Mirtazapine
Noradrenergic and Specific Serotonergic Antidepressant (NaSSA)
Mirtazapine is a widely prescribed noradrenergic and specific serotonergic antidepressant (NaSSA) used primarily to treat major depressive disorder in adults. Unlike SSRIs and SNRIs, mirtazapine works by a unique dual mechanism — enhancing both noradrenergic and serotonergic neurotransmission while blocking specific serotonin receptor subtypes. Its pronounced sedating and appetite-stimulating properties make it particularly useful for patients experiencing depression with insomnia or significant weight loss. Mirtazapine typically begins to show therapeutic effects within 1 to 2 weeks, with more substantial improvement expected after 2 to 4 weeks of consistent treatment.
Quick Facts: Mirtazapine
Key Takeaways
- Mirtazapine treats major depression in adults: It is a noradrenergic and specific serotonergic antidepressant (NaSSA) with a unique dual mechanism of action that enhances both noradrenergic and serotonergic neurotransmission.
- Allow 1-4 weeks for effects: Some improvement may be felt within 1 to 2 weeks, but full therapeutic benefit typically requires 2 to 4 weeks. Continue treatment as directed even if you do not feel immediate results.
- Pronounced sedation and appetite stimulation: Weight gain and drowsiness are very common side effects. Mirtazapine is often taken at bedtime as a single dose, and its sedative properties can benefit patients with insomnia.
- Never combine with MAO inhibitors: Do not take mirtazapine within 2 weeks of stopping an MAO inhibitor, and do not start an MAO inhibitor within 2 weeks of stopping mirtazapine, due to the risk of serotonin syndrome.
- Monitor for suicidal thoughts in young people: Patients under 25 years should be closely monitored for worsening depression and suicidal ideation, especially during the first weeks of treatment.
What Is Mirtazapine and What Is It Used For?
Mirtazapine is a noradrenergic and specific serotonergic antidepressant (NaSSA) used to treat major depressive disorder in adults. It works by enhancing the release of noradrenaline and serotonin in the brain while selectively blocking certain serotonin receptor subtypes, which helps improve mood, restore sleep, and stimulate appetite.
Mirtazapine belongs to a class of medications called noradrenergic and specific serotonergic antidepressants (NaSSAs). Unlike selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine or citalopram, mirtazapine does not primarily block serotonin reuptake. Instead, it works by blocking alpha-2 adrenergic autoreceptors and heteroreceptors on nerve endings, which enhances the release of both noradrenaline (norepinephrine) and serotonin into the synaptic cleft. Additionally, mirtazapine selectively blocks 5-HT2 and 5-HT3 serotonin receptors, which means that the increased serotonin activity is directed primarily through 5-HT1 receptors — the receptor subtype most associated with antidepressant effects.
This unique pharmacological profile gives mirtazapine several distinctive clinical properties. Its strong affinity for histamine H1 receptors produces a sedative effect that is often therapeutically beneficial for depressed patients suffering from insomnia. Interestingly, this sedative effect is paradoxically more pronounced at lower doses (15 mg) because at higher doses (30–45 mg), the increased noradrenergic activity partially counteracts the antihistaminic sedation. Mirtazapine also stimulates appetite — a property that can be helpful in patients with depression-associated weight loss and poor appetite, but that may be unwanted in others.
It is important to understand that mirtazapine does not provide immediate relief of depression symptoms. Typically, it takes 1 to 2 weeks before the medication begins to have an effect, and noticeable improvement usually develops after 2 to 4 weeks of consistent use. If you do not feel better after this period, your doctor may increase the dose. You should not stop taking mirtazapine without medical advice, even if you do not feel immediate improvement, as the full benefit requires sustained treatment.
Approved Uses
Mirtazapine is approved for the treatment of major depressive disorder (MDD) in adults. The recommended starting dose is 15 to 30 mg daily, usually taken as a single dose at bedtime. Your doctor may increase the dose to a maximum of 45 mg daily based on your clinical response. Treatment should continue for at least 4 to 6 months after depressive symptoms have resolved, to reduce the risk of relapse.
In clinical practice, mirtazapine is sometimes prescribed off-label for conditions such as insomnia (due to its sedating properties), anxiety disorders, and appetite stimulation in patients with chronic illness or cancer. However, these uses are not part of the standard approved indications and should only be considered under medical supervision.
How Does Mirtazapine Work?
