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PubMed1998

Mirtazapine: efficacy and tolerability in comparison with fluoxetine in patients with moderate to severe major depressive disorder. Mirtazapine-Fluoxetine Study Group.

OBJECTIVE: To compare the efficacy and tolerability of mirtazapine and fluoxetine in depressed inpatients and outpatients. METHOD: Patients with a major depressive episode (DSM-III-R), a baseline score of > or=21 on the 17-item Hamilton Rating Scale for Depression (HAM-D), and > or=2 on HAM-D Item 1 (depressed mood) were randomly assigned to a 6-week treatment with either mirtazapine (N=66, 15-60 mg/day) or fluoxetine (N=67, 20-40 mg/day). The upper limit of the mirtazapine dose range was above the dose range approved in the United States (15-45 mg/day). Efficacy was evaluated by the HAM-D, Clinical Global Impressions, the Visual Analogue Mood Rating Scale (VAMRS), and the Quality of Life Enjoyment and Satisfaction Questionnaire (QLESQ). The efficacy analyses were performed on the intent-to-treat group using the last-observation-carried-forward method. RESULTS: Mean total 17-item HAM-D scores at baseline were 26.0 for the mirtazapine- and 26.1 for the fluoxetine-treated group. The decrease from baseline on the HAM-D was larger in the mirtazapine than in the fluoxetine group throughout the treatment period, reaching statistical significance at days 21 and 28. At assessments from day 21 and onward, the absolute difference between the 2 study groups favoring mirtazapine ranged from 3.7 to 4.2 points, the magnitude of difference usually seen between an efficacious antidepressant drug and placebo. Mean dosages at weeks 1-4 were 36.5 mg/day for mirtazapine and 19.6 mg/day for fluoxetine; the respective dosages at weeks 5-6 were 56.3 mg and 35.8 mg. Similar numbers of patients dropped out due to adverse events; tolerability profiles were comparable except for changes in body weight from baseline which were statistically significantly more pronounced in the mirtazapine group compared to the fluoxetine group. CONCLUSION: We found that mirtazapine was as well tolerated as fluoxetine and significantly more effective after 3 and 4 weeks of therapy.

Adolescent↗
PubMed2006

Therapeutic drug monitoring of mirtazapine, desmethylmirtazapine, 8-hydroxymirtazapine, and mirtazapine-N-oxide by enantioselective HPLC with fluorescence detection.

The tetracyclic antidepressant mirtazapine has been in clinical use for several years as a racemic drug. Because of a relatively narrow therapeutic index, therapeutic drug monitoring may be helpful to individually optimize therapy with mirtazapine. An enantioselective high-performance liquid chromatography (HPLC) method with fluorescence detection has been developed for the quantification of mirtazapine, desmethyl mirtazapine, 8-hydroxy mirtazapine, and mirtazapine N-oxide. The method is suitable for the analysis of plasma and urine samples in the range from 1 to 100 ng/mL with precision (coefficient of variation, or CV) between 12% and 19%. The sample preparation step comprises a liquid-solid extraction procedure with good recoveries, between 85% and 99%. Patient samples for therapeutic drug monitoring as well as concentration-time series were assayed and the resulting enantiomer ratios analyzed. Typical trough levels were between 1 and 100 ng/mL, with enantiomer ratios of approximately 0.42 (S/R). In concentration-time series, enantiomer ratios distinctively greater than 1 were observed at early time points. Because the enantiomers of mirtazapine and desmethyl mirtazapine have different pharmacological properties, the method is believed to be helpful in understanding the concentration-effect relationships in the former.

Antidepressive Agents, Tricyclic↗
PubMed2005

Tissue distribution of mirtazapine and desmethylmirtazapine in a case of mirtazapine poisoning.

An ingestion of an unknown quantity of mirtazapine in a suicide attempt leading to death is described. Sertraline and amitriptyline have been co-ingested. Because mirtazapine is reported to be relatively safe in overdose, body fluids and tissues were investigated for both mirtazapine and desmethylmirtazapine by high-pressure liquid chromatography/tandem mass spectrometry following liquid-liquid extraction. The limit of detection was sufficiently low to also apply the assay in pharmacokinetic studies. The levels of amitriptyline and nortriptyline were very low (38 and 19 ng/mL femoral venous blood) and the amount of sertraline in blood taken from the femoral vein (880 ng/mL) was considerably lower than those seen in overdosage. Accumulation of mirtazapine and N-desmethylmirtazapine was evident in fluids and tissues involved in enterohepatic circulation and excretion. The concentration determined in a brain sample suggests a contribution of the metabolite to the drug's pharmacodynamic activity. Based on literature data, significant adverse or synergistic effects among the drugs detected as well as adverse reactions such as a serotonin reaction appeared less probable. Mirtazapine exhibits alpha(1)-antagonistic properties on the cardiac-vascular system and may cause hyponatraemia. In the face of the cardiac findings at autopsy and the lack of an apparent cause of death, these effects of mirtazapine may have initiated a process leading to death.

