Medication approval journey
mirtazapine (Remeron)
Approved for Major depressive disorder in adults
Before changing anything
Stopping abruptly causes withdrawal effects that can be severe
Withdrawal effects vary a lot across this group but are real. Any change should be prescriber-supervised rather than abrupt.
How long the trials actually ran
The longest trial behind the mirtazapine approval ran 40 weeks.
The gap between how long the trials ran and how long people actually take these medications is the single most important thing on this page. It is not evidence that longer use is unsafe or ineffective. It is evidence that longer use was not what got tested.
The boxed warning
The strongest warning the FDA puts on a label, reproduced word for word — not our summary of it.
WARNING: SUICIDAL THOUGHTS AND BEHAVIORS Antidepressants increased the risk of suicidal thoughts and behaviors in pediatric and young adult patients in short-term studies. Closely monitor all antidepressant-treated patients for clinical worsening, and for emergence of suicidal thoughts and behaviors [see Warnings and Precautions (5.1) ] . Mirtazapine tablets are not approved for use in pediatric patients [see Use in Specific Populations (8.4) ]. WARNING: SUICIDAL THOUGHTS AND BEHAVIORS See full prescribing information for complete boxed warning. Increased risk of suicidal thoughts and behavior in pediatric and young adult patients taking antidepressants. Closely monitor all antidepressant-treated patients for clinical worsening and emergence of suicidal thoughts and behaviors. Mirtazapine tablets are not approved for use in pediatric patients. ( 5.1 , 8.4 )
FDA label effective August 26, 2026 — read the full label on DailyMed
How many Americans take mirtazapine
Survey-based federal estimates, published with a lag of about two years. They count prescriptions filled, not outcomes.
- 5,605,882
- prescriptions in the United States (2024)
- 1,458,927
- people filling them (2024)
Prescriptions are down 15% since 2014. Whatever you decide about mirtazapine, you are deciding alongside about 1,458,927 other people this year.
Source: ClinCalc DrugStats (Medical Expenditure Panel Survey (MEPS), Agency for Healthcare Research and Quality), CC BY-SA 4.0, release 2026.08.
What people report to the FDA about mirtazapine
Read this before the numbers.
Anyone can file an adverse event report — patients, doctors, manufacturers — and nobody verifies that the drug caused what was reported. There is no denominator: tens of millions of prescriptions generate reports at an unknowable rate, and reporting rises with news coverage, not necessarily with harm. Counts below are report volumes, not rates, and cannot be compared between drugs. The FDA itself says not to use this data to make medical decisions — we show it because you deserve to see what is in the public record, with its limits stated plainly.
- 91,067
- reports mentioning mirtazapine, all time
- 76,315
- filed as serious (a report-level flag covering every drug and outcome in the report)
Most-reported reactions
- Nausea5,028
- Fatigue4,903
- Drug ineffective4,788
- Fall4,168
- Diarrhoea4,114
- Off label use3,998
- Toxicity to various agents3,837
- Dizziness3,586
- Anxiety3,582
- Dyspnoea3,535
“Drug ineffective” ranking this high is worth noticing: a report of not being helped counts as an adverse event too, and people file them in large numbers.
Source: FDA Adverse Event Reporting System (FAERS), via openFDA, data through 2026-07-30.
Known interactions, from the label
The FDA label’s interactions section, verbatim. A pharmacist checking your actual medication list beats any published list — including this one.
