What are the side effects of Remeron (mirtazapine)?

Side Effects of Remeron (Mirtazapine)

The most common side effects of Remeron are sleepiness (23% vs 14% placebo), increased appetite (11% vs 2% placebo), weight gain (10% vs 1% placebo), dry mouth (25% vs 16% placebo), and dizziness. 1, 2

Most Common Side Effects

• Sedation/Somnolence occurs in approximately 23% of patients compared to 14% with placebo, making it the most frequently reported side effect 1
• Dry mouth affects approximately 25% of patients versus 16% with placebo 1, 2
• Increased appetite occurs in about 11% of patients versus 2% with placebo 1
• Weight gain is reported in approximately 10% of patients versus 1% with placebo 1, 2
• Dizziness is commonly reported 2
• Constipation is a frequently reported gastrointestinal side effect 3

Serious Side Effects Requiring Immediate Medical Attention

Life-Threatening Conditions

• Serotonin syndrome can occur when combined with certain other medications, presenting with agitation, confusion, fast heart rate, dizziness, flushing, tremors, stiff muscles, seizures, hallucinations, coma, blood pressure changes, sweating, high body temperature, loss of coordination, nausea, vomiting, or diarrhea 2
• Low white blood cell count (agranulocytosis/neutropenia) may present with fever, sore throat, flu-like symptoms, chills, mouth and nose sores, or infections 2
• Severe skin reaction may include rash, fever, swollen glands, and organ involvement (liver, kidney, lung, heart) that can sometimes be fatal 2

Other Serious Side Effects

• Angle-closure glaucoma may cause eye pain, vision changes, or swelling/redness in or around the eye 2
• Heart rhythm problems including QT prolongation 2
• Seizures (convulsions) 2
• Hyponatremia (low sodium levels) is particularly concerning in elderly patients and may cause headache, memory changes, weakness, unsteadiness leading to falls, difficulty concentrating, confusion, hallucinations, seizures, respiratory arrest, fainting, coma, or death 2
• Mania or hypomania in patients with bipolar disorder history, presenting with greatly increased energy, racing thoughts, unusually grand ideas, talking more/faster than usual, severe trouble sleeping, reckless behavior, or excessive happiness/irritability 2

Metabolic and Laboratory Changes

• Increased cholesterol and triglyceride levels in the blood 2
• Changes in liver function tests 2
• Elevated cholesterol levels (mean 3-4% increase) have been reported 4

Discontinuation Syndrome

• Abrupt discontinuation may cause dizziness, irritability, agitation, anxiety, sweating, seizures, tinnitus, nausea, vomiting, sleep problems, tiredness, confusion, electric shock sensations (paresthesia), tremor, headache, abnormal dreams, mood changes, or hypomania 2
• Gradual dose reduction over 10-14 days is recommended to limit withdrawal symptoms 3

Special Population Considerations

• Elderly patients are more susceptible to sedation, orthostatic hypotension, and hyponatremia 1
• Increased suicide risk in children and young adults under 24 years of age, especially within the first few months of treatment or when dose is changed 2

Comparative Tolerability Profile

• Mirtazapine causes more sedation and weight gain than most other antidepressants 3
• Fewer anticholinergic, cardiac, and neurological adverse events compared to tricyclic antidepressants like amitriptyline 4
• Minimal cardiovascular and anticholinergic effects compared to tricyclics 5
• Essentially lacks serotonergic effects such as gastrointestinal symptoms, insomnia, and sexual dysfunction commonly seen with SSRIs 5, 6

Clinical Pitfalls and Caveats

• Sedation may be dose-related: Paradoxically, sedation appears more prominent at subtherapeutic dosages and may decrease when appropriate dosages (≥15 mg as a single evening dose) are used from the beginning 7
• Avoid alcohol and benzodiazepines during treatment as they may impair cognitive and motor performance 2, 4
• Do not drive or operate heavy machinery until you know how the medication affects you 2
• The sedative and appetite-stimulating effects can be beneficial in specific populations, such as elderly patients with dementia and depression who have weight loss, or patients with insomnia 3, 1