Mirtazapine for anxiety: What you need to know

Mirtazapine for anxiety: What you need to know

Reviewed by:
Michael Roman, MD
Staff Psychiatrist
at Talkiatry
March 18, 2024
In this article

Around 40 million American adults have an anxiety disorder, making it the most common mental health condition in the country. Effective treatments for this condition are available, including cognitive behavioral therapy and medications.  

One medication that is sometimes used to treat symptoms of anxiety is mirtazapine. This antidepressant medication is mainly used as a treatment of depression, but may also be prescribed by medical professionals for other uses.

In this article, we'll cover the basics of mirtazapine, including how it works for the treatment of anxiety, its side effects, and how it compares to other anxiety treatments.

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What is mirtazapine and how does it work?

Mirtazapine is the generic name for an antidepressant medication sold under the brand name Remeron. This drug is an atypical antidepressant, meaning it doesn’t work the same way as other traditional antidepressants (like SSRIs and SNRIs). Your brain naturally produces chemicals that make you feel good, such as serotonin and norepinephrine, and mirtazapine causes neurons to release more of these chemicals so higher amounts of it are available in your brain, which can help you manage symptoms of depression and anxiety.

Mirtazapine vs other antidepressants

Other antidepressants also change the level of neurotransmitters in your brain, but do it differently. For example, selective serotonin reuptake inhibitors (SSRIs) block cells in the brain from taking in serotonin, which makes more of this neurotransmitter available for sending signals. SSRIs are the most common type of antidepressant prescribed as a treatment of depression. They include fluoxetine (Prozac), paroxetine (Paxil), and sertraline (Zoloft). A serotonin–norepinephrine reuptake inhibitor (SNRI), such as venlafaxine, may also be used for depression.

Sometimes clinicians prescribe mirtazapine in combination with an SSRI or SNRI. However, there is no “best” combination of medications for the treatment of anxiety. Your doctor will review your symptoms and your medical history when deciding on your treatment.

What conditions does mirtazapine treat?

Mirtazapine is approved by the FDA as a treatment for major depressive disorder (MDD), and it can help manage symptoms of depression, like persistent feelings of sadness or worthlessness, and a loss of interest or pleasure in previously enjoyable activities.

Doctors may also prescribe mirtazapine off-label for other conditions. This means experts have noticed that the drug works for treating these conditions in some people, but there is currently limited research showing how effective the drug is.  

Some off-label uses of mirtazapine include:

Can you take mirtazapine for sleep?

Many people with anxiety and depression struggle with sleep, and you may be wondering if mirtazapine can help. In one of the earliest clinical trials for mirtazapine, the drug had a sedating effect, with around half of people experiencing drowsiness or a strong desire to fall asleep. Because of this side effect, doctors sometimes prescribe mirtazapine as a treatment for insomnia, or difficulty falling or staying asleep.  

There is a fair amount of research on the use of mirtazapine as a treatment for insomnia. One small study showed that people with insomnia who took low doses of this drug slept longer and woke up fewer times during the night. Some research even suggests that mirtazapine may help people with major depressive disorder sleep better.

In another small study, people with insomnia who also had suicidal thoughts were given mirtazapine. Most of the participants who took this drug slept better and had fewer suicidal thoughts. (However, others stopped taking the medication due to adverse effects, including sleepiness.)

There are currently larger clinical trials happening to find out whether mirtazapine is truly effective for treating insomnia. If you have trouble sleeping alongside your anxiety, reach out to your psychiatrist. They can help you figure out proper treatment and any underlying reasons for sleep issues.

Mirtazapine dosage

Mirtazapine comes as a tablet that you take orally, and you can take it with or without meals. Because it can make you sleepy, doctors generally recommend that you take this medication in the evening just before bedtime. If you miss a dose, take your tablet at your next regular time.

The starting dose of mirtazapine for anxiety is generally 15 milligrams (mg) per day. Your doctor may prescribe you a higher dose or adjust it as needed, until your anxiety symptoms have improved. The maximum dose is generally 60 mg per day. For insomnia, your doctor may prescribe a lower dose, starting at 7.5 mg. Figuring out the right dosage can take time, so be patient. Your doctor will work closely with you to make sure you land on something effective.

