Side effects of zopiclone, including next-day effects

The most common side effects of zopiclone are a bitter or metallic taste, a dry mouth and feeling drowsy the next day. Less often it can cause nightmares, dizziness, headache or feeling sick. Rare but serious side effects include sleep-walking, hallucinations, low mood and allergic reactions, which need urgent medical advice.

This guide explains each side effect listed in the official UK product information for zopiclone, how often it happens, and what to do about it. It also covers the questions people search for most, such as weight gain, constipation and low mood. For an overview of the medicine itself, read our complete guide to zopiclone.

How common are the side effects of zopiclone?

The Summary of Product Characteristics (SmPC) for zopiclone 7.5 mg tablets sorts side effects by how often they were reported. No side effect is listed as “very common” (more than 1 in 10 people). Most people who take it for a short course have few or mild problems.

How often	Side effects listed in the SmPC
Common (up to 1 in 10 people)	Bitter taste, dry mouth, leftover drowsiness
Uncommon (up to 1 in 100)	Nightmares, agitation, dizziness, headache, nausea, vomiting, tiredness
Rare (up to 1 in 1,000)	Confusion, reduced sex drive, irritability, aggression, hallucinations, memory loss for events after a dose, breathlessness, itchy rash or hives, falls
Very rare (up to 1 in 10,000)	Swelling under the skin (angioedema), severe allergic reaction, mild changes in liver blood tests
Not known	Restlessness, delirium, delusions, anger, sleep-walking and other complex sleep behaviours, dependence, withdrawal, unsteadiness, tingling skin, poor memory or attention, slurred speech, double vision, slowed breathing, indigestion, muscle weakness, light-headedness

“Not known” means the frequency cannot be worked out from the available data. It does not mean these effects are common.

Common side effects and how to cope

Bitter or metallic taste

A bitter taste is one of the most typical zopiclone side effects. The patient information leaflet describes it as “a mild bitter or metallic taste in your mouth”.

The leaflet says to tell your doctor or pharmacist if it gets serious or lasts longer than a few days. They may suggest ways to manage it.

Dry mouth

Sipping water through the day may help. Tell your pharmacist if it does not settle.

Drowsiness and feeling dazed the next day

The NHS lists next-day tiredness, sleepiness, a dazed feeling and reduced alertness as common. This “hangover” feeling is covered in more detail below, because it affects driving.

Whatever the side effect, keep taking zopiclone as prescribed unless a doctor or pharmacist tells you to stop. Do not stop suddenly without advice.

Zopiclone side effects the next day, and driving

Zopiclone can still affect your brain and reactions the morning after you take it. You might not feel sleepy, yet your driving may be slower or less accurate.

A pooled analysis of four placebo-controlled driving studies by Leufkens and Vermeeren (2014) tested 101 healthy volunteers. After 7.5 mg at bedtime, highway driving was still impaired 10 to 11 hours later. The effect did not differ between men and women and did not increase with age up to 75.

New Zealand’s medicines regulator Medsafe warned prescribers in June 2014 that people may be impaired the next day without realising it. It noted that even small amounts of alcohol add to the risk.

What UK guidance says

• The NHS advises you not to drive, ride a bike or use machinery for 12 hours after taking zopiclone. If you still feel drowsy or dazed after that, wait until it passes.
• The SmPC warns that next-day impairment is more likely if you take it less than 12 hours before you need to be alert, take more than prescribed, or combine it with alcohol or other sedating medicines.
• Only take zopiclone when you can have a full night’s sleep of 7 to 8 hours, as the SmPC advises.

The drug-driving law

Under the GOV.UK drug-driving rules, it is illegal to drive if any medicine makes you unfit to drive, even one you are prescribed. A conviction brings a minimum one-year ban, an unlimited fine, up to 6 months in prison and a criminal record. GOV.UK notes that the specific drug-driving law does not cover Northern Ireland, but you can still be arrested there if you are unfit to drive. Our guide to controlled drugs in the UK explains more about driving and travelling with prescribed medicines.

Less common and rare side effects

Uncommon effects include nightmares, agitation, dizziness, headache, feeling or being sick, and tiredness. Tell your doctor or pharmacist if any of these get worse or last more than a few days.

