Mirtazapine: uses, dosage and side effects

Mirtazapine is an antidepressant taken as a tablet, usually at night, and prescribed mainly for depression, in particular where sleep is disturbed and appetite is poor. It works differently from the SSRIs and is often chosen for that reason. In Ireland it is prescription-only and it is not a controlled drug. This page explains what it is used for, how it is taken, which side effects are reported most often and how continuing an existing course works. It is information, not an offer of the medicine.

What mirtazapine is used for

Mirtazapine is licensed for the treatment of major depressive episodes in adults. It is a tetracyclic antidepressant that increases noradrenaline and serotonin signalling by blocking particular receptors rather than by blocking reuptake, which is how the SSRIs work. Because it also blocks histamine receptors, it is markedly sedating at lower doses and tends to increase appetite; prescribers often choose it for people whose depression comes with early waking, poor sleep and weight loss. It is sometimes prescribed outside its licensed indication for other conditions, which is a decision for the treating doctor. Mirtazapine treats symptoms, it does not cure depression, and it works best combined with psychological therapy, structure and support. Treatment is usually continued for a period after you feel better, because stopping as soon as mood lifts is one of the commonest reasons for relapse. Your prescriber decides how long that period should be.

Side effects of mirtazapine

The effects reported most often are drowsiness and sedation, increased appetite and weight gain, dry mouth, dizziness, headache and swelling of the ankles. Sedation is usually strongest early on and, unusually among antidepressants, it can be more pronounced at lower doses. Less commonly people report vivid dreams, restless legs, tremor or a drop in blood pressure when standing up quickly. Rare but serious problems include a fall in white blood cells, so a sore throat, mouth ulcers, fever or flu-like illness during treatment should be reported to a doctor without waiting for the next appointment, and a blood test may be arranged. Serotonin syndrome is rare and more likely when mirtazapine is combined with other serotonergic medicines. Antidepressants can, especially in the first weeks and after a dose change, increase anxiety, agitation and thoughts of self-harm, most clearly in people under 25. Seek help urgently if that happens; in an emergency ring 112 or 999. How often each effect occurs, with its formal frequency category, is set out in the patient information leaflet rather than in the words used here.

Dosage and how to take it

Mirtazapine tablets, including orodispersible tablets that melt on the tongue, are usually taken once a day in the evening because of their sedating effect, swallowed with water and with or without food. The dose is set by the prescriber and adjusted according to response and tolerance; do not change it yourself. Mood usually improves over some weeks rather than days, while sleep and appetite often change earlier, so it is worth continuing through the first fortnight even if you notice little benefit. If you miss a dose, take the next one at the usual time rather than doubling up. Do not stop suddenly after regular use: withdrawal effects such as dizziness, agitation, anxiety, nausea and disturbed sleep are well described, and treatment is normally tapered over weeks under medical supervision. Because the tablets are sedating, be careful about driving or operating machinery until you know how they affect you.

Is mirtazapine available without a prescription in Ireland?

No. Mirtazapine is prescription-only in Ireland and cannot be bought over the counter in a pharmacy. It is not a controlled drug, which is a separate legal category covering substances such as opioids, benzodiazepines and stimulants. Antidepressant treatment requires assessment before it starts, monitoring in the first weeks and a plan for how long it will continue, which is why the prescription requirement exists rather than being a formality. Buying antidepressants from websites that offer them without any prescription means you have no assurance about what the tablets contain, no monitoring and no route to help if the first weeks go badly. A prescription written by a doctor in another EU or EEA country can be dispensed in Ireland when it carries the details required for cross-border prescriptions, and the PSI publishes guidance for pharmacists on exactly that situation.

Why we do not assess mirtazapine online

We do not assess antidepressants online at the moment, not even as a continuation of treatment a prescriber has already established. There is nothing to buy on this page and no fee to pay. The reason is the nature of the service: you answer a written questionnaire and a doctor reviews it separately, with no video consultation, no telephone appointment and no live chat. With a medicine whose dose is adjusted against mood, sleep and side effects, that adjustment belongs with a prescriber who knows you and can speak to you. If you are already taking mirtazapine and your supply is running low, contact your GP or the service following you in good time, and do not stop on your own, because stopping abruptly can cause withdrawal symptoms. If you are newly unwell, if your symptoms have changed, or if you are having thoughts of harming yourself, contact your GP, an out-of-hours GP service, or an emergency service on 112 or 999.

Cost and reimbursement in Ireland

Mirtazapine is an old molecule available from several manufacturers, so private prices are usually modest, though they differ between pharmacies because each sets its own. If you hold a medical card, prescribed medicines are supplied under the GMS scheme for a small charge per item with a monthly household cap. Without a medical card, the Drugs Payment Scheme limits what one household pays for prescribed medicines in a calendar month; the HSE publishes the current charge and cap, so take the figure from there rather than from an older page. Mental health conditions are not on the Long Term Illness Scheme list, so that scheme does not usually apply here. Cost is worth raising with your prescriber if it is a reason you might stop treatment, because within a class there is often more than one option, and stopping an antidepressant abruptly for financial reasons is the worst of the available choices.

