Mirtazapine

Boxed warning

Boxed warnings (formerly “black box warnings”) are the strongest safety-related warnings issued by the US Food and Drug Administration (FDA).

Mirtazapine has a boxed warning for increased risk of suicidal thoughts and behaviors in children and young adults.¹ The medication is not approved for pediatric patients. All individuals who take mirtazapine, regardless of age, should be monitored for emerging or increased suicidal thoughts and behaviors.

What is mirtazapine?

Mirtazapine is a prescription tetracyclic antidepressant (TeCA) medication used in the treatment of depression.²

What You Need To Know About Depression

It works by blocking alpha-2 receptors, which increases the mood-enhancing activity of serotonin and norepinephrine. Mirtazapine helps balance these chemicals in the brain and optimize nervous system communication.

The medication also has sedative, anti-nausea, anti-anxiety, and appetite-stimulating effects.

Mirtazapine is the generic form of the medicine. It is also sold under the brand name Remeron or Remeron SolTab, depending on the formulation.

What is mirtazapine used to treat?

The FDA approved mirtazapine in 1996 for use in treating major depressive disorder in adults.

Although the FDA has only approved the drug for this indication, clinicians also prescribe it for certain off-label uses. Off-label uses of mirtazapine include the following:³ ⁴

• Insomnia

• Generalized anxiety disorder

• Social anxiety disorder

• Post-traumatic stress disorder

• Obsessive-compulsive disorder

• Migraines and headaches

• Panic disorder

• Hot flashes

• Weight loss and appetite stimulation

• Fibromyalgia

Dosage forms and strengths

Mirtazapine is available in two forms: an immediate-release oral tablet (Remeron) and a disintegrating tablet (Remeron SolTab).

• Remeron is available in the following strengths: 15mg and 30mg.

• Remeron SolTab is available in the following strengths: 15mg, 30mg, and 45mg.⁵

• Generic mirtazapine oral tablet is available in the following strengths: 7.5mg, 15mg, 30mg, and 45mg.⁶

• Generic mirtazapine disintegrating tablet is available in the following strengths: 15mg, 30mg, and 45mg.⁷

Recommended dosing for major depressive disorder ranges from 15mg to a maximum of 45mg per day. Typically, prescribers will begin with the lowest dose of 15mg and increase it as needed.⁸

Since older adults may clear mirtazapine from their systems at reduced rates, a dose of 7.5–15mg per day is advised for people aged 65 and over.⁹

Always follow your doctor’s instructions for your dose and frequency.

How do you take mirtazapine?

Mirtazapine is typically prescribed to be taken once a day.¹⁰ Dosing adjustments won’t usually be made for at least 1–2 weeks.

If you are prescribed an immediate-release tablet, swallow it with water without crushing or chewing it. If your doctor prescribes a disintegrating tablet, allow it to dissolve on your tongue.

Food doesn’t affect mirtazapine absorption, so you can take your medication with or without food.

Since the drug has sedative effects, taking it shortly before going to sleep is usually recommended.

Always follow your doctor or pharmacist’s instructions carefully when taking mirtazapine.

Seeing results

When taking mirtazapine as indicated by your doctor, your symptoms will usually improve within 4–6 weeks of starting the medication.

In a large, short-term multicenter study of over 4,700 people with depression, there were at least some improvements in symptoms for 95% of participants within the first two weeks of taking mirtazapine.¹¹ These included improvements in apparent sadness levels, suicidal thoughts, and sleep.

Who should not take mirtazapine?

Mirtazapine may be unsuitable for some people, including those with the following conditions:¹²

• Hypersensitivity to mirtazapine or any of its ingredients

• Liver impairment

• Kidney impairment

• Bipolar disorder

• Seizure disorder

• Electrolyte abnormalities

• Long QT syndrome, including a family history of the condition

• Family history of torsades de pointes

• Ventricular arrhythmia

• Bradycardia

• Recent myocardial infarction

• Congestive heart failure

• Cardiovascular disease

• Cerebrovascular disease

• Hypotension (low blood pressure)

• Hypovolemia

• Dehydration

• Angle-closure glaucoma

• Cigarette smoking

• Phenylketonuria (phenylalanine-containing form)

Mirtazapine is not approved by the FDA for use in children.¹³

Mirtazapine should not be taken if you have a history of suicidal thoughts. You should stop taking the medication if your depression symptoms worsen during the course of your treatment.

