Case report: asenapine and anticholinergic toxicity.

While antipsychotic medications have long been associated with anticholinergic effects, asenapine has been purported to have no capacity for muscarinic cholinergic antagonism based on in vitro studies. Research in rat brain tissue has yielded different results, with one study finding more cholinergic M1-5 binding in the medial prefrontal cortex, dorsolateral frontal cortex and hippocampal CA1 and CA3 areas than would be predicted from in vitro findings. Moreover, it is structurally similar to other anticholinergic antipsychotics such as loxapine and, to a lesser degree, quetiapine, olanzapine and clozapine. This case report describes the anticholinergic toxidrome in a patient treated with benztropine and paroxetine at stable doses, with the emergence of the toxidrome after upward titration of asenapine. A broad differential was considered. With further consideration of the history, time-course, clinical features and physical examination, the presentation is most indicative of the anticholinergic toxidrome. Although not employed, physostigmine, the antidote for anticholinergic delirium, could help to differentiate this toxidrome and serve as a diagnostic and therapeutic intervention. We have presented this case to highlight the importance for clinicians to integrate history and bedside examination data with principles of pharmacology. In particular, asenapine should be added to the list of compounds with recognized anticholinergic potential.

Surface-engineered nanoliposomes with lipidated and non-lipidated peptide-dendrimeric scaffold for efficient transdermal delivery of a therapeutic agent: Development, characterization, toxicological and preclinical performance analyses.

The current study aimed to develop novel peptide dendrimer (PD)-conjugated nanoliposomal formulations of asenapine maleate (ASP) for improvement in the transdermal delivery and pharmacokinetic profile of the drug. Novel arginine-terminated PDs (+/-lipidation) were prepared by solid phase peptide synthesis, followed by conjugation onto ASP nanoliposomes. The nanoliposomes were characterized for particle size (and polydispersity index), zeta potential (ZP), drug entrapment efficiency, shape and morphology, differential scanning calorimetry and FT-IR spectroscopy. Ex vivo skin permeation and retention studies demonstrated considerably higher percutaneous permeation of ASP from the developed nanoliposomes (Q24 = 794.31 ± 54.89 µg/cm2, Jss = 105.40 ± 4.8 µg/cm2/h, ER = 36.85 ± 2.89 for liposomes with lipidated peptide dendrimer (Lipo-PD2)) in comparison with passive diffusion studies (Q24 = 63.09 ± 3.56 µg/cm2, Jss = 3.01 ± 0.23 µg/cm2/h). Confocal Laser Scanning Microscopy (CLSM) confirmed the higher percutaneous penetration of Lipo-PD2 in comparison with liposomes without the dendrimer. In vitro cytotoxicity determined on HaCaT cell line demonstrated CTC50 of >1000 µg/mL for both the synthesized PDs and Lipo-PD2. Pharmacokinetic studies in male Sprague Dawley rats revealed considerably and significantly higher t1/2 = 82.32 ± 14.48 h and AUC0-t = 4403.34 ± 367.10 h.ng/mL, from the developed formulation, compared to orally administered ASP (t1/2 = 21.64 ± 2.53 h and AUC0-t = 2303.55 ± 444.5 h.ng/mL), demonstrating higher bioavailability and longer retention in vivo. Additionally, in vivo skin retention, brain uptake studies and pharmacodynamics of the developed formulations were investigated. Stability studies indicated that the formulations were stable up to relatively stable with respect to size, ZP and drug content for 4 months at the tested conditions. This study demonstrates that the developed PD-conjugated nanoliposomal formulations can effectively serve as a transdermal delivery strategy for ASP.

Clinical effects and P-glycoprotein inhibition in patients with acute myeloid leukemia treated with zosuquidar trihydrochloride, daunorubicin and cytarabine.

