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Differential enhancement of antidepressant penetration into the brain in mice with abcb1ab (mdr1ab) P-glycoprotein gene disruption.

Uhr M, Grauer MT, Holsboer F.

Max Planck Institute of Psychiatry, Kraepelinstrasse 10, D-80804 Munich, Germany.

BACKGROUND: Mice with a genetic disruption (knockout) of the multiple drug resistance (abcb1ab) gene were used to examine the effect of the absence of the drug-transporting P-glycoprotein (P-gp) at the blood-brain barrier on the uptake of the antidepressants venlafaxine, paroxetine, mirtazapine, and doxepin and its metabolites into the brain. METHODS: One hour after subcutaneous injection of venlafaxine, paroxetine, mirtazapine, or doxepin, knockout and wildtype mice were sacrificed, and the drug concentrations in brain, spleen, kidney, liver, and plasma were measured. RESULTS: The cerebrum concentrations of doxepin, venlafaxine, and paroxetine were higher in knockout mice, demonstrating that these substances are substrates of P-gp and that abcb1ab activity at the level of the blood-brain barrier reduces the penetration of these substances into the brain. In contrast, brain distribution of mirtazapine was indistinguishable between the groups. CONCLUSIONS: The differences reported here in brain penetration of antidepressant drugs that depend on the presence of the abcb1ab gene may offer an explanation for poor or nonresponse to antidepressant treatment. Furthermore, they may be able to explain in part the discrepancies between plasma levels of an antidepressant and its clinical effects and side effects.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14550684&dopt=Abstract mirtazapine Remeron



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Influence of mirtazapine on urinary free cortisol excretion in depressed patients.

Schule C, Baghai T, Rackwitz C, Laakmann G.

Department of Psychiatry, University of Munich, Nussbaumstr. 7, Munich 80336, Germany.

Mirtazapine has been shown to acutely inhibit cortisol secretion in healthy subjects. In the present study, the impact of mirtazapine treatment on urinary free cortisol (UFC) excretion was investigated in depression. Twenty patients (six men, 14 women) suffering from major depression according to DSM-IV criteria were treated with mirtazapine for 3 weeks. The patients received 15 mg mirtazapine on day 0; 30 mg mirtazapine on day 1; and 45 mg mirtazapine per day from day 2 to the end of the study (day 21). UFC excretion was measured before treatment (day 1), at the beginning (day 0), after 1 week (day 7) and after 3 weeks (day 21) of treatment with mirtazapine. Urine samples were collected from 08:00 to 08:00 h the following day. On the days of urine sampling, the severity of depressive symptoms was assessed using the 21-item version of the Hamilton Rating Scale for Depression (21-HAMD). There was a significant reduction of UFC excretion during 3-week mirtazapine therapy, which was already obvious after the first day of treatment (day 0). However, there were no significant across-subjects correlations between UFC reduction and decrease in 21-HAMD sum scores. Apparently, the mirtazapine-induced rapid reduction of cortisol secretion in depressed patients is not necessarily correlated with a favorable therapeutic response.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14561437&dopt=Abstract mirtazapine Remeron



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Influence of mirtazapine on the sexual behavior of male rats.

Benelli A, Frigeri C, Bertolini A, Genedani S.

Department of Biomedical Sciences, Section of Pharmacology, University of Modena and Reggio Emilia, via G. Campi 287, 41100 Modena, Italy. benelli.augusta unimo.it

RATIONALE: Impairment of sexual activity is one of the most frequent side effects of antidepressant drugs. The increase in the synaptic concentrations of serotonin seems to be mainly responsible. Mirtazapine is a novel antidepressant that increases the synaptic concentrations of both noradrenaline and serotonin; moreover, it is an antagonist at 5-HT(2C) receptors, whose activation is considered to be responsible for some typical effects of serotonin on the ejaculation process (retardation of ejaculation, anorgasmia). OBJECTIVES: To study the influence of mirtazapine on copulatory performance and sexual motivation in male rats, in comparison-or in combination-with fluoxetine. METHODS: Copulatory performance was studied either in sexually experienced or in sexually naive rats; sexual motivation was studied in sexually experienced rats. Mirtazapine (1, 5 or 10 mg/kg), fluoxetine (10 mg/kg), and the combination of mirtazapine + fluoxetine (10+10 mg/kg) were subcutaneously (s.c.) administered either acutely or daily for 13 days. RESULTS: After acute administration, mirtazapine decreased mount latency (ML) and intromission latency (IL), and increased mount frequency (MF) and ejaculation latency (EL). Fluoxetine had no significant effect on any of the sexual behavior parameters. After a 13-day treatment, mirtazapine increased ML, IL and MF; fluoxetine increased ML, IL and the intercopulatory interval (ICI); the addition of mirtazapine to fluoxetine produced a reduction of ICI and an increase of MF. Moreover, mirtazapine significantly improved the performance of rats in the sexual motivation test. CONCLUSIONS: The present results show that, on the whole, the acute administration of mirtazapine improves several parameters of the copulatory performance of male rats and strongly stimulates sexual motivation, while the repeated administration produces minor, conflicting effects. This effect of mirtazapine on male rat sexual behavior is to be ascribed to the antagonism at brain alpha(2) adrenergic auto- and hetero-receptors, with consequent increased release of noradrenaline and serotonin, and antagonism at 5-HT(2C) receptors, which are involved in the negative influence of serotonin on male sexual behavior.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14615872&dopt=Abstract mirtazapine Remeron



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Regulation of platelet alpha 2A-adrenoceptors, Gi proteins and receptor kinases in major depression: effects of mirtazapine treatment.

