Medications Directory

Approved indications: Mirtazapine is FDA-approved as an oral medication for the treatment of major depressive disorder in adults.

Common off-label uses and evidence: Clinicians may use mirtazapine off label for conditions such as generalized anxiety disorder, posttraumatic stress disorder, panic disorder, social anxiety disorder, insomnia associated with depression, and appetite or weight loss in certain medical or psychiatric conditions; evidence ranges from small randomized trials and open-label studies to clinical experience, varying by condition and population.

Efficacy expectations and onset: Some people notice improvement in sleep and appetite within the first 1–2 weeks, while mood and interest in activities often improve over 2–4 weeks or longer, with full effect sometimes taking 6–8 weeks.

Typical clinical outcomes: In clinical trials, mirtazapine reduces depressive symptom scores significantly more than placebo and helps a substantial proportion of patients achieve response (meaningful symptom reduction) or remission (minimal or no symptoms) when taken regularly at therapeutic doses.

Comparison to similar drugs: Its overall antidepressant effectiveness is broadly comparable to SSRIs and SNRIs, but it tends to cause more sedation and weight gain and less sexual dysfunction and gastrointestinal upset than many first-line antidepressants, which may make it preferable for patients with insomnia or poor appetite but less suitable when weight gain or daytime drowsiness are concerns.

Typical dosing and how to take: For adults with major depressive disorder, the usual starting dose is 15 mg by mouth once daily, typically at bedtime because it can be sedating, and the dose may be increased gradually, usually in 15-mg increments at intervals of at least 1–2 weeks, up to a usual maximum of 45 mg once daily. It is available as standard tablets and orally disintegrating tablets; both can be taken with or without food, swallowed as directed (or allowed to dissolve on the tongue for the disintegrating form) without chewing.

Special dosing instructions: Dose adjustments may be needed in older adults or in people with significant kidney or liver impairment, usually starting at the lower end of the dosing range and titrating more slowly. Treatment should not be stopped suddenly after long-term use unless directed by a clinician, as a gradual dose reduction helps lower the risk of discontinuation symptoms (such as anxiety, irritability, sleep problems, or flu-like feelings).

Missed dose guidance: If a once-daily bedtime dose is missed and remembered the same night, it may generally be taken unless it is very close to the time for the next dose; if remembered the next day, skip the missed dose and resume the regular schedule at the usual time, without doubling up.

Overdose: In case of suspected overdose—especially if there is severe drowsiness, confusion, fast or irregular heartbeat, or loss of consciousness—call poison control or emergency services immediately; medical evaluation and monitoring of heart rhythm, breathing, and vital signs may be needed.

Common side effects: Very common effects include drowsiness or sedation, increased appetite, weight gain, dry mouth, and dizziness; these often appear in the first days to weeks of treatment, may lessen over time, and are usually mild to moderate but can be bothersome, especially sedation and weight gain.

Serious or rare adverse effects: Seek urgent medical attention for signs of severe allergic reaction (such as swelling of the face, lips, tongue, or throat, trouble breathing, or rash with blisters), thoughts of self-harm or worsening depression, severe restlessness or agitation, seizures, confusion, jaundice or dark urine (possible liver problems), low sodium symptoms (headache, confusion, weakness, seizures), or symptoms of serotonin syndrome when combined with other serotonergic drugs (fever, sweating, rapid heart rate, muscle stiffness, tremor, confusion).

Warnings and precautions: Mirtazapine carries a boxed warning for increased risk of suicidal thoughts and behaviors in children, adolescents, and young adults, especially in the first months of treatment or around dose changes, so close monitoring is needed; it is generally not approved for use in pediatric patients. Use cautiously and with dose adjustments in people with significant liver or kidney impairment, cardiovascular disease, or a history of seizures. It may cause low blood pressure on standing and impair alertness, so patients should avoid driving or operating machinery until they know how it affects them. During pregnancy, it is used only if the potential benefits outweigh risks; small amounts pass into breast milk, so breastfeeding decisions are individualized with the prescriber.

Comparative safety: Compared with many SSRIs and SNRIs, mirtazapine tends to cause less sexual dysfunction and fewer gastrointestinal side effects but more sedation and weight gain; it has relatively low risk of QT prolongation at usual doses but should still be used carefully in people with known heart rhythm problems or on other QT-prolonging medicines.

Reporting and safety updates: Patients and caregivers can report suspected side effects to the FDA’s MedWatch program (online or by phone) and can review current safety communications and prescribing information through FDA and manufacturer resources.

Drug and supplement interactions: Mirtazapine should not be used with monoamine oxidase inhibitors (MAOIs) or within 14 days of stopping an MAOI because of the risk of serious reactions, including serotonin syndrome; caution is needed when combining it with other medicines that increase serotonin (such as SSRIs, SNRIs, certain migraine triptans, linezolid, or St. John’s wort). Other sedating drugs (such as benzodiazepines, opioids, some antihistamines, or alcohol) can increase drowsiness and impair coordination. Medicines that affect heart rhythm (QT-prolonging drugs) or electrolyte balance may add to cardiac risks in susceptible patients.

Food, alcohol, and lifestyle interactions: There are no major food restrictions with mirtazapine, and it can be taken with or without meals; however, alcohol should generally be limited or avoided because it can significantly increase sedation and impair judgment. Because mirtazapine may increase appetite and weight, attention to diet and physical activity can help manage weight changes.

Precautions and contraindications: Use with caution in people with a history of bipolar disorder (risk of mood switching to mania or hypomania), seizures, significant liver or kidney disease, low blood pressure, heart disease, or glaucoma, and in those who are elderly or very frail, as they may be more sensitive to side effects such as dizziness, falls, and confusion. It is contraindicated in patients with known hypersensitivity to mirtazapine or any component of the formulation and in those currently taking or very recently taking MAOIs.

Monitoring needs: Clinicians may monitor mood, anxiety, and suicidality, particularly early in treatment and after dose changes, and periodically assess weight, appetite, and metabolic parameters (such as lipids and blood sugar) in patients at risk for metabolic complications. In patients with heart disease or on other QT-prolonging medications, periodic ECGs and electrolyte checks may be considered.

Q: How long does it take for mirtazapine to start working?
A: Many people notice better sleep and appetite within 1–2 weeks, but mood and energy often take 2–4 weeks or longer to improve, with full benefit sometimes taking up to 6–8 weeks of regular use.

Q: Will mirtazapine make me gain weight?
A: Weight gain is common with mirtazapine because it can increase appetite and cause cravings, so monitoring your weight, paying attention to diet, and staying physically active can help manage this effect.

Q: Is mirtazapine addictive or habit-forming?
A: Mirtazapine is not considered addictive in the way that benzodiazepines or opioids are, but stopping it suddenly may cause uncomfortable symptoms, so it should be tapered under medical guidance.

Q: Can I drink alcohol while taking mirtazapine?
A: Alcohol can increase mirtazapine’s sedative effects and impair coordination and judgment, so it is generally safest to avoid or strictly limit alcohol and discuss any drinking with your prescriber.

Q: What should I do if I feel worse or have suicidal thoughts after starting mirtazapine?
A: Contact your prescriber right away or seek emergency help, especially if you have new or worsening depression, agitation, or thoughts of self-harm, as your treatment plan or dose may need to be adjusted promptly.