2.1 Recommended Dosage

The recommended starting dose of mirtazapine tablets is 15 mg once daily, administered orally, preferably in the evening prior to sleep. If patients do not have an adequate response to the initial 15 mg dose, increase the dose up to a maximum of 45 mg per day. Dose changes should not be made in intervals of less than 1 to 2 weeks to allow sufficient time for evaluation of response to a given dose [see Clinical Pharmacology (12.3)] .

2.3 Screen for Bipolar Disorder Prior to Starting Mirtazapine Tablets

Prior to initiating treatment with mirtazapine tablets or another antidepressant, screen patients for a personal or family history of bipolar disorder, mania, or hypomania [see Warnings and Precautions (5.9)].

2.4 Switching Patients to or from a Monoamine Oxidase Inhibitor Antidepressant

At least 14 days must elapse between discontinuation of a monoamine oxidase inhibitor (MAOI) antidepressant and initiation of mirtazapine tablets. In addition, at least 14 days must elapse after stopping mirtazapine tablets before starting an MAOI antidepressant [see Contraindications (4)and Warnings and Precautions (5.3)] .

2.5 Dosage Modifications Due to Drug Interactions

2.6 Discontinuation of Mirtazapine Tablets Treatment

Adverse reactions may occur upon discontinuation or dose reduction of mirtazapine tablets [see Warnings and Precautions (5.14)] . Gradually reduce the dosage of mirtazapine tablets rather than stopping abruptly whenever possible.

5.1 Suicidal Thoughts and Behaviors in Adolescents and Young Adults

In pooled analyses of placebo-controlled trials of antidepressant drugs (SSRIs and other antidepressant classes) that included approximately 77,000 adult patients and 4,500 pediatric patients, the incidence of suicidal thoughts and behaviors in antidepressant-treated patients age 24 years and younger was greater than in placebo-treated patients. There was considerable variation in risk of suicidal thoughts and behaviors among drugs, but there was an increased risk identified in young patients for most drugs studied. There were differences in absolute risk of suicidal thoughts and behaviors across the different indications, with the highest incidence in patients with MDD. The drug-placebo differences in the number of cases of suicidal thoughts and behaviors per 1000 patients treated are provided in Table 1.

It is unknown whether the risk of suicidal thoughts and behaviors in children, adolescents, and young adults extends to longer-term use, i.e., beyond four months. However, there is substantial evidence from placebo-controlled maintenance trials in adults with MDD that antidepressants delay the recurrence of depression and that depression itself is a risk factor for suicidal thoughts and behaviors.

Monitor all antidepressant-treated patients for any indication of clinical worsening and emergence of suicidal thoughts and behaviors, especially during the initial few months of drug therapy, and at times of dosage changes. Counsel family members or caregivers of patients to monitor for changes in behavior and to alert the healthcare provider. Consider changing the therapeutic regimen, including possibly discontinuing mirtazapine tablets, in patients whose depression is persistently worse, or who are experiencing emergent suicidal thoughts or behaviors.

5.2 Agranulocytosis

In premarketing clinical trials, 2 (1 with Sjögren’s Syndrome) out of 2796 patients treated with mirtazapine developed agranulocytosis [absolute neutrophil count (ANC) < 500/mm 3with associated signs and symptoms, e.g., fever, infection, etc.] and a third patient developed severe neutropenia (ANC < 500/mm 3without any associated symptoms). For these 3 patients, onset of severe neutropenia was detected on days 61, 9, and 14 of treatment, respectively. All 3 patients recovered after mirtazapine was stopped. If a patient develops a sore throat, fever, stomatitis, or other signs of infection, along with a low white blood cell (WBC) count, treatment with mirtazapine tablets should be discontinued and the patient should be closely monitored.

5.3 Serotonin Syndrome

Serotonergic antidepressants, including mirtazapine tablets, can precipitate serotonin syndrome, a potentially life-threatening condition. The risk is increased with concomitant use of other serotonergic drugs (including triptans, tricyclic antidepressants, fentanyl, lithium, tramadol, tryptophan, buspirone, amphetamines, and St. John’s Wort) and with drugs that impair metabolism of serotonin, i.e., MAOIs [see Contraindications (4), Drug Interactions (7)] . Serotonin syndrome can also occur when these drugs are used alone.

