Medication guide

Duloxetine (Cymbalta)

What is duloxetine?

Duloxetine is known as Cymbalta in the United States, the European Union, and Japan alike (サインバルタ on Japanese packaging). It belongs to the SNRI group of antidepressants: it works on serotonin and noradrenaline, two chemical messengers linked to mood and to how we feel pain.

How is it different from other antidepressants?

Mood and pain together: in Japan it is approved for depression and for several long-term pain conditions
Works on two systems at once: serotonin and noradrenaline, where SSRIs work on serotonin alone
One medicine can cover both: when low mood and physical pain occur together, it can be used for both
Once a day, in the morning: a simple routine

What is it used for in Japan?

Depression
Chronic pain of several types: nerve pain from diabetes, fibromyalgia, chronic low back pain, and osteoarthritis pain

How does it help?

By gradually increasing serotonin and noradrenaline in the brain, it eases low mood over time, and can also calm certain kinds of pain. The full effect often takes a few weeks. If you don't feel better right away, that's normal; keep taking it as prescribed.

What should I tell my doctor before starting?

A few situations rule it out entirely; your doctor will choose something else if any of these apply:

A past allergic reaction to duloxetine
Taking, or recently stopping, an MAO inhibitor (a medicine for depression or Parkinson's); these can't overlap
Severe liver problems
Severe kidney problems
Closed-angle (narrow-angle) glaucoma that isn't well controlled

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

High blood pressure, or a heart condition
Any other glaucoma, including closed-angle glaucoma that is well controlled, or raised pressure in the eye
Difficulty passing urine (an enlarged prostate, for example)
Other antidepressants, tramadol (a painkiller), migraine triptans, or lithium
The antidepressant fluvoxamine, or antibiotics such as ciprofloxacin (they can raise duloxetine's level)
Blood thinners, or regular painkillers like ibuprofen
A history of seizures, or bipolar disorder
Past suicidal thoughts, or strong impulsivity: the label asks for closer monitoring
Diabetes: blood sugar can rise, so it is watched
Drinking heavily (it may make liver problems worse)
Being older
St John's Wort supplements
Pregnant, planning to be, or breastfeeding (see the section below)

Your doctor may also check your blood pressure and pulse from time to time, as duloxetine can raise them in some people, and may check your liver with a blood test.

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

Duloxetine is taken once a day, after breakfast (the Japanese label specifies the morning), and the capsule is swallowed whole, without crushing or chewing.

If you miss a dose: take it when you remember that day, or just skip it if the next one is close. Never take a double dose to catch up
Early on: nausea can appear when you start, and it often eases as your body adjusts. Some effects can continue, so tell your doctor if they do
Agitation: if you notice unusual agitation or feeling wired, contact your doctor promptly
Alcohol: drinking can add to drowsiness and may affect the liver, so the Japanese label calls for caution with alcohol

What side effects should I expect?

Many are mild and ease 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 25%), or trouble sleeping in some people: drowsiness is often noticed when you start; tell your doctor if it is a problem, as the dose can be adjusted
Nausea (around 20%): mostly when you start, and it often eases as your body adjusts; if it bothers you, tell your doctor, as a counter-medicine can help
Dry mouth (around 10%)
Constipation (around 10%)
Headache
Dizziness
Reduced appetite
Feeling more anxious or restless at first
Sexual side effects

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.

Will I become dependent? How do I stop safely?

No; duloxetine 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 withdrawal-like symptoms: dizziness, headache, nausea, tingling or electric-shock-like sensations, anxiety, or muscle aches. So never stop suddenly on your own.

Tapering makes this manageable for most people: the dose comes down in small steps, moving to the next step once any symptoms have settled, with a gentler pace near the end. If symptoms do appear along the way, stepping back up briefly and slowing down helps, though they may take a few days to settle. Many people continue for some months after they feel better, and coming off is planned together.

Can I drive while taking it?

Yes, with care, especially at the start. Duloxetine can cause drowsiness or dizziness, so see how it affects you before driving, particularly when starting or changing the dose, and don't drive if you notice them. The Japanese label asks for caution here, not a ban.

What about pregnancy and breastfeeding?

Pregnancy and breastfeeding don't automatically mean stopping; the decision is made individually with your doctor. It's weighed against the real risks of untreated illness. Never stop on your own on learning you're pregnant. Our guides to medication in pregnancy and medication while breastfeeding cover the details.