Aged↗
PubMed1998

Review of the results from clinical studies on the efficacy, safety and tolerability of mirtazapine for the treatment of patients with major depression.

Mirtazapine is a presynaptic alpha-2 antagonist that has dual action by increasing noradrenergic and serotonergic neurotransmission. The enhancement of serotonergic neurotransmission is specifically mediated via 5-HT1 receptors because mirtazapine is a postsynaptic serotonergic 5-HT2 and 5-HT3 antagonist. In addition, mirtazapine has only a weak affinity for 5-HT1 receptors and has very weak muscarinic anticholinergic and histamine (H1) antagonist properties. As a consequence of its unique pharmacodynamic properties, mirtazapine is an effective, safe and well-tolerated addition to the antidepressant armamentarium. Mirtazapine is well absorbed from the gastrointestinal tract following oral administration, and it is extensively metabolized in the liver to four metabolites via demethylation and hydroxylation, followed by glucuronide conjugation. The unconjugated desmethyl metabolite is pharmacologically less active than the parent compound. Mirtazapine lacks auto-induction of hepatic isoenzymes. Although mirtazapine is a substrate of P450 isoenzymes 1A2, 2D6 and 3A4, in vitro studies show that it is not a potent inhibitor or inducer of any of these enzymes. Mirtazapine has been evaluated in a worldwide clinical development program involving approximately 4500 patients. Controlled clinical trials involving almost 2800 mirtazapine-treated patients have demonstrated the compound to be effective for the treatment of moderate-to-serve major depression. Mirtazapine was consistently superior to placebo, and equivalent in efficacy to the tricyclic antidepressants amitriptyline, doxepin and clomipramine, but with an improved tolerability profile. Mirtazapine has shown a rapid onset of action in patients with predominantly severe depressive illness in a comparative study against fluoxetine. Mirtazapine has a unique tolerability profile, since the specific postsynaptic 5-HT2 and 5-HT3 receptor blockade of mirtazapine provides early antidepressant effects without causing unwanted serotonin-related side-effects. Transient somnolence, hyperphagia and weight gain are the most commonly reported adverse events, which may be attributed to the antihistaminic (H1) activity of mirtazapine at low doses. Somnolence, the most commonly reported side-effect, appears to be less frequent at higher dosages. Mirtazapine also demonstrates important anxiolytic and sleep-improving effects, which may be related to its pharmacodynamic properties. In addition, mirtazapine does not appear to be associated with sexual dysfunction. Mirtazapine has shown no significant cardiovascular adverse effects at multiples of 7 to 22 times the maximum recommended dose. Mirtazapine is a unique addition to the antidepressant armamentarium as first-line therapy in patients with major depression and symptoms of anxiety/agitation or anxiety/somatization or complaints of insomnia and as a useful alternative in depressed patients who do not adequately respond to or are intolerant of tricyclic antidepressants or serotonin-specific reuptake inhibitors.

Administration, Oral↗
PubMed2000

Mirtazapine. A pharmacoeconomic review of its use in depression.