Most doctors recommend that you continue taking mirtazapine for 6 months to a year after your insomnia or anxiety symptoms have improved. If you have been feeling better for 6 months or more, your doctor may recommend that you stop taking mirtazapine. If so, your doctor will instruct you to slowly and gradually reduce the dose you are taking. This will decrease your chance of experiencing antidepressant discontinuation or withdrawal symptoms, such as depression, panic attacks, restlessness, decreased appetite, or mania. Be sure to follow your doctor’s instructions for how and when to take your medication, and talk to them if you have any questions.

Want to learn more about whether or not your medication is working for you? Check out: Signs your antidepressant dose is too low or too high

How long does it take for mirtazapine to work?

You may see some improvements in sleep or energy within the first 2 weeks of taking mirtazapine. Improvement in these symptoms may be an early sign that the drug is working. It usually takes 8 to 12 weeks for depression or anxiety symptoms to fully improve.  

One way to track your progress is with a journal. Write down your symptoms, your experience with the drug, and your feelings and emotions. You may even want to share the journal with your healthcare provider. This will give them a clear understanding of how you’re feeling and they can adjust your medication if needed.

The half-life of mirtazapine is 20 to 40 hours. This is the time it takes for the amount of the drug in the body to be reduced by one-half. Because of this, your doctor will wait at least 1 to 2 weeks before changing your dose, in order to see how you are responding to the drug.

Remember that it can take time for your medication to kick in. If you’re feeling anxious and think the drug is not working, talk to a licensed mental health professional before stopping your medication or changing your dose.

Potential side effects

Like many medications, mirtazapine comes with side effects. Common side effects of mirtazapine are mild and usually go away. They include:

  • Drowsiness or sedation
  • Dry mouth
  • Increased appetite and weight gain
  • Increased cholesterol/triglyceride levels
  • Constipation

Rare but serious side effects

Certain more serious side effects can also occur, but they’re usually rare. Your doctor will talk to you about these ahead of time, and ask you questions about your family and medical history in order to find the right treatment for you. Serious side effects of mirtazapine include:

  • Inflammation of the pancreas (pancreatitis), which can cause pain in your back or stomach, and nausea.
  • Low sodium levels in the blood (hyponatremia), which can lead to headache, confusion, nausea and vomiting, and muscle weakness or cramps.
  • Liver problems, which in some cases can result in a yellow color in the whites of your eyes or skin.
  • Low white blood cell count (agranulocytosis), which can increase the risk of infection, with symptoms such as fever, chills, and sore throat.
  • Serotonin syndrome, which can cause symptoms such as shivering, diarrhea, fever, increased blood pressure, and fast heart rate.
  • Increased risk of suicidal thinking and behavior in certain groups, like children, adolescents, and young adults

If you experience any of these serious side effects, call your doctor or 911 right away.

Before taking mirtazapine: Precautions and considerations

As with all prescription medications, mirtazapine may interact with other drugs. If you are prescribed mirtazapine, talk to your doctor or pharmacist about whether you can safely use it with your other medications or supplements. Potential drug interactions of mirtazapine include:

  • Diazepam, an anticonvulsant
  • Tramadol, a synthetic opioid
  • Cimetidine, a stomach acid reducer
  • Ketoconazole, an antifungal medication
  • St. John’s wort, an herbal supplement used to manage symptoms of depression, menopause, and other conditions
  • Tryptophan, an essential amino acid that is converted in the body into serotonin and niacin
  • Phenytoin and carbamazepine, both seizure medications  
  • Sumatriptan and zolmitriptan, both migraine medications  
  • Medications for mood and thought disorders such as lithium, other antidepressants, and antipsychotics

Who should not use mirtazapine?

There are some instances when someone shouldn’t take mirtazapine. This includes:

  • People with an allergy or hypersensitivity to mirtazapine or any other substance in the medication.
  • People who are currently on an MAO inhibitor (monoamine oxidase inhibitor). You should wait at least 14 days after stopping an MAO inhibitor before starting mirtazapine. You should also wait at least 14 days after discontinuation of mirtazapine before starting treatment with an MAO inhibitor.

