Mirtazapine (Page 7 of 9)


13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility


Carcinogenicity studies were conducted with mirtazapine given in the diet at doses of 2, 20, and 200 mg/kg/day to mice and 2, 20, and 60 mg/kg/day to rats. The highest doses used are approximately 20 and 12 times the maximum recommended human dose (MRHD) of 45 mg/ day, based on body surface area (mg/m 2) in mice and rats, respectively. There was an increased incidence of hepatocellular adenoma and carcinoma in male mice at the high dose. In rats, there was an increase in hepatocellular adenoma in females at the mid and high doses and in hepatocellular tumors and thyroid follicular adenoma/cystadenoma and carcinoma in males at the high dose.


Mirtazapine was not mutagenic or clastogenic and did not induce general DNA damage as determined in several genotoxicity tests: Ames test, in vitro gene mutation assay in Chinese hamster V 79 cells, in vitro sister chromatid exchange assay in cultured rabbit lymphocytes, in vivo bone marrow micronucleus test in rats, and unscheduled DNA synthesis assay in HeLa cells.

Impairment of Fertility
In a fertility study in rats, mirtazapine was given at doses up to 100 mg/kg [20 times the maximum recommended human dose (MRHD), based on body surface area (mg/m 2)]. Mating and conception were not affected by the drug, but estrous cycling was disrupted at doses that were 3 or more times the MRHD, and pre-implantation losses occurred at 20 times the MRHD.


The efficacy of mirtazapine tablets as a treatment for major depressive disorder was established in 4 placebo-controlled, 6-week trials in adult outpatients meeting DSM-III criteria for major depressive disorder. Patients were titrated with mirtazapine tablets from a dose range of 5 mg to 35 mg/day. The mean mirtazapine dose for patients who completed these 4 studies ranged from 21 to 32 mg/day. Overall, these studies demonstrated mirtazapine tablets to be superior to placebo on at least 3 of the following 4 measures: 21-Item Hamilton Depression Rating Scale (HDRS) total score; HDRS Depressed Mood Item; CGI Severity score; and Montgomery and Asberg Depression Rating Scale (MADRS). Superiority of mirtazapine tablets over placebo was also found for certain factors of the HDRS, including anxiety/somatization factor and sleep disturbance factor.

Examination of age and gender subsets of the population did not reveal any differential responsiveness on the basis of these subgroupings.

In a longer-term study, patients meeting (DSM-IV) criteria for major depressive disorder who had responded during an initial 8 to 12 weeks of acute treatment on mirtazapine tablets were randomized to continuation of mirtazapine tablets or placebo for up to 40 weeks of observation for relapse. Response during the open phase was defined as having achieved a HAM-D 17 total score of ≤8 and a CGI-Improvement score of 1 or 2 at 2 consecutive visits beginning with week 6 of the 8 to 12 weeks in the open-label phase of the study. Relapse during the double-blind phase was determined by the individual investigators. Patients receiving continued mirtazapine tablets treatment experienced significantly lower relapse rates over the subsequent 40 weeks compared to those receiving placebo. This pattern was demonstrated in both male and female patients.


Mirtazapine tablets, USP are supplied as:

Tablet Strength

Tablet Color/Shape

Tablet Markings

Package Configuration

NDC Code

7.5 mg

Yellow, circular, biconvex tablet

film coated tablets with “C” debossed on one side and plain on the other side

Bottle / 30 count

NDC 42291-494-30


Store at 20° to 25°C (68° to 77°F); excursions permitted 15° to 30°C (59° to 86°F). [see USP Controlled Room Temperature]. Protect from light and moisture.


Advise the patient to read the FDA-approved patient labeling (Medication Guide).

Suicidal Thoughts and Behaviors

Advise patients and caregivers to look for the emergence of suicidality, especially early during treatment and when the dosage is adjusted up or down, and instruct them to report such symptoms to the healthcare provider [see Boxed Warning and Warnings and Precautions (5.1)].


Advise patients to contact their physician if they experience fever, chills, sore throat, mucous membrane ulceration, flu-like complaints, or other symptoms that might suggest infection [see Warnings and Precautions (5.2)].

Serotonin Syndrome

Caution patients about the risk of serotonin syndrome, particularly with the concomitant use of mirtazapine tablets with other serotonergic drugs including triptans, tricyclic antidepressants, fentanyl, lithium, tramadol, tryptophan, buspirone, amphetamines, St. John’s Wort, and with drugs that impair metabolism of serotonin (in particular, MAOIs, both those intended to treat psychiatric disorders and also others, such as linezolid). Advise patients to contact their healthcare provider or report to the emergency room if they experience signs or symptoms of serotonin syndrome [see Dosage and Administration (2.4),Contraindications (4),Warnings and Precautions (5.3),Drug Interactions (7)].

QT Prolongation and Torsades de Pointes

Inform patients to consult their physician immediately if they feel faint, lose consciousness, or have heart palpitations [see Warnings and Precautions (5.5),Drug Interactions (7),Overdosage (10)].Advise patients to inform physicians that they are taking mirtazapine tablets before any new drug is taken.

Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)

Advise patients to report to their healthcare provider at the earliest onset of fever, rash, swollen lymph nodes, or other signs and symptoms suggestive of Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) [ see Contraindications (4), Warnings and Precautions (5.6)].


Advise patients that mirtazapine tablets may impair judgment, thinking, and particularly, motor skills, because of its prominent sedative effect. Caution patients about performing activities requiring mental alertness, such as operating hazardous machinery or operating a motor vehicle, until they are reasonably certain that mirtazapine tablets therapy does not adversely affect their ability to engage in such activities. [see Warnings and Precautions (5.8)].


Advise patients to avoid alcohol while taking mirtazapine tablets [see Warnings and Precautions (5.8),Drug Interactions (7)].

Activation of Mania/Hypomania

Advise patients and their caregivers to observe for signs of activation of mania/hypomania and instruct them to report such symptoms to the healthcare provider [see Warnings and Precautions (5.9)].

Discontinuation Syndrome

Advise patients not to abruptly discontinue mirtazapine tablets and to discuss any tapering regimen with their healthcare provider. Adverse reactions can occur when mirtazapine tablets are discontinued [see Dosage and Administration (2.6),Warnings and Precautions (5.14)].

Allergic Reactions

Advise patients to notify their healthcare provider if they develop an allergic reaction such as rash, hives, swelling, or difficulty breathing [see Contraindications (4),Adverse Reactions (6.2)].


  • Advise patients to notify their physician if they become pregnant or intend to become pregnant during mirtazapine tablets therapy.
  • Advise patients that there is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to mirtazapine tablets during pregnancy [see Use in Specific Populations (8.1)].


Advise patients to notify their physician if they are breastfeeding an infant [see Use in Specific Populations (8.2)].

Angle-Closure Glaucoma

Patients should be advised that taking mirtazapine tablets can cause mild pupillary dilation, which in susceptible individuals, can lead to an episode of angle-closure glaucoma. Pre-existing glaucoma is almost always open-angle glaucoma because angle-closure glaucoma, when diagnosed, can be treated definitively with iridectomy. Open-angle glaucoma is not a risk factor for angle-closure glaucoma. Patients may wish to be examined to determine whether they are susceptible to angle closure, and have a prophylactic procedure (e.g., iridectomy), if they are susceptible [see Warnings and Precautions (5.4)].

Manufactured for:
Pulaski, TN 38478

Mfg. Rev. 11/21
AV 07/22 (W)

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