Everyone has neurotransmitters called noradrenaline and serotonin in the brain. These chemical messengers play crucial roles in regulating mood, sleep, appetite, and anxiety. People with depression often have disrupted signaling in the noradrenergic and serotonergic systems. Mirtazapine helps correct this by enhancing the release of both noradrenaline and serotonin.
Specifically, mirtazapine blocks alpha-2 adrenergic receptors that normally act as “brakes” on noradrenaline and serotonin release. By blocking these receptors, mirtazapine removes the inhibitory feedback and allows more of these neurotransmitters to be released. At the same time, it blocks 5-HT2A, 5-HT2C, and 5-HT3 serotonin receptors, which helps reduce anxiety, nausea, and sexual side effects that are commonly associated with SSRI antidepressants. The net result is enhanced serotonergic transmission specifically through 5-HT1A receptors, which is considered the key pathway for antidepressant activity.
Mirtazapine has an elimination half-life of 20 to 40 hours, which supports once-daily dosing. Steady-state plasma concentrations are typically reached after 3 to 4 days of consistent dosing. The drug is extensively metabolized in the liver, primarily through the cytochrome P450 enzymes CYP2D6, CYP3A4, and CYP1A2.
Because of its strong antihistaminic properties, mirtazapine often improves sleep quality within the first few days of treatment — well before the full antidepressant effect emerges. This early improvement in sleep can be encouraging and may help patients persevere with treatment during the initial weeks when antidepressant effects have not yet fully developed.
What Should You Know Before Taking Mirtazapine?
Before taking mirtazapine, tell your doctor about all medical conditions, especially epilepsy, liver or kidney disease, heart disease, diabetes, glaucoma, or a history of mania. Do not take mirtazapine if you are allergic to it or if you have used an MAO inhibitor within the past 2 weeks.
Contraindications
Mirtazapine must not be taken in the following situations:
- Allergy to mirtazapine or any other ingredient in the formulation. If you develop signs of an allergic reaction such as skin rash, itching, swelling, or difficulty breathing, stop taking mirtazapine and seek medical attention immediately.
- Concurrent use of MAO inhibitors (monoamine oxidase inhibitors), such as moclobemide, tranylcypromine, or selegiline. Do not take mirtazapine within 2 weeks of stopping an MAO inhibitor, and do not start an MAO inhibitor within 2 weeks of stopping mirtazapine. Combining these medications can cause a potentially fatal condition called serotonin syndrome.
Warnings and Precautions
Talk to your doctor, pharmacist, or nurse before taking mirtazapine if you have any of the following conditions or circumstances:
- Epilepsy (seizures): Mirtazapine may lower the seizure threshold. If you experience seizures or your seizures become more frequent, stop taking mirtazapine and contact your doctor immediately.
- Liver disease, including jaundice: Mirtazapine is metabolized in the liver. If you develop jaundice (yellowing of the skin or eyes), stop mirtazapine and contact your doctor immediately. A dose reduction may be necessary for patients with impaired liver function.
- Kidney disease: Dose adjustments may be required for patients with significantly reduced kidney function.
- Heart disease or low blood pressure: Mirtazapine can cause orthostatic hypotension (a drop in blood pressure when standing up). Patients with heart conditions or those taking blood pressure medications should be monitored carefully.
- Schizophrenia: If psychotic symptoms such as paranoid thoughts become more frequent or severe, contact your doctor immediately.
- Manic depression (bipolar disorder): If you begin to feel elated, euphoric, or overexcited, stop mirtazapine and contact your doctor immediately. Mirtazapine may trigger manic episodes in patients with bipolar disorder.
- Diabetes: Mirtazapine may affect blood sugar control. Your doctor may need to adjust the dose of your insulin or other diabetes medications.
- Glaucoma (increased eye pressure): Inform your doctor if you have narrow-angle glaucoma or elevated intraocular pressure.
- Urinary retention: If you have difficulty urinating (which may be caused by an enlarged prostate), discuss this with your doctor before starting mirtazapine.
- Certain heart rhythm disorders: Including conditions that may affect your heart rhythm, a recent heart attack, heart failure, or if you are taking medications that affect heart rhythm (QT-prolonging drugs).
If you develop unexplained high fever, sore throat, and mouth ulcers while taking mirtazapine, stop the medication immediately and contact your doctor for a blood test. In rare cases, these symptoms may indicate bone marrow suppression (agranulocytosis) — a serious reduction in white blood cells that impairs the body's ability to fight infection. This is most likely to occur after 4 to 6 weeks of treatment.