Read the label’s interactions section
7 DRUG INTERACTIONS Table 5 includes clinically important drug interactions with mirtazapine [see Clinical Pharmacology (12.3) ]. Table 5: Clinically Important Drug Interactions with Mirtazapine Monoamine Oxidase Inhibitors (MAOIs) Clinical Impact The concomitant use of serotonergic drugs, including mirtazapine, and MAOIs increases the risk of serotonin syndrome. Intervention Mirtazapine is contraindicated in patients taking MAOIs, including MAOIs such as linezolid or intravenous methylene blue [see Dosage and Administration (2.4) , Contraindications (4) , Warnings and Precautions (5.3) ]. Examples selegiline, tranylcypromine, isocarboxazid, phenelzine, linezolid, methylene blue Other Serotonergic Drugs Clinical Impact The concomitant use of serotonergic drugs with mirtazapine increases the risk of serotonin syndrome. Intervention Monitor patients for signs and symptoms of serotonin syndrome, particularly during treatment initiation and dosage increases. If serotonin syndrome occurs, consider discontinuation of mirtazapine and/or concomitant serotonergic drugs [see Warnings and Precautions (5.3) ]. Examples SSRIs, SNRIs, triptans, tricyclic antidepressants, fentanyl, lithium, amphetamines, St. John’s Wort, tramadol, tryptophan, buspirone Strong CYP3A Inducers Clinical Impact The concomitant use of strong CYP3A inducers with mirtazapine decreases the plasma concentration of mirtazapine [see Clinical Pharmacology (12.3) ]. Intervention Increase the dose of mirtazapine if needed with concomitant CYP3A inducer use. Conversely, a decrease in dosage of mirtazapine may be needed if the CYP3A inducer is discontinued [see Dosage and Administration (2.5) ]. Examples phenytoin, carbamazepine, rifampin Strong CYP3A Inhibitors Clinical Impact The concomitant use of strong CYP3A inhibitors with mirtazapine may increase the plasma concentration of mirtazapine [see Clinical Pharmacology (12.3) ]. Intervention Decrease the dose of mirtazapine if needed with concomitant strong CYP3A inhibitor use. Conversely, an increase in dosage of mirtazapine may be needed if the CYP3A inhibitor is discontinued [see Dosage and Administration (2.5) ]. Examples itraconazole, ritonavir, nefazodone Cimetidine Clinical Impact The concomitant use of cimetidine, a CYP1A2, CYP2D6, and CYP3A inhibitor, with mirtazapine may increase the plasma concentration of mirtazapine [see Clinical Pharmacology (12.3) ]. Intervention Decrease the dose of mirtazapine if needed with concomitant cimetidine use. Conversely, an increase in dosage of mirtazapine may be needed if cimetidine is discontinued [see Dosage and Administration (2.5) ]. Benzodiazepines and Alcohol Clinical Impact The concomitant use of benzodiazepines or alcohol with mirtazapine increases the impairment of cognitive and motor skills produced by mirtazapine alone. Intervention Avoid concomitant use of benzodiazepines and alcohol with mirtazapine [see Warnings and Precautions (5.8) , Clinical Pharmacology (12.3) ]. Examples diazepam, alprazolam, alcohol Drugs that Prolong QTc Interval Clinical Impact The concomitant use of other drugs which prolong the QTc interval with mirtazapine, increase the risk of QT prolongation and/or ventricular arrhythmias (e.g., Torsades de Pointes). Intervention Use caution when using mirtazapine concomitantly with drugs that prolong the QTc interval [see Warnings and Precautions (5.5) , Clinical Pharmacology (12.3) ]. Warfarin Clinical Impact The concomitant use of warfarin with mirtazapine may result in an increase in INR [see Clinical Pharmacology (12.3) ]. Intervention Monitor INR during concomitant use of warfarin with mirtazapine. Strong CYP3A inducers: Dosage increase may be needed for mirtazapine with concomitant use of strong CYP3A inducers. ( 2.5 , 7 ) Strong CYP3A inhibitors: Dosage decrease may be needed when mirtazapine is coadministered with strong CYP3A inhibitors. ( 2.5 , 7 ) Cimetidine: Dosage decrease may be needed when mirtazapine is coadministered with cimetidine. ( 2.5 , 7 ) Warfarin: Monitor INR during concomitant use. ( 7 )
FDA label for mirtazapine, effective August 26, 2026 — DailyMed.
Who pays for mirtazapine
Two claims datasets and one survey, covering different populations with different instruments — they cannot be reconciled by arithmetic, and where their sum crowds the all-payer estimate, that is a finding about the estimates rather than a percentage.
- Medicare Part D
- Read the under-65 group correctly before the numbers: Medicare before 65 means the disabled and dual-eligible population — among the sickest, highest-need people in the program — and reading their utilization as typical adult use would be a category error. The beneficiary total sums brand-level rows, so treat it as an upper bound on distinct people. 1,647,984 beneficiaries filled 8,337,695 claims in 2024 — 1,403,164 aged 65 and over, and 244,820 under 65.
- Medicaid
- At least 2,690,928 prescriptions in 2024 — a floor, because 113 of 575 national data rows are suppressed for privacy and contribute zero. Medicaid covers more children than any insurer in the country and publishes no age split — how much of this number is pediatric use is not knowable from public data.
- All payers (survey estimate)
- The MEPS-based estimate above puts the whole country at 5,605,882 prescriptions and 1,458,927 people in 2024. Subtracting the public programs from it would produce a number for everyone else — and we do not print that number, because subtracting a survey from claims counts manufactures precision that does not exist.