UNLABELLED: Mirtazapine is a noradrenergic and specific serotonergic antidepressant (NaSSA). The antidepressant efficacy of mirtazapine has been established in randomised, double-blind comparative studies. Mirtazapine has generally shown similar efficacy to other antidepressants. There is evidence for a faster onset of action with mirtazapine than with the selective serotonin (5-hydroxytryptamine; 5-HT) re-uptake inhibitors (SSRIs) on the basis of mean depression rating scale scores. Data from a long term (mean 240 days) clinical trial that was subsequently used in pharmacoeconomic analyses showed that mirtazapine was associated with significantly higher sustained remission rates and rates of discontinuation because of improvement than amitriptyline and placebo. Although differences were not statistically significant, mirtazapine had higher response rates at 6 weeks than the SSRI fluoxetine in an analysis that was also used as the basis of pharmacoeconomic studies. Mirtazapine improved quality of life to a similar extent to fluoxetine, citalopram and paroxetine in unpublished studies of 6 and 8 weeks' duration. Pooled analyses suggest that mirtazapine may be associated with greater improvement than fluoxetine and citalopram in quality of life after 2 and 4 weeks, although confirmation is required. In a decision analytical model of approximately 6 months' duration, mirtazapine was associated with a higher proportion of successfully treated patients and lower total direct costs than amitriptyline. The direct cost per successfully treated patient with mirtazapine was lower than that with amitriptyline by 33,112 Austrian schillings (S; year of costing not stated), 24,212 French francs (FF; 1995/1996 values), 13,851 Swedish kronor (SEK; 1997 values) and 553 Pounds (1997/1998 values) in Austrian, French, Swedish and UK analyses, respectively. Compared with fluoxetine, mirtazapine was associated with higher per-patient costs in all 4 countries but a higher proportion of successfully treated patients. Mirtazapine was more cost effective than fluoxetine: the direct cost per successfully treated patient was lower by S32,046 in Austria, FF25,914 in France, SEK9796 in Sweden and 327 Pounds in the UK. The additional cost of mirtazapine versus fluoxetine for each additional successfully treated patient at 6 months was S11,732, SEK17,229, 750 Pounds and FF3342 in the Austrian, Swedish, UK and French analyses, respectively. Mirtazapine was generally associated with lower indirect costs (for lost productivity of employed patients) than amitriptyline and similar indirect costs to fluoxetine in the analyses. CONCLUSIONS: Available data suggest that mirtazapine is a cost-effective alternative to amitriptyline and fluoxetine for the treatment of depression. Mirtazapine also has similar effects to SSRIs on quality of life with possibly a shorter time to onset of action, although published trial results are required to confirm these preliminary data.

Amitriptyline↗
PubMed1995

Clinical efficacy of mirtazapine: a review of meta-analyses of pooled data.

Mirtazapine is a novel antidepressant with a unique mode of action, which can be best summarized as a noradrenaline and specific serotonin antidepressant. Its unique mode of action, involving both the noradrenergic and serotonergic neurotransmitter systems, results in strong clinical efficacy. A comprehensive clinical trial programme in Europe and the United States has demonstrated that mirtazapine has clear clinical benefits in a broad range of patients treated across different therapeutic settings. The individual placebo-controlled trials and a meta-analysis on pooled efficacy data from all available placebo-controlled studies have shown that mirtazapine has sustained antidepressant efficacy, as assessed by changes from baseline in group mean scores on the Hamilton Rating Scale for Depression (HAMD) and in the depressed mood item, from week 1 throughout the whole study period. Corroborative evidence on the clinical efficacy of mirtazapine has been obtained in comparative studies with antidepressant drugs of well established efficacy, such as amitriptyline, clomipramine, doxepin and trazodone. As with the placebo-controlled studies, a meta-analysis was performed on data from all the randomized, double-blind, comparative studies of mirtazapine and amitriptyline. Data from 732 patients were available (364 patients taking mirtazapine and 368 taking amitriptyline) for efficacy analysis. Equivalent improvements in total 17-item HAMD scores from baseline were observed in both treatment groups at all scheduled assessments and at the end of the study period, and similarly high percentages of patients responded to treatment with either mirtazapine (70%) or amitriptyline (73%). The efficacy of mirtazapine was also assessed in the treatment of moderately (baseline 17-item HAMD score 18-24) or severely depressed patients (baseline 17-item HAMD score > or = 25). A meta-analysis was performed on the pooled data from the moderately or severely depressed patients in the comparative studies of mirtazapine and placebo or mirtazapine and amitriptyline. Statistically and clinically significant improvements from baseline were seen in both moderately and severely depressed patients treated with mirtazapine compared with placebo, while an equivalent extent of improvement was present with mirtazapine and amitriptyline. A similar pattern was observed in the improvement of depressed mood (HAMD item 1) and other clinically important symptoms of depression: mirtazapine was significantly more efficacious than placebo, and of equivalent efficacy to amitriptyline. Therefore, it can be concluded that the new antidepressant mirtazapine offers distinct therapeutic benefits for a variety of depressed patients in either in- or outpatient settings.

Antidepressive Agents, Tricyclic↗
PubMed2000

Clinical pharmacokinetics of mirtazapine.