Serious skin reactions including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reaction with eosinophilia and systemic symptoms (DRESS) have been reported with mirtazapine. If you develop reddish target-like spots on the trunk, skin peeling, mouth sores, widespread rash with fever and enlarged lymph nodes, stop mirtazapine and seek emergency medical care immediately. If you have ever had a severe skin reaction to mirtazapine, you must never take it again.
Suicidal Thoughts and Worsening Depression
Patients with depression may sometimes have thoughts of self-harm or suicide. These thoughts may paradoxically increase when first starting antidepressant treatment, because the medication typically takes at least 2 weeks to produce a full therapeutic effect. This risk is particularly important in the following groups:
- Patients who have previously had thoughts of self-harm or suicide
- Young adults under 25 years of age — clinical studies have shown an increased risk of suicidal thinking in this age group during early treatment with antidepressants
If you experience thoughts of self-harm or suicide at any point during treatment, contact your doctor immediately or seek emergency care. It can be helpful to tell a family member or close friend about your condition and ask them to read this information. You may also ask them to tell you if they notice changes in your mood or behavior.
Children and Adolescents
Mirtazapine should not normally be used in patients under 18 years of age, as efficacy has not been demonstrated in this age group. Furthermore, the risk of adverse effects including suicidal behavior, self-harm, hostility (primarily aggression, oppositional behavior, and anger) is greater in patients under 18 who take antidepressant medications. Despite this, a doctor may prescribe mirtazapine to a patient under 18 if they determine it is appropriate. Long-term safety data regarding the effects of mirtazapine on growth, maturation, and cognitive and behavioral development in children and adolescents have not been established. Additionally, significant weight gain has been observed more frequently in this age group compared to adults.
Pregnancy and Breastfeeding
Pregnancy: If you are pregnant, think you may be pregnant, or are planning to have a baby, ask your doctor for advice before taking mirtazapine. Limited data from pregnant women using mirtazapine does not indicate an increased risk of birth defects. However, caution should be exercised when using mirtazapine during pregnancy. If you take mirtazapine up to or near the time of delivery, your newborn should be monitored for potential withdrawal effects. Tell your midwife or doctor that you are taking mirtazapine. When similar antidepressants are taken during pregnancy, there may be an increased risk of a serious condition called persistent pulmonary hypertension of the newborn (PPHN), which causes the baby to breathe faster and appear bluish. Symptoms typically appear within 24 hours of birth. If this affects your baby, contact your midwife or doctor immediately.
Breastfeeding: Ask your doctor whether you can breastfeed while taking mirtazapine. Small amounts of mirtazapine may pass into breast milk, and a decision should be made by your doctor weighing the benefits of breastfeeding against the potential risks to the infant.
Driving and Operating Machinery
Mirtazapine can significantly impair your concentration and alertness, particularly when you first start treatment or after a dose increase. Do not drive or operate machinery until you are certain that your ability is not affected. Drowsiness is one of the most common side effects and may be particularly pronounced during the first few days of treatment.
Alcohol
You should not drink any alcohol while taking mirtazapine. Mirtazapine enhances the sedative effect of alcohol, which can lead to excessive drowsiness, impaired judgment, reduced coordination, and an increased risk of accidents. Alcohol can also worsen symptoms of depression and reduce the effectiveness of antidepressant treatment.
How Does Mirtazapine Interact with Other Drugs?
Mirtazapine has significant drug interactions, particularly with MAO inhibitors (which must never be combined), serotonergic drugs (risk of serotonin syndrome), sedative medications (increased drowsiness), and certain enzyme inhibitors or inducers that can alter mirtazapine blood levels. Always tell your doctor about all medications you are taking.
Mirtazapine is metabolized in the liver by cytochrome P450 enzymes, primarily CYP2D6, CYP3A4, and CYP1A2. Drugs that inhibit or induce these enzymes can alter the blood levels of mirtazapine, potentially increasing the risk of side effects or reducing therapeutic efficacy. Additionally, mirtazapine's serotonergic and sedating properties mean that combinations with other central nervous system depressants or serotonergic drugs require careful medical supervision.