- The population nobody counts
- The commercially insured working-age adult — statistically, the likeliest person to be reading this page — is the one population with no public per-drug count anywhere. Private claims data exists and is sold, but nothing a patient can check is published. For children the record is thinner still: no public source counts pediatric use of mirtazapine specifically; the closest the public record comes is condition-level treatment rates for children, which we have traced for one condition in how childhood ADHD got counted.
Sources: Medicare Part D Prescribers — by Geography and Drug, data.cms.gov, National rows, data year 2024 (published with ~17-month lag). Medicaid State Drug Utilization Data 2024, data.medicaid.gov, national aggregate rows. Retrieved 2026-09-01.
The approval, step by step
Step 1
What the approval was actually based on
Which studies did the FDA rely on, how long did they run, and who was in them?
The efficacy of REMERON 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... 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 REMERON were randomized to continuation of REMERON or placebo for up to 40 weeks of observation for relapse.
FDA-approved labelling, 14 CLINICAL STUDIES — read the label on DailyMed
Our reading
Four six-week trials, plus a forty-week continuation study of the enriched kind: only people who had already responded were randomised, so it measures whether the drug keeps working for people it already works for. Mirtazapine is very often prescribed at low dose specifically for sleep and appetite rather than for depression. That use is not in these trials and is not in the indication.
Step 2
The approval
When was it approved, under what application, and by whose review?
- Approved
- June 14, 1996
- Application
- NDA020415
- Review
- STANDARD
- Original sponsor
- Organon
- Holds it now
- Organon
- Label submissions since
- 31
Source: openFDA Drugs@FDA, original application ORIG-1
Step 3
What was added after it was on the market
Which warnings arrived only after millions of people were already taking it?
The antidepressant suicidality warning has an age ceiling most people never hear about
Antidepressants carry a boxed warning about suicidal thoughts and behaviour in children, adolescents and young adults. It came from pooling 24 short-term placebo-controlled trials of nine antidepressants in more than 4,400 young patients: suicidality was reported in about 4% on drug against 2% on placebo. There were no completed suicides in those trials.
The part that usually gets lost is the age boundary, which is in the label itself. The studies did not show an increased risk above age 24, and in patients 65 and older the risk went in the other direction — it was reduced. The warning is real and it is specific, not a blanket statement about everyone who takes one.
Worth asking
Given my age, which side of that line am I on, what specifically should I or the people around me watch for in the first two months, and who do I call if it happens.
Step 4
What independent research has found since
What has been learned by people who were not selling it?
Comparative efficacy and acceptability of 21 antidepressant drugs for the acute treatment of adults with major…
22 years after approval
In a network meta-analysis of 522 randomised trials covering 116,477 adults with major depression, mirtazapine was one of the seven antidepressants (of 21) that proved more effective than the others in head-to-head comparisons (odds ratios for that group ranged 1.19 to 1.96), while its dropout rate was about average — neither among the best- nor the worst-tolerated drugs.
Worth asking
Worth asking your prescriber why mirtazapine was chosen for you over other antidepressants that ranked similarly on effectiveness but differ on side effects like weight gain and sedation.
The risks of adverse events with mirtazapine for adults with major depressive disorder: a systematic review with…
29 years after approval
Pooling 17 placebo-controlled randomised trials (2,131 adults), mirtazapine roughly quintupled the risk of weight gain (RR 4.75, 95% CI 2.05 to 10.99; about 1 extra person affected per 10 treated) and more than doubled somnolence (RR 2.61, 95% CI 1.26 to 5.37; about 1 per 4) and dizziness, while serious adverse events showed a possible but statistically unconfirmed increase (OR 1.82, 95% CI 0.95 to 3.48).
Worth asking
Worth asking your prescriber how you will monitor weight and daytime sleepiness on mirtazapine, and at what point you would adjust the dose or switch.
Mirtazapine added to SSRIs or SNRIs for treatment resistant depression in primary care: phase III randomised placebo…
22 years after approval
In 480 primary-care patients still depressed after at least six weeks on an SSRI or SNRI, adding mirtazapine gave no clinically important benefit over adding placebo at 12 weeks (adjusted BDI-II difference -1.83, 95% CI -3.92 to 0.27), and 46 people on mirtazapine versus 9 on placebo stopped the drug because of adverse effects.
Worth asking
Worth asking your prescriber, if mirtazapine is being added on top of an SSRI or SNRI you already take, what specific benefit they expect — a large placebo-controlled trial found the combination added little and was harder to tolerate.