Mirtazapine is the first noradrenergic and specific serotonergic antidepressant ('NaSSA'). It is rapidly and well absorbed from the gastrointestinal tract after single and multiple oral administration, and peak plasma concentrations are reached within 2 hours. Mirtazapine binds to plasma proteins (85%) in a nonspecific and reversible way. The absolute bioavailability is approximately 50%, mainly because of gut wall and hepatic first-pass metabolism. Mirtazapine shows linear pharmacokinetics over a dose range of 15 to 80mg. The presence of food has a minor effect on the rate, but does not affect the extent, of absorption. The pharmacokinetics of mirtazapine are dependent on gender and age: females and the elderly show higher plasma concentrations than males and young adults. The elimination half-life of mirtazapine ranges from 20 to 40 hours, which is in agreement with the time to reach steady state (4 to 6 days). Total body clearance as determined from intravenous administration to young males amounts to 31 L/h. Liver and moderate renal impairment cause an approximately 30% decrease in oral mirtazapine clearance; severe renal impairment causes a 50% decrease in clearance. There were no clinically or statistically significant differences between poor (PM) and extensive (EM) metabolisers of debrisoquine [a cytochrome P450 (CYP) 2D6 substrate] with regard to the pharmacokinetics of the racemate. The pharmacokinetics of mirtazapine appears to be enantioselective, resulting in higher plasma concentrations and longer half-life of the (R)-(-)-enantiomer (18.0 +/-2.5h) compared with that of the (S)-(+)-enantiomer (9.9+/-3. lh). Genetic CYP2D6 polymorphism has different effects on the enantiomers. For the (R)-(-)-enantiomer there are no differences between EM and PM for any of the kinetic parameters; for (S)-(+)-mirtazapine the area under the concentration-time curve (AUC) is 79% larger in PM than in EM, and a corresponding longer half-life was found. Approximately 100% of the orally administered dose is excreted via urine and faeces within 4 days. Biotransformation is mainly mediated by the CYP2D6 and CYP3A4 isoenzymes. Inhibitors of these isoenzymes, such as paroxetine and fluoxetine, cause modestly increased mirtazapine plasma concentrations (17 and 32%, respectively) without leading to clinically relevant consequences. Enzyme induction by carbamazepine causes a considerable decrease (60%) in mirtazapine plasma concentrations. Mirtazapine has little inhibitory effects on CYP isoenzymes and, therefore, the pharmacokinetics of coadministered drugs are hardly affected by mirtazapine. Although no concentration-effect relationship could be established, it was found that with therapeutic dosages of mirtazapine (15 to 45 mg/day), plasma concentrations range on average from 5 to 100 microg/L.

Animals↗
PubMed1999

Mirtazapine: a review of its use in major depression.

UNLABELLED: Mirtazapine is a noradrenergic and specific serotonergic antidepressant (NaSSA) which has predominantly been evaluated in the treatment of major depression. The drug had equivalent efficacy to tricyclic antidepressants and it was at least as effective as trazodone in the majority of available short term trials in patients with moderate or severe depression, including those with baseline anxiety symptoms or sleep disturbance and the elderly. A continuation study also showed that sustained remission rates were higher with mirtazapine than with amitriptyline and that the drugs had similar efficacy for the prevention of relapse. There is some evidence for a faster onset of action with mirtazapine than with the selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitors (SSRIs). Mirtazapine was more effective than the SSRI fluoxetine at weeks 3 and 4 of therapy and it was also more effective than paroxetine and citalopram at weeks 1 and 2, respectively, in short term assessments (6 or 8 weeks). Preliminary data suggest that the drug may be effective as an augmentation or combination therapy in patients with refractory depression. Anticholinergic events and other events including tremor and dyspepsia are less common with mirtazapine than with tricyclic antidepressants. There was a greater tendency for SSRI-related adverse events with fluoxetine than with mirtazapine, but, overall, mirtazapine had a similar tolerability profile to the SSRIs. Increased appetite and bodyweight gain appear to be the only events that are reported more often with mirtazapine than with comparator antidepressants. In vitro and in vivo data have suggested that mirtazapine is unlikely to affect the metabolism of drugs metabolised by cytochrome P450 (CYP)2D6, although few formal drug interaction data are available. CONCLUSIONS: Mirtazapine is effective and well tolerated for the treatment of patients with moderate to severe major depression. Further research is required to define the comparative efficacy of mirtazapine in specific patient groups, including the elderly and those with severe depression. Clarification of its efficacy as an augmentation therapy and in patients with refractory depression and its role in improving the efficacy and reducing the extrapyramidal effects of antipsychotic drugs would also help to establish its clinical value. The low potential for interaction with drugs that are metabolised by CYP2D6, including antipsychotics, tricyclic antidepressants and some SSRIs, may also make mirtazapine an important option for the treatment of major depression in patients who require polytherapy. Mirtazapine also appears to be useful in patients with depression who present with anxiety symptoms and sleep disturbance.

Antidepressive Agents, Tricyclic↗
PubMed1995

Safety of mirtazapine: a review.

