Flexeril (cyclobenzaprine hydrochloride) is a centrally acting skeletal muscle relaxant indicated as an adjunct to rest and physical therapy for the relief of muscle spasm associated with acute, painful musculoskeletal conditions. It works by acting primarily within the central nervous system at the brain stem to reduce tonic somatic motor activity, influencing both gamma and alpha motor systems. Clinical efficacy is demonstrated through improved patient mobility, reduced pain, and increased range of motion, making it a valuable component in short-term management protocols. Proper diagnosis and supervision are essential for optimal therapeutic outcomes.

Features

• Active ingredient: Cyclobenzaprine hydrochloride
• Available in 5 mg and 10 mg oral tablets
• Rapid onset of action, typically within one hour
• Short-term use recommendation (up to two or three weeks)
• Central nervous system-mediated mechanism of action
• Bioavailability approximately 55% with extensive first-pass metabolism
• Protein binding: 93%
• Half-life: 18 hours (range 8-37 hours) for immediate-release formulation

Benefits

• Effectively reduces acute muscle spasm and associated local pain
• Facilitates earlier implementation of physical therapy and rehabilitation
• Improves range of motion and functional mobility
• Reduces muscle stiffness and tenderness
• May decrease need for additional analgesic medications when used appropriately
• Supports faster return to normal activities when combined with rest and therapy

Common use

Flexeril is primarily prescribed for the short-term relief of muscle spasm associated with acute, painful musculoskeletal conditions. It is most commonly used in cases of acute muscle strains and sprains, particularly in the lumbar and cervical regions. The medication is typically employed as an adjunct to rest, physical therapy, and other measures such as heat application and analgesics. Clinical studies demonstrate effectiveness in conditions where muscle spasm is a significant component of pain and functional limitation. It is not indicated for treatment of spasticity associated with cerebral or spinal cord diseases, or in children.

Dosage and direction

The recommended dosage of Flexeril for most adults is 5 mg three times daily. Based on individual patient response and tolerability, the dosage may be increased to 10 mg three times daily. The medication should be taken with a full glass of water and may be administered with or without food. Use should be limited to two or three weeks due to insufficient evidence of effectiveness for longer periods and because muscle spasm associated with acute musculoskeletal conditions is generally transient. Dosage adjustment is recommended for elderly patients and those with hepatic impairment, typically starting with 5 mg and monitoring closely for adverse effects.

Precautions

Patients should be cautioned about performing activities requiring mental alertness, such as operating machinery or driving, as Flexeril may impair mental and/or physical abilities. Concurrent use with alcohol or other CNS depressants may produce additive sedative effects. Use with caution in patients with mild hepatic impairment; contraindicated in moderate to severe impairment. May enhance effects of alcohol, barbiturates, and other CNS depressants. Anticholinergic effects may be problematic in patients with urinary retention, angle-closure glaucoma, increased intraocular pressure, and in the elderly. Abrupt discontinuation after prolonged use may produce withdrawal symptoms including nausea, headache, and malaise.

Contraindications

Flexeril is contraindicated in patients hypersensitive to cyclobenzaprine hydrochloride or any component of the formulation. Concurrent use with monoamine oxidase (MAO) inhibitors or within 14 days after their discontinuation due to risk of hyperpyretic crisis, severe convulsions, and deaths. Contraindicated in patients during the acute recovery phase of myocardial infarction, and those with arrhythmias, heart block or conduction disturbances, or congestive heart failure. Should not be used in patients with hyperthyroidism. Not recommended in patients with moderate to severe hepatic impairment.

Possible side effect

The most common adverse reactions (occurring in approximately 3% or more of patients) include drowsiness (29%), dry mouth (21%), and dizziness (11%). Less frequent side effects may include fatigue/tiredness (6%), nausea (5%), constipation (5%), dyspepsia (4%), and unpleasant taste (3%). Nervousness and agitation have been reported. Rare but serious side effects may include allergic reactions, tachycardia, syncope, and seizures. Patients should be advised that the sedative effects are usually transient and may diminish with continued therapy. Any persistent or severe side effects should be reported to a healthcare provider immediately.

Drug interaction

Flexeril may have significant interactions with several medication classes. Concomitant use with MAO inhibitors is absolutely contraindicated. May potentiate effects of alcohol, barbiturates, benzodiazepines, and other CNS depressants. May enhance anticholinergic effects when used with other anticholinergic medications. Use with tramadol may increase seizure risk. May interact with guanethidine and similarly acting compounds. Cyclobenzaprine may enhance the effects of norepinephrine. Caution is advised with SSRIs, SNRIs, and tricyclic antidepressants due to potential serotonin syndrome risk. Always inform your healthcare provider of all medications, including over-the-counter drugs and supplements.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is almost time for the next scheduled dose. In that case, skip the missed dose and resume the regular dosing schedule. Do not double the dose to make up for a missed one. Maintaining consistent blood levels is important for therapeutic effect, but occasional missed doses are unlikely to cause significant problems given the medication’s half-life. Patients should not take extra medication to compensate for a missed dose, as this may increase the risk of adverse effects.

Overdose

Overdose of Flexeril may manifest as severe drowsiness, tachycardia, tremor, agitation, confusion, hallucinations, and cardiac arrhythmias. Severe overdose may lead to coma, cardiac arrest, and death. Other symptoms may include hypertension or hypotension, convulsions, and respiratory depression. Management of overdose should include gastric lavage if presented early, followed by activated charcoal. Appropriate supportive measures should be instituted with close monitoring of cardiac function and vital signs. There is no specific antidote for cyclobenzaprine overdose. Treatment should be symptomatic and supportive, possibly including intravenous administration of physostigmine salicylate in severe cases under careful monitoring.

Storage

Store Flexeril tablets at controlled room temperature 20°-25°C (68°-77°F) with excursions permitted to 15°-30°C (59°-86°F). Keep in the original container with the lid tightly closed to protect from moisture and light. Keep out of reach of children and pets. Do not store in bathroom cabinets where moisture levels may fluctuate. Properly discard any expired or unused medication through medication take-back programs or according to FDA-recommended disposal methods. Do not flush medications down the toilet unless specifically instructed to do so.

Disclaimer

This information is provided for educational purposes only and does not constitute medical advice. Flexeril is a prescription medication that should be used only under the supervision of a qualified healthcare professional. Individual response to medication may vary, and only your healthcare provider can determine the appropriate treatment for your specific condition. The information provided here is not exhaustive and should not replace professional medical consultation. Always follow your healthcare provider’s instructions regarding dosage, administration, and duration of therapy. Report any adverse effects to your healthcare provider promptly.

Reviews

Clinical studies demonstrate that Flexeril provides statistically significant relief of muscle spasm compared to placebo when used as directed. In controlled clinical trials, 74% of patients experienced good to excellent results with Flexeril versus 60% with placebo. Many healthcare providers report satisfactory results in appropriate patient populations when used for the recommended duration. Patient experiences vary, with many reporting significant relief of muscle spasm and associated pain, while some note sedation as a limiting factor. The medication is generally well-tolerated when used short-term for indicated conditions. Long-term efficacy and safety beyond three weeks have not been established.