Withdrawal from these medications can take months, and NICE says so
26 years after approval
NICE guideline NG215 covers safe prescribing and managed withdrawal for five groups of medication: opioids, benzodiazepines, gabapentinoids, Z-drugs and antidepressants. It is the closest thing there is to an official answer on how coming off actually goes.
It states that withdrawal can be difficult and may take several months or more, that symptoms vary widely in type and severity, that they affect both physical and mental health, and that they can be delayed in onset and can persist. Two recommendations are worth quoting to a prescriber. Do not stop a medicine abruptly except in exceptional medical circumstances. And taper using a slow, stepwise reduction proportionate to the current dose, so the decrements get smaller as the dose gets lower — not a fixed cut each time.
That last detail is the one most commonly missed. Gabapentinoids are the exception in the guideline and are reduced by a fixed amount at each step.
Worth asking
Can we write the taper down, what size are the steps near the end, and how long do I hold at each step before the next reduction.
In 2019 the Royal College of Psychiatrists changed its position on withdrawal
23 years after approval
For years people reporting long, severe antidepressant withdrawal were told it lasted a week or two. In May 2019 the Royal College of Psychiatrists published a position statement conceding the point: while withdrawal symptoms are often mild and self-limiting, there is substantial variation, and for some patients symptoms last much longer and are more severe.
It went further and asked for changes — that guidelines and patient information recognise the potential for severe and long-lasting withdrawal, that pharmacologically-informed tapering guidance be developed, that discontinuation be tapered at a rate the patient can tolerate over potentially several months, and that clinicians actively work to tell withdrawal apart from relapse.
One thing it explicitly does not say, and it is worth being accurate about: the College states that from a clinical perspective antidepressant use is not associated with dependence in the addiction sense. Withdrawal and dependence are not the same claim.
Worth asking
If I feel bad three weeks after a dose reduction, how will we decide whether that is withdrawal or my depression returning, and what do we do differently in each case.
Mirtazapine versus other antidepressive agents for depression
15 years after approval
Across 29 randomised trials (4,974 people), mirtazapine produced response faster than SSRIs at two weeks (OR 1.57, 95% CI 1.30 to 1.88) with a small edge remaining at 6-12 weeks (OR 1.19, 95% CI 1.01 to 1.39), but caused more weight gain or increased appetite and more sleepiness, and less nausea and sexual dysfunction, than SSRIs.
Worth asking
Worth asking your prescriber whether mirtazapine's faster early effect matters for your situation, and how you will handle the trade-off of more weight gain and daytime sleepiness compared with an SSRI.
Treatment-emergent sexual dysfunction related to antidepressants: a meta-analysis.
13 years after approval
When sexual function is actually asked about with a questionnaire rather than waited for as a spontaneous complaint, treatment-emergent sexual dysfunction ranged from 25.8% to 80.3% of patients across antidepressants, all significantly above placebo. In descending order of impact the drugs were sertraline, venlafaxine, citalopram, paroxetine, fluoxetine, imipramine, phenelzine, duloxetine, escitalopram, and fluvoxamine. Agomelatine, amineptine, bupropion, moclobemide, mirtazapine, and nefazodone showed no significant difference from placebo.
Worth asking
Where does the antidepressant I'm on sit on the sexual side-effect ranking, and is there a drug with a lower rate that would still treat my condition?
Antidepressants and body weight: a comprehensive review and meta-analysis
14 years after approval
In a meta-analysis of 116 studies of antidepressants and body weight, mirtazapine was — alongside amitriptyline and paroxetine — associated with the greatest risk of weight gain among the antidepressants examined, while drugs such as bupropion and (short-term) fluoxetine tended toward weight loss.
Worth asking
Worth asking your prescriber whether an antidepressant with less weight-gain risk would fit your treatment plan if weight is already a concern for you.
Step 5
What still is not known
Which questions you might reasonably have has nobody answered yet?
- If you were prescribed it for sleep or appetite, these trials are not about that use.
- The forty-week study randomised only people who had already responded. It does not tell you your chance of responding.
- Weight gain and sedation are the most common reasons people stop. Six weeks is short for judging either.
Deciding about mirtazapine?
- 12 questions to ask before starting a psychiatric medication — each with the study behind it
- Already on it? The 10-question annual review — including the honest case for staying
- How long every drug here was tested before approval — one chart, all medications
Open mirtazapine (Remeron) in Resolv
The app has the full approval journey, the resources behind it, and people working through the same questions.
