Mirtazepine treats depression. Can cause weight gain and drowsiness.

Mirtazapine Overview

Reviewed: September 14, 2012

Mirtazapine is a prescription medication used to treat depression. Mirtazapine belongs to a group of drugs called antidepressants, which may help maintain mental balance by blocking certain receptors in the brain.

This medication comes as a regular tablet and in an orally disintegrating tablet which dissolves on the tongue with no need for water. It is taken once a day in the evening, with or without food.   

Common side effects include increased appetite, dry mouth, and constipation. Mirtazapine can cause drowsiness and dizziness. Do not drive or operate machinery until you know how this medication will affect you. 

How was your experience with Mirtazapine?

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What are you taking Mirtazapine for?

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  • Other
  • Depressive Disorder

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  • A couple weeks
  • A month or so
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  • A year or so
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Mirtazapine Cautionary Labels


Uses of Mirtazapine

Mirtazapine is a prescription medicine used to treat depression. 

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.

Mirtazapine Brand Names

Mirtazapine may be found in some form under the following brand names:

Mirtazapine Drug Class

Mirtazapine is part of the drug class:

Side Effects of Mirtazapine

Mirtazapine may cause serious side effects, including all of those described in the section entitled "Drug Precautions".

Common possible side effects in people who take mirtazapine include:

  • sleepiness
  • increased appetite, weight gain
  • dry mouth
  • constipation
  • dizziness
  • abnormal dreams

Tell your healthcare provider if you have any side effect that bothers you or that does not go away. These are not all the possible side effects of mirtazapine. For more information, ask your healthcare provider or pharmacist.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Mirtazapine Interactions

Tell your healthcare provider about all the medicines that you take, including prescription and non-prescription medicines, vitamins, and herbal supplements. 

Especially tell your doctor if you take:

  • monoamine oxidase inhibitors (MAOI) such as:
  • tricyclic antidepressants such as:
  • ketoconazole (Nizoral)
  • buspirone (Buspar)
  • carbamazepine (Carbatrol, Equetro, Tegretol)
  • cimetidine (Tagamet)
  • diazepam (Valium)
  • lithium (Lithobid)
  • 'Triptan' medications such as:
  • phenytoin (Dilantin)
  • rifampicin
  • rifampin (Rimactane, Rifadin)
  • selective serotonin reuptake inhibitors (SSRIs) such as:
    • citalopram (Celexa)
    • escitalopram (Lexapro)
    • fluoxetine (Prozac, Sarafem)
    • fluvoxamine (Luvox)
    • paroxetine (Paxil, Pexeva)
    • sertraline (Zoloft)
  • selective serotonin and norepinephrine reuptake inhibitors (SNRIs) such as:
  • tramadol (Ultram)
  • tryptophan or St. John's Wort

This is not a complete list of mirtazapine drug interactions.

Your healthcare provider or pharmacist can tell you if it is safe to take mirtazapine with your other medicines. Do not start or stop any medicine while taking mirtazapine without talking to your healthcare provider first.

Mirtazapine Precautions

Mirtazapine and other antidepressant medicines may cause serious side effects, including:

1.  Suicidal thoughts or actions:
  • Antidepressant medicines may increase suicidal thoughts or actions in some children, teenagers, or young adults within the first few months of treatment or when the dose is changed.
  • Depression or other serious mental illnesses are the most important causes of suicidal thoughts or actions.
  • Watch for these changes and call your healthcare provider right away if you notice:
    • New or sudden changes in mood, behavior, actions, thoughts, or feelings, especially if severe.
    • Pay particular attention to such changes when mirtazapine is started or when the dose is changed.

