Zopiclone vs Eszopiclone: Same Molecule, Different Doses and Different Countries

Zopiclone and eszopiclone are not two similar drugs. They are one drug, sold two different ways, in two mostly non overlapping sets of countries, at doses that differ by roughly a factor of two and a half.

Almost every point of confusion about these two medicines traces back to that single fact. This guide explains the chemistry in plain terms, gives the dose conversion, sets out what the trial data shows about side effects at each dose, and covers which one you can actually get depending on where you live.

The chemistry in one paragraph

Zopiclone is a chiral molecule, meaning it exists in two mirror image forms that cannot be superimposed on each other, the way a left hand cannot be superimposed on a right. Standard zopiclone is a racemic mixture: a one to one blend of both mirror images. The hypnotic activity at the GABA-A receptor sits almost entirely in one of those two forms, the S enantiomer. The other half contributes little sedation but is still absorbed, metabolised and capable of causing side effects.

Eszopiclone is that active S half, isolated and sold on its own. The prefix is literally a contraction of the chemical designation. So a person taking eszopiclone is taking the working part of zopiclone without the passenger.

The dose conversion

Because a 7.5 mg zopiclone tablet contains roughly 3.75 mg of the active S form, the doses line up like this.

Zopiclone (racemic)	Approximate eszopiclone equivalent	Typical patient group
7.5 mg	3 mg	Standard adult dose
3.75 mg	1 mg to 2 mg	Adults over 65, liver impairment, sedative sensitive

This is an approximation, not a bioequivalence statement. The two drugs are licensed separately, have separate prescribing information and are not interchangeable at the pharmacy counter. The conversion is useful for understanding why a 3 mg tablet of one drug and a 7.5 mg tablet of the other are described in the same terms, not for swapping one for the other without a prescriber.

Where you can actually get each one

This is the part that catches people out, because the two drugs barely overlap geographically.

Market	Zopiclone	Eszopiclone
United States	Never FDA approved	Approved as Lunesta, Schedule IV controlled substance
United Kingdom	Licensed, Class C controlled drug	Not licensed
Australia	Licensed, Schedule 4	Not licensed
Canada	Licensed, prescription only	Not marketed
India	Both manufactured for export	Both manufactured for export

So an American reading British sleep advice will find a drug that does not exist at home, and a British patient reading American advice will find a 3 mg dose that no UK prescriber can write. Neither source is wrong. They are describing different halves of the same molecule.

Eszopiclone dosing, exactly as the FDA label sets it

The eszopiclone label is unusually specific, and every clause in it exists because of a reported harm.

• Starting dose is 1 mg, taken immediately before bedtime, with at least seven to eight hours remaining before the planned time of waking
• The dose may be raised to 2 mg or 3 mg if clinically indicated, and 3 mg is the absolute daily maximum
• Older or debilitated patients should not exceed 2 mg
• Severe hepatic impairment, or taking a potent CYP3A4 inhibitor, caps the dose at 2 mg
• Do not take it with or immediately after a meal. A heavy high fat meal slows absorption and reduces the effect on how quickly you fall asleep

The label is explicit that the higher morning blood levels which follow a 2 mg or 3 mg dose increase the risk of next day impairment of driving and other activities requiring full alertness. That is not a generic caution. It is the specific reason 1 mg is the starting point rather than 2 mg.

What side effects look like at each dose

Eszopiclone has something zopiclone does not: a dose stratified adverse reaction table from placebo controlled trials. Comparing the numbers by dose is far more useful than reading an undifferentiated list of possible effects.

The figures below come from a six week placebo controlled trial in non elderly adults, with 99 people on placebo, 104 on 2 mg and 105 on 3 mg.

Adverse reaction	Placebo	Eszopiclone 2 mg	Eszopiclone 3 mg
Unpleasant taste	3 percent	17 percent	34 percent
Headache	13 percent	21 percent	17 percent
Somnolence	3 percent	10 percent	8 percent
Respiratory infection	3 percent	5 percent	10 percent
Dizziness	4 percent	5 percent	7 percent
Dry mouth	3 percent	5 percent	7 percent
Rash	1 percent	3 percent	4 percent
Hallucinations	0 percent	1 percent	3 percent
Depression	0 percent	4 percent	1 percent
Anxiety	0 percent	3 percent	1 percent

Read the taste row again. Going from 2 mg to 3 mg doubles the chance of the bitter metallic taste, from roughly one person in six to one in three. The label singles this out as the clearest dose response relationship in the whole dataset. If taste is the reason someone is considering stopping, dropping from 3 mg to 2 mg is the obvious first move.

The elderly picture is different again. Pooled two week trials in adults aged 65 to 86, with 208 on placebo, 72 on 1 mg and 215 on 2 mg, showed unpleasant taste at 0 percent, 8 percent and 12 percent respectively, dry mouth at 2, 3 and 7 percent, and dizziness at 2, 1 and 6 percent. Headache was effectively identical to placebo at 14, 15 and 13 percent.

