Mirtazapine

What is mirtazapine used for?

Mirtazapine is a prescription-only antidepressant that is primarily used to treat depression (also known as major depressive disorder or MDD) in adults. It can also be used to treat conditions including anxiety and obsessive-compulsive disorder (OCD).  

How does mirtazapine work?

Mirtazapine is an antidepressant that primarily works by increasing the activity of two neurotransmitters in the brain - noradrenaline and serotonin[2][1]. These chemicals are known to enhance mood and help alleviate symptoms of depression[1].  

Who can take mirtazapine?

Mirtazapine is only available on prescription. It is suitable for most adults but may not be recommended for people:  

• With liver or kidney problems  

• With a history of seizures, bipolar disorder, or heart conditions  

• Who are pregnant or breastfeeding (please consult your doctor or pharmacist first)  

If you have diabetes, mirtazapine can impact your blood sugar levels. Your doctor or pharmacist may recommend that you monitor it more closely during the first few weeks of taking it and adjust your diabetes treatment if and when appropriate.  

Please tell your doctor or pharmacist about any conditions you may have before starting mirtazapine, and always follow the instructions in the Patient Information Leaflet[9]. 

What is the typical dosage of mirtazapine? 

The usual starting dose is 15 to 30mg per day, which can be increased to a maximum of 45mg per day. Your doctor or pharmacist may recommend dividing your daily dose into 2 doses of different sizes. Dosage adjustments may be necessary if you live with liver or kidney issues.  

How do you take mirtazapine?

Mirtazapine is usually taken once daily at bedtime. It comes in the form of:  

• Tablets - swallowed whole with water  

• Mouth-dissolving tablets - dissolved on the tongue  

• Liquid - measured with a syringe or spoon  

Mirtazapine can be taken with or without food, but you should swallow the tablets with a drink of water, and without breaking, crushing, or chewing them.  

If you take the dissolving tablet, you can swallow it without a drink of water. If you take the liquid form, it should come with a syringe or spoon designed to hold the correct amount. If you do not have either, ask your pharmacist rather than using a kitchen teaspoon.  

If your doctor or pharmacist tells you to take it twice a day, the smaller dose should be taken in the morning and the higher dose in the evening, as it can make you sleepy.  

Can you stop taking mirtazapine? 

If you've been feeling better for 6 months or more, your doctor or pharmacist may suggest coming off mirtazapine. They may also recommend reducing your dose gradually over several months, or longer if you've been taking mirtazapine for a long time. This is to help prevent you getting any extra side effects as you come off the medicine.  

Do not stop taking mirtazapine suddenly, or without talking to your doctor or pharmacist first.

What do you do if you take too much mirtazapine?

Taking more than the prescribed dose can lead to symptoms like drowsiness, confusion, or a fast/irregular heartbeat. If this happens:  

• Contact 111 for advice or call 999 for emergency assistance  

If you need to go to A&E do not drive – either get someone else to drive, or call 999 and ask for an ambulance. Make sure you take the mirtazapine packet or leaflet, any remaining medicine, and any other medicines you take with you.

What do you do if you forget to take mirtazapine? 

If you miss a dose:  

• Once daily dosing: Skip the missed dose and take the next dose at the usual time. Do not double dose.  

• Twice daily dosing: If it’s your morning dose, take it together with your evening dose. If it’s your evening dose, skip this dose and just take your morning dose only when you wake up. If you miss both doses, skip them both and continue the next day with your usual dosage routine. 

What medicines can you and can't take with mirtazapine? 

When you’ve been prescribed mirtazapine, avoid taking it with:  

• MAO inhibitors (e.g., phenelzine, tranylcypromine)  

• Other antidepressants or serotonergic drugs due to the risk of serotonin syndrome  

• Alcohol, as it can increase drowsiness 

Always inform your doctor or pharmacist about all medications and supplements you take before you start a new medicine, and follow the instructions in the Patient Information Leaflet[9].

What are the side effects of mirtazapine?

Common side effects of taking mirtazapine include:  

• Drowsiness or feeling sleepy  

• Dry mouth  

• Increased appetite and weight gain  

• Headaches  

• Nausea or feeling sick  

Rare but serious side effects include low sodium levels, severe stomach pain, and suicidal thoughts.

The information provided in the side effects section is not a comprehensive list of all possible side effects associated with this medication. For a complete list of side effects, please refer to the Patient Information Leaflet (PIL) provided with your medication or consult your healthcare professional[9].

If you experience any side effects, including those not listed, you are encouraged to report them via the Yellow Card Scheme or contact your doctor, pharmacist, or nurse. This information is intended as a summary for general awareness and does not replace professional medical advice.

Frequently asked questions about mirtazapine

How long does mirtazapine take to work?   

It may take 4-6 weeks to feel the full benefits once you’ve started taking mirtazapine.  

Can I drive while taking mirtazapine?   

Mirtazapine can make you feel drowsy. You should always avoid driving if you feel drowsy.  

Are there long-term side effects of taking mirtazapine?   

Mirtazapine is generally considered safe for long-term use.  

Is it safe to drink alcohol while taking mirtazapine?  

It’s best to avoid alcohol as it can increase certain side effects, like drowsiness and dizziness.  

What should I do in case of an overdose of mirtazapine?  

Symptoms of an overdose may include confusion, memory problems, drowsiness, and a fast heart rate. You should seek immediate medical attention if you believe you may have taken more mirtazapine than you should have.  

Why does mirtazapine cause weight gain?  

Mirtazapine may cause weight gain, but it’s not the same for every person who takes it. It can cause weight gain as it may alter your metabolic processes, induce insulin and leptin resistance, and stimulate your appetite. But if you take mirtazapine while maintaining a healthy, balanced diet and a regular exercise routine, then you can minimise the impact. 

For the official NHS guide to mirtazapine, visit their website.