HALF-LIFE: 20-40 hours
METABOLISM: Metabolized primarily through CYP1A2, CYP2D6, and CYP3A4
STARTING DOSE: 15mg-30mg per day
TARGET DOSING RANGE: 30mg-60mg per day
BEST TIME TO DOSE: Bedtime
TYPICAL DOSING: Initial 15mg-30mg at bedtime for 2 weeks. Increase dose by 15mg per day every 1-2 weeks. Max dose generally 60mg/day
PREGNANCY: Minimal data on safety. Not a contraindication.
BREASTFEEDING: Minimal date on safety. Not a contraindication.
Weight Gain, dry mouth, sedation, fatigue, drowsiness, increased appetite, mild elevations in liver enzymes (in about 2% of people)
Avoid using with Monoamine Oxidase Inhibitors (MAOIs) due to risk of hypertensive crisis
- Major Depressive Disorder
Off Label Uses: Good agent for patients with depression, anxiety, and insomnia. Good choice for depressed patients with cancer or depressed elderly frail patients.
Mechanism(s) of Action
Mirtazapine is unique in that it does not inhibit reuptake of any monoamines. Instead, Mirtazapine is a presynaptic alpha-2 receptor antagonist, 5HT3 receptor antagonist, 5HT2A receptor antagonist, and 5HT2C receptor antagonist. Mirtazapine has little to no anticholinergic effects and has little to no activity on postsynaptic alpha-1 receptors. Lastly, mirtazapine has potent antihistamine effects.
Different doses have different effects: Low doses more sedating. Higher doses less sedating due to increase in noradrenergic effects relative to antihistaminergic effects at higher doses.
- Available in orally disintegrating tablets
- Minimal sexual dysfunction. Best used for patients who have had sexual side effects with other agents.
- The combination of Mirtazapine and Venlafaxine is colloquially termed “California Rocket Fuel” as this combination targets most neurotransmitter systems and can “propel” patients out of depression quicker than SSRIs