    Keep all follow-up visits with your healthcare provider and call between visits if you are worried about symptoms.
    Call your healthcare provider right away if you have any of the following symptoms, or call 911 if an emergency, especially if they are new, worse, or worry you:
    • attempts to commit suicide
    • acting on dangerous impulses
    • acting aggressive or violent
    • thoughts about suicide or dying
    • new or worse depression
    • new or worse anxiety or panic attacks
    • feeling agitated, restless, angry or irritable
    • trouble sleeping
    • an increase in activity or talking more than what is normal for you
    • other unusual changes in behavior or mood

Call your healthcare provider right away if you have any of the following symptoms, or call 911 if an emergency. Mirtazapine may be associated with these serious side effects:

  • trouble breathing, swelling of the face, tongue, eyes or mouth
2.  Manic episodes:
  • greatly increased energy
  • severe trouble sleeping
  • racing thoughts
  • reckless behavior
  • unusually grand ideas
  • excessive happiness or irritability
  • talking more or faster than usual
3.  Decreased White Blood Cells called neutrophils, which are needed to fight infections. Tell your doctor if you have any indication of infection such as fever, chills, sore throat, or mouth or nose sores, especially symptoms which are flu-like.
4.  Serotonin Syndrome or Neuroleptic Malignant Syndrome-like reactions. This condition can be life-threatening and may include:
  • agitation, hallucinations, coma or other changes in mental status
  • coordination problems or muscle twitching (overactive reflexes)
  • racing heartbeat, high or low blood pressure
  • sweating or fever
  • nausea, vomiting, or diarrhea
  • muscle rigidity
5.  Seizures
6.  Low salt (sodium) levels in the bloodElderly people may be at greater risk for this. Symptoms may include:
  • headache
  • weakness or feeling unsteady
  • confusion, problems concentrating or thinking or memory problems
7.  Sleepiness. It is best to take mirtazapine close to bedtime.
8.  Severe skin reactions: Call your doctor right away if you have any or all of the following symptoms:
  • severe rash with skin swelling (including on the palms of the hands and soles of the feet)
  • painful reddening of the skin and/or blisters/ulcers on the body or in the mouth
9.  Severe allergic reactions:
  • rash, itchy welts (hives) or blisters, alone or with fever or joint pain
10. Increases in appetite or weight. Children and adolescents should have height and weight monitored during treatment.
11. Increased cholesterol and triglyceride levels in your blood

Do not stop mirtazapine without first talking to your healthcare provider. Stopping mirtazapine too quickly may cause potentially serious symptoms including:

  • dizziness
  • abnormal dreams
  • agitation
  • anxiety
  • fatigue
  • confusion
  • headache
  • shaking
  • tingling sensation
  • nausea, vomiting
  • sweating

Do not take mirtazapine if you:

  • are allergic to mirtazapine or any of the ingredients in it. 
  • take a Monoamine Oxidase Inhibitor (MAOI). Ask your healthcare provider or pharmacist if you are not sure if you take an MAOI, including the antibiotic linezolid. It is recommended that mirtazapine not be used in combination with an MAOI within 14 days of initiating or discontinuing therapy with an MAOI. People who take mirtazapine close in time to an MAOI may have serious or even life-threatening side effects. Get medical help right away if you have any of these symptoms:
  • high fever
  • uncontrolled muscle spasms
  • stiff muscles
  • rapid changes in heart rate or blood pressure
  • confusion
  • loss of consciousness (pass out)

Mirtazapine Food Interactions

Medications can interact with certain foods. In some cases, this may be harmful and your doctor may advise you to avoid certain foods. In the case of mirtazapine, there are no specific foods that you must exclude from your diet when receiving this medication. Do not drink alcohol while taking this medication.

Inform MD

Before starting mirtazapine, tell your healthcare provider if you:

  • have or had liver problems
  • have or had kidney problems
  • have or had heart problems
  • have or had seizures or convulsions
  • have or had bipolar disorder or mania
  • have or had a tendency to get dizzy or faint
  • are pregnant or plan to become pregnant. It is not known if mirtazapine will harm your unborn baby. Talk to your healthcare provider about the benefits and risks of treating depression during pregnancy.
  • are breastfeeding or plan to breastfeed. Some mirtazapine may pass into your breast milk. Talk to your healthcare provider about the best way to feed your baby while taking mirtazapine.

Tell your healthcare provider about all the medicines that you take, including prescription and non-prescription medicines, vitamins, and herbal supplements.