Serotonin syndrome signs and symptoms may include mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, and gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea).

The concomitant use of mirtazapine tablets with MAOIs is contraindicated. In addition, do not initiate mirtazapine tablets in a patient being treated with MAOIs such as linezolid or intravenous methylene blue. No reports involved the administration of methylene blue by other routes (such as oral tablets or local tissue injection). If it is necessary to initiate treatment with an MAOI such as linezolid or intravenous methylene blue in a patient taking mirtazapine tablets, discontinue mirtazapine tablets before initiating treatment with the MAOI [see Contraindications (4), Drug Interactions (7)] .

Monitor all patients taking mirtazapine tablets for the emergence of serotonin syndrome. Discontinue treatment with mirtazapine tablets and any concomitant serotonergic agents immediately if the above symptoms occur, and initiate supportive symptomatic treatment. If concomitant use of mirtazapine tablets with other serotonergic drugs is clinically warranted, inform patients of the increased risk for serotonin syndrome and monitor for symptoms.

5.4 Angle-Closure Glaucoma

The pupillary dilation that occurs following use of many antidepressant drugs, including mirtazapine tablets, may trigger an angle-closure attack in a patient with anatomically narrow angles who does not have a patent iridectomy.

5.5 QT Prolongation and Torsades de Pointes

The effect of mirtazapine on QTc interval was assessed in a clinical randomized trial with placebo and positive (moxifloxacin) controls involving 54 healthy volunteers using exposure response analysis. This trial showed a positive relationship between mirtazapine concentrations and prolongation of the QTc interval. However, the degree of QT prolongation observed with both 45 mg and 75 mg (1.67 times the maximum recommended daily dose) doses of mirtazapine was not at a level generally considered to be clinically meaningful. During postmarketing use of mirtazapine, cases of QT prolongation, Torsades de Pointes, ventricular tachycardia, and sudden death, have been reported [see Adverse Reactions (6.1, 6.2)] . The majority of reports occurred in association with overdose or in patients with other risk factors for QT prolongation, including concomitant use of QTc-prolonging medicines [see Drug Interactions (7)and Overdosage (10)] . Exercise caution when mirtazapine tablets are prescribed in patients with known cardiovascular disease or family history of QT prolongation, and in concomitant use with other drugs thought to prolong the QTc interval.

5.6 Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)

Drug reaction with eosinophilia and systemic symptoms (DRESS) has been reported with postmarketing use of mirtazapine. DRESS may present with a cutaneous reaction (such as rash or exfoliative dermatitis), eosinophilia, fever, and/or lymphadenopathy with systemic complications such as hepatitis, nephritis, pneumonitis, myocarditis, and/or pericarditis. DRESS is sometimes fatal. Discontinue mirtazapine tablets immediately if DRESS is suspected and institute appropriate treatment [seeContraindications (4), Adverse Reactions (6.2)] .

5.7 Increased Appetite and Weight Gain

In U.S. controlled clinical studies, appetite increase was reported in 17% of patients treated with mirtazapine, compared to 2% for placebo. In these same trials, weight gain of ≥ 7% of body weight was reported in 7.5% of patients treated with mirtazapine, compared to 0% for placebo. In a pool of premarketing U.S. clinical studies, including many patients for long-term, open-label treatment, 8% of patients receiving mirtazapine discontinued for weight gain.

In an 8-week-long pediatric clinical trial of doses between 15 to 45 mg/day, 49% of mirtazapine-treated pediatric patients had a weight gain of at least 7%, compared to 5.7% of placebo-treated patients. The safety and effectiveness of mirtazapine tablets in pediatric patients with MDD have not been established [see Use in Specific Populations (8.4)] .

5.8 Somnolence

In U.S. controlled studies, somnolence was reported in 54% of patients treated with mirtazapine, compared to 18% for placebo. In these studies, somnolence resulted in discontinuation for 10.4% of mirtazapine-treated patients, compared to 2.2% for placebo. It is unclear whether tolerance develops to the somnolent effects of mirtazapine tablets. Because of the potentially significant effects of mirtazapine tablets on impairment of performance, caution patients about engaging in activities that require alertness, including operating hazardous machinery and motor vehicles, until they are reasonably certain that mirtazapine tablets do not affect them adversely. The concomitant use of benzodiazepines and alcohol with mirtazapine tablets should be avoided [see Drug Interactions (7)] .