You should not take this medication if you have taken an MAO inhibitor in the last 14 days.¹⁴ Don’t take this medication if you are also taking tryptophan (L-tryptophan) or if you have taken certain antidepressants in the past that may interact with mirtazapine.

Potential side effects of mirtazapine

In addition to the potential benefits mirtazapine offers for people with major depressive disorder, the drug may cause certain side effects.

Common side effects

Mirtazapine may cause the following common side effects:¹⁵ ¹⁶

• Dry mouth

• Drowsiness

• Constipation

• Increased appetite, weight gain

• Loss of appetite

• Nausea and vomiting

• Headaches

• Dizziness

• Muscle or back pain

• Abdominal pain

• Urinary frequency

• Tremor

• Abnormal dreams, sleepwalking

• Sensitivity to the sun

• Swelling

Severe side effects

Serious side effects are rare when taking mirtazapine. They may include the following:¹⁷

• Acute pancreatitis, marked by intense back or stomach pain and nausea

• Acute liver injury, marked by yellowing of the skin and the whites of the eyes

• Low sodium levels in the blood, marked by muscle cramps, confusion, and recurring headaches

• Infections, marked by sore throats, mouth ulcers, and high body temperatures

• Serious rashes including Steven-Johnson syndrome and toxic epidermal necrolysis

• Serotonin syndrome, which manifests as agitation, hallucinations, dizziness, rapid heart rate, flushing, sweating, tremor, vomiting, diarrhea, seizures, and coma

• Neutropenia — a low level of certain white blood cells

• Suicidal thoughts or behaviors, particularly in people aged 24 years and under

• QT prolongation — a heart rhythm disturbance

• Seizures

• Worsening depression

• Mania in bipolar disease

• Acute pancreatitis

When to seek medical attention

Seek medical assistance immediately if you experience any severe side effects when taking mirtazapine.

Overdose information

Although it’s rare, taking too much mirtazapine can be fatal. Symptoms of overdose include any of the adverse effects above, as well as an elevated heart rate or blood pressure, disorientation, drowsiness, mild sedation, and memory lapses.

If you overdose on mirtazapine, immediately call 911 or go to the nearest emergency department.

Missed doses

Always follow your doctor or pharmacist’s instructions on how to handle your next dose if you miss a dose of mirtazapine.

In general, you can take your missed dose as soon as you remember, unless you are within two hours of the next scheduled dose. If this is the case, skip the dose you missed and take your regularly scheduled dose.

Never take a double dose of mirtazapine.

Allergy information

Allergic reactions to mirtazapine are rare.

Visit the nearest emergency department or call 911 immediately if you experience:

• Wheezing

• Difficulty breathing

• Swelling of the throat and tongue

• Hives

• Tightness in the throat or chest

• Vomiting

• Loss of consciousness

Long-term use of mirtazapine

Mirtazapine is usually prescribed for the long-term treatment of depression.

Your doctor will monitor your symptoms. They may prescribe the medication for six months to a year after you notice that the signs of depression stop.

Long-term mirtazapine use does not seem to be associated with any adverse effects.

Mirtazapine and pregnancy

Mirtazapine is a pregnancy category C drug as designated by the FDA, meaning no adequate studies had been carried out with pregnant women.¹⁸

Animal studies have shown a risk of decreased offspring survival both during and after pregnancy. However, this effect was observed when 20 times the maximum recommended human dose (MRHD) of mirtazapine was given and not when three times the MRHD was given.

Recent human research has not shown any adverse effects due to mirtazapine use during pregnancy.¹⁹

Mirtazapine and breastfeeding

There is limited data that shows mirtazapine can be passed to breastfeeding infants. For example, one study showed that a dose-adjusted average of 1.5% of the mirtazapine taken by nursing mothers (with daily doses of 30–120mg) was passed to their nursing babies.²⁰

The risk for adverse effects on nursing babies is low based on this limited data — but it cannot be ruled out because there are inadequate studies in humans.

It’s a good idea to speak with your doctor about whether the risks of taking mirtazapine while pregnant or nursing outweigh the benefits in your case.

