Medication guide

Paroxetine (Paxil)

What is paroxetine?

Paroxetine is known as Paxil in the United States and Japan (パキシル on Japanese packaging), and Seroxat in the UK; it's all the same medicine. In Japan it comes in two forms: regular tablets, and a controlled-release tablet called Paxil CR (パキシルCR), which is approved for depression only. It belongs to the SSRI group of antidepressants. It works on serotonin, a chemical messenger in the brain linked to mood and anxiety.

How is it different from other antidepressants?

The widest set of Japanese approvals of any SSRI (regular tablets): depression, panic disorder, OCD, social anxiety disorder, and PTSD
Two forms for depression: regular tablets, or Paxil CR, which releases the medicine gradually
Low levels in breast milk: it is one of the antidepressants often preferred during breastfeeding
Evening dosing: the Japanese label sets it after the evening meal, which places any drowsiness in the evening

What is it used for in Japan?

In Japan, the regular paroxetine tablets are approved for:

Depression
Panic disorder
Obsessive-compulsive disorder (OCD)
Social anxiety disorder
Post-traumatic stress disorder (PTSD)

The controlled-release tablet, Paxil CR, is approved for depression only.

How does it help?

By gradually increasing serotonin in the brain, it eases low mood, anxiety, panic, and obsessive symptoms over time. 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?

Paroxetine 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 paroxetine
Taking, or recently stopping, an MAO inhibitor (a medicine for depression or Parkinson's); these can't overlap
The medicine pimozide; the combination isn't allowed

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

Tamoxifen (a breast cancer medicine): paroxetine can make it less effective, and worse breast cancer outcomes have been reported with the combination
Other antidepressants, tramadol (a painkiller), migraine triptans, or lithium
Blood thinners, or regular painkillers like ibuprofen
Certain heart rhythm or blood pressure medicines (paroxetine can raise their levels)
A heart rhythm problem (including long QT), or heart disease
Liver problems, or severe kidney problems
Glaucoma
A history of seizures, or bipolar disorder
Past suicidal thoughts, or strong impulsivity: the label asks for closer monitoring
St John's Wort supplements
Pregnant, planning to be, or breastfeeding (see the section below)

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

Paroxetine is taken once a day, after the evening meal (that's how the Japanese label specifies it), which places any drowsiness in the evening.

If you miss a dose: take it when you remember, unless the next dose is close; in that case just skip. Never take a double dose to catch up
Early on: drowsiness, dizziness, and restlessness are seen mostly in the first weeks of treatment, and nausea can appear when you start; many of these ease as your body adjusts. Some can continue, so tell your doctor if they do
Agitation: if you notice unusual agitation, irritability, or feeling wired, contact your doctor promptly rather than waiting it out
Alcohol: avoid it while taking paroxetine; the Japanese label advises against drinking

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 (over 20%): seen mostly early in treatment, and the evening dose means much of it comes at night; if it carries into the day, tell your doctor
Nausea
Dizziness
Constipation
Dry mouth
Feeling more anxious or restless at first
Sexual side effects
Weight gain (less common)

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; paroxetine isn't addictive, but among the SSRIs it is one that particularly needs a planned, gradual stop. There's no craving and no urge to take more. Stopping too quickly, though, is noticeable with paroxetine: dizziness, tingling or brief electric-shock-like sensations, sleep problems including vivid dreams, anxiety, nausea, or headache can appear, usually within a few days of a missed or stopped dose. For most people these are mild to moderate and settle in about two weeks, though for some they are stronger or take two to three months or more to clear. So never stop suddenly on your own.

Tapering makes this manageable: the dose comes down in very small steps over weeks or months, with the pace slowing near the end, and if symptoms appear the answer is to step back up briefly and go slower. The Japanese label notes that these symptoms are not a sign of dependence. 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. Paroxetine can cause drowsiness or dizziness, so see how it affects you before driving, particularly when starting or changing the dose. The Japanese label asks for caution here, not a ban.

What about pregnancy and breastfeeding?

Talk to your doctor about pregnancy early; the Japanese label is more cautious with paroxetine than with sertraline or escitalopram. Paroxetine isn't banned in pregnancy. The label says it should be started during pregnancy only when the benefit is judged to outweigh the risk, and that if a pregnancy is found during treatment, it is stopped or switched unless continuing is judged the right course. The label also notes that overseas studies found a small increase in heart defects in babies exposed in early pregnancy. Any change is made gradually: never stop on your own on learning you're pregnant; sudden stops carry their own real risks. Breastfeeding on paroxetine is often possible in practice (very little passes into milk). Our guides to medication in pregnancy and medication while breastfeeding cover the details.