5.9 Activation of Mania or Hypomania

In patients with bipolar disorder, treating a depressive episode with mirtazapine tablets or another antidepressant may precipitate a mixed/manic episode. In controlled clinical trials, patients with bipolar disorder were generally excluded; however, symptoms of mania or hypomania were reported in 0.2% of patients treated with mirtazapine. Prior to initiating treatment with mirtazapine tablets screen patients for any personal or family history of bipolar disorder, mania, or hypomania.

5.10 Seizures

Mirtazapine tablets have not been systematically evaluated in patients with seizure disorders. In premarketing clinical trials, 1 seizure was reported among the 2796 U.S. and non-U.S. patients treated with mirtazapine. Mirtazapine tablets should be prescribed with caution in patients with a seizure disorder.

5.11 Elevated Cholesterol and Triglycerides

In U.S. controlled studies, nonfasting cholesterol increases to ≥ 20% above the upper limits of normal were observed in 15% of patients treated with mirtazapine, compared to 7% for placebo. In these same studies, nonfasting triglyceride increases to ≥ 500 mg/dL were observed in 6% of patients treated with mirtazapine, compared to 3% for placebo.

5.12 Hyponatremia

Hyponatremia may occur as a result of treatment with serotonergic antidepressants, including mirtazapine tablets. Cases with serum sodium lower than 110 mmol/L have been reported.

Signs and symptoms of hyponatremia include headache, difficulty concentrating, memory impairment, confusion, weakness, and unsteadiness, which may lead to falls. Signs and symptoms associated with more severe or acute cases have included hallucination, syncope, seizure, coma, respiratory arrest, and death. In many cases, this hyponatremia appears to be the result of the syndrome of inappropriate antidiuretic hormone secretion (SIADH).

In patients with symptomatic hyponatremia, discontinue mirtazapine tablets and institute appropriate medical intervention. Elderly patients, patients taking diuretics, and those who are volume-depleted may be at greater risk of developing hyponatremia [see Use in Specific Populations (8.5)] .

5.13 Transaminase Elevations

Clinically significant ALT (SGPT) elevations (≥ 3 times the upper limit of the normal range) were observed in 2.0% (8/424) of patients treated with mirtazapine in a pool of short-term, U.S. controlled trials, compared to 0.3% (1/328) of placebo patients. While some patients were discontinued for the ALT increases, in other cases, the enzyme levels returned to normal despite continued mirtazapine treatment. Mirtazapine tablets should be used with caution in patients with impaired hepatic function [see Use in Specific Populations (8.6), Clinical Pharmacology (12.3)] .

5.14 Discontinuation Syndrome

There have been reports of adverse reactions upon the discontinuation of mirtazapine tablets (particularly when abrupt), including but not limited to the following: dizziness, abnormal dreams, sensory disturbances (including paresthesia and electric shock sensations), agitation, anxiety, fatigue, confusion, headache, tremor, nausea, vomiting, and sweating, or other symptoms which may be of clinical significance.

A gradual reduction in the dosage, rather than an abrupt cessation, is recommended [see Dosage and Administration (2.6)].

5.15 Use in Patients with Concomitant Illness

Mirtazapine tablets have not been systematically evaluated or used to any appreciable extent in patients with a recent history of myocardial infarction or other significant heart disease. Mirtazapine was associated with significant orthostatic hypotension in early clinical pharmacology trials with normal volunteers. Orthostatic hypotension was infrequently observed in clinical trials with depressed patients [see Adverse Reactions (6.1)] . Mirtazapine tablets should be used with caution in patients with known cardiovascular or cerebrovascular disease that could be exacerbated by hypotension (history of myocardial infarction, angina, or ischemic stroke) and conditions that would predispose patients to hypotension (dehydration, hypovolemia, and treatment with antihypertensive medication).

6.1 Clinical Trial Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The data described below are from clinical trials in which mirtazapine tablets were administered to 2796 patients in phase 2 and 3 clinical studies. The trials consisted of double-blind controlled and open-label studies, inpatient and outpatient studies, fixed dose, and titration studies.

