Mirtazapine (Remeron / Reflex)

What is mirtazapine?

Mirtazapine is known as Remeron in the United States, Zispin in the UK, and in Japan it's sold as Reflex or Remeron (リフレックス／レメロン on Japanese packaging; two brands, same medicine). It belongs to the NaSSA group of antidepressants: it works on serotonin and noradrenaline in a different way from SSRIs, and because it tends to help with sleep and appetite, it's often chosen when low mood comes together with poor sleep or a reduced appetite.

How is it different from other antidepressants?

• Helps sleep and appetite from the first nights, while the mood effect builds
• A different mechanism: a real alternative when SSRIs haven't been the right fit
• Gentler on the stomach: nausea is much less common than with SSRIs
• Evening dosing fits naturally: one dose at night, working with your sleep rather than against it

What is it used for in Japan?

Depression.

How does it help?

By adjusting serotonin and noradrenaline through its own route, it eases low mood over time, and often helps sleep and appetite along the way. The full effect on mood often takes a few weeks, though sleep frequently improves earlier. If you don't feel better right away, that's normal; keep taking it as prescribed.

What should I tell my doctor before starting?

Mirtazapine suits most people, but a few situations rule it out entirely; your doctor will choose something else if any of these apply:

• A past allergic reaction to mirtazapine
• Taking, or recently stopping, an MAO inhibitor (a medicine for depression or Parkinson's); these can't overlap

And tell your doctor first if any of these apply; these usually just need adjustments or a closer eye:

• Other antidepressants, tramadol (a painkiller), or migraine triptans
• Serious liver or kidney problems
• A history of seizures, or bipolar disorder
• Being older, or taking water tablets (diuretics)
• Pregnant, planning to be, or breastfeeding (see the section below)

Your doctor may keep an eye on your weight from time to time, as mirtazapine can increase appetite.

How do I take it, and what if I miss a dose?

Mirtazapine is taken once a day, at bedtime; its sleepiness works for you at night.

• If you miss a dose: just skip it if the next one is close. Never take a double dose to catch up
• The drowsiness is strongest in the first days and usually eases as you continue
• Go easy on alcohol; it stacks with the drowsiness

What side effects should I expect?

Most are mild and settle within the first week or two as your body adjusts, and many can be eased with a counter-medicine (for nausea, for example). Not everyone gets them; the rough figures below just give a sense of how common each one is.

• Drowsiness (around 50%): strongest at first and often eases; when sleep is part of the problem, this is usually the point rather than a drawback
• Dry mouth (around 20%): usually mild
• Tiredness (around 15%)
• Constipation (over 10%)
• Weight gain, often with a bigger appetite
• Feeling a bit more anxious or restless at first; this usually passes as the medicine starts working

If anything is bothering you, tell your doctor; there's often a way to adjust. And if you ever feel worse instead of better, tell us straight away; it's easily managed, and that's what we're here for.

Finally, one thing that is rare (most people never experience it) but good to know:

• A fever with a sore throat or mouth ulcers: worth a prompt check, as very rarely mirtazapine can lower the white blood cells that fight infection; caught early, it recovers when the medicine is stopped

Will I become dependent? How do I stop safely?

No; mirtazapine isn't addictive, but it does need a planned, gradual stop. There's no craving and no urge to take more. Your body does get used to it, though, and stopping suddenly can cause uncomfortable symptoms, so never stop suddenly on your own. Changes are tapered with your doctor, and many people continue for some months after they feel better before coming off together.

Can I drive while taking it?

The Japanese label advises against driving while taking it. Mirtazapine's drowsiness is real, especially early on, and the prescribing information here instructs that patients on it shouldn't drive or operate dangerous machinery. Discuss your own situation with your doctor, particularly once you're stable and the sedation has eased.

What about pregnancy and breastfeeding?

Often, treatment can continue; the decision is individual. Neither pregnancy nor breastfeeding is an automatic reason to stop, and untreated depression carries real risks too. Never stop on your own on learning you're pregnant. Our guides to medication in pregnancy and medication while breastfeeding cover the details.