Interactions and alcohol

Alcohol and mirtazapine both cause sedation, and together the effect is stronger than either alone, so drinking while taking it is discouraged, particularly at the start of treatment or after a dose change. Mirtazapine must not be combined with monoamine oxidase inhibitors, and a gap between the two treatments is required in both directions. Combining it with other serotonergic medicines, including SSRIs, SNRIs, triptans, tramadol, lithium or St John's wort, raises the risk of serotonin syndrome. Sedating medicines such as antihistamines, antipsychotics and sleep medicines add to drowsiness. Some medicines that affect liver enzymes, including certain antifungals and antibiotics, and carbamazepine or phenytoin in the opposite direction, can change mirtazapine levels. Tell your pharmacist about everything you take, including herbal products; St John's wort in particular is sold without prescription and is a genuine problem with antidepressants. Do not drive until you know how the tablets affect your alertness.

Who should not take mirtazapine

Mirtazapine must not be taken by anyone allergic to it or to any ingredient of the tablets, or by anyone taking a monoamine oxidase inhibitor or who has taken one recently. Caution and closer supervision apply in epilepsy, in liver or kidney disease, in heart disease including recent heart attack or low blood pressure, in glaucoma of the narrow-angle type, in prostate enlargement causing urinary difficulty, and in diabetes, because appetite changes affect blood glucose control. People with bipolar disorder can switch into mania on any antidepressant, so a personal or family history matters and should be declared. A history of a blood disorder is relevant because of the rare effect on white cells. Anyone under 18 should be treated only by a specialist service, as mirtazapine is not licensed for that age group. Tell the prescriber about a history of self-harm, because monitoring in the first weeks then matters more.

Generic and brand names

The active substance is mirtazapine. Several generic versions are marketed in Ireland, and the original brand name most people recognise is Remeron, though which products are on the shelf changes over time. Generic tablets contain the same active substance in the same strength as the originator and are approved on that basis, so a pharmacist may supply a different manufacturer from the one you had last time. Orodispersible tablets that dissolve on the tongue exist alongside standard film-coated tablets and are useful for people who struggle to swallow. If a change of manufacturer coincides with a change in how you feel, tell your pharmacist rather than stopping the tablets. On a cross-border prescription the medicine should be named by its international non-proprietary name, mirtazapine, together with the strength and form, because that is what an Irish pharmacist needs to dispense it correctly.

Pregnancy and breastfeeding

Mirtazapine is not routinely recommended in pregnancy, but the decision is not a simple ban: untreated depression carries its own risk for both parent and baby, so the balance is judged individually by a doctor who knows your history. Data in pregnancy are limited compared with some other antidepressants. If mirtazapine is used late in pregnancy, the newborn can show short-lived withdrawal or adaptation effects, so the maternity team should know about it in advance. Small amounts pass into breast milk; breastfeeding is sometimes continued under supervision, with the infant watched for sedation and poor feeding. If you are pregnant, planning a pregnancy or breastfeeding, discuss it with your GP or mental health team before changing anything, and do not stop an antidepressant abruptly on your own. Our online questionnaire does not lead to prescriptions for use during pregnancy or breastfeeding.

Patient information leaflet

Every pack sold in Ireland contains a patient information leaflet, and the same leaflet is published online. The Health Products Regulatory Authority (HPRA) is the medicines regulator here and lists authorised products together with their leaflets and summaries of product characteristics; medicines.ie publishes the same documents for products marketed in Ireland. Because mirtazapine is supplied by several manufacturers, look up the leaflet for the pack you actually hold, since the list of excipients and the appearance of the tablets differ between them. Read it before starting a new pack, as wording on warnings and side effects is updated from time to time. If anything there does not match what you were told, ask your pharmacist rather than guessing; pharmacists in Ireland are registered with the Pharmaceutical Society of Ireland. A suspected side effect can be reported by you directly to the HPRA.

Who wrote and checked this page

This page was prepared by the medical content team at MEDINOW Sp. z o.o. and reviewed by lek. Damian Wojno, a doctor registered in Poland, PWZ no. 3211301. He holds no Irish registration and does not practise in Ireland; he works to Polish professional rules and issues cross-border prescriptions under Directive 2011/24/EU and Directive 2012/52/EU, which is the framework an Irish pharmacist applies when a prescription comes from another EU or EEA country. The content was verified on 29 August 2026 against the sources listed below, all of them official or regulator-published. This page is general information about a medicine: it is not personal medical advice, not a diagnosis and not an offer of the medicine itself, which we never supply. If your symptoms are new, severe or changing, contact your GP or a pharmacist; in an emergency in Ireland ring 112 or 999.

Is mirtazapine prescription-only in Ireland?

Yes, it is prescription-only, though it is not a controlled drug. A prescription written by a doctor in another EU or EEA country can be dispensed in an Irish pharmacy when it carries the details required for cross-border prescriptions.

How long does it take to work?

Sleep and appetite often change within the first days because of the sedating and appetite-increasing effect, while the improvement in mood usually builds over several weeks. If nothing has changed after a few weeks at a stable dose, tell your prescriber rather than stopping.

What are the common side effects?

Drowsiness, increased appetite and weight gain, dry mouth, dizziness and headache are the most frequently reported. Report a sore throat, mouth ulcers or fever during treatment, because a rare effect on white blood cells needs a blood test.

Can I drink alcohol with it?

Alcohol is best avoided. Both alcohol and mirtazapine are sedating and the combination increases drowsiness and impairs judgement and driving, particularly in the first weeks of treatment or after a dose change.

How do I get a repeat prescription?

If you are already on mirtazapine and nothing has changed, you can complete our online questionnaire and a doctor reviews it separately; there is no video consultation. If treatment can continue you receive a cross-border prescription as a PDF by e-mail. The fee covers the assessment, not the issuing of a document, and the service does not replace ongoing mental health care.