Quetiapine (Seroquel)

What is quetiapine?

Quetiapine is known as Seroquel in the United States, the UK, and Japan alike (セロクエル on Japanese packaging). It's a medication in the family called antipsychotics: it works mainly by calming overactive dopamine signalling in the brain, and it also acts on serotonin, which helps it work more smoothly than the older generation. It has a sedating effect, so drowsiness is common.

How is it different from other antipsychotics?

• Calming: its sedating effect is one of its main characteristics
• Tablets or fine granules: two forms are available in Japan, so the form can suit you
• Started low and raised in steps: the dose is adjusted gradually to what you need
• The same medicine in several countries: it is prescribed as Seroquel in the United States, the UK, and Japan, which helps if you move between them

What is it used for in Japan?

Schizophrenia.

How does it help?

By calming overactive dopamine signalling, it eases symptoms over time. The full effect builds over a few weeks; keep taking it as prescribed even if you don't notice a change straight away.

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:

• Diabetes, or a history of diabetes: quetiapine isn't used in this case, as it can raise blood sugar to dangerous levels
• A past allergic reaction to quetiapine
• Being in a coma, or under the strong influence of sedating medicines such as barbiturates
• Treatment with adrenaline (epinephrine), except emergency allergy injections and some dental anesthesia

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

• A family history of diabetes, borderline blood sugar, or being overweight
• Heart or blood-vessel disease, low blood pressure, or a heart rhythm problem
• Other sedating medicines, or drinking alcohol
• Some antifungal medicines like itraconazole, or epilepsy medicines like carbamazepine or phenytoin (they change quetiapine's level)
• A history of seizures
• Liver problems (a lower starting dose is used)
• Being older
• Pregnant, planning to be, or breastfeeding (see the section below)

Even without diabetes, your blood sugar and weight are checked during treatment.

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

Quetiapine is usually taken two or three times a day, as your doctor directs.

• If you miss a dose: take it when you remember, unless the next one is close; in that case just skip. Never take a double dose to catch up
• Light-headedness on standing: most likely at the start; get up slowly
• Drowsiness: if it is a problem, the timing of the doses can be adjusted with your doctor

What side effects should I expect?

Most are manageable and settle as your body adjusts, and many can be eased with a counter-medicine if needed. Not everyone gets them; the rough figures below just give a sense of how common each one is.

• Trouble sleeping (just under 20%): tell your doctor; how the doses are spread through the day can be adjusted
• Drowsiness (around 15%): tell your doctor if it is a problem, as the timing of the doses can be adjusted
• Restlessness or tremor: tell your doctor; adding a medicine that counters this is an option
• Feeling anxious or irritable
• Tiredness, or reduced appetite
• Headache
• Dizziness, or light-headedness on standing: get up slowly at first
• Constipation
• Dry mouth
• Weight gain: weight is checked regularly, and diet and exercise help

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, three things that are rare (most people never experience them) but good to know:

• A lot of thirst, drinking, or passing urine much more than usual: these can signal a serious rise in blood sugar; stop the medicine and see a doctor straight away. The routine blood sugar checks are there to catch this early
• Weakness, cold sweats, shakiness, or unusual drowsiness or confusion: blood sugar can sometimes drop too low instead; stop the medicine and see a doctor straight away
• High fever, muscle stiffness, and confusion together, in about 2 in 1,000 people: get medical care promptly; recognised early, it's manageable

Will I become dependent? How do I stop safely?

No; quetiapine isn't addictive and doesn't cause cravings, but it still shouldn't be stopped suddenly. Stopping abruptly, or cutting the dose quickly, can bring withdrawal symptoms such as sleeplessness, nausea, headache, or vomiting, and coming off too early can let the illness return. So the decision and the pace are planned with your doctor, with the dose reduced gradually; don't stop it on your own, even when you feel well.

Can I drive while taking it?

The Japanese label advises against driving while taking it. Quetiapine can cause drowsiness and slow your attention and reactions, and the label here instructs that patients on it shouldn't drive or operate dangerous machinery. Discuss your own situation with your doctor.

What about pregnancy and breastfeeding?

Treatment can continue in pregnancy when the benefit is judged to outweigh the risk; the decision is individual. Untreated illness carries real risks in pregnancy too, so this is a planning conversation, not an automatic stop; never stop on your own on learning you're pregnant. If it is used late in pregnancy, the newborn is watched for signs such as poor feeding, sleepiness or stiffness. Breastfeeding is decided case by case. Our guides to medication in pregnancy and medication while breastfeeding cover the details.