Mirtazapine
Generic: mirtazapine · Brand: Remeron® · Class: NaSSA
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How It Works
Mirtazapine is a noradrenergic and specific serotonergic antidepressant (NaSSA). Rather than blocking reuptake like SSRIs and SNRIs, it works by blocking alpha-2 adrenergic receptors and certain serotonin receptors, which indirectly increases both norepinephrine and serotonin activity. It also blocks histamine receptors, which causes significant sedation — making it particularly useful for patients with insomnia or anxiety. It is one of the few antidepressants that stimulates appetite and promotes weight gain.
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What It Treats
Major Depressive Disorder (MDD)Especially helpful when insomnia, poor appetite, or anxiety are prominent features
InsomniaStrongly sedating — often used at low doses specifically for sleep
Anxiety DisordersEffective for GAD and PTSD, particularly when sleep disruption is present
Appetite StimulationUsed in patients with depression and significant weight loss or poor appetite
NauseaUsed off-label to reduce nausea in chemotherapy or other medical conditions
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Dosing Overview
| Population | Start | Typical Range | Max |
|---|---|---|---|
| Adults Depression / Anxiety | 15 mg at bedtime | 15–45 mg | 45 mg |
| Older Adults Start low | 7.5 mg at bedtime | 15–30 mg | 45 mg |
| Insomnia only Off-label | 7.5–15 mg | 15 mg | 15 mg |
Always taken at bedtime due to strong sedating effects. Paradoxically, lower doses (7.5–15 mg) are MORE sedating than higher doses because at higher doses the stimulating norepinephrine effects partially counteract the sedation.
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What to Expect — Timeline
1–2
Weeks 1–2
Body adjusting. May notice changes in sleep, appetite, or mild side effects
3–4
Weeks 3–4
Energy and motivation often improve before full mood lift
6–8
Weeks 6–8
Mood and anxiety typically improve significantly at a therapeutic dose
3–6m
3–6 Months
Full therapeutic benefit. Duration discussed based on your history and goals
⏳ Be patient. Most people need at least 4–8 weeks at a therapeutic dose before evaluating effectiveness. Do not stop without talking to your provider.
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Side Effects
Common (often temporary)
- Significant drowsiness (take at bedtime)
- Increased appetite and weight gain
- Dry mouth
- Constipation
- Dizziness
- Vivid dreams
- Increased cholesterol
- Fluid retention
Call us if you notice
- Agranulocytosis (rare but serious blood condition)
- New or increased suicidal thoughts
- Hypomania or mania
- Severe allergic reaction
- Serotonin syndrome signs
Weight gain and increased appetite are very common and expected with mirtazapine. Sedation is the most prominent effect — this can be beneficial for sleep but may be problematic during the day. Sexual side effects are rare, which many patients appreciate.
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Tips for Success
Same Time DailyTake at the same time each day for consistent levels in your system.
With FoodTaking with food can reduce nausea and stomach upset.
Don't Stop AbruptlyAlways taper slowly with your provider guidance to avoid withdrawal effects.
Limit AlcoholAlcohol worsens depression and anxiety and increases side effects.
Tell All ProvidersLet other prescribers know what you are taking — interactions matter.
Track Your MoodJournaling or a mood app helps you and your provider see what is changing.
Bedtime OnlyAlways take at bedtime — the sedation is strong and intentional for nighttime use.
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Important Safety Information
Black Box Warning (under 25): Antidepressants may increase risk of suicidal thinking in children, adolescents, and young adults especially in the first few weeks. Monitor closely and contact us right away if new or worsening thoughts of self-harm appear.
Serotonin Syndrome: Can occur when combined with MAOIs, triptans, tramadol, or St. John's Wort. Signs include fever, agitation, rapid heart rate, and muscle twitching — seek emergency care immediately.
Drug Interactions: Do not take with MAOIs. Always share your full medication list with your provider.
Pregnancy & Breastfeeding: Discuss risks and benefits with your provider. Do not stop without consultation.
Agranulocytosis: A rare but serious condition where white blood cell counts drop dangerously low. Contact your provider immediately if you develop fever, sore throat, or signs of infection while taking mirtazapine.
Weight Gain: Significant weight gain is common and expected. Discuss appetite and weight management strategies with your provider if this is a concern.
Questions? I am here.
Reach me between appointments if you have concerns about side effects, notice mood changes, or have questions about your medication.
360-389-3712
info@rootedmindspsychiatry.com