One more figure is worth knowing before committing to long term use. In the six month adult study, 12.8 percent of 593 people on 3 mg stopped because of an adverse reaction, against 7.2 percent of 195 on placebo. The gap is real but modest, and it is one of the few places where controlled data past a few weeks exists for any hypnotic.

The boxed warning applies to both

Eszopiclone carries a boxed warning in the United States for complex sleep behaviours: sleepwalking, sleep driving, and doing other things while not fully awake. Some of these events have caused serious injury and death.

The instruction that follows is absolute rather than graded. If a patient experiences a complex sleep behaviour, the drug is discontinued immediately, and having experienced one is a formal contraindication to ever taking it again. There is no dose reduction option.

Zopiclone does not carry a formal boxed warning in the UK because the regulatory format differs, but the same behaviours are documented for it and the same practical rule applies. This is a class effect, not a Lunesta specific problem.

Is one better than the other?

On efficacy, the honest answer is that no properly powered head to head trial has settled it, and the theoretical argument that removing the inactive enantiomer improves the side effect profile has never been convincingly demonstrated in patients.

What the indirect evidence does show is that both sit in the same tier. A network meta-analysis of 170 trials and 47,950 participants found benzodiazepines, eszopiclone, zolpidem and zopiclone all more effective than placebo and all more effective than melatonin, ramelteon and zaleplon. Neither Z drug pulled clearly ahead of the other.

Eszopiclone does have one genuine evidence advantage: duration of study. A separate network meta-analysis found eszopiclone ranked highly for subjectively measured sleep onset latency and Insomnia Severity Index not only at four weeks but at three months and six months, which is longer follow up than most hypnotics can offer. The same analysis found eszopiclone had fewer discontinuations for any cause than ramelteon, with an odds ratio of 0.71.

That does not make eszopiclone a long term drug. Every major guideline still puts cognitive behavioural therapy for insomnia first and positions medication as short term support.

Practical differences that matter day to day

	Zopiclone	Eszopiclone
Standard adult dose	7.5 mg	3 mg maximum, 1 mg start
Reduced dose group	3.75 mg	2 mg maximum
Half life	About 5 hours	About 6 hours
Food interaction	Heavy meals slow absorption	Label specifically says not with or immediately after a meal
Bitter taste	Very common	Very common, clearly dose related
Licensed duration	Up to 4 weeks in UK practice	No fixed limit on the US label, but guidelines advise short term use
Controlled status	Class C, Schedule 4 Part I in UK	Schedule IV in the US

The half life difference is small on paper and matters more than it looks for anyone who has to be alert early. Both drugs need a full seven to eight hours in bed. Neither is a middle of the night rescue option.

Stopping either one

Tapering advice is identical for both, because dependence is a class property rather than a molecule specific one. A 2025 European expert consensus on switching and deprescribing hypnotics recommended reductions of 10 to 25 percent per week for benzodiazepines and Z drugs, with the schedule slowed whenever a step proves difficult.

The same consensus noted something useful for anyone stuck: eszopiclone itself is one of the agents that can be used within a cross taper to help someone come off a benzodiazepine or another Z drug. The full week by week approach is set out in our zopiclone dosage and duration guide.

Which one should you ask about?

In most cases the question answers itself, because only one of the two is licensed where you live. Where both are genuinely available:

• If bitter taste is the main obstacle, the dose stratified data on eszopiclone gives you a clear lever, since dropping from 3 mg to 2 mg roughly halves the risk
• If next day grogginess is the main obstacle, the lower end of either drug is the answer, and 1 mg eszopiclone or 3.75 mg zopiclone is the place to start
• If cost matters, generic zopiclone is generally the cheaper of the two per treated night
• If you have liver impairment or take a CYP3A4 inhibitor, both need dose reduction, and this needs to be discussed rather than assumed

The insomnia treatment page covers where both sit against the non drug options. Products we carry at licensed strengths include zopiclone 7.5 mg, zopiclone 3.75 mg, eszopiclone 3 mg, eszopiclone 2 mg and eszopiclone 1 mg.

References

• FDA prescribing information for eszopiclone tablets: boxed warning (Complex Sleep Behaviors), section 2 (Dosage and Administration), section 4 (Contraindications), section 6.1 (Clinical Trials Experience, Tables 1 and 2)
• DailyMed label for eszopiclone tablets, description and clinical pharmacology sections
• De Crescenzo F et al. Comparative effects of pharmacological interventions for the acute and long-term management of insomnia disorder in adults: a systematic review and network meta-analysis. PMID 35843245
• Rosenberg R et al. Comparative efficacy of lemborexant and other insomnia treatments: a network meta-analysis. PMID 34121443
• Palagini L et al. Clinical practice guidelines for switching or deprescribing hypnotic medications for chronic insomnia. PMID 39923608

Medical disclaimer: this article is for information only and is not medical advice. Zopiclone and eszopiclone are prescription medicines and controlled substances in several countries. They are licensed separately and are not interchangeable without a prescriber. Do not start, switch or stop either drug on the basis of anything written here.