The clinical trial development programme of mirtazapine (Org 3770), performed in Europe and the United States, demonstrated an outstanding safety profile of this compound. The evaluation of the safety was based on data from all patients who took at least one dose of study medication during studies comparing mirtazapine with placebo, amitriptyline or other active comparators. A general indication of mirtazapine's safety is the significantly lower percentage of patients (65%) who complained of any adverse clinical experiences compared with the placebo- (76%) or amitriptyline-treated group (87%). Moreover, drop-out rates due to adverse clinical experiences were significantly lower than in the amitriptyline-treatment group. Mirtazapine has virtually no anticholinergic, adrenergic or typical selective serotonin reuptake inhibitor (SSRI) side effects. The only significantly higher incidences versus placebo were seen in the adverse clinical effects of drowsiness (23% versus 14%), excessive sedation (19% versus 5%), dry mouth (25% versus 16%), increased appetite (11% versus 2%) and weight increase (10% versus 1%). These complaints were typically mild and transient in nature, and decreased over time despite increased doses of mirtazapine. In contrast, significantly higher incidences of headache (5% versus 10%) and weight decrease (2% versus 6%), symptoms commonly seen in depressed patients, were recorded in the placebo-treated patients. Also, typical SSRI adverse events, such as nausea, vomiting, diarrhoea and insomnia, and symptoms of sexual dysfunction were registered less frequently in mirtazapine-treated patients than in the placebo-treated patients. Approximately 10% of the mirtazapine-treated patients in the clinical trial programme were older than 65 years. The pattern of adverse clinical experiences seen in this group of patients is fully in line with that seen in the overall patient population. The analysis of vital sign indices, i.e. blood pressure and heart rate, showed that no changes occurred with mirtazapine treatment; this pattern was fully comparable to that seen with placebo. Furthermore, very low incidences of clinically relevant changes in laboratory indices, such as the liver enzymes alanine aminotransferase and aspartate aminotransferase or neutropenia, were recorded in each treatment group. Mirtazapine has a very low seizure-inducing potential: only one case was recorded in a patient with a history of seizures during previous treatment with clomipramine. The low seizure-inducing potential combined with a lack of cardiotoxic properties allows safety in an overdose of mirtazapine, even in elderly patients. The only symptom seen in the patients taking an overdose of mirtazapine alone or in combination with other drugs was excessive but transient somnolence, which resolved spontaneously within a few hours. In conclusion, the new antidepressant mirtazapine offers clinicians a unique combination of strong efficacy and good safety.

Adult↗
PubMed1999

Efficacy and tolerability of mirtazapine versus citalopram: a double-blind, randomized study in patients with major depressive disorder. Nordic Antidepressant Study Group.

We aimed to compare the antidepressant and anxiolytic effects, tolerability and effects on quality of life of mirtazapine and citalopram in a randomized, double-blind, multicentre, 8-week study. Patients with a Major Depressive Episode (DSM-IV) and a baseline score of > or = 22 on the Montgomery-Asberg Depression Rating Scale (MADRS) were randomized to 8 weeks treatment with either mirtazapine (n = 137, 15-60 mg/day) or citalopram (n = 133, 20-60 mg/day). Efficacy was evaluated by the MADRS, Hamilton Anxiety Scale (HAM-A), Clinical Global Impression scales (CGI), the Leeds Sleep Evaluation Questionnaire (LSEQ) and Quality of Life Enjoyment and Satisfaction Questionnaire (QLESQ). The efficacy analyses were performed on the Intent-To-Treat Group using the Last Observation Carried Forward method. Vital signs and laboratory variables are measured and adverse events recorded at each weekly visit. The magnitude of reduction from baseline in group mean MADRS scores was large in both groups, reaching after 8 weeks of treatment mean scores of 9.1 in the mirtazapine group and 8.9 in the citalopram group. Both treatments also resulted in a substantial improvement in anxiety symptoms, sleep disturbances and quality of life, and high percentage of responders. However, at day 14, statistically significantly larger magnitudes of change favouring mirtazapine were present in the group mean MADRS, HAM-A and CGI-Severity of illness and Quality of life scores. A difference of 2.3 points on MADRS favouring mirtazapine is considered indicative for a clinically relevant superiority between two proven antidepressants. Mirtazapine treatment was also related to faster improvement of sleep, quality of sleep and improved alertness following awakening, as shown by statistically significant differences on the self-rating LSEQ at various time points. There were no differences between two treatment groups on self-rating QLSEQ. Both drugs were well tolerated, with a low number of patients in either group prematurely terminating the study due to adverse events (mirtazapine: 3.6%, citalopram, 3.0%). Sweating and nausea were statistically significantly more frequent in the citalopram group and increased appetite and complaints of weight increase in the mirtazapine group. There were no clinically relevant changes in laboratory parameters and vital sign variables with either treatment, except for clinically relevant increase in body weight, occurring more frequently in mirtazapine patients. In this study, mirtazapine and citalopram were equally effective in reducing symptoms of depression and anxiety, and well tolerated. However, mirtazapine was significantly more effective than citalopram after 2 weeks of treatment on the MADRS, HAM-A and CGI Severity of illness and Quality of life scales. This finding, consistently present at all major efficacy variables, suggests potentially faster onset of efficacy of mirtazapine over citalopram.

