Flexabenz ER
✅ Relieves muscle spasms
✅ Reduces muscle stiffness
✅ Improves mobility
✅ Alleviates musculoskeletal pain
✅ Enhances physical therapy effectiveness
Flexabenz ER contains Cyclobenzaprime.
✓ Medically reviewed by Morgan Ellis — Pharmacy Researcher · 8 years experience · Last reviewed: May 2026
⚡ Quick Answer — What is Flexabenz ER?
Flexabenz ER is a cyclobenzaprine 15 mg extended-release capsule used as a short-course adjunct for acute musculoskeletal muscle spasm. It offers once-daily dosing with smoother plasma levels and typically less peak-related drowsiness than immediate-release cyclobenzaprine. Usual adult dose is one 15 mg capsule once daily for 2 to 3 weeks maximum; 30 mg once daily may be used in patients who need more effect and tolerate the 15 mg dose well.
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Flexabenz ER 15 mg is the extended-release capsule form of cyclobenzaprine, designed for once-daily oral administration. The ER formulation releases cyclobenzaprine gradually over 24 hours, giving a smoother and more prolonged plasma level than the 5 mg immediate-release tablet dosed three times daily. This has two clinical benefits: simpler adherence (one dose a day) and fewer dose-related peak side effects (lower peak drowsiness, lower peak anticholinergic effect).
Like all cyclobenzaprine formulations, Flexabenz ER is intended as a short-course treatment (2–3 weeks) for acute painful muscle spasm associated with musculoskeletal injury. It is not a chronic pain medication and is not useful for spasticity from upper motor neuron disease.
What Is Flexabenz ER Used For?
- Acute low back pain with muscle spasm
- Acute neck pain and cervical strain
- Muscle strain of the shoulder, trunk, or limb
- Post-traumatic muscle spasm (whiplash, soft-tissue injury)
- Myofascial pain syndrome (adjunct)
- Fibromyalgia-associated muscle pain and sleep disturbance (off-label, short courses)
How Does Flexabenz ER Work?
The active molecule, cyclobenzaprine, acts at the brainstem (primarily locus coeruleus) to reduce descending excitatory drive to spinal alpha motor neurons. This lowers the tonic muscle spasm that accompanies painful musculoskeletal injury. The ER capsule technology spreads the delivery of the full dose across 12–24 hours, flattening the plasma peak and giving steady cover.
Flexabenz ER Dosing
- Starting dose: 15 mg once daily, with or without food
- Increase: to 30 mg once daily (two 15 mg capsules) if the 15 mg dose is tolerated but not fully effective
- Duration: up to 2 to 3 weeks
- Elderly: avoid or use the 5 mg immediate-release form instead — ER cyclobenzaprine at 15 mg is generally not recommended in patients > 65 years
- Mild hepatic impairment: not recommended
- Moderate or severe hepatic impairment: contraindicated
Swallow Flexabenz ER capsules whole. Do not open, crush, or chew — this destroys the extended-release matrix and converts a 24-hour dose into an immediate burst, raising peak drowsiness and anticholinergic load.
Many patients take the capsule in the evening to use the drowsiness for sleep.
Driving and CNS safety for Flexabenz ER. Centrally-acting muscle relaxants cause drowsiness, dizziness, and slowed reaction time — especially in the first few days of treatment. Do not drive, operate machinery, or make safety-critical decisions until you know how you react to this medicine. The effect is stronger with alcohol, opioid pain medication, sleeping tablets, or anti-anxiety medication — avoid these combinations unless your doctor has cleared them. Muscle relaxants are short-course medicines — typically used for 1–3 weeks at the start of a musculoskeletal injury while physiotherapy and exercise do the longer-term work.
Who Should Not Take Flexabenz ER?
