7 Mirtazapine Interactions You Should Know About

Depression is one of the most common mental health conditions, affecting about 5% of the world’s population. Antidepressants are one of many treatment options for managing this condition. One atypical antidepressant your healthcare provider might prescribe is mirtazapine (Remeron). It’s thought to work by raising levels of the chemicals serotonin and norepinephrine in the brain.

Once mirtazapine is taken, the liver helps break it down using certain enzymes (proteins). When your body needs to use these same enzymes to break down other medications, interactions can happen. Mirtazapine interactions can also happen when it’s taken with other medications that have similar side effects. In some cases, interactions can lead to serious complications. So it’s important to share a current list of all of your current medications and supplements with your healthcare provider and pharmacist.

Below, we’ll discuss seven important mirtazapine interactions and how you might manage them. 

1. Monoamine oxidase inhibitors (MAOIs)

Monoamine oxidase inhibitors (MAOIs) are a group of medications that can treat depression and Parkinson’s disease. They have many possible side effects and interactions, and even require certain dietary restrictions. MAOIs shouldn’t be combined with other antidepressants, including mirtazapine.

Mirtazapine and MAOIs both raise serotonin levels in the brain. Taking them together can cause serotonin levels to rise too much. This can cause a potentially life-threatening condition called serotonin syndrome. Symptoms of serotonin syndrome include rigid muscles, fever, and high blood pressure. If you notice these symptoms while taking mirtazapine, call 911 or seek emergency care.

For this reason, you should never take mirtazapine and an MAOI together. If you’re switching from one to the other, you should separate them by at least 14 days. This gap between treatments allows your body to clear one medication out of your body before being exposed to the other.

2. Other antidepressants

Many antidepressants help to boost serotonin levels. Common examples include selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs). Taking mirtazapine with another antidepressant can raise the risk of serotonin syndrome.

The risk of complications from this mirtazapine interaction is lower than with MAOIs. Many people can safely take mirtazapine along with other antidepressants. But you should still be cautious if you take this combination. If you notice symptoms of serotonin syndrome, such as stiff muscles, get medical help right away.

3. St. John’s wort

St. John’s wort is an over-the-counter (OTC) dietary supplement that’s commonly taken for depression symptoms. But OTC doesn’t mean free of interactions. St. John’s wort also raises serotonin levels in the brain. So taking it with mirtazapine can raise your risk of serotonin syndrome.

If you take St. John’s wort — or any OTC products — make sure your healthcare provider and pharmacist know. Many OTC medications and supplements can interact with prescription medications. In this case, if you’re taking St. John’s wort, your provider may make changes to your mirtazapine prescription.

If your healthcare provider gives you the OK to combine mirtazapine and St. John’s wort, let them know what side effects you experience. If you notice rigid muscles, a fever, or unexplained confusion, get medical help right away. These may be symptoms of serotonin syndrome.

4. Benzodiazepines

Benzodiazepines are medications that are commonly prescribed for the short-term treatment of anxiety. Examples include alprazolam (Xanax) and clonazepam (Klonopin). They can cause dizziness and drowsiness. Mirtazapine can also cause these side effects.

Taking mirtazapine and a benzodiazepine can make these side effects more intense. You shouldn’t drive or perform activities that require focus until you know how this combination affects you. You may also want to ask your healthcare provider if you should take these medications at different times. This may help lessen the amount of drowsiness you feel.

5. Alcohol

Alcohol affects the body in many ways. Most commonly, it causes sleepiness, dizziness, or confusion. Mirtazapine can also cause these sensations. Mixing the two can make these side effects more likely to happen and more intense when they do.

It’s best to avoid drinking alcohol if you're taking mirtazapine. But there’s no hard rule about whether an occasional alcoholic beverage is safe to drink. It’s best to ask your healthcare provider whether it would be OK to consume any amount of alcohol while taking mirtazapine.

6. Ritonavir-containing medications

Ritonavir (Norvir) is prescribed along with other medications for people living with HIV. It’s also one of the two medications in Paxlovid (nirmatrelvir/ritonavir), an oral COVID-19 treatment. Ritonavir tends to have many interactions because of how the liver breaks it down. Mirtazapine is one example.

When taken together, ritonavir can cause a build-up of mirtazapine in the body. This can raise the risk of side effects. Despite this mirtazapine interaction, the two medications can often still be combined. But a dosage change might be needed.

If you notice more mirtazapine side effects after starting ritonavir, let your healthcare provider know. They may suggest lowering your mirtazapine dose to help relieve side effects.

7. Warfarin

Warfarin (Coumadin, Jantoven) is a blood thinner used to treat and prevent blood clots. Warfarin treatment is monitored regularly with a blood test called an international normalized ratio (INR). An INR represents how “thin” your blood is. A low INR could mean you’re at risk for blood clots. A high INR could mean you’re at risk for serious bleeding.

Taking mirtazapine with warfarin can cause your INR to increase. This means you may have a higher risk of severe bleeding. But this mirtazapine interaction can be managed with close monitoring and dose changes. If your INR is high, your warfarin dose is typically lowered. If your INR is very high, you may be told to temporarily stop taking warfarin.

It’s important to let the healthcare provider that prescribes your warfarin know if you also take mirtazapine. You should also let them know if you’ve had mirtazapine dose adjustments. They may want to monitor your INR more frequently in the weeks following your medication change.

When should I contact my healthcare provider about a mirtazapine interaction?

Keep in mind, the list of interactions we’ve discussed doesn’t include all possible interactions. So it’s important to share an updated medication list with your healthcare provider and pharmacist. Make sure your list includes all your prescription and OTC medications, as well as dietary supplements and vitamins. Review this information with your healthcare team whenever medication changes happen. A medication list is a great tool for helping to prevent or manage interactions.

If you believe you may be taking a medication that interacts with mirtazapine, contact your healthcare provider. You should also reach out to them if you’ve noticed new or worse side effects, especially if you recently changed other medications. These can be symptoms of a possible mirtazapine interaction.

If any severe side effects occur, such as stiff muscles or high fevers, seek emergency medical help. These can be symptoms of serotonin syndrome and need immediate care.

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Written by:

Sonia Amin Thomas, PharmD, BCOP

Sonia Amin Thomas, PharmD, BCOP, has been practicing as a clinical pharmacist for 12 years and in oncology pharmacy for over 10 years. She practices both academic and clinical pharmacy and is board certified as an oncology pharmacist and integrative health coach.

Edited by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

Reviewed by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

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