BACKGROUND AND OBJECTIVES: P-glycoprotein (P-gp) is a major cause of multidrug resistance (MDR) in acute myelogenous leukemia (AML) and is thought to contribute to the failure of chemotherapy. Zosuquidar trihydochloride (Z.3HCL) is a potent and selective inhibitor of P-gp which rapidly and effectively inhibits drug efflux. DESIGN AND METHODS: The aim of this study was to evaluate the clinical effects of Z.3HCL and determine its influence on P-gp activity. Sixteen AML patients were entered into a phase 1 dose ranging clinical trial of Z.3HCL, co-administered intravenously with daunorubicin and cytosine arabinoside (ARA-C). Clinical outcomes, toxicity abd adverse events were assessed. P-gp function was analyzed by flow cytometry. In vitro cytotoxicity was studied using the MTT assay. RESULTS: Eleven patients achieved a complete remission and one a partial remission with a median survival of 559 (range 38-906) days. Non-hematologic grade 3 and 4 toxicities were seen in 4 patients. Z.3HCL infusion was associated with rapid inhibition of Rh123 efflux in CD56+ cells in 16/16 patients and in CD33+ cells from 6/10 patients. The median inhibition was 95% for CD56+ cells and 85.25% for CD33+ cells was significantly elevated in 6/16 patients. The median IC50, using a MTT assay for daunorubicin, decreased significantly between Z.3HCL modulated and unmodulated cells (n=11,153 and 247 ng/mL respectively, p=0.01). INTERPRETATION AND CONCLUSIONS: The modulator Z.3HCL is a specific inhibitor of P-gp efflux and can be given safely to patients with AML in combination with induction doses of conventional cytotoxic drugs.

Structurally distinct MDR modulators show specific patterns of reversal against P-glycoproteins bearing unique mutations at serine939/941.

The mechanism by which P-glycoprotein (P-gp) interacts with a number of structurally unrelated substrates or inhibitors remains unknown. We have recently shown that a serine residue within the predicted transmembrane (TM) domain 11 of P-gps encoded by mouse mdr1 (Ser941) and mdr3 (Ser939) plays an important role in the substrate specificity of P-gp. We wished to determine if Ser939/941 is also important for efficient interaction of P-gp with structurally different modulating agents, a cyclic peptide (cyclosporin A, CsA), a diaminoquinazoline (CP100356), and a chiral, tricyclic structure (CP117227). For this, the capacity of these compounds to modulate the vinblastine (VBL) resistance phenotype of transfected cells expressing similar levels of P-gps bearing either the wild-type Ser or a mutant Phe at position 941 (mdr1) or 939 (mdr3) was initially tested. The Ser-->Phe substitution indeed affected the potency and P-gp isoform specificity of some of the modulators, in particular that of CP117227 (racemic mixture and enantiomers), which were active against wild-type but not mutant mdr3. The modulatory effect of the mutation on CP117227-mediated reversal of VBL resistance was parallelled by a comparable modulation of the steady-state levels of VBL accumulation in Ser939- and Phe939-expressing cells, but was not linked to differential cellular accumulation of the modulator, which was identical in both cell types. To further assess the role of this amino acid residue in P-gp interactions with modulators, the effect of additional mutations (Ala, Cys, Thr, Asp, Tyr, Trp) at that site on potencies of CsA, CP117227 enantiomers, and CP100356 was evaluated.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic predisposition to drug hepatotoxicity: role in hepatitis caused by amineptine, a tricyclic antidepressant.

Amineptine-induced immunoallergic hepatitis is unpredictable. It may be related to its oxidation into a reactive metabolite acting as hapten. We have looked for a possible genetic predisposition involving drug oxidation capacity and/or cell defense mechanisms in nine patients with previous amineptine hepatitis. Drug oxidation capacity was assessed using dextromethorphan, a test compound recently proposed as a substitute for debrisoquine. The eight patients tested had the extensive metabolizer phenotype. The susceptibility to amineptine metabolites was studied by an in vitro test assessing the destruction of the patients' lymphocytes by reactive metabolites generated from amineptine by a standardized oxidation microsomal system. Lymphocyte death increased with the dose of amineptine (1 to 2.5 mM); it was increased by preincubation with trichloropropene oxide, but was absent when amineptine was omitted or when the oxidation system was not operating. Mean lymphocyte death was twice higher in the nine patients with amineptine hepatitis than in 17 healthy controls. In contrast, when the test was performed with acetaminophen (3 to 10 mM), lymphocyte death was similar in controls and in patients. Basal epoxide hydrolase activity toward benzo[a]pyrene-4,5-oxide and glutathione concentration was similar in lymphocytes from controls and patients. Family studies showed an increased susceptibility to amineptine metabolites in lymphocytes from several first-degree relatives of two patients. These results show that amineptine hepatitis occurs in patients with extensive dextromethorphan oxidation capacity but with an increased susceptibility to amineptine reactive metabolites, probably related to a genetic deficiency in a cell defense mechanism.

Pathological changes induced in cerebrocortical neurons by phencyclidine and related drugs.

