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. It belongs to the SSRI group of antidepressants. It works on serotonin, a chemical messenger in the brain linked to mood and anxiety, and it has been in worldwide use for decades.

How is it different from other antidepressants?

• The widest set of Japanese approvals of any SSRI: depression, panic disorder, OCD, social anxiety disorder, and PTSD
• A strong track record across the anxiety spectrum, not just low mood
• Decades of experience worldwide, so its effects are thoroughly understood
• Evening-friendly: its drowsiness can be turned into an advantage by taking it at night

What is it used for in Japan?

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

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, so we'd usually choose differently
• 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 history of seizures
• 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 conveniently folds its drowsiness into bedtime.

• 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
• The first week or two is when nausea and restlessness are most likely; they usually fade as your body adjusts
• Rarely, the early weeks bring the opposite of calm: unusual agitation, irritability, or feeling wired. If that happens, contact your doctor promptly rather than waiting it out

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 (over 20%): many people simply take it in the evening
• Nausea: mostly early on; taking it with food helps
• Dizziness
• Constipation
• Dry mouth
• Feeling a bit more anxious or restless at first; this usually passes as the medicine starts working
• 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; paroxetine isn't addictive, but of all the SSRIs it's the one that most needs a planned, gradual stop. There's no craving and no urge to take more. Stopping too quickly, though, is more noticeable with paroxetine than with most: dizziness, tingling or brief electric-shock-like sensations, and vivid dreams can appear, usually starting a few days after a missed or stopped dose. So never stop suddenly on your own.

Tapering makes this manageable: the dose comes down in very small steps over weeks, with the pace slowing near the end, and if symptoms appear the answer is to step back up briefly and go slower. This is not dependence, and it's entirely avoidable with a plan. 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.

What about pregnancy and breastfeeding?

This is the one antidepressant where the pregnancy conversation should happen extra early. Paroxetine isn't banned in pregnancy, but when a pregnancy is planned, doctors often prefer to build treatment on a different antidepressant, and any switch 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.