The leaflet asks you to tell your doctor as soon as possible about these rarer effects:

• Memory loss (amnesia). Forgetting what happened after taking a dose. The SmPC says this is more likely if your sleep is interrupted or you go to bed later than planned after taking it.
• Hallucinations. Seeing or hearing things that are not there.
• Falls, especially in older people.
• Delusions (believing things that are not true) and low mood.

Zopiclone and hallucinations

Hallucinations are listed as rare. The SmPC groups them with other “paradoxical” reactions, such as restlessness, agitation, aggression and delirium. These reactions are more likely in older people. If they happen, the SmPC says zopiclone should be stopped, so contact your doctor.

Sleep-walking and other complex sleep behaviours

Some people have done things while not fully awake after taking zopiclone. Examples include sleep-walking, eating, making phone calls or driving, often with no memory of it afterwards.

The NHS lists this as a serious side effect. The SmPC says treatment should be stopped straight away if it happens, because of the risk to you and others. Alcohol, other sedating medicines and taking more than the prescribed dose may raise the risk. See our guide to zopiclone interactions for the medicines involved.

Regulators take this seriously across the Z-drug family. In April 2019 the US Food and Drug Administration added its strongest warning to eszopiclone, zaleplon and zolpidem after reports of serious injuries and deaths linked to these behaviours. Zopiclone itself is not sold in the US, but its UK warnings cover the same risk.

Can zopiclone cause depression?

Low mood is a possible side effect. The leaflet lists “feeling low or sad (depressed mood)” with a frequency that is not known. The NHS lists low mood, depression and thoughts of suicide or self-harm under serious side effects.

The SmPC also says zopiclone is not a treatment for depression and may hide its symptoms. The SmPC advises that if insomnia continues, its cause should be looked at again.

If your mood drops or you have thoughts of harming yourself, contact your GP or call NHS 111 now. If you feel you may act on these thoughts, call 999.

Does zopiclone cause weight gain or constipation?

Weight gain and constipation are not listed as side effects in the UK SmPC or patient leaflet for zopiclone. The NHS zopiclone pages do not mention them either.

The gut-related effects that are listed are nausea, vomiting and indigestion. If you notice a change in weight or bowel habit while taking zopiclone, mention it to your doctor. Another cause, or another medicine, may be responsible. You can also report it through the Yellow Card scheme.

Allergic reactions and breathing problems

Severe allergic reactions are very rare. Signs include a rash, swelling of the lips, face, tongue or throat, and trouble swallowing or breathing. The leaflet says to stop taking zopiclone and get help straight away if this happens.

Zopiclone can also slow breathing. The NHS says it may not be suitable if you have sleep apnoea, breathing problems or muscle weakness, and that alcohol can cause breathing problems and make it very hard to wake up.

Dependence and withdrawal

Your body can get used to zopiclone. That is why the SmPC says a course should not go beyond four weeks, including the time spent reducing the dose. Dependence and withdrawal are both listed as side effects.

Withdrawal symptoms listed in the SmPC include poor sleep coming back (rebound insomnia), anxiety and tremor. The NHS advises not to stop suddenly, as your doctor will reduce the dose gradually. Our zopiclone guide explains dependence in more detail, and our guide to coming off zopiclone covers withdrawal symptoms and how long they can last.

Who is more likely to get side effects, and how to lower the risk

Older people are more likely to have confusion, falls and paradoxical reactions. For this reason the SmPC sets a lower starting dose for them, as our guide to the zopiclone dose explains. Take zopiclone exactly as your prescriber tells you.

1. Take it just before bed, only when you can sleep for 7 to 8 hours.
2. Never take an extra dose in the same night.
3. Do not drink alcohol while taking it.
4. Tell your prescriber and pharmacist about every other medicine you take, especially other sleeping tablets, opioid painkillers or medicines that make you drowsy.
5. Read the leaflet that comes with your medicine every time.
6. Only get zopiclone on a prescription from a registered UK pharmacy. Our guide on how to check a UK online pharmacy shows what to look for.

Zopiclone is only meant for short-term use. Our insomnia guide explains the options.

This article is for information only and does not replace advice from your doctor or pharmacist. Read our medical disclaimer.