Major Interactions (Avoid Combination)
| Drug / Class | Risk | Action Required |
|---|---|---|
| MAO inhibitors (moclobemide, tranylcypromine, selegiline) | Serotonin syndrome (potentially fatal) | Contraindicated. Wait 2 weeks after stopping either drug before starting the other |
| Linezolid (antibiotic) / Methylene blue | Serotonin syndrome | Avoid combination; use alternatives if possible |
Serotonin Syndrome Risk
The following medications, when combined with mirtazapine, can increase the risk of serotonin syndrome — a rare but potentially life-threatening condition characterized by unexplained fever, sweating, rapid heart rate, diarrhea, involuntary muscle contractions, tremor, hyperactive reflexes, restlessness, mood changes, and impaired consciousness:
- SSRI antidepressants (fluoxetine, citalopram, escitalopram, sertraline)
- SNRI antidepressants (venlafaxine)
- L-Tryptophan (a serotonin precursor)
- Triptans (used for migraine, e.g., sumatriptan)
- Tramadol (a pain reliever)
- Lithium (used for bipolar disorder)
- St. John’s Wort (Hypericum perforatum, a herbal remedy for depression)
If you experience a combination of these symptoms while taking mirtazapine, contact your doctor immediately.
Moderate Interactions (Use with Caution)
| Drug / Class | Effect | Action Required |
|---|---|---|
| Benzodiazepines (e.g., diazepam, lorazepam) | Increased drowsiness and sedation | Use with caution; dose adjustments may be needed |
| Olanzapine and other antipsychotics | Increased drowsiness and sedation | Monitor for excessive sedation |
| Antihistamines (e.g., cetirizine) | Increased drowsiness | Monitor for excessive sedation |
| Opioid analgesics (e.g., morphine) | Increased CNS depression and drowsiness | Use with caution under medical supervision |
| Warfarin (blood thinner) | Increased anticoagulant effect of warfarin | Monitor INR closely; dose adjustment may be needed |
| Nefazodone (antidepressant) | Increased mirtazapine blood levels | Reduce mirtazapine dose; increase again when nefazodone is stopped |
Drugs That Increase Mirtazapine Blood Levels
The following medications can inhibit the liver enzymes that metabolize mirtazapine, leading to higher blood levels and an increased risk of side effects. Your doctor may need to reduce your mirtazapine dose when co-prescribing these drugs, and increase it again when they are discontinued:
- Erythromycin (antibiotic)
- Ketoconazole (antifungal)
- HIV protease inhibitors
- Cimetidine (antacid)
Drugs That Decrease Mirtazapine Blood Levels
The following medications induce the liver enzymes that metabolize mirtazapine, which can reduce its blood levels and diminish therapeutic effectiveness. Your doctor may need to increase your mirtazapine dose, and then reduce it again when these drugs are discontinued:
- Carbamazepine (anti-epileptic)
- Phenytoin (anti-epileptic)
- Rifampicin (anti-tuberculosis)
What Is the Correct Dosage of Mirtazapine?
The recommended starting dose of mirtazapine is 15 to 30 mg per day, taken as a single dose at bedtime. Your doctor may increase the dose to a maximum of 45 mg daily after a few days, depending on your response. The same dosage range applies to all age groups, but elderly patients and those with liver or kidney disease may require dose adjustments.
Always take mirtazapine exactly as your doctor or pharmacist has told you. Do not change the dose on your own. Mirtazapine tablets should be swallowed with water or juice, without chewing. If you are using the orodispersible (orally disintegrating) tablets, place the tablet on your tongue, where it will dissolve rapidly with saliva and can be swallowed without water.
Adults
Standard Adult Dosage
Starting dose: 15 to 30 mg per day
Maintenance dose: 15 to 45 mg per day
Maximum dose: 45 mg per day
Your doctor may increase the dose after a few days based on your response. Mirtazapine is best taken as a single dose at bedtime, as it can cause drowsiness. However, your doctor may suggest splitting the dose — one dose in the morning and one at bedtime, with the higher dose taken at bedtime.
Elderly Patients
Elderly Dosage
The dosage for elderly patients is the same as for other adults. However, dose increases should be made more cautiously and under close medical supervision, as elderly patients may be more sensitive to the side effects of antidepressants, particularly drowsiness and orthostatic hypotension (dizziness when standing up).
Liver and Kidney Impairment
Dose Adjustments for Organ Impairment
If you have liver disease or kidney disease, your doctor may need to reduce your dose of mirtazapine or monitor you more closely. Mirtazapine is extensively metabolized in the liver and eliminated primarily through the kidneys, so impaired organ function can lead to higher drug levels in the body.