- Known hypersensitivity to cyclobenzaprine
- Concurrent MAOI use or within 14 days of stopping one
- Acute post-myocardial infarction period
- Heart block or significant arrhythmia
- Congestive heart failure
- Hyperthyroidism
- Mild, moderate, or severe hepatic impairment (ER form is contraindicated in all hepatic impairment per label)
- Angle-closure glaucoma
- Significant urinary retention or prostatic obstruction
- Age > 65 years (use immediate-release 5 mg instead)
Side Effects
- Very common: drowsiness, dry mouth, dizziness, fatigue
- Common: headache, nausea, constipation, urinary retention, blurred vision, mild palpitations
- Uncommon: confusion (especially if taken in the elderly), raised liver enzymes, skin rash
- Rare but serious: serotonin syndrome with serotonergic drugs (SSRIs, SNRIs, tramadol, MAOIs), cardiac arrhythmias, severe hepatotoxicity
Drug Interactions
- MAOIs — absolute contraindication
- SSRIs, SNRIs, tramadol, triptans — serotonin syndrome risk
- Alcohol, opioids, benzodiazepines — additive CNS depression
- Anticholinergic drugs — additive anticholinergic load
- CYP1A2/CYP3A4 inhibitors — raise cyclobenzaprine exposure
Ordering & Delivery
MedsBase offers worldwide shipping on every order. Orders are dispatched in discreet packaging and arrive in branded manufacturer packs. If your preferred pack size is out of stock, contact customer support for an ETA.
Medical disclaimer. The information on this page is provided for general education only. It is not a substitute for advice from your own doctor or pharmacist. Talk to a qualified healthcare professional before starting, stopping, or changing therapy, especially if you have a history of ulcer disease, heart disease, kidney disease, asthma, liver disease, or are pregnant.
Frequently Asked Questions
What is Flexabenz ER used for?
Flexabenz ER (cyclobenzaprine 15 mg extended release) is used for acute muscle spasm from musculoskeletal injury — low back pain, neck pain, torticollis, and muscle strain. Once-daily dosing with 24-hour cover.
How is Flexabenz ER different from Flexabenz 5 mg?
Same molecule (cyclobenzaprine). Flexabenz 5 mg is immediate release, dosed 3 times a day. Flexabenz ER is 15 mg extended release, dosed once daily — smoother plasma profile, simpler schedule, usually less peak drowsiness.
Can I crush or open the Flexabenz ER capsule?
No. The extended-release mechanism must stay intact. Crushing or opening converts the full 15 mg into an immediate dose, which raises peak sedation and anticholinergic side effects.
How long does Flexabenz ER take to work?
Muscle-relaxing effect usually begins within 1–2 hours of the first dose; full effect builds over 3–5 days of daily use.
Should I take Flexabenz ER in the morning or at bedtime?
Either is acceptable. Many patients take it in the evening to use the drowsiness for sleep; daytime dosing is fine once you know how you react.
How long can I take Flexabenz ER?
Up to 2 to 3 weeks. It is not intended for long-term use.
Is Flexabenz ER safe in older adults?
The 15 mg ER dose is generally not recommended in patients over 65 — anticholinergic and cardiac effects are stronger and clearance is slower. The 5 mg immediate-release form, at low doses, is the preferred option in the elderly.
Can I take Flexabenz ER with an SSRI?
Use with caution. Combined use raises the risk of serotonin syndrome. Discuss with your doctor; watch for agitation, confusion, shivering, diarrhoea, rapid heart rate, or fever.
Can I drink alcohol while taking Flexabenz ER?
Avoid alcohol. The combination greatly increases drowsiness and fall risk.
Is Flexabenz ER addictive?
Cyclobenzaprine is not a controlled substance and is not considered to cause meaningful physical dependence. Take as prescribed.
What if I miss a dose?
Take it when you remember unless your next dose is due within 12 hours — then skip. Never double up.
See also: tolperisone alternative (Synaptol) — tolperisone alternative when cyclobenzaprine sedation is unacceptable — centrally acting without H1 antihistamine drowsiness.
Where Flexabenz ER (cyclobenzaprine extended-release) delivers strong relief but pronounced anticholinergic side effects, Synaptol (tolperisone 50 mg) offers a non-sedating substitute for spasticity and musculoskeletal spasm without the dry mouth or daytime grogginess.
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| Strength | 15 mg |
|---|---|
| Quantity | 30 Tablet/s, 60 Tablet/s, 90 Tablet/s, 180 Tablet/s |
Flexabenz ER
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