Before you are prescribed mirtazapine, your doctor will weigh the benefits and risks of the medication based on your individual circumstances.

Is mirtazapine a good choice for my anxiety?

If you’re experiencing a mental health issue such as anxiety, it may be a result of an imbalance in brain chemicals such as serotonin or norepinephrine. An antidepressant such as mirtazapine can boost the level of these neurotransmitters to help manage symptoms of anxiety that disrupt your quality of life.

While this drug is approved by the FDA for the treatment of depression, some doctors prescribe mirtazapine off-label for anxiety. And since this medication can cause sleepiness, some doctors prescribe it off-label for insomnia.

If you think you have an anxiety disorder, know that help is available and treatment works. The first step is getting a diagnosis from a licensed mental health provider. It might feel daunting, but together you can explore what medication options might be right for you, including whether or not mirtazapine fits into your treatment.  

If you’re looking for a psychiatrist, consider Talkiatry. We’re a national mental health practice that treats people with anxiety, depression, PTSD, and more. To get started, take our free online assessment and be matched with the right Talkiatry psychiatrist for your needs.

Mirtazapine FAQs

Here are more answers to all your questions about mirtazapine.

How is mirtazapine different from other antidepressants?

Mirtazapine works by causing an increased release of two brain chemicals—serotonin and norepinephrine. In contrast, selective serotonin reuptake inhibitors (SSRIs) such as Zoloft and Prozac block brain cells from taking in serotonin, which makes this brain chemical more available for sending signals. Both types of drugs can help manage depression and anxiety symptoms.

Is 15 mg mirtazapine enough for anxiety?

The starting dose for mirtazapine is usually 15 mg per day. This may be enough to help manage your anxiety symptoms. However, if after a few weeks you are still experiencing symptoms, your doctor may increase your dose. It takes 8-12 weeks to see the full clinical benefit.

Does mirtazapine make you gain weight?

Mirtazapine and other drugs act as appetite stimulants, which can lead to increased weight gain. In one clinical trial, 7 out of 100 patients taking mirtazapine saw a weight gain of 7% or more. If you have any concerns about how medications might affect your weight, make sure to discuss it with your psychiatrist.

Learn more about antidepressants that cause weight loss and weight gain

What is the most recommended drug for anxiety?

A number of medications are available for the treatment of anxiety, including SSRIs, SNRIs, benzodiazepines, tricyclic antidepressants, mild tranquilizers, and beta-blockers. Mirtazapine may also be used. However, there is no “best” drug for everyone with this condition. In deciding which medication to prescribe for you, your doctor will take into account your symptoms and other aspects of your health.

The information in this article is for education and informational purposes only and should never be substituted for medical advice, diagnoses, or treatment. If you or someone you know may be in danger, call 911 or the National Suicide and Crisis Lifeline at 988 right away.

Dr. Michael Roman is currently a Staff Psychiatrist at Talkiatry. He completed his adult psychiatry residency training at the University of Pennsylvania. Dr. Roman is a board-certified Adult Psychiatrist and a diplomate of the American Board of Psychiatry and Neurology (ABPN).

Dr. Roman’s clinical practice centers primarily around medication management and psychopharmacological treatment approaches. He also specializes in a variety of psychotherapeutic modalities which he utilizes in conjunction with medication management in order to provide patients with the best possible treatment outcomes.

Dr. Roman’s curiosity for the studies of the human mind began with pursuing a bachelor’s degree in psychobiology at the University of California, Los Angeles (UCLA). He was intrigued by the way our mind, body, emotions, and behavior were intertwined to comprise our everyday life experiences. His interest in the intricacy of the human mind was deepened in medical school, and he received his medical degree from the David Geffen School of Medicine at UCLA. He completed his adult psychiatry residency training at the University of Pennsylvania.

Dr. Roman treats a wide spectrum of patients, but his primary clinical focus is treating mood disorders, ADHD, anxiety disorders, and PTSD. Dr. Roman also specializes in treating substance use disorders and possesses clinical expertise in implementing high quality motivational interviewing and motivational enhancing therapy.

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