Adult↗
PubMed2000

Concomitant use of mirtazapine and cimetidine: a drug-drug interaction study in healthy male subjects.

OBJECTIVE: The objective of this study was to examine the pharmacokinetics and the tolerability/safety of mirtazapine and cimetidine separately and in combination following oral administration of multiple doses. METHODS: This was a double-blind, placebo-controlled, two-period cross-over, multiple-dose pharmacokinetic interaction study in 12 healthy male subjects. They received either cimetidine (800 mg b.i.d.) or placebo in combination with (commercially available, racemic) mirtazapine (30 mg nocte). Cimetidine and placebo were administered for 14 days, with mirtazapine added during days 6-12 of each period. Serial blood samples for kinetic profiling were taken on day 5 and day 12 for cimetidine and on days 12-14 for mirtazapine. RESULTS: The co-administration of cimetidine resulted in a statistically significant increase in the area under the curve (AUC(0-24)) and Cmax of mirtazapine (54% and 22% respectively). The AUC(0-24) of demethylmirtazapine increased only slightly, and there was no effect on Cmax. The elimination half-lives for both mirtazapine and its demethyl metabolite were unaffected by cimetidine co-administration. The trough and average plasma concentrations during the steady state were elevated during cimetidine treatment (62% and 54%, respectively). Mirtazapine had no effect on the pharmacokinetics of cimetidine. CONCLUSION: Co-administration of cimetidine (800 mg b.i.d.) and mirtazapine (30 mg nocte) resulted in increased steady-state plasma levels of mirtazapine (C(ss,min) = +61%, P < 0.05; C(ss,av) = +54%, P < 0.05), probably as a result of increased bio-availability. The Cmax (+22%, P < 0.05) and AUC(0-24) (+54%, P < 0.05) also increased. Due to the variability of the mirtazapine plasma levels in patients, the clinical meaning of these increases is probably limited. Co-administration of mirtazapine did not alter cimetidine pharmacokinetics.

Administration, Oral↗
PubMed2002

The antinociceptive effect of mirtazapine in mice is mediated through serotonergic, noradrenergic and opioid mechanisms.

The antinociceptive effects of the noradrenergic and specific serotonergic antidepressant (NaSSA) drug mirtazapine and its interaction with various opioid receptor subtypes were evaluated in mice with a hotplate analgesicmeter. Mirtazapine elicited an antinociceptive effect in a dose-dependent manner following doses from 1 to 7.5mg/kg. As the mirtazapine dose increased beyond 10mg/kg latencies returned to baseline, yielding a biphasic dose-response curve. The effect of opioid, adrenergic, and serotonergic receptor antagonists was examined as to their ability to block mirtazapine antinociception. Mirtazapine (at 10mg/kg)-induced antinociception was significantly inhibited by naloxone, nor-BNI, and naltrindole, but neither by beta-FNA nor by naloxonazine, implying the involvement of kappa(1)- and delta-opioid mechanisms. When adrenergic and serotonergic antagonists were used, both metergoline and yohimbine, decreased antinociception elicited by mirtazapine, implying a combined serotonergic and noradrenergic mechanism of antinociception. When mirtazapine was administered together with various agonists of the opioid receptor subtypes, it significantly potentiated antinociception mediated only by kappa(3)-opioid receptor subtypes. Summing up these results we conclude that the antinociceptive effect of mirtazapine is mainly influenced by the kappa(3)-opioid receptor subtype combined with both serotonergic and noradrenergic receptors. These results suggest a potential use of mirtazapine in the management of some pain syndromes, and raise questions regarding a possible indirect opioid-dependence induced by mirtazapine. However, further research is needed in order to establish both the exact clinical indications and the effective doses of mirtazapine when prescribed for pain.

Adrenergic Agonists↗
PubMed1998

Mirtazapine versus amitriptyline in the long-term treatment of depression: a double-blind placebo-controlled study.

