Mirtazapine for Anxiety: Here’s What to Know About This Antidepressant’s Off-Label Use

Anxiety is a normal part of life. Most people experience fear or worrying to some degree. But for those with an anxiety disorder, anxiety can be persistent and interfere with daily life. Having generalized anxiety disorder (GAD) can mean living with constant worry that is out of proportion or not in your control.

Cognitive behavior therapy (CBT) and prescription medications are two recommended ways to treat anxiety. First-choice anxiety medications include selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs). These classes of medications are FDA approved to treat anxiety and have the most research to back up their use.

If you’ve tried a few of these first-choice medications but haven’t found relief, there are still several options to consider. An antidepressant called mirtazapine (Remeron, Remeron SolTab) is a second-choice anxiety treatment that some people turn to. 

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Here, we’ll take a closer look at the ins and outs of taking mirtazapine for anxiety. 

Can mirtazapine treat anxiety?

Yes, mirtazapine can treat anxiety. But it’s not FDA approved to treat GAD. Using it for this purpose is considered off-label. 

What is mirtazapine FDA approved to treat?

Mirtazapine is approved to treat major depressive disorder, often referred to simply as depression. It’s a tetracyclic antidepressant that boosts the levels of serotonin and norepinephrine (chemical messengers) in your brain, which can help regulate mood. It also blocks histamine receptors (chemical binding sites). This combination effect makes it a potential option for treating anxiety.

Recommended mirtazapine dosage for anxiety

Mirtazapine is available as an oral tablet and orally disintegrating tablet (ODT). It’s taken once a day, typically at night since it can make you drowsy. The oral tablet comes in four different doses ranging from 7.5 mg to 45 mg. The ODT is only available in three doses, though: 15 mg, 30 mg, and 45 mg.

Mirtazapine’s typical starting dose is 15 mg every night. This dose can then be adjusted upward to 30 mg nightly if needed, and then to a maximum of 45 mg nightly. Your target dose will depend on how well your anxiety symptoms are managed. 

When you and your prescriber are adjusting your dose to find what works for you, it’s important to space each adjustment apart by at least a week. This gap should give your body adequate time to respond to each dose.

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How effective is mirtazapine for anxiety?

Research suggests that mirtazapine is effective for a few different anxiety disorders. 

For example, in a 12-week, open-label study of 44 people with GAD taking mirtazapine 30 mg daily, nearly 80% of participants saw a meaningful improvement in their anxiety symptoms. GAD is the most commonly diagnosed anxiety disorder.

What’s more, mirtazapine can be beneficial when anxiety is happening alongside other symptoms. For example, it can be helpful for people struggling with both depression and anxiety or social anxiety disorder. 

Mirtazapine can also make you feel sleepy and hungrier than normal. So it can be useful for those struggling with insomnia or low appetite due to anxiety. This is commonly seen among older adults. 

How long does mirtazapine take to work for anxiety?

You’ll likely feel the sedating effect of mirtazapine soon after taking it, which can calm severe anxiety symptoms. But it does take about 4 to 6 weeks to see mirtazapine’s full anxiety-lowering effects. This is when it can more effectively lessen symptoms such as restlessness or excessive worrying. 

Keep in mind: This minimum 4-week wait period for improvement is common for many mood and anxiety medications. That’s why it can be useful to pair these medications with CBT or mental grounding techniques, especially when you’re feeling strong symptoms of anxiety.

What are the side effects of mirtazapine for anxiety?

Mirtazapine is generally well-tolerated. And it has some advantages over other antidepressants; it’s less likely to cause sexual side effects or cause an initial worsening of anxiety symptoms compared to some SSRIs. But it does have some side effects of its own, including: 

• Drowsiness

• Dizziness 

• Weight gain 

• Dry mouth

• Constipation

These side effects may resolve after you've been taking mirtazapine for about 4 to 6 weeks. But if you continue to experience them or they worsen, it’s important to keep your prescriber informed. They can adjust your dose or switch you to another anxiety medication. 

If you stop mirtazapine abruptly, though, your symptoms may return. There have been reports of anxiety as a side effect in this situation. If you’re thinking of stopping mirtazapine, working closely with a healthcare professional to make slow changes is a safer bet.

Mirtazapine alternatives for anxiety

The best anxiety medication typically depends on the type of anxiety disorder you have, other mental health conditions you may be living with, and side effects. 

First-choice medications for anxiety disorders are traditionally SSRIs and SNRIs. Escitalopram (Lexapro) is a common SSRI for anxiety. Duloxetine (Cymbalta) is a common SNRI for anxiety.

Sometimes, these options alone aren’t enough to treat your symptoms. You may also consider over-the-counter natural remedies or even a combination of prescription medications. Medications like these recommended by anxiety experts in certain situations:

• Buspirone

• Pregabalin (Lyrica)

• Antipsychotics such as quetiapine (Seroquel)

• Benzodiazepines such as diazepam (Valium) 

Other tips for taking mirtazapine for anxiety

There are a few ways to maximize your experience with mirtazapine. Here are some tips when taking mirtazapine for anxiety:

• Although mirtazapine can help you get a good night's sleep right away, it can take up to 6 weeks to fully treat anxiety symptoms. Try to be patient throughout this process, especially if you don’t feel any different at first.

• People generally start by taking mirtazapine 15 mg every night. Your dose can then be increased every 1 to 2 weeks as needed, up to 45 mg nightly.

• Mirtazapine can initially cause dizziness, dry mouth, and constipation. This should improve as you continue to take the medication.

• Don’t suddenly stop taking mirtazapine. Talk to a healthcare professional first about how to safely adjust your dose.

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Written by:

Hindu Rao, PharmD, APh, BCACP

Hindu Rao, PharmD, APh, BCACP is a clinical assistant professor of pharmacy practice at Chapman University School of Pharmacy and a clinical pharmacist at Providence Medical Foundation. She specializes in chronic disease management and has her board certification in ambulatory care.

Edited by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Reviewed by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

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