Children and Adolescents
Pediatric Use
Mirtazapine is not recommended for use in children and adolescents under 18 years of age due to a lack of demonstrated efficacy. If a doctor does prescribe mirtazapine for a patient under 18 in exceptional circumstances, close monitoring for suicidal behavior, self-harm, and hostility is essential.
When to Take Mirtazapine
Take mirtazapine at the same time every day. It is best to take the full dose at bedtime, as the sedative effect helps promote sleep. However, if your doctor has prescribed a split dose, take the smaller dose in the morning and the larger dose at bedtime. Treatment should generally continue for at least 4 to 6 months after your depressive symptoms have resolved, as early discontinuation increases the risk of relapse.
When to Expect Improvement
Mirtazapine usually begins to show effects within 1 to 2 weeks, with more significant improvement typically apparent after 2 to 4 weeks. It is important that you speak to your doctor 2 to 4 weeks after starting treatment to discuss the effects. If you still do not feel better, your doctor may increase the dose. After any dose adjustment, speak to your doctor again after another 2 to 4 weeks.
Missed Dose
If you are taking mirtazapine once daily and forget a dose, do not take a double dose to make up for it. Simply take your next dose at the usual time the following day.
If you are taking mirtazapine twice daily:
- If you forget your morning dose, take it together with your evening dose
- If you forget your evening dose, do not take it with your next morning dose — skip it and continue with your regular schedule
- If you forget both doses, skip them entirely and resume your usual morning and evening doses the next day
Overdose
If you or someone else takes too much mirtazapine, seek emergency medical attention immediately by contacting your doctor, going to the nearest emergency room, or calling your local poison control center.
The most common symptoms of mirtazapine overdose (without other drugs or alcohol) include drowsiness, confusion, and rapid heart rate. In more serious cases, symptoms may include changes in heart rhythm (rapid, irregular heartbeats) and/or fainting, which could indicate a potentially life-threatening condition called Torsades de Pointes.
Mirtazapine overdose can be life-threatening, particularly when combined with alcohol or other medications. If overdose is suspected, do not wait for symptoms — seek emergency medical care immediately.
What Are the Side Effects of Mirtazapine?
The most common side effects of mirtazapine are increased appetite, weight gain, drowsiness, and dry mouth. Mirtazapine may also cause dizziness, headache, fatigue, and edema. Serious but rare side effects include bone marrow suppression (agranulocytosis), serotonin syndrome, severe skin reactions, and seizures.
Like all medications, mirtazapine can cause side effects, although not everyone will experience them. Most side effects are mild and tend to improve as your body adjusts to the medication. However, some side effects are serious and require immediate medical attention. If you experience any of the serious side effects listed below, stop taking mirtazapine and contact your doctor immediately.
Very Common
May affect more than 1 in 10 people
- Increased appetite and weight gain
- Drowsiness or sleepiness (somnolence)
- Headache
- Dry mouth
Common
May affect up to 1 in 10 people
- Fatigue and lethargy
- Dizziness
- Tremor or shaking
- Nausea
- Diarrhea
- Vomiting
- Constipation
- Skin rash or eczema (exanthem)
- Joint pain (arthralgia) or muscle pain (myalgia)
- Back pain
- Dizziness or lightheadedness when standing up (orthostatic hypotension)
- Swelling of ankles and feet (peripheral edema)
- Vivid dreams
- Confusion
- Anxiety
- Sleep problems (insomnia)
- Memory problems (usually reversible after stopping treatment)
Uncommon
May affect up to 1 in 100 people
- Abnormal skin sensations such as burning, tingling, or prickling (paresthesia)
- Restless legs
- Fainting (syncope)
- Numbness in the mouth (oral hypoesthesia)
- Low blood pressure
- Nightmares
- Agitation
- Hallucinations
- Restlessness and strong urge to move
- Feeling of elation or mania
Rare
May affect up to 1 in 1,000 people
- Muscle twitching or contractions (myoclonus)
- Aggression
- Abdominal pain and nausea suggesting pancreatitis
Frequency Not Known
Cannot be estimated from available data
- Signs of infection such as unexplained high fever, sore throat, and mouth ulcers (agranulocytosis, bone marrow suppression)
- Seizures (convulsions)
- Serotonin syndrome (fever, sweating, rapid heart rate, muscle twitching, confusion)
- Suicidal thoughts or behavior
- Severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis, DRESS syndrome)
- Oral tingling or swelling (oral paresthesia, oral edema)
- Generalized edema (body-wide swelling)
- Low sodium levels (hyponatremia)
- Inappropriate secretion of antidiuretic hormone (SIADH)
- Sleepwalking (somnambulism)
- Speech disorders
- Elevated creatine kinase levels
- Difficulty emptying the bladder (urinary retention)
- Muscle pain, stiffness, and dark urine (rhabdomyolysis)
- Elevated prolactin levels (hyperprolactinemia, with possible breast enlargement and milk discharge)
- Prolonged painful erection (priapism)
Side Effects in Children and Adolescents
In clinical studies of patients under 18 years of age, the following side effects were commonly observed: significant weight gain, urticaria (hives), and elevated blood lipid levels (hyperlipidemia). These effects were observed more frequently than in adult populations.