Of 580 patients randomly assigned to short-term, double-blind treatment with either mirtazapine, amitriptyline or placebo, a total of 217 patients clinically judged to be responders subsequently continued on the same medication for up to 2 years in the long-term treatment study (mirtazapine, n = 74; amitriptyline, n = 86 and placebo, n = 57). The efficacy of mirtazapine in relapse prevention was seen in an analysis of the first 20 weeks data. Significantly fewer patients relapsed during treatment with mirtazapine compared with placebo (p < 0.05), and a significantly longer time to relapse was shown on the survival analysis. There was a significant advantage for amitriptyline compared with placebo in the first 20 weeks, with fewer patients relapsing. There was a significant advantage for mirtazapine compared with amitriptyline at 20 weeks seen on the survival analysis (p < 0.05). The significant advantage for mirtazapine compared with placebo was also seen in the prophylactic phase of treatment after 20 weeks. At the endpoint there were significantly more patients in the placebo group with a return of symptoms and significantly fewer showing sustained response. Amitriptyline was better than placebo with fewer patients suffering a recurrence of symptoms, but there was no difference from placebo in the proportion of patients with sustained response. Mirtazapine was well tolerated with a side-effect profile similar to that of placebo. The only adverse event reported significantly more frequently on mirtazapine than on placebo was weight gain. Objectively measured weight gain was more frequent with amitriptyline (22% of patients) compared with mirtazapine (13% of patients). Amitriptyline was associated with significantly more adverse events than either mirtazapine or placebo, in particular sedative and anticholinergic side effects. The efficacy of mirtazapine in reducing the risk of relapse and the recurrence of depression, which on some measures showed an advantage compared with amitriptyline, coupled with its improved side-effect profile, commends this antidepressant for the long-term treatment of depression.

Adolescent↗
PubMed2000

Mirtazapine compared with paroxetine in major depression.

BACKGROUND: The aim was to compare the efficacy and tolerability of mirtazapine with those of paroxetine. METHOD: 275 outpatients with a diagnosis of major depressive episode (DSM-IV) and a score > or = 18 on the 17-item Hamilton Rating Scale for Depression (HAM-D-17) were randomly assigned to 6 weeks of treatment with mirtazapine (15-45 mg/day) or paroxetine (20-40 mg/day). Efficacy was assessed by the HAM-D-17, Hamilton Rating Scale for Anxiety (HAM-A), and Clinical Global Impressions scales (Severity and Improvement), and analyses were performed on the intent-to-treat sample (127 mirtazapine-treated patients and 123 paroxetine-treated patients). RESULTS: Mean daily doses were 32.7 mg of mirtazapine and 22.9 mg of paroxetine. Thirty patients in the mirtazapine group and 33 in the paroxetine group dropped out. Both drugs were equally effective in reducing symptoms of depression. At week 1, the mean HAM-D-17 total score was significantly lower in mirtazapine- than paroxetine-treated patients (16.5 vs. 18.8, p = .0032). Similarly, significantly more mirtazapine-treated patients were HAM-D-17 responders (> or = 50% decrease from baseline) at weeks 1 (23.2% vs. 8.9%, p = .002) and 4 (58.3% vs. 44.5%, p = .04). Both treatments were equally effective in reducing anxiety. However, the reduction in mean HAM-A total score was significantly greater with mirtazapine than with paroxetine at week 1 (-5.1 vs. -3.5, p = .0435). Tolerability of both treatments was good, with more nausea, vomiting, tremor, and sweating in the paroxetine group and more weight increase and influenza-like symptoms in the mirtazapine group. CONCLUSION: Mirtazapine and paroxetine were equally effective after 6 weeks of therapy and were both well tolerated. A potentially faster onset of overall therapeutic efficacy of mirtazapine was suggested by significant differences between treatments after 1 week of therapy that were due to slightly larger improvements of several core symptoms of depression as well as distinct prevention of treatment-emergent worsening of anxiety and physical components of depression.

Adult↗
PubMed2001

Mirtazapine versus venlafaxine in hospitalized severely depressed patients with melancholic features.

