Venlafaxine (Effexor SR)

What is venlafaxine?

Venlafaxine is known as Effexor in the United States, Efexor XL in the UK, and Effexor SR in Japan (イフェクサーSR on Japanese packaging); it's all the same medicine. It belongs to the SNRI group of antidepressants: it works on two chemical messengers in the brain, serotonin and noradrenaline, linked to mood, anxiety, and energy. In Japan it comes as a slow-release capsule taken once a day.

How is it different from other antidepressants?

• The medicine with Japan's generalized anxiety disorder (GAD) approval, which no other antidepressant here holds
• Works on two systems at once: serotonin for mood and worry, noradrenaline for drive and energy
• Builds stepwise: the dose is raised gradually, so treatment can be tuned to your response
• Once-daily slow-release capsule, simple to live with

What is it used for in Japan?

• Depression
• Generalized anxiety disorder (GAD)

How does it help?

By gradually increasing serotonin and noradrenaline in the brain, it eases low mood, worry, and loss of energy over time. The full effect often takes a few weeks, and the dose is usually stepped up gradually. 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 venlafaxine
• Taking, or recently stopping, an MAO inhibitor (a medicine for depression or Parkinson's); these can't overlap
• Severe liver problems
• Severe kidney problems, or being on dialysis

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 (including rhythm problems)
• Other antidepressants, tramadol (a painkiller), migraine triptans, or lithium
• Blood thinners, or regular painkillers like ibuprofen
• A history of seizures
• St John's Wort supplements
• Pregnant, planning to be, or breastfeeding (see the section below)

Your doctor may also check your blood pressure now and then, as venlafaxine can raise it slightly in some people, mainly at higher doses.

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

Venlafaxine is taken once a day, after food, and the capsule is swallowed whole, without crushing or chewing; it's designed to release slowly.

• 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
• The first week or two is when nausea is most likely; taking it after food helps, and it usually fades
• Rarely, the early weeks bring unusual agitation or feeling wired. If that happens, contact your doctor promptly

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.

• Nausea (just under 30%): taking it after food helps, and it usually fades within a couple of weeks
• Drowsiness (around 25%): mostly early on
• Dizziness (around 20%): usually early; stand up slowly
• Dry mouth (around 20%): usually mild
• Headache (around 15%)
• Trouble sleeping (around 15%)
• Palpitations (around 10%)
• Sweating
• 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; venlafaxine 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 is more noticeable with SNRIs: dizziness, a "buzzing" or electric sensation, and flu-like feelings can appear, usually starting a day or two after stopping. So never stop suddenly on your own, and try not to run out mid-supply.

Tapering makes this manageable: the dose comes down in small steps, staying a week or two at each, with a gentler pace near the end; if symptoms appear, stepping back up briefly and slowing down solves it. 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. Venlafaxine can cause drowsiness or dizziness, so see how it affects you before driving, particularly when starting or raising the dose.

What about pregnancy and breastfeeding?

Often, treatment can continue through both. Neither pregnancy nor breastfeeding is an automatic reason to stop; the decision is made individually with your doctor, weighing the real risks of untreated illness. Never stop on your own on learning you're pregnant; with venlafaxine especially, sudden stops are uncomfortable. Our guides to medication in pregnancy and medication while breastfeeding cover the details.