Lunesta Side Effects: What to Expect and When to Call Your Doctor

Lunesta (eszopiclone) is one of the most effective FDA-approved treatments for chronic insomnia, but it comes with a range of potential side effects that patients should understand before starting treatment. Some side effects are mild and manageable; others are serious enough to warrant stopping the medication. Here's what to expect.

The Boxed Warning: Complex Sleep Behaviors

Lunesta carries the FDA's most serious warning — a boxed warning — for complex sleep behaviors. This is the risk of getting out of bed while not fully awake and doing activities you're not conscious of, including:

Sleepwalking

Sleep-driving (driving a car while not fully awake — this has caused deaths)

Making phone calls, preparing and eating food, or having sex while asleep

People often have no memory of these events the next morning

Complex sleep behaviors can occur even at recommended doses, and even without alcohol or other medications.

If you or a family member notice any sleep-related behavior you don't remember, stop taking Lunesta and call your doctor immediately. Do not take another dose.

Common Side Effects of Lunesta

The following side effects are reported by many patients taking eszopiclone. They are generally mild to moderate and often improve as your body adjusts to the medication:

Unpleasant or bitter taste in the mouth — One of the most distinctive and common complaints about Lunesta. Some patients describe it as metallic or chemical. This is normal and not dangerous, but can be bothersome.

Headache — Common, particularly in the first few weeks of treatment.

Next-day drowsiness ("hangover" feeling) — Lunesta has a half-life of ~6 hours, and at the 3 mg dose, blood levels can remain high enough the morning after (7.5+ hours after taking it) to impair driving and other activities. This risk led the FDA to lower the recommended starting dose from 2 mg to 1 mg in 2014.

Dry mouth — Common, often goes away as your body adjusts.

Dizziness — Can increase fall risk, especially in elderly patients.

Nausea — Usually mild; taking the medication immediately before bedtime (not when sitting up) can minimize this.

Cold-like symptoms — Runny nose, cough, or other minor respiratory symptoms are occasionally reported.

Serious Side Effects: When to Call Your Doctor

Complex sleep behaviors — Any sleepwalking, sleep-driving, or activities done while not fully awake. Stop the medication and call immediately.

Severe allergic reaction — Hives, swelling of the face/lips/tongue/throat (angioedema), difficulty breathing. Seek emergency care immediately (call 911).

Abnormal thoughts or behaviors — Hallucinations, confusion, aggression, agitation, or unusual changes in behavior or mood. Contact your doctor promptly.

Worsening depression or suicidal thoughts — Lunesta may worsen depression in some patients. If you experience increased sadness, hopelessness, or thoughts of self-harm, call your doctor immediately or contact the 988 Suicide & Crisis Lifeline.

Memory loss — Short-term memory impairment, particularly if the medication is taken without getting a full 7-8 hours of sleep. Tell your doctor if this occurs.

Next-Day Impairment: A Special Warning

One of the most clinically important side effects of Lunesta — particularly at the 3 mg dose — is next-day impairment that patients often don't recognize in themselves. Studies found that even 7.5 hours after taking eszopiclone 3 mg, blood levels in some adults (particularly ages 25-40) remained high enough to impair driving, memory, and coordination.

The FDA lowered the recommended starting dose from 2 mg to 1 mg in 2014 precisely because of this concern. If you take the 3 mg dose, be especially careful about driving and operating machinery the morning after — even if you feel alert.

Who Is at Higher Risk for Side Effects?

Elderly patients (65+): Metabolize eszopiclone more slowly; at higher risk for next-day impairment, dizziness, and falls. Starting dose should be 1 mg; maximum dose is 2 mg.

Patients with severe hepatic impairment: Doubled systemic exposure to eszopiclone; maximum dose is 2 mg.

Patients who drink alcohol: Alcohol has an additive effect with eszopiclone, significantly increasing next-day impairment and the risk of complex sleep behaviors.

Patients on CYP3A4 inhibitors: Certain antifungals (ketoconazole), antibiotics (clarithromycin), and antivirals (Paxlovid) can significantly increase eszopiclone blood levels, amplifying side effects.

The Bottom Line

Lunesta is effective for many patients with insomnia, but it requires thoughtful use. Taking only the lowest effective dose, never combining with alcohol, and always getting a full 7-8 hours of sleep after taking it substantially reduce your risk of side effects. For a complete guide on what interacts with Lunesta, see Lunesta Drug Interactions: What to Avoid and What to Tell Your Doctor.