The aim of this multicenter, randomized, double-blind, 8-week study was to compare the antidepressant efficacy and tolerability of mirtazapine and venlafaxine in the treatment of hospitalized patients with DSM-IV diagnosis of severe depressive episode with melancholic features. Patients with a baseline score of > or = 25 on the 17-item Hamilton Rating Scale for Depression (HAM-D-17) were randomly assigned to receive treatment with either mirtazapine (N = 78, 15-60 mg/day) or venlafaxine (N = 79, 75-375 mg/day, twice a day) in a rapid up-titration schedule. Efficacy was assessed with the Montgomery-Asberg Depression Rating Scale (MADRS), HAM-D-17, and Clinical Global Impression scale, and quality of life was assessed with the Quality of Life, Enjoyment, and Satisfaction Questionnaire and Quality of Life in Depression Scale. Tolerability was assessed with the Utvalg for Kliniske Undersogelser (UKU) side effect scale and by reporting adverse events. Both drugs were effective in reducing overall symptoms of depression, showing substantial reductions in group mean MADRS scores (-20.1 for mirtazapine and -17.5 for venlafaxine) and HAM-D-17 scores (-17.1 for mirtazapine and -14.6 for venlafaxine) at the end of the treatment. Although not statistically significant, at all assessment times higher percentages of patients treated with mirtazapine were classified as responders (> or =50% reduction) on the HAM-D (at endpoint, 62% vs. 52%) and MADRS (at endpoint: 64% vs. 58%). Likewise were the percentages of remitters (HAM-D score < or =7; MADRS score < or =12) also higher in the mirtazapine group. A statistically significant difference favoring mirtazapine was found on the HAM-D Sleep Disturbance factor at all assessment points (p < or = 0.03). Both treatments were well tolerated. Although slightly more subjects treated with mirtazapine reported at least one adverse event, a statistically significantly higher percentage of patients treated with venlafaxine (15.3%) than mirtazapine (5.1%) dropped out because of adverse events (p = 0.037). Quality of life improved in both treatment groups. In this study, treatment with mirtazapine resulted in a trend toward more responders and remitters than treatment with venlafaxine and in significantly fewer dropouts as a result of adverse events.

Adolescent↗
PubMed2006

Inhibition of [11C]mirtazapine binding by alpha2-adrenoceptor antagonists studied by positron emission tomography in living porcine brain.

We have developed [(11)C]mirtazapine as a ligand for PET studies of antidepressant binding in living brain. However, previous studies have determined neither optimal methods for quantification of [(11)C]mirtazapine binding nor the pharmacological identity of this binding. To obtain that information, we have now mapped the distribution volume (V(d)) of [(11)C]mirtazapine relative to the arterial input in the brain of three pigs, in a baseline condition and after pretreatment with excess cold mirtazapine (3 mg/kg). Baseline V(d) ranged from 6 ml/ml in cerebellum to 18 ml/ml in frontal cortex, with some evidence for a small self-displaceable binding component in the cerebellum. Regional binding potentials (pBs) obtained by a constrained two-compartment model, using the V(d) observation in cerebellum, were consistently higher than pBs obtained by other arterial input or reference tissue methods. We found that adequate quantification of pB was obtained using the simplified reference tissue method. Concomitant PET studies with [(15)O]-water indicated that mirtazapine challenge increased CBF uniformly in cerebellum and other brain regions, supporting the use of this reference tissue for calculation of [(11)C]mirtazapine pB. Displacement by mirtazapine was complete in the cerebral cortex, but only 50% in diencephalon, suggesting the presence of multiple binding sites of differing affinities in that tissue. Competition studies with yohimbine and RX 821002 showed decreases in [(11)C]mirtazapine pB throughout the forebrain; use of the multireceptor version of the Michaelis-Menten equation indicated that 42% of [(11)C]mirtazapine binding in cortical regions is displaceable by yohimbine. Thus, PET studies confirm that [(11)C]mirtazapine affects alpha(2)-adrenoceptor binding sites in living brain.

Adrenergic alpha-2 Receptor Antagonists↗
PubMedDate not supplied

Drug-drug interaction studies with mirtazapine and carbamazepine in healthy male subjects.

In two studies, the effects of the potentially interacting drugs mirtazapine and carbamazepine on their pharmacokinetics have been investigated. Subjects were treated with carbamazepine combined with placebo for 21 days and subsequently with carbamazepine combined with mirtazapine for another 7 days (Study A) or with mirtazapine combined with placebo for 7 days and subsequently mirtazapine combined with carbamazepine for another 21 days (Study B). Pharmacokinetic results indicate that carbamazepine decreased significantly AUC and Cmax values for mirtazapine and increased values for demethyl-mirtazapine Cmax. Mirtazapine had no effect on carbamazepine pharmacokinetic parameters, but did lower carbamazepine-10,11-epoxide levels. Mirtazapine did not affect the single dose kinetics or the enzyme inducing properties of carbamazepine. VAMRS alertness scores reflected the somnolence-inducing effects of carbamazepine and mirtazapine and psychometric test results revealed impairment of specific tasks. The combination was safe and routine laboratory testing did not reveal clinically relevant abnormalities. The dose of mirtazapine in patients on carbamazepine may have to be increased for optimal antidepressant efficacy.

Adolescent↗