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

Flurazepam is effective for insomnia but carries a unique set of side effects related to its long-acting nature. Because its active metabolite can remain in your bloodstream for 40–114 hours after a single dose, the effects of flurazepam extend well beyond bedtime — sometimes into the next day and beyond, especially with nightly use. Understanding what to expect helps you use it safely and recognize when something needs medical attention.

Common Side Effects of Flurazepam

These side effects are experienced by many patients, particularly early in treatment or when dosage is increased:

Next-day drowsiness ("hangover effect"): The most characteristic side effect of flurazepam. Because of its long-acting metabolite, residual sedation often persists into the next morning and afternoon, especially when the drug first accumulates in your system over the first week of nightly use.

Dizziness and lightheadedness: Common, particularly in elderly patients. Can increase fall risk substantially when rising from bed at night.

Ataxia (unsteadiness/staggering): Impaired balance and coordination, especially in the first hours after taking the medication and upon waking.

Memory impairment (anterograde amnesia): Flurazepam can cause difficulty forming new memories, particularly during the night and morning hours. Some patients don't recall activities they performed after taking the drug.

Headache: Mild headaches are reported by some patients.

Gastrointestinal symptoms: Nausea, upset stomach, heartburn, constipation, and diarrhea have been reported.

Muscle weakness: General weakness and fatigue are common, especially when starting treatment.

Serious Side Effects — Call Your Doctor Promptly

Sleep-driving and complex sleep behaviors: Some patients have driven cars, prepared food, made phone calls, or had sex while not fully conscious — with no memory of the event. If this happens, stop flurazepam and contact your doctor immediately.

Paradoxical agitation: In some patients — particularly the elderly — flurazepam can cause increased agitation, aggression, confusion, restlessness, or disinhibition rather than sedation.

Signs of physical dependence: If you feel you cannot sleep at all without flurazepam, notice increasing anxiety, or feel the need to take more to get the same effect, these may be signs of dependence. Discuss with your doctor.

Suicidal thoughts or worsening mood: Benzodiazepines can worsen depression and in rare cases may increase suicidal ideation. Contact your doctor right away if you notice mood changes or thoughts of self-harm.

Cholestatic jaundice (liver injury): Very rare, but reported cases of flurazepam-related liver injury exist. Symptoms include yellowing of the skin or eyes, dark urine, fatigue, or right-sided abdominal pain. Seek care immediately.

Emergency Warning Signs — Go to the ER or Call 911

Slow, shallow, or difficult breathing — especially after combining with alcohol or opioids

Extreme drowsiness, unresponsiveness, or loss of consciousness

Severe allergic reaction: hives, swelling of the face/lips/tongue/throat, difficulty swallowing or breathing

Seizures (especially during or after discontinuation)

The Boxed Warning: What You Need to Know

The FDA requires all benzodiazepines to carry a Boxed Warning — the most serious warning level — covering two key risks:

Combined use with opioids: Using flurazepam with any opioid pain medication (oxycodone, morphine, fentanyl, codeine, etc.) can cause profound sedation, respiratory depression, coma, and death. Never combine these without your doctor explicitly approving and monitoring the combination.

Abuse, misuse, addiction, and withdrawal: Flurazepam carries risk for physical dependence even at prescribed doses. Stopping suddenly can cause life-threatening withdrawal reactions including seizures. Always taper under medical supervision.

Special Populations: Who Needs Extra Caution

Elderly patients: Listed on the Beers Criteria as potentially inappropriate. Higher risk of falls, fractures, cognitive impairment, and over-sedation. Dose is limited to 15 mg.

Pregnancy: Contraindicated. Can cause fetal harm and neonatal withdrawal syndrome.

Liver disease: Flurazepam is extensively metabolized in the liver. Impaired liver function increases drug accumulation and toxicity risk.

Sleep apnea: Flurazepam can worsen breathing during sleep in patients with uncontrolled sleep apnea.

For a full list of drug interactions, see our Flurazepam Drug Interactions guide. If you can't find flurazepam at your pharmacy, medfinder can help you locate it near you.