It is important to report suspected side effects after a medicine has been authorized. This allows continuous monitoring of the benefit-risk balance of the medicine. Healthcare professionals and patients are encouraged to report side effects to their national medicines agency (e.g., EMA in Europe, FDA in the United States, MHRA in the United Kingdom).
How Should You Stop Taking Mirtazapine?
Never stop taking mirtazapine suddenly without your doctor's advice. Abrupt discontinuation can cause withdrawal symptoms including nausea, dizziness, anxiety, agitation, and headache. Your doctor will help you taper the dose gradually over several weeks.
You should only stop taking mirtazapine when you and your doctor have agreed on this together. Stopping too early increases the risk of your depression returning. When you feel better, speak with your doctor, who will decide when and how to gradually reduce your dose.
Do not stop mirtazapine suddenly, even if your depression has improved. Abrupt discontinuation can cause the following withdrawal symptoms:
- Nausea or vomiting
- Dizziness
- Agitation and irritability
- Anxiety
- Headache
These symptoms can be avoided by tapering the dose gradually under medical supervision. Your doctor will create a tapering schedule, typically reducing the dose in steps over several weeks. If withdrawal symptoms are troublesome despite gradual reduction, your doctor may recommend a slower taper.
As a general guideline, mirtazapine treatment should continue for at least 4 to 6 months after depressive symptoms have fully resolved, to reduce the risk of relapse. Some patients with recurrent depression may benefit from longer-term maintenance treatment, as determined by their doctor.
How Should You Store Mirtazapine?
Store mirtazapine at room temperature, out of the sight and reach of children. Do not use after the expiry date printed on the packaging. No special storage conditions are required.
- Keep out of the sight and reach of children
- Do not use after the expiry date stated on the packaging (EXP). The expiry date refers to the last day of that month.
- No special storage conditions are required
- Do not dispose of medications via wastewater or household waste. Ask your pharmacist how to properly dispose of medications that are no longer needed. These measures help protect the environment.
What Does Mirtazapine Contain?
The active ingredient is mirtazapine. Film-coated tablets are available in 15 mg, 30 mg, and 45 mg strengths. Orodispersible (orally disintegrating) tablets are also available.
Active Ingredient
Each tablet contains mirtazapine as the active substance:
- 15 mg tablets: 15 mg mirtazapine per film-coated tablet
- 30 mg tablets: 30 mg mirtazapine per film-coated tablet
- 45 mg tablets: 45 mg mirtazapine per film-coated tablet
Inactive Ingredients (Excipients)
The inactive ingredients may vary slightly between different brands and formulations. Common excipients in mirtazapine film-coated tablets include lactose monohydrate, pregelatinized maize starch, croscarmellose sodium (anhydrous), and magnesium stearate. The film coating typically contains hypromellose, macrogol, titanium dioxide (E171), talc, and iron oxide colorants (E172) depending on the tablet strength.
Lactose: Mirtazapine film-coated tablets contain lactose. If your doctor has told you that you have an intolerance to certain sugars, speak to your doctor before taking this medicine.
Sodium: This medicine contains less than 1 mmol (23 mg) sodium per film-coated tablet, meaning it is essentially sodium-free.
