Flexeril (Cyclobenzaprine)

Description

Flexeril, which is also known by its generic name Cyclobenzaprine, is a medicine used to help relieve muscle spasms. It works by affecting the brain and nerves to relax muscles that are strained or overworked. Flexeril is classified as a skeletal muscle relaxant that is mostly prescribed to help with pain from muscle injuries like strains and sprains. Doctors usually suggest taking this medication along with rest and physical therapy for the best results in recovering from muscle problems.

Directions

When taking Flexeril, you should swallow the medicine with or without food as your doctor advises. Usually, adults take a dose of 5 to 10 milligrams three times a day. However, the amount you need might change based on how you respond to the treatment. It’s important to stick to a regular schedule and not take more than what your doctor prescribed or for longer than advised. A Flexeril dose usually starts working within 20 to 30 minutes, and its effects may improve over the next week or so.

Ingredients

The active ingredient in Flexeril is Cyclobenzaprine.

Contraindications

Avoid taking or using this medication if any of the following apply:

• Allergy to Cyclobenzaprine or any ingredient in Flexeril
• Recent heart attack
• Heart arrhythmias or blockages
• Congestive heart failure
• Hyperthyroidism
• Current use of monoamine oxidase inhibitors (MAOIs) or use within the past 14 days
• Severe liver impairment

Cautions

• Before starting treatment with Flexeril, be sure to inform your healthcare provider if you have:
• Any existing health conditions
• Any allergies
• A list of all medications you are currently taking
• Whether you are pregnant or breastfeeding

• Flexeril may cause a life-threatening condition called serotonin syndrome, especially when combined with certain medications like SSRIs, SNRIs, tricyclic antidepressants (TCAs), tramadol, bupropion, or MAO inhibitors. Symptoms include confusion, agitation, hallucinations, sweating, rapid heartbeat, muscle stiffness, and nausea. Stop the medication and seek immediate medical attention if these symptoms occur.
• Flexeril should never be used with MAO inhibitors due to the risk of severe interactions.
• Flexeril enhances the effects of alcohol, barbiturates, and other central nervous system (CNS) depressants, potentially causing excessive sedation.
• If you have mild liver impairment, Flexeril should be started at a lower dose (5 mg) and increased gradually. It is not recommended for patients with moderate to severe liver impairment.
• Flexeril is related to tricyclic antidepressants, which can cause heart rhythm issues, tachycardia, or even myocardial infarction. Let your doctor know if you have any heart conditions.
• Flexeril may impair your ability to operate machinery or drive. Elderly patients are more susceptible to side effects such as confusion, hallucinations, or falls.
• Flexeril is classified as Pregnancy Category B, meaning there is no evidence of harm in animal studies, but human studies are limited. Consult your doctor if you are pregnant or breastfeeding.
• Safety and effectiveness in children under 15 years old have not been established.
• The elderly may have higher blood levels of Flexeril and increased risks of adverse effects. Doses should start at 5 mg and be adjusted cautiously.
• Use Flexeril with caution if you have a history of urinary retention, glaucoma, or are taking anticholinergic medications, as it may worsen these conditions.
• Store Flexeril at room temperature and keep it out of reach of children.
• Inform your doctor of all medications you are taking, as Flexeril may interact with other drugs and reduce their effectiveness or increase side effects.

Side Effects

In clinical trials, the most common side effects of Flexeril included drowsiness (29%), dry mouth (21%), and fatigue (6%). These effects were more common with higher doses. Other reported side effects, occurring in 1% to 3% of patients, included dizziness, nausea, constipation, diarrhea, and upper respiratory symptoms. Headache and nervousness were also observed but were less frequent.

Rare but serious side effects have been reported, including allergic reactions (such as rash, angioedema, and anaphylaxis), heart rhythm issues, and serotonin syndrome. Gastrointestinal issues like liver dysfunction and hepatitis, as well as psychiatric symptoms such as hallucinations, anxiety, or confusion, have also been noted. If you experience severe reactions like chest pain, difficulty breathing, or significant mood changes, seek medical attention immediately.

References

1. Flexeril (Cyclobenzaprine) Product Monograph. Fort Washington, PA: McNeil Consumer Healthcare; 2013.
2. Flexeril (Cyclobenzaprine) Drug Label Information. Grover Beach, CA: H. J Harkins Company Inc; 2017.

About Dr. Gerardo Sison (Page Author)

An honors graduate of the University of Florida, Dr. Sison started his pharmacy career in a community setting, extending his services to hospitals and clinics over time. He has also worked in medication therapy management, advising patients on proper medication use for their chronic health conditions. Read More....