Mirtazapine

(mer-taz-uh-peen)

Trade/other name(s): Remeron, Remeron SolTab

Why would this drug be used?

Mirtazapine is an antidepressant (sometimes called an atypical or tetracyclic antidepressant). It is used to help treat depression. Doctors may prescribe it for other reasons as well.

How does this drug work?

Mirtazapine seems to work by enhancing the activity of key chemicals in the brain (serotonin and norepinephrine).

Before taking this medicine

Tell your doctor…

• If you are allergic to any medicines, dyes, additives, or foods.
• If you have ever thought about or attempted suicide. Treatment with an antidepressant may raise the risk of suicidal thoughts, especially during the first few months of treatment.
• If you drink alcohol or are taking any type of sedative. This drug could possibly increase their effects on the nervous system, which in some cases could be dangerous.
• If you take any blood pressure medicines, have ever had a stroke, or have ever fainted. This drug may lower your blood pressure, which could be dangerous if it is already affected by other medicines.
• If you have phenylketonuria. The orally disintegrating form of mirtazapine (Remeron SolTab) contains phenylalanine.
• If you have ever had high cholesterol, heart disease, or a heart attack. This drug may raise cholesterol levels or affect the heart rate in some people.
• If you have any kidney disease or liver disease (including hepatitis or cirrhosis). This drug is cleared from the body by these organs. It may also affect the liver. Reduced kidney or liver function may result in more drug than expected staying in the body. This could lead to unwanted side effects. Your doctor will want to monitor you closely and may need to adjust your dose accordingly.
• If you have ever had seizures or bipolar disorder (manic depressive illness). This drug could make these conditions worse.
• If you have any other medical conditions such as lung disease, congestive heart failure, diabetes, gout, or infections. You may need closer monitoring of these conditions while being treated.
• If you are pregnant, trying to get pregnant, or if there is any chance of pregnancy. This drug might cause problems if the woman is taking it at the time of conception or during pregnancy. It is important to check with your doctor about whether birth control should be used with this medicine. This drug should be used during pregnancy only if clearly needed.
• If you are breast-feeding. Small amounts of this drug may pass into breast milk and affect the baby. Talk with your doctor about the possible risks of breast-feeding while taking this drug.
• About any other prescription or over-the-counter medicines you are taking, including vitamins and herbs.

Interactions with other drugs

Mirtazapine may interact with a number of other drugs.

Antidepressants known as monoamine oxidase inhibitors (MAOIs) such as phenelzine (Nardil), tranylcypromine (Parnate), isocarboxazid (Marplan), or selegiline (Emsam) may interact with mirtazapine in a dangerous way. Mirtazapine should not be taken within 2 weeks of taking an MAOI. The antibiotic linezolid (Zyvox) and the dye methylene blue, which are both given in the vein, also act as MAOIs and increase the risk of serotonin syndrome (see “Precautions”).

Mirtazapine may make you drowsy. Other medicines that could have similar effects, including sedatives (sleeping pills), anxiety medicines, tricyclic antidepressants (amitriptyline, desipramine, doxepin, imipramine, nortriptyline), or antihistamines should be avoided or used with extreme caution.

This drug may cause a sudden drop in blood pressure when sitting or standing up quickly. It should be used with caution in people who are taking any type of blood pressure medicine.

Medicines that affect serotonin in your body, such as antidepressants, lithium, or tramadol can increase your risk of serotonin syndrome (see “Precautions) if they are taken while you are on mirtazapine. Supplements such as tryptophan or St. John’s wort can cause the same problem.

These drugs can raise the levels of mirtazapine in your blood and/or cause a higher risk of serious side effects if you take them while on mirtazapine:

• Antidepressant drugs such as nefazodone (Serzone), fluvoxamine (Luvox), fluoxetine (Prozac, Serafem)

• Antibiotics such as erythromycin (E.E.S., E-Mycin, Erythrocin), or clarithromycin (Biaxin), or norfloxacin (Noroxin)

• Antifungal drugs such as ketoconazole (Nizoral), itraconazole (Sporanox), voriconazole (Vfend)

• Certain blood pressure medicines such as diltiazem (Cardizem) and verapamil (Calan)

• HIV drugs such as indinavir, ritonavir, saquinavir, and nelfinavir

The anti-seizure drugs carbamazepine and phenytoin can make the body get rid of mirtazapine faster, as can the TB drugs rifampin and rifabutin, and the herb St. John's wort. If you are taking any of these, be sure your doctor knows about it. Your dose may have to be changed.

The blood thinner warfarin (Coumadin) may be affected by mirtazapine and increase the risk of bleeding.

There may be other interactions not listed above. Check with your doctor, nurse, or pharmacist about all of your medicines, herbs, and supplements.

Interactions with foods

If you're taking mirtazapine, you should avoid alcohol, which can have more potent effects on the nervous system when combined with mirtazapine.

Talk with your doctor about eating grapefruit or drinking grapefruit juice while on mirtazapine. Check with your doctor, nurse, or pharmacist about whether other foods may be a problem.

Tell all the doctors, dentists, nurses, and pharmacists you visit that you are taking this drug.

How is this drug taken or given?

Mirtazapine is taken by mouth as a standard tablet or as a tablet that dissolves on the tongue in about 30 seconds (Remeron SolTab). It is usually taken once a day, at bedtime. It can be taken with or without food.