Garcia-Sevilla JA, Ventayol P, Perez V, Rubovszky G, Puigdemont D, Ferrer-Alcon M, Andreoli A, Guimon J, Alvarez E.

Laboratory of Neuropharmacology, Associate Unit of the Institute of Neurobiology 'Ramon y Cajal', Department of Biology, University of the Balearic Islands, Palma de Mallorca, Spain. jesus.garcia-sevilla hcuge.ch

Major depression is associated with the upregulation of alpha(2A)-adrenoceptors in brain tissue and blood platelets. The homologous regulation of these receptors by G-protein-coupled receptor kinases (GRKs) might play a relevant role in the pathogenesis and treatment of depression. This study was designed to assess the status of the complex alpha(2A)-adrenoceptor/Galphai/GRK 2 in the platelets of depressed patients (n=22) before and after treatment with the antidepressant mirtazapine, an antagonist at alpha(2A)-adrenoceptors (30-45 mg/day for up to 6 months). A second series of depressed suicide attempters (n=32) were also investigated to further assess the status of platelet GRK 2 and GRK 6. Platelet alpha(2A)-adrenoceptors and Galphai protein immunoreactivities were increased in depressed patients (49 and 35%) compared with matched controls. In contrast, GRK 2 content was decreased in the two series of depressed patients (27 and 28%). GRK 6 (a GRK with different properties) was found unchanged. In drug-free depressed patients, the severity of depression (behavioral ratings with two different instruments) correlated inversely with the content of platelet GRK 2 (r=-0.46, n=22, p=0.032, and r=-0.55, n=22, p=0.009). After 4-24 weeks of treatment, mirtazapine induced downregulation of platelet alpha(2A)-adrenoceptors (up to 34%) and Galphai proteins (up to 28%), and the upregulation of GRK 2 (up to 30%). The results indicate that major depression is associated with reduced platelet GRK 2, suggesting that a defect of this kinase may contribute to the observed upregulation of alpha(2A)-adrenoceptors. Moreover, treatment with mirtazapine reversed this abnormality and induced downregulation of alpha(2A)-adrenoceptor/Galphai complex. The results support a role of supersensitive alpha(2A)-adrenoceptors in the pathogenesis and treatment of major depression.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14628003&dopt=Abstract mirtazapine Remeron



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Measurement of total mirtazapine and normirtazapine in plasma/serum by liquid chromatography with fluorescence detection.

Morgan PE, Tapper J, Spencer EP.

Medical Toxicology Unit, Guy's and St. Thomas' Hospital Trust, London SE14 5ER, UK. phillip.morgan gstt.nhs.uk

A simple high performance liquid chromatography (HPLC) method for the measurement of the new antidepressant mirtazapine and its N-demethyl metabolite, normirtazapine, in human plasma or serum during low dose mirtazapine therapy has been developed. A Waters Spherisorb S5 SCX column was used with ammonium perchlorate (50 mmol/l) in methanol/water (95 + 5 (v/v)), apparent pH 6.7, as eluent, and fluorescence detection. Only small volumes of sample (0.2 ml) and extraction solvent are used. An interference study found no significant co-elution with drug or metabolite, although paroxetine co-elutes with the internal standard. The recovery of mirtazapine and normirtazapine (mean +/- S.D.) was 79 +/- 2, and 64 +/- 3%, respectively. The LOD was estimated as 0.5 microg/l, LLOQ was 1 microg/l, with a linear response over the concentration range 4-1000 microg/l (both analytes). The analytes were stable in serum for at least 10 months when stored at -20 degrees C. Intra- and inter-day accuracy were in the range 91-107 and 93-103%, respectively. In clinical samples (n = 14, median mirtazapine dose 45 mg per day, range 15-45 mg per day) the median (range) mirtazapine and normirtazapine concentrations were 26 (8-40) and 21 (8-32) microg/l, respectively.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14643499&dopt=Abstract mirtazapine Remeron



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Oestradiol and mirtazapine restore the disturbed tail-temperature of oestrogen-deficient rats.

Berendsen HH, Kloosterboer HJ.

Pharmacology Department, N.V. Organon, P.O.B. 20, 5340 BH Oss, The Netherlands. hemmie.berendsen organon.com

The purpose of the present study was to further evaluate the tail-temperature test as a tool to test potential steroidal and non-steroidal compounds for the treatment of hot flushes. Ovariectomized rats were implanted with a temperature sensitive probe. After a recovery period of 5 weeks, the effect of oestradiol (given via a silastic tube) and the 5-HT(2) receptor antagonist mirtazapine (10 mg/kg i.p.) on the tail-temperature in the active phase of the animals was measured. Oestradiol completely restored the disturbed tail temperature after 3 days. Treatment with mirtazapine also restored the oestrogen withdrawal-induced disturbed tail-temperature. The effect of mirtazapine was already seen on the first day of treatment. These experiments confirm and extend the idea that measuring the oestradiol withdrawal-induced disturbance of tail-temperature may be a useful tool to select compounds that might have beneficial effects in the treatment of hot flushes. Blockade of the 5-HT(2A) receptors prevented or reduced the ovariectomy-induced disturbance of the rat tail-temperature, which may validate this model to evaluate the effect of compounds on hot flushes.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14660040&dopt=Abstract mirtazapine Remeron