Mirtazapine

Mirtazapine can start to work on depression within the first one to two weeks of treatment, and the improvement continues over the following few weeks. It may take four weeks or longer for you to feel the full effect.

Your doctor might start you on a low dose and then increase it slowly over a few weeks to your full dose.

How people respond to treatment can vary. Sometimes improvement is slow, and you may not feel any different to start with. This can be hard when your mood is low, and if you experience any side effects from your medication you may think you feel worse and not better. If you can, give your medication a chance to work and continue to take it for at least three to four weeks to see if it makes a difference.

Your parents, friends and doctor may notice an improvement in you before you feel it yourself, so it’s a good idea to talk to them.

If you think your medicine has not made any difference to how you feel after three to four weeks, you should go back to your doctor. They might recommend a change in dose or a different medication. However, it can take longer to work for some people than for others, so they may suggest you wait six to eight weeks before deciding.

A potential side effect of mirtazapine is an increase in appetite and weight gain. This happens more often in young people than in adults.

It is not possible to predict how mirtazapine will affect each person before they start taking it. Talk to your doctor or pharmacist if you are concerned about your weight, or changes to your weight, while taking mirtazapine.

A very common side effect of mirtazapine is a dry mouth. Over a long time, this can increase your risk of developing tooth decay or gum disease. Make sure you brush your teeth well and have regular dental check-ups. Speak to your dentist, doctor or pharmacist about things you can do to help.

You may want to let your family and friends know you are taking mirtazapine so they can support you and help you look out for side effects.

Mirtazapine can make you feel very sleepy, especially when you first start taking it. This should improve within a few weeks. If it makes you feel drowsy, try taking it just before you go to bed.

Some people can get a side effect where it makes it difficult to get to sleep.

If you have been taking mirtazapine for more than a month and you continue to feel very tired, sleepy or struggle to function during the day, you should go back to your doctor and discuss what changes could be made to help. This may include switching to a different medicine.

Alcohol

It may be possible to drink some alcohol while taking mirtazapine but having the two together might make you very sleepy and unsteady on your feet.

During the first few weeks of treatment, it is recommended that you don’t drink alcohol until you know how the medicine affects you.

Drinking alcohol every day, or in large amounts, can make your symptoms worse and may mean you won’t get the maximum benefit from your medication.

Street drugs

Cannabis can make drowsiness worse with mirtazapine and give you a fast heartbeat.

Cannabis and other drugs may have their own side effects on your mental health, like anxiety or psychosis.

Methadone or heroin can make drowsiness worse with mirtazapine.

Mirtazapine could raise the level of cocaine in your body, giving you a bigger reaction.

Taking mirtazapine with cocaine or ecstasy is likely to dampen the stimulant effects. Ecstasy may also increase your levels of mirtazapine as it interferes with its breakdown in the liver.

You should not mix mirtazapine and amfetamines unless you are under close medical supervision, as an increased amfetamine response may be dangerous.

There are many other street drugs, but we don’t know what effect taking them with mirtazapine will have, so it’s best to be cautious. There is no regulation of street drugs or ‘legal highs’, so even if there are no known issues with the medication you take, the supply you receive might be mixed with other substances that could be dangerous.

Smoking

Cigarette smoke affects the amount of mirtazapine in your body.

If you smoke, you may need a higher dose of mirtazapine than someone who does not smoke.

Tell your doctor if you smoke, so that you get the right dose for you.

If you stop smoking, the body’s mirtazapine level rises, and you might need to reduce your dose of mirtazapine slowly over one week.

If you start or restart smoking, you will probably need to increase your dose of mirtazapine again.

Go to your doctor for advice if you stop or start smoking, or if you switch to vaping or a nicotine replacement product instead of smoking.

Get more advice on our drugs and alcohol guide.

Mirtazapine does not mix well with some other medicines, including herbal remedies. It may affect how they work or could cause more side effects.

Do not take mirtazapine if you take monoamine oxidase inhibitor antidepressants (MAOIs) or have taken them in the last two weeks. MAOIs include isocarboxazid, moclobemide, phenelzine and tranylcypromine.

Before you start taking mirtazapine, tell your doctor if you are taking any other medications including things you have bought from a pharmacy or other shop for common illnesses like colds and flu or medications that you put on your skin.

Always tell the pharmacist that you are taking mirtazapine if you buy any medicines from a pharmacy.

Look at the leaflet inside your medicine box for more information about other medicines that can interact with mirtazapine. With some medicines your doctor may need to adjust the dose of your medicines if you take them together. Ask a doctor or pharmacist for more information if you have any questions.