Available Formulations
- Film-coated tablets: 15 mg (yellow, scored, oval), 30 mg (brown, scored, oval), 45 mg (white, oval)
- Orodispersible tablets: Dissolve rapidly on the tongue without the need for water
Frequently Asked Questions About Mirtazapine
Mirtazapine typically takes 1 to 2 weeks before you notice any improvement, with more significant effects appearing after 2 to 4 weeks of consistent treatment. The sedative and appetite-stimulating effects often begin within the first few days, but the full antidepressant effect requires longer. If you do not feel better after 2 to 4 weeks, your doctor may increase the dose. Do not stop taking mirtazapine early without consulting your doctor.
Yes, increased appetite and weight gain are very common side effects of mirtazapine, affecting more than 1 in 10 people. This is related to its strong antihistaminic activity, which stimulates appetite. Significant weight gain is observed more frequently in children and adolescents than in adults. If weight gain is a concern, speak with your doctor about dietary strategies, exercise recommendations, or potential alternative medications.
No, you should not drink alcohol while taking mirtazapine. Mirtazapine enhances the sedative effects of alcohol, which can result in excessive drowsiness, impaired judgment, reduced coordination, and an increased risk of falls and accidents. Alcohol can also worsen symptoms of depression and reduce the effectiveness of your treatment.
No, you should never stop taking mirtazapine suddenly without consulting your doctor. Abrupt discontinuation can cause withdrawal symptoms such as nausea, dizziness, agitation, anxiety, and headache. Your doctor will create a gradual dose-tapering plan to minimize these effects. Even if you feel well, continue taking mirtazapine until your doctor advises you to stop, as depression can return if treatment is discontinued too early.
Limited data on mirtazapine use during pregnancy does not show an increased risk of birth defects, but caution is recommended. If you take mirtazapine close to delivery, your newborn should be monitored for potential effects. The decision to use or continue mirtazapine during pregnancy must be made together with your doctor, weighing the benefits of treating depression against potential risks to the baby. Untreated depression during pregnancy also carries significant risks. Never stop mirtazapine abruptly without medical guidance.
Mirtazapine has strong antihistaminic (H1 receptor blocking) properties, which cause drowsiness and sedation. Interestingly, this sedative effect is more pronounced at the lower dose of 15 mg than at higher doses of 30-45 mg, because at higher doses the increased noradrenergic activity partially counteracts the sedation. This is why mirtazapine is typically taken as a single dose at bedtime. The drowsiness usually diminishes after the first few weeks of treatment as your body adjusts to the medication.
References and Sources
- European Medicines Agency (EMA). Mirtazapine – Summary of Product Characteristics (SmPC). Amsterdam: EMA. Available at: www.ema.europa.eu
- National Institute for Health and Care Excellence (NICE). Depression in adults: treatment and management. NICE guideline [NG222], 2022. London: NICE. Available at: www.nice.org.uk/guidance/ng222
- Cipriani A, Furukawa TA, Salanti G, et al. Comparative efficacy and acceptability of 21 antidepressant drugs for the acute treatment of adults with major depressive disorder: a systematic review and network meta-analysis. Lancet. 2018;391(10128):1357-1366. doi: 10.1016/S0140-6736(17)32802-7
- British National Formulary (BNF). Mirtazapine. London: BMJ Group and Pharmaceutical Press. Available at: bnf.nice.org.uk
- U.S. Food and Drug Administration (FDA). Remeron (mirtazapine) Prescribing Information. Silver Spring: FDA. Available at: www.accessdata.fda.gov
- Watanabe N, Omori IM, Nakagawa A, et al. Mirtazapine versus other antidepressive agents for depression. Cochrane Database Syst Rev. 2011;(12):CD006528. doi: 10.1002/14651858.CD006528.pub2
- Anttila SAK, Leinonen EVJ. A review of the pharmacological and clinical profile of mirtazapine. CNS Drug Rev. 2001;7(3):249-264. doi: 10.1111/j.1527-3458.2001.tb00198.x
- World Health Organization (WHO). WHO Model List of Essential Medicines – 23rd List, 2023. Geneva: WHO. Available at: www.who.int/publications
Editorial Team and Medical Review
This article has been written and medically reviewed by the iMedic Medical Editorial Team, comprising board-certified specialists in psychiatry, clinical pharmacology, and internal medicine.
Medical Content
Written by licensed physicians with specialization in clinical pharmacology and psychiatry
Medical Review
Reviewed by the iMedic Medical Review Board according to EMA, FDA, WHO, and NICE guidelines
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Level 1A evidence based on systematic reviews, meta-analyses, and randomized controlled trials
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Last medically reviewed: | Next review due: January 2027