Drug interactions

Mirtazapine can interact with prescription and non-prescription drugs, as well as certain herbal remedies, including the following:²¹

• Tryptophan

• Pain medications such as tramadol, codeine, hydrocodone, and morphine

• MAO inhibitors like selegiline (Eldepryl, Zelapar), isocarboxazid (Marplan), phenelzine (Nardil), and safinamide (Xadago)

• Antipsychotics such as pimozide (Orap) and thioridazine (Mellaril)

• Migraine medications such as dihydroergotamine (Migranal) and lasmiditan (Reyvow)

• St. John’s wort

• IV methylene blue

• Sedatives such as diazepam (Valium)

• Muscle relaxants such as cyclobenzaprine (Flexeril) and metaxalone (Skelaxin)

• Sleeping medicines such as doxepin (Silenor)

• Antidepressants like amitriptyline (Elavil), citalopram (Celexa), bupropion (Wellbutrin, Zyban), clomipramine (Anafranil), and levomilnacipran (Fetzima)

• Anti-seizure medications such as phenytoin (Dilantin) and carbamazepine (Tegretol)

• Antiarrhythmics such as dronedarone (Multaq) and sotalol (Betapace)

• ADHD medicines like methylphenidate (Concerta, Aptensio) and methamphetamine (Desoxyn)

• Antibiotics like linezolid (Zyvox), isoniazid (INH), and lefamulin (Xenleta)

• Medicines for gastrointestinal problems, such as eluxadoline (Viberzi), ondansetron (Zofran), and trimethobenzamide (Tigan)

• Diabetes medicines such as pramlintide (Symlin)

• Dextromethorphan (Robitussin, Delsym, and other cough medicines)

Avoid or minimize alcohol consumption when taking mirtazapine. Alcohol can increase certain side effects of the drug, including drowsiness.

This is not an exhaustive list of possible drug interactions. It’s best to review with your doctor all of the medicines, herbs, and supplements you take regularly or even occasionally before taking mirtazapine.

What to discuss with your doctor before starting mirtazapine

Here are some of the things you should address with your doctor before taking mirtazapine:

• Your most common and intense symptoms

• If you’ve had suicidal thoughts or behaviors

• If you’re nursing, pregnant, or planning to get pregnant

• Your current list of medications, supplements, and herbs

• Your medical history, especially if you have a history of heart problems, low blood pressure, seizures, or glaucoma

• Any allergies you have

• Any side effects you’ve experienced from taking another medication

• Previous medications you’ve taken, especially antidepressants taken recently

• Your work and lifestyle habits, since mirtazapine may have sedative effects

Stopping mirtazapine

Talk to your doctor before you stop taking mirtazapine. Stopping the drug suddenly can lead to antidepressant discontinuation syndrome, which can cause depression, nausea, vomiting, insomnia, abnormal dreams, anxiety, fatigue, confusion, panic attacks, vertigo (spinning sensations), mania, tinnitus (ringing in the ears), vomiting, and decreased appetite.²² ²³

It’s recommended to reduce your dose of mirtazapine gradually as directed by your doctor.

Drug approval history

1996: The FDA approved mirtazapine — to be sold as the brand Remeron — for use in treating major depressive disorder.²⁴ The initial approval was for 15mg and 30mg doses of the drug in oral tablet form.

1997: A 45mg dose of Remeron was approved by the FDA. Note that this dosage is now only available as a generic medication — the brand version is discontinued.²⁵

2001: Mirtazapine was approved as a disintegrating tablet to be sold as Remeron SolTab.²⁶

Tips for taking mirtazapine

• Take mirtazapine at the same time each day, typically in the evening or right before you go to sleep. It’s best to take the drug at this time because it can cause sedative effects.

• Avoid driving, using machinery, or doing activities that require your full attention. Mirtazapine may cause drowsiness.

• Consuming alcohol when taking mirtazapine may increase feelings of drowsiness and should be limited or avoided.

• Keep mirtazapine away from moisture and light and store it at room temperature.²⁷

Frequently asked questions

What is the drug mirtazapine used for?

Mirtazapine is approved by the FDA for the treatment of major depressive disorder.

What are the main side effects of mirtazapine?

Common side effects include drowsiness, dry mouth, increased appetite, weight gain, constipation, increased cholesterol levels, headaches, nausea, and vomiting.

Is mirtazapine a sleeping pill?

Mirtazapine is approved by the FDA for the treatment of major depressive disorder. It is sometimes prescribed off-label to treat insomnia because of its sedative effects. However, it is not a sleeping pill and is not approved by the FDA to help with sleep issues.

Is mirtazapine the same as Xanax?

Xanax and mirtazapine are two entirely different drugs. Mirtazapine is a tetracyclic antidepressant used to treat major depressive disorder, while Xanax is a benzodiazepine used primarily to treat anxiety and panic disorder.

The two drugs do share some side effects, but they have different indications. They also target different areas of the brain