Phencyclidine (PCP), a dissociative anesthetic and widely abused psychotomimetic drug, and MK-801, a potent PCP receptor ligand, have neuroprotective properties stemming from their ability to antagonize the excitotoxic actions of endogenous excitatory amino acids such as glutamate and aspartate. There is growing interest in the potential application of these compounds in the treatment of neurological disorders. However, there is an apparent neurotoxic effect of PCP and related agents (MK-801, tiletamine, and ketamine), which has heretofore been overlooked: these drugs induce acute pathomorphological changes in specific populations of brain neurons when administered subcutaneously to adult rats in relatively low doses. These findings raise new questions regarding the safety of these agents in the clinical management of neurodegenerative diseases and reinforce concerns about the potential risks associated with illicit use of PCP.

Subchronic administration of MK-801 in the rat decreases cortical binding of [3H]D-AP5, suggesting down-regulation of the cortical N-methyl-D-aspartate receptors.

The effects of the subchronic administration of (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine (MK-801) (0.5 mg/kg twice daily, 7 days) on N-methyl-D-aspartate, phencyclidine and sigma binding sites, behaviour and catecholamine turnover were investigated in the rat. Overt behaviours induced by MK-801 on day 7 were significantly altered relative to day 1 with subchronically treated rats not showing head weaving, goss ataxia or loss of hindlimb control: locomotion and sniffing were largely unaffected. The mean intensities of behaviour were 1.8 and 5.4 for days 7 and 1, respectively. Behavioural tolerance was accompanied by a significant reduction in the density of cortical N-methyl-D-aspartate receptors as measured by [3H]D-2-amino-5-phosphonopentanoic acid binding, while affinity was unchanged: the density of binding sites was 3.52 and 1.88 pmol/mg protein for saline- and MK-801-treated rats, respectively. The N-methyl-D-aspartate ion channel as measured by the binding of [3H]N-(1-[2-thienyl]cyclohexyl)piperidine was not affected by the schedule of MK-801. Additionally, changes were not observed to N-methyl-D-aspartate- or glycine-stimulated [3H]N-(1-[2-thienyl]cyclohexyl)piperidine binding or to sigma binding. Catecholamine turnover was unaltered in the nucleus accumbens septi after the schedule of MK-801. Our results demonstrate that the subchronic administration of MK-801 produces behavioural tolerance and down-regulation of N-methyl-D-aspartate binding sites and suggest differential regulation of the domains of the N-methyl-D-aspartate receptor-ionophore complex.

Mucosal lesions induced in the rat intestinal tract by the anti-inflammatory drug, Wy-41,770, a weak inhibitor of prostaglandin synthesis, contrasted with those from the potent prostaglandin inhibitor, indomethacin.

The intestinal ulcerogenic activity of the weak prostaglandin synthesis inhibitor drug Wy-41,770 [5H-dibenzo(a,d)-cyclohepten-5-ylidine] was contrasted with the potent synthesis inhibitor, indomethacin, in rats to establish the relationship of inhibition of prostaglandin synthesis to the intestinal damage. Wy-41,770 induced superficial erosions only in the cecum 26 hr after a single oral dose of 250 or 500 mg/kg of the drug, progressing to ulcers after 5 days dosing with ultrastructural evidence of bacteria in the mucosa. Indomethacin (5 or 10 mg/kg po) induced mucosal erosions in the ileum, initially at 26 hr progressing to ulcers after 5 days. Fewer bacteria were seen in the ileal mucosa of indomethacin-treated rats. Both drugs reduced prostaglandin E in those regions of the intestine coincident with the known accumulation of these drugs at sites of mucosal injury. Site-specific intestinal damage from these 2 drugs is associated with inhibition of the synthesis of mucosal-protective prostanoids, followed by pronounced bacterial invasion through the damage mucosae with consequent appearance of local immuno-inflammatory reactions.

New tricyclic enamine derivatives with CNS depressant properties.

63 tricyclic enamine derivatives were synthetized and pharmacologically tested. Many of the screened compounds showed remarkable CNS depressant chlorpromazine-like activities. The compounds no. 9 (substituents CH3, Cl, H), 18 (substituents CH3, F, H) and 27 substituents CH3, OCH3, H) resulted the most interesting and were studied in comparison with chlorpromazine and chlordiazepoxide. They were submitted to further studies in view of trials in humans.

A central nervous system depressant-antidepressant.

A new tricyclic agent with an allenyl side chain experimentally shows antidepressant activity similar to amitriptyline and imipramine but also exerts marked CNS depression. Such dual activity should be of clinical interest for treatment of mixed anxiety and depression.