The mirtazapine tablets that you swallow may not be suitable for you if you have problems eating some sugars or dairy foods, as they contain lactose.

The mirtazapine orodispersible (‘melt in your mouth’) tablets contain aspartame, which can be a problem for people who have a condition called phenylketonuria.

The oral solution contains maltitol, which can be a problem for anyone who has an intolerance to a sugar called fructose.

There are several companies that manufacture this medicine and the non-active ingredients may vary between products.

Always let your pharmacist know if you have any food allergies or intolerances, and always check with them if you’re concerned about any of the ingredients in your medication.

If you need to avoid animal products, please note that non-active ingredients used in the production of medicines may sometimes be of animal origin. Ask your pharmacist if you have any questions about the ingredients.

Further information about practical considerations for medicines if you need to avoid animal products can be found on the Vegan Society website.

Taking mirtazapine may make you feel tired, dizzy or less alert when you start taking it.

This could affect you if you drive a car, ride a bike, use machines, or do anything else that needs a lot of focus.

It might be best to stop doing these things for the first few days or weeks until you know how it affects you or the side effects pass.

Most people drive as normal while taking mirtazapine. If you are worried about this or have any concerns you would like to discuss, speak to your doctor or pharmacist.

Pregnancy

If you become pregnant while you are on mirtazapine, you should carry on taking it and make an appointment to see your doctor as soon as possible They can discuss the benefits and risks of continuing mirtazapine and help you to make a decision that is best for you and your baby.

They may refer you to a specialist perinatal mental health team to support you with this decision.

You can find out more information about taking amitriptyline during pregnancy at Bumps (Best Use of Medicines in Pregnancy).

Untreated depression can also be harmful to you and your developing baby, so decisions about stopping or avoiding medication when you are pregnant need to be discussed carefully with your doctor. If you and your doctor agree that it is best for you to continue taking mirtazapine while pregnant, you should tell your midwife. If you are planning to get pregnant, it is recommended that you take folic acid while you are trying for a baby and during pregnancy. It is safe to take this together with mirtazapine.

Post-natal

With some anti-depressants taken in the later stages of pregnancy, there is evidence that there is an increased risk of particular health conditions. There are no studies that show mirtazapine increases this risk, but it cannot be ruled out.

Some newborn babies might experience symptoms at birth or soon after if the mothers take mirtazapine in the last three months of pregnancy like feeding problems or restlessness.

Tell your midwife if you are taking mirtazapine, so that they can help if the baby has any symptoms after birth.

Breastfeeding

Mirtazapine is passed to the baby in breastmilk in small amounts.
If your baby was born early, then breastfeeding while you are taking mirtazapine may not be recommended. Talk to your midwife and doctor about feeding options.

If you breastfeed while taking mirtazapine, seek urgent medical advice if your baby becomes restless, very sleepy or developing feeding problems.

Sex

Antidepressants, such as mirtazapine can have side effects that affect your sex life. These include:

• Painful erections or difficulty getting an erection.
• Bleeding from the vagina.
• Problems with reaching orgasm.
• Reduced genital sensation.
• Lower sex drive.
• A long-lasting and painful erection (priapism) that continues for more than a few hours. This is a very rare side effect but if this happens, you need to go to hospital for treatment.

Untreated depression can have a negative effect on your sex life, so if mirtazapine helps you to recover, positive effects can include improving your desire, experience and enjoyment of sex as your mood lifts and you become interested in life and relationships again.

Fertility

There is no evidence to show that mirtazapine affects human fertility. Talk to your doctor about your mirtazapine if you are trying to get pregnant or planning a family.

Mirtazapine is not a banned substance in sport.

Most people play sports as normal while taking mirtazapine, but if mirtazapine affects your concentration, eyesight or co-ordination, then you may want to wait to see if those effects go away before playing sports that need a lot of focus. If you have concerns, discuss this with your doctor.

Mirtazapine may affect your concentration, make you feel tired or dizzy or less alert.

Ideally it is best not to take mirtazapine for the first time just before your exams.

It is not possible to predict how the medication will make you feel, and if you do get any side effects, these are more likely to occur when you first start taking mirtazapine.

You should talk to your doctor about any future exams if you are starting mirtazapine. You might decide together to delay starting it until you have done them.

If they are more than a month away, however, you might find that it is better to start mirtazapine to improve your motivation and ability to study.

Most people take exams as normal while taking mirtazapine, but if you have any concerns, discuss this with your doctor.