Mirtazapine (Remeron) Risks, Warnings, and Complications

SUICIDAL IDEATION: Taking antidepressant drugs, including mirtazapine (Remeron), can lead to new or worsening symptoms of depression in depressed patients as well as suicidal thoughts and behaviors. The risk is particularly high in young adults under 24 years of age. Tell your doctor without delay if you notice any unusual behaviors (for example, panic attacks, anxiety, trouble sleeping, irritation, sadness, agitation, restlessness). People in your household should know how to get medical help in case you are unable to do so yourself. 

EXTREME DROWSINESS: Mirtazapine (Remeron) can cause extreme drowsiness, dizziness, and a reduced ability to focus, react, think, and concentrate. Do not drive, operate heavy machinery, or do anything that requires your full attention until you know how this medicine affects you. The risk of extreme drowsiness on mirtazapine is more in elderly patients (65 years and older), those taking a higher mirtazapine dose, people who drink alcohol, and those taking other medications like sleep aids, muscle relaxants, anti-anxiety drugs, or sedating drugs. Tell your doctor right away if you feel extremely sleepy after taking mirtazapine.

RISK OF INFECTION: Controlled clinical trials have shown that, very rarely, mirtazapine (Remeron) can lead to a low white blood cell count. White blood cells (WBCs) help the body fight infections. Taking mirtazapine can therefore increase the risk of infections in a small number of people. This is more likely to happen when you first start mirtazapine (in the first 8 weeks of treatment). WBC levels usually return to normal after you stop mirtazapine. Tell your doctor if you develop flu-like symptoms such as fever, chills, fatigue, or sore throat. Your doctor may order a blood test to check WBC levels.

RISK OF SEROTONIN SYNDROME: People who take mirtazapine can develop a rare but serious condition called serotonin syndrome, in which there is too much serotonin in the brain. The risk of this happening is higher with concomitant treatment with medications that also increase serotonin levels in the brain, such as certain other antidepressants, medications used to treat certain other psychiatric disorders, migraine medications, and pain medications. Also, you should not take mirtazapine with or within 2 weeks of taking a medicine called a monoamine oxidase inhibitor (MAO inhibitor) because this can lead to a dangerous drug interaction. Give your doctor and pharmacist a full list of your medications before starting mirtazapine. Seek immediate medical help if you develop symptoms of serotonin syndrome such as sweating, fast heart rate, muscle spasms, muscle stiffness, fever, and confusion.

WITHDRAWAL SYMPTOMS: Suddenly stopping mirtazapine can lead to withdrawal symptoms like dizziness, nausea, agitation, anxiety, sleep difficulties, and flu-like symptoms. Your doctor will tell you how to lower the dose of mirtazapine gradually to avoid withdrawal symptoms.

RISK IN PEOPLE WITH BIPOLAR DISORDER: Bipolar disorder is characterized by extreme mood swings and alternating episodes of lows (depression) and highs (mania). If people with bipolar disorder take antidepressant drugs, it can trigger an episode of mania or hypomania. Your healthcare provider will rule out bipolar disorder before prescribing mirtazapine or other antidepressant drugs. Seek medical attention right away if you or your loved ones notice any unusual behavior changes, such as restlessness, talkativeness, agitation, racing thoughts, unusual risk-taking behavior, and other such symptoms. 

QT PROLONGATION: Rarely, mirtazapine can cause heart rhythm abnormalities such as QT prolongation, which can be life-threatening. The risk is greater on higher doses of mirtazapine and in people who are on other medications that also affect heart rhythm. Tell your doctor if you have a family history of heart problems. Your doctor may order an electrocardiogram (EKG) before and during mirtazapine treatment. Call your doctor without delay or seek emergency medical help if you develop chest pounding, chest pain, trouble breathing, or lightheadedness while on mirtazapine.

SEVERE SKIN REACTION: A small number of people can develop a severe skin rash, itching, and hives after taking mirtazapine. Allergic reactions can also include life-threatening anaphylaxis (throat closing) and facial swelling. Mirtazapine can also cause a skin reaction called drug reaction with eosinophilia and systemic symptoms (DRESS). Before starting mirtazapine, tell your doctor if you have an allergy to antibiotics. Stop taking mirtazapine and seek emergency medical help if you develop skin rash, hives, skin blistering, reddening or peeling, swelling of the tongue or lips, or trouble breathing.

GLAUCOMA: Mirtazapine can cause or worsen angle-closure glaucoma, an eye condition associated with increased pressure in the eye. Your doctor might send you for regular eye checks while on mirtazapine therapy. Call your doctor if you develop any vision changes while on this medication. 

RISK IN PEOPLE WITH PHENYLKETONURIA: The orally disintegrating tablets of mirtazapine (Remeron SolTab) contain an artificial sweetener aspartame, which contains phenylalanine. People who have a genetic condition called phenylketonuria cannot metabolize phenylalanine and can develop brain and nerve damage if they take it. Tell your doctor if you have phenylketonuria (PKU). Your doctor will tell you not to take the orally disintegrating tablets of mirtazapine. The regular tablets are safe to take for people with PKU.