsThe number of temporally associated medical events per drug ranged from 11 to 307 (median 50) for the 42 selected drugs. Out of the 509 relevant drug–event combinations subjected to the assessment, 127 (25 %) were classified as known ADRs. Ninety-one (24 %) of the remaining pairs were classified as potential signals meriting further evaluation and 291 (76 %) were dismissed. Suggestive temporal patterns and lack of clear alternative explanations were the most common reasons that drug–event pairs were classified as meriting further evaluation. Earlier signs and symptoms and confounding by the underlying disease were the most common reasons that drug–event pairs were dismissed.ConclusionsExploratory analysis of electronic medical records can detect important potential safety signals. However, effective signal detection requires that statistical signal detection be combined with clinical and epidemiological review to achieve an acceptable false positive rate.