Mirtazapine dosage, forms, and strengths

Mirtazapine is a prescription atypical tetracyclic antidepressant (TeCA). The FDA has approved mirtazapine to treat major depressive disorder (MDD). Doctors sometimes use it off-label for other medical conditions such as generalized anxiety disorder, panic attacks, obsessive compulsive disorder, migraines, insomnia, or PTSD. Doses are taken orally at bedtime because of the sedative effects of the drug. While healthcare professionals consider it a safe antidepressant, it is not typically their first choice when treating depression.

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The dosages listed are general guidelines; your healthcare provider may adjust your dose based on individual health factors.

Mirtazapine dosage for major depressive disorder

Mirtazapine is a unique antidepressant classified as a tetracyclic antidepressant. These drugs work similarly to antidepressants called SNRIs. Mirtazapine is not typically a doctor’s first choice for the treatment of depression, but it is a viable antidepressant medication when SSRIs (selective serotonin reuptake inhibitors) like Prozac (fluoxetine) don’t work. Unlike many other antidepressants, it’s best to take the mirtazapine daily dose before bedtime because of its sedative effects. Because mirtazapine is known to cause drowsiness in 23% of patients and sedation in 19%, some doctors choose mirtazapine for patients who also have sleep problems.

Personalized dosing considerations

Dosage reductions are not required for older adults or people with kidney or liver dysfunction, but prescribers do take precautions to monitor elderly patients or people with liver or renal impairment for adverse effects. The dose may be reduced if side effects are too pronounced. Prescribers may also reduce the dose in people taking certain types of drugs that either slow down or speed up the body’s metabolism of mirtazapine. No specific dosage reductions are recommended. 

Mirtazapine safety info

Mirtazapine is considered a safe antidepressant for use in adults. People who have had allergic reactions to mirtazapine are an exception and can never safely take this drug.

The most important thing to know about mirtazapine is that it has strong sedative effects. Take doses at night. Do not drive or engage in other risky activities until you are certain that it’s safe. If you wake up feeling groggy, consider taking your dose earlier before going to bed so the medication has more time to wear off before you need to be active.

There is an increased risk of suicidal thoughts in pediatric patients and young adults first taking mirtazapine. Immediately tell the prescriber about worsening depression, unusual behaviors, or any thoughts of suicide or self-harm. If you ever feel suicidal, call 911 right away or reach out to a trusted loved one to stay with you and help keep you safe.

To avoid serious adverse effects, make sure the prescriber knows about all your medical conditions, particularly:

• A history of suicide attempt

• A history or family history of bipolar disorder or mania

• Cardiovascular disease

• Irregular heartbeat

• Kidney problems

• Liver problems

• Seizures

• High cholesterol or fats

• Low sodium levels

• Low blood pressure

• Glaucoma (particularly a history of angle-closure glaucoma)

• Low white blood cell counts

Mirtazapine can cause serious side effects. The Medication Guide discusses all of these and outlines many of the symptoms. Contact the prescriber or get medical help if you notice any of these signs of a serious side effect.

Mirtazapine is a Category C medication during pregnancy. This means risks versus benefits need to be weighed. It may be risky during pregnancy, so prescribers are advised to use it only when necessary. 

Mirtazapine is considered safe to take while breastfeeding, though a small amount of the drug is present in breast milk. Women should monitor the nursing child for side effects and report them to the prescriber. 

Mirtazapine has several significant drug interactions, so tell the prescriber and pharmacist about all the medications, over-the-counter remedies, and supplements that are regularly used. Also, tell other healthcare professionals about mirtazapine before they prescribe new drugs.

Mirtazapine should never be taken with monoamine oxidase inhibitors (MAOIs) or within 14 days of taking one. MAOIs are rarely prescribed drugs, and the prescriber and pharmacist should recognize them.

The most important drug interactions to be aware of are other drugs that make you sleepy. Mirtazapine has strong sedative effects and can cause impairment. These effects are amplified when mirtazapine is combined with drugs like narcotic pain relievers, sedatives (benzodiazepines), sleeping pills, antihistamines, drugs that treat seizures, drugs that treat other mental health issues, and alcohol. 