6.2 Postmarketing Experience

The following adverse reactions have been identified during post-approval use of mirtazapine. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Cardiac Disorders:ventricular arrhythmia (Torsades de Pointes)

Endocrine Disorders:  hyperprolactinemia (and related symptoms, e.g., galactorrhea and gynecomastia)

Musculoskeletal and Connective Tissue Disorders:  increased creatine kinase blood levels and rhabdomyolysis

Psychiatric Disorders:  somnambulism (ambulation and other complex behaviors out of bed)

Reproductive System and Breast Disorders: priapism

Skin and Subcutaneous Tissue Disorders:severe skin reactions, including DRESS, Stevens-Johnson syndrome, bullous dermatitis, erythema multiforme and toxic epidermal necrolysis

8.1 Pregnancy

8.2 Lactation

8.4 Pediatric Use

The safety and effectiveness of mirtazapine tablets have not been established in pediatric patients with MDD. Two placebo-controlled trials in 258 pediatric patients with MDD have been conducted with mirtazapine, and the data were insufficient to establish the safety and effectiveness of mirtazapine tablets in pediatric patients with MDD.

Antidepressants increased the risk of suicidal thoughts and behaviors in pediatric patients [see Boxed Warningand Warnings and Precautions (5.1)] .

In an 8-week-long clinical trial in pediatric patients receiving doses between 15 to 45 mg per day, 49% of mirtazapine-treated patients had a weight gain of at least 7%, compared to 5.7% of placebo-treated patients. The mean increase in weight was 4 kg (2 kg SD) for mirtazapine-treated patients versus 1 kg (2 kg SD) for placebo-treated patients [see Warnings and Precautions (5.7)] .

8.5 Geriatric Use

Approximately 190 patients ≥ 65 years of age participated in clinical studies with mirtazapine. Mirtazapine tablets are known to be substantially excreted by the kidney (75%), and the risk of decreased clearance of this drug is greater in patients with impaired renal function. Pharmacokinetic studies revealed a decreased clearance of mirtazapine in the elderly [see Clinical Pharmacology (12.3)] .

Sedating drugs, including mirtazapine tablets, may cause confusion and over-sedation in the elderly. Elderly patients may be at greater risk of developing hyponatremia. Caution is indicated when administering mirtazapine tablets to elderly patients [see Warnings and Precautions (5.12), (5.15)and Clinical Pharmacology (12.3)] . In general, dose selection for an elderly patient should be conservative, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

8.6 Renal or Hepatic Impairment

The clearance of mirtazapine is reduced in patients with moderate to severe renal or hepatic impairment. Consequently, plasma mirtazapine levels may be increased in these patient groups, compared to levels observed in patients without renal or hepatic impairment. Dosage decrease may be necessary when administering mirtazapine tablets to patients with moderate to severe renal or hepatic impairment [see Warnings and Precautions (5.13), Use in Specific Populations (8.5), and Clinical Pharmacology (12.3)] .

12.1 Mechanism of Action

The mechanism of action of mirtazapine for the treatment of major depressive disorder, is unclear. However, its efficacy could be mediated through its activity as an antagonist at central presynaptic α 2-adrenergic inhibitory autoreceptors and heteroreceptors and enhancing central noradrenergic and serotonergic activity.

12.2 Pharmacodynamics

In preclinical studies, mirtazapine acts as an antagonist at α 2-adrenergic inhibitory autoreceptors and heteroreceptors and as an antagonist at serotonin 5-HT 2and 5-HT 3receptors. Mirtazapine has no significant affinity for the 5-HT 1Aand 5-HT 1Breceptors.

Mirtazapine also acts as an antagonist of histamine (H 1) receptors, peripheral α1-adrenergic receptors, and muscarinic receptors. Actions at these receptors may explain some of the other clinical effects of mirtazapine (e.g., its prominent somnolent effects and orthostatic hypotension may be explained by its inhibition of histamine (H 1) receptors and peripheral α1-adrenergic receptors, respectively).

12.3 Pharmacokinetics

Plasma levels of mirtazapine are linearly related to dose over a dose range of 15 to 80 mg (1.78 times the maximum recommended dose). Steady state plasma levels of mirtazapine are attained within 5 days, with about 50% accumulation (accumulation ratio = 1.5). The (–) enantiomer has an elimination half-life that is approximately twice as long as the (+) enantiomer and therefore achieves plasma levels that are about 3 times as high as that of the (+) enantiomer.

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility