Generic Name

Remeron

Mechanism

Remeron (mirtazapine) is a noradrenergic‑selective antagonist and specific inhibitor of serotonin reuptake.
• Increases norepinephrine (NE) by blocking presynaptic α₂‑adrenergic autoreceptors.
• Enhances serotonin (5‑HT) release through 5‑HT₂/5‑HT₃ receptor blockade.
• Sedative and appetite‑stimulating effects arise from potent H₁–histamine and H₂–histamine antagonism.

The combined NE/5‑HT elevation improves mood while the H₁ blockade facilitates sleep and weight gain.

Pharmacokinetics

• Absorption: ~80 % oral bioavailability; peak plasma 3–4 h postdose.
• Distribution: plasma protein binding ~73 %; crosses the blood‑brain barrier.
• Metabolism: primarily CYP2D6 and CYP3A4; extensive inter‑individual variability.
• Elimination: half‑life 20–26 h (active metabolite), renal/hepatic clearance minimal; dose adjustment generally not required except severe hepatic impairment.

Indications

• Major Depressive Disorder (MDD) – preferred for patients with insomnia or weight concerns.
• Adjunctive therapy for depression with comorbid insomnia.
• Off‑label use: Post‑traumatic Stress Disorder (insomnia), Obsessive–Compulsive Disorder.

Contraindications

• Absolute: hypersensitivity to mirtazapine; bipolar disorder (mania risk); severe hepatic impairment.
• Relative: pregnancy (category C), geriatric patients (orthostatic hypotension risk).
• Precautions: MAOIs (QT prolongation), other serotonergic agents (serotonin syndrome), antihypertensives (syncope).
• Warnings: Monitor for suicidality, orthostatic hypotension, anticholinergic side effects.

Dosing

• Initiate 15 mg nightly; titrate 15 mg/week to a max of 45 mg nightly as tolerated.
• Preferably bed‑time dosing to maximize sedation and improve sleep.
• Taper over 2–4 weeks when discontinuing to prevent withdrawal.

Adverse Effects

Monitoring

• Baseline: mood assessment, weight, blood pressure.
• Follow‑up: weight every 4 weeks; BP monthly; HbA1c in diabetics or metabolic syndrome.
• Mood: daily for first 2 weeks; use Beck Depression Inventory or equivalent.
• Liver function tests: annually or if clinically indicated.

Clinical Pearls

1. Sedation as a therapeutic asset—ideal for depressed patients who also have insomnia or significant sleep disturbance.

2. Progressive titration—use 3–5 mg increases to minimize orthostatic hypotension, especially in geriatric or hypotensive patients.

3. Avoid daytime dosing unless targeting anxiety; daytime use often leads to unwanted fatigue.

4. Metabolic vigilance—start low in patients with BMI > 30 and monitor for early weight gain or glycemic changes.

5. Drug‑interaction awareness—avoid concurrent serotonergic drugs (e.g., SSRI + Venlafaxine) unless monitored closely for serotonin syndrome.

6. Elderly dosing—begin at 3.75 mg nightly; consider dose reduction or discontinuation if falls or orthostatic symptoms ensue.

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