There is a risk of serotonin syndrome, a potentially severe complication of taking more than one serotonergic drug like mirtazapine. Other serotonergic drugs include other antidepressants, other drugs that treat mental health issues, migraine medications called triptans, narcotic pain relievers, and others. These drugs aren’t prohibited, but patients should be aware of the symptoms of serotonin syndrome just to be safe.

Some drugs speed up or slow down the body’s breakdown of mirtazapine. The prescriber may need to give a higher dose or lower dose of mirtazapine with these drugs.

Some people experience unpleasant withdrawal symptoms when mirtazapine is suddenly discontinued, so prescribers gradually reduce the dose when it’s time to stop. No specific tapering schedule is recommended, but the process should take two or four weeks.

How to take mirtazapine

Following the dosing instructions is particularly important for this medication. Taking mirtazapine before bedtime typically works best, owing to its potential for sedation. Any dose increase or decrease should be done under the direction of a healthcare professional. The list below reviews other important treatment elements to consider:

• Follow all the prescriber’s directions. The prescriber may change the dose during treatment.

• It may take several weeks before the therapeutic effects of the medicine are noticeable.

• Take one dose daily. Do not exceed the prescribed dose.

  • The best time to take the dose is before bedtime.

  • Tablets can be taken without regard to food.

• Swallow the tablets whole with a drink of water.

• Allow the mirtazapine orally disintegrating tablets to completely dissolve on the tongue before swallowing. Do not crush, break, or chew.

  • Use dry hands to handle the tablet.

  • Do not push the tablet through the foil. Gently peel back the foil backing.

  • Immediately place the tablet on the tongue once it’s removed from the blister pack.

• Store the tablets at room temperature, away from light and moisture.

Mirtazapine dosage FAQs

What is the typical starting dose of mirtazapine for adults?

The usual starting dose of mirtazapine is 15 mg daily. 

How long does mirtazapine take to work?

The antidepressant effect of mirtazapine may be noticeable in the first week, but it usually takes two to four weeks for people to feel better. If there isn’t an adequate response in two months, treatment guidelines suggest increasing the dose or switching to another drug. 

What happens if I miss a dose of mirtazapine?

Ask the prescriber or pharmacist how to handle a missed dose. Generally, a missed dose should not be taken the next morning. Instead, take the next day’s dose before bedtime. Do not take extra medicine to make up for a missed dose.

How should I adjust my mirtazapine dosage if I miss a dose?

Do not adjust the dose if a dose is missed. 

What happens when you mix mirtazapine and alcohol?

Avoid drinking alcohol when taking mirtazapine. The combination can increase the drug’s adverse reactions, such as drowsiness, sedation, and impaired thinking and judgment. 

What is the dosage of mirtazapine for dogs/cats?

Veterinarians use mirtazapine in pets primarily to relieve nausea and vomiting or as an appetite stimulant for weight gain. The standard oral dosage for dogs is based on weight, from 3.75 mg to 15 mg every 24 hours (every 12 hours for giant dogs). For cats, oral doses are given every three days. Cat owners can also use a topical ointment (Mirataz) as an appetite stimulant for cats with a history of weight loss. They will apply a 1.5-inch ribbon (a 2 mg dose) to the inner surface of the cat’s ear once daily for 14 days.

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Sources:

• Mirataz mirtazapine ointment animal drug information, DailyMed (NIH National Library of Medicine)

• Mirtazapine, StatPearls

• Mirtazapine orally disintegrating tablet prescribing information, DailyMed (NIH National Library of Medicine)

• Nonpharmacologic and pharmacologic treatments of adults in the acute phase of major depressive disorder: a living clinical guideline from the American College of Physicians, Annals of Internal Medicine

• Plumb’s Veterinary Drug Handbook, 7th ed

• Remeron drug summary, Prescriber’s Digital Reference (PDR)

• Remeron mirtazapine tablets, Organon

• Remeron / Remeron SolTab mirtazapine tablet / orally disintegrating tablet prescribing information, DailyMed (NIH National Library of Medicine)

• Safety of mirtazapine: A review, International Clinical Pharmacology