Mirtazapine and Pregnancy

Tell your healthcare provider if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Mirtazapine falls into category C. In animal studies, pregnant animals were given this medication and had some babies born with problems. No well-controlled studies have been done in humans, though. Therefore, this medication may be used if the potential benefits to the mother outweigh the potential risks to the unborn child.

Mirtazapine and Lactation

Tell your healthcare provider if you are breastfeeding or plan to breastfeed. Some mirtazapine may pass into your breast milk. Talk to your healthcare provider about the best way to feed your baby while taking mirtazapine.

Mirtazapine Usage

Mirtazapine Regular Tablet

  • Take mirtazapine at the same time each day, preferably in the evening at bedtime.
  • Swallow mirtazapine as directed.

Mirtazapine Orally Disintegrating Tablet

  • Take your mirtazapine orally disintegrating tablet at the same time each day, preferably in the evening at bedtime.
  • Open the tablet blister pack with dry hands and place the tablet whole on the tongue, immediately after removal from the blister pack.
  • The tablet will disintegrate rapidly on the tongue and can be swallowed with saliva. No water is needed for taking it.
  • Do not attempt to split the orally disintegrating tablet.

Regular and Orally Disintegrating Tablets

  • Do not stop taking or change the dose of mirtazapine (regular or orally disintegrating) without first talking to your doctor, even if you feel better.
  • Mirtazapine may be taken with or without food.
  • If you miss a dose of mirtazapine, take the missed dose as soon as you remember. If it is almost time for the next dose, skip the missed dose and take your next dose at the regular time. Do not take two doses of mirtazapine at the same time.
  • If you take too much mirtazapine, call your healthcare provider or poison control center right away, or get emergency treatment.
  • Mirtazapine can cause sleepiness or may affect your ability to make decisions, think clearly, or react quickly. You should not drive, operate heavy machinery, or do other dangerous activities until you know how mirtazapine affects you.
  • Avoid drinking alcohol or taking diazepam (a medicine used for anxiety, insomnia and seizures, for example) or similar medicines while taking mirtazapine. If you are uncertain about whether certain medication can be taken with mirtazapine, please discuss with your doctor.

Mirtazapine Dosage

Take this medication exactly as prescribed by your doctor. Follow the directions on your prescription label carefully.

The dose your doctor recommends may be based on the following:

  • how you respond to this medication
  • your age
  • your renal function
  • your hepatic function

The recommended dose range of mirtazapine for the treatment of depression is 15 to 45 mg/day.

The recommended starting dose for mirtazapine is 15 mg/day, administered in a single dose, in the evening prior to sleep.

Mirtazapine Overdose

If you take too much mirtazapine, call your healthcare provider or poison control center right away, or get emergency treatment.


Other Requirements

  • Store mirtazapine at room temperature 25°C (77°F). Storage at 15°C-30°C (59°F-86°F) is permitted occasionally.
  • Keep mirtazapine away from light and moisture.
  • Orally disintegrating tablet: Use immediately upon opening individual tablet blister.

Keep this and all medicines out of the reach of children.

Mirtazapine FDA Warning

Suicidality and Antidepressant Drugs

Antidepressants increased the risk compared to placebo of suicidal thinking and behavior (suicidality) in children, adolescents, and young adults in short-term studies of major depressive disorder (MDD) and other psychiatric disorders. Anyone considering the use of mirtazapine or any other antidepressant in a child, adolescent, or young adult must balance this risk with the clinical need. Short-term studies did not show an increase in the risk of suicidality with antidepressants compared to placebo in adults beyond age 24; there was a reduction in risk with antidepressants compared to placebo in adults aged 65 and older. Depression and certain other psychiatric disorders are themselves associated with increases in the risk of suicide. Patients of all ages who are started on antidepressant therapy should be monitored appropriately and observed closely for clinical worsening, suicidality, or unusual changes in behavior. Families and caregivers should be advised of the need for close observation and communication with the prescriber. Mirtazapine is not approved for use in pediatric patients.