The dose may depend on a number of factors, including your age, your kidney and liver function, and how well you respond to the drug. If needed, the dose may be increased after waiting at least a week. Lower doses may be recommended in older patients and in those with kidney or liver problems.

Store the medicine in a tightly closed container and out of the reach of children or pets.

Precautions

This drug can interact with other medicines and should be used cautiously in people with a number of different medical conditions. See the "Before Taking This Medicine" section of this document for more detailed information.

This drug may make you feel drowsy when you first start taking it or if the dose is increased. Do not drive or operate heavy machinery until you know how the drug affects you. It can cloud your judgment or thinking and make cause you to be clumsy or uncoordinated. Use caution if taking cold or allergy medicines, sedatives, anxiety medicines, or sleeping pills while taking this medicine. Avoid alcohol while taking this drug. Talk to your doctor or nurse if you feel too drowsy or the drowsiness does not go away.

This medicine may take a few weeks to start working. Speak to your doctor or nurse before changing the dose or stopping the drug. If you are going to stop taking this drug, it should be done so gradually over the course of several weeks, as directed by your doctor. Suddenly stopping the drug can sometimes cause anxiety, dizziness, nausea and vomiting, and tiredness. This drug may stay in your body for several weeks after the last dose is taken. Talk to your doctor before starting any new medicines.

This drug may raise your heart rate and/or cholesterol level. If you have a history of high cholesterol or any type of heart disease, talk to your doctor about this. Your doctor will likely want to check your cholesterol level during your treatment.

This drug may cause a quick drop in blood pressure when you go from lying down to sitting up, or from sitting to standing up (postural hypotension). This may cause you to feel dizzy or faint if you sit up or stand up too quickly, which can cause falls or injuries. Changing position slowly can reduce the risk of these problems. Let your doctor know if this happens to you.

Mirtazapine should be used with caution if you have ever had seizures or bipolar disorder (manic depressive illness). This drug could make these conditions worse.

Phenylketonurics should be aware that the orally disintegrating form of mirtazapine (Remeron SolTab) contains phenylalanine.

This drug should be used with caution if you have a history of kidney problems or liver disease (including hepatitis or cirrhosis). This drug is cleared from the body by these organs. Reduced kidney or liver function may result in more drug than expected staying in the body, which could lead to unwanted side effects. Your doctor will want to watch you closely and may need to adjust your dose.

This drug may also affect liver function. Your doctor will likely check your liver function with blood tests on a regular basis. The drug may need to be stopped if these tests become abnormal. Tell your doctor right away if you notice yellowing of the eyes or skin, abdominal pain, or bloating.

As with other antidepressants, this drug may raise the risk of suicidal thoughts and actions, mostly in depressed people under age 25. This is more common during the first few months of treatment. If you notice any strange or unusual thoughts or behavior, such as irritability, sleep problems, aggressiveness, restlessness, panic attacks, or thoughts of suicide while on this medicine, call your doctor. Tell family members, loved ones, and caregivers that you are taking this drug, so that they can help you if they notice behavior changes.

This drug can cause a rare problem called neuroleptic malignant syndrome, with symptoms like fever, tight muscles, tremors, sweating, constipation, and confusion. This syndrome can become life-threatening if not treated right away. If you have symptoms like these, call your doctor without delay.

This drug can rarely cause a problem called serotonin syndrome, with symptoms such as nausea, vomiting, diarrhea, sweating, headache, fast heartbeat, dizziness, restlessness, fever, confusion, tremors, loss of coordination, muscle spasms, and even seizures. This syndrome can become life-threatening if not treated quickly. If you have symptoms like these, call your doctor right away.

In very rare cases, this drug may cause a very low white blood cell count, which greatly increases the risk of serious infections. Your doctor may check your white blood cell count during treatment. Let your doctor or nurse know right away if you have any signs of infection, such as fever (100.5° or higher), chills, mouth sores, pain when passing urine, sore throat, a new cough, or coughing up sputum.

Possible side effects

You will probably not have most of the following side effects, but if you have any talk to your doctor or nurse. They can help you understand the side effects and cope with them.

Common

• Feeling drowsy*
• Dry mouth

Less common

• Increased appetite
• Weight gain
• Constipation
• Feeling tired or weak
• Feeling dizzy
• Abnormal dreams
• Faster heart rate*
• Higher cholesterol level*
• Abnormal blood tests which suggest that the drug is affecting the liver (Your doctor will discuss the importance of this finding, if any.) *

Rare

• Drop in blood pressure when sitting or standing up quickly*
• Very low white blood cell count*
• Retaining fluid
• Trembling
• Fever, tight muscles, tremors, sweating, confusion (neuroleptic malignant syndrome)*
• Nausea, vomiting, diarrhea, headache, restlessness, confusion (serotonin syndrome)*
• Suicidal thoughts or actions*

*See "Precautions" section for more detailed information.

There are some other side effects not listed above that can also occur in some patients. Tell your doctor or nurse if you develop these or any other problems.

FDA approval

Yes – first approved in 1996

Disclaimer: This information does not cover all possible uses, actions, precautions, side effects, or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for talking with your doctor, who is familiar with your medical needs.