How Long Does Flexeril (Cyclobenzaprine) Stay In Your System?

How Long Does Flexeril (Cyclobenzaprine) Stay In Your System?


  • Flexeril (Cyclobenzaprine) can be detected in the urine specimen from 3 to 8 days after its last use. Use our Drug Calculator to learn how long it takes to leave your system based on your dosage.
  • It can be detected in the blood test and urine drug test from 3 to 4 days after the last dose and stays in the saliva for up to 36 hours.
  • There are no hair drug tests to screen for Flexeril, and it has not been determined how long it stays in the hair.
  • Average half-life of Flexeril is 18 hours. Therefore, after the last dose, Flexeril should be eliminated from the system in 4 days. 
  • Employers generally don’t test for Flexeril.  Since the molecular structure of Flexeril resembles TCA, it is frequently misidentified on urine tests.


What is Flexeril?

Flexeril (Cyclobenzaprine) is a muscle relaxant prescribed by physicians to treat acute musculoskeletal conditions such as muscle spasms/cramps, acute pain, or injury. It is classified as Skeletal Muscle Relaxants and may be used with other medications.

Flexeril acts on the central nervous system by blocking the neural impulses (or pain sensations) that are transmitted from painful and spasming muscles to the brain. It is usually prescribed as part of a treatment plan, including rest and physiotherapy.

Flexeril tablets come in 5 mg, 7.5 mg and 10 mg doses and purported for short-term use (3 weeks or less unless directed by the doctor). It has two variants; Immediate Release and Extended Release. It is taken by mouth with or without food as directed by the prescribing physician. The dosage varies based on the medical condition and treatment response.

Flexeril is available in two forms:  Tablet and capsule.  For adults and pediatric (15 years and older), 5 mg, 7.5 mg and 10 mg tablets are prescribed. The extended-release available in 15 mg and 30 mg doses are recommended only for adults.

The safety and effectiveness of the Flexeril has not been manifested in patients younger than 15 years.

Is Flexeril A Controlled Substance?

Cyclobenzaprine is an FDA-approved drug since 1977. It is marketed under the brand names - Flexeril and Amrix. 

Flexeril is not a controlled substance according to the United States Controlled Substances Act, of 1970.  Flexeril is prescribed for short-term treatment of muscle spasms, muscle sprain, and strain, and musculoskeletal-related injuries. Prescribing guidelines for Flexeril are that it should be used in combination with rest and physical therapy.

Flexeril isn’t addictive according to Drug Enforcement Administration, but there are reports suggesting Flexeril abuse/misuse. People use Flexeril along with central nervous system depressants such as alcohol, sedatives or sedative-hypnotic drugs to enhance the effects.

It is recommended not to drive or operate heavy machinery while using Flexeril. It is also urged to avoid alcohol, as combining muscle relaxants with alcohol increases the risk of accidents.

How Flexeril Affects the Brain and Body?

Flexeril acts as a central nervous system depressant, targeting the brain stem. It causes a sedative effect or forbids the nerves from transmitting pain signals to the brain. Flexeril effects are rapid and typically last anywhere from 4 to 6 hours.

Higher doses of Flexeril may cause a sensation of relaxation, which potentially can lead to drug abuse. Very high doses of Flexeril can cause physical and cognitive impairment as well as ataxia (inability to coordinate voluntary muscle movements). People using extremely higher doses of Flexeril may experience staggering gait, stumbling, falling and incoordination.

Some of the common side effects include:

  • Drowsiness
  • Dizziness
  • Fatigue
  • Dry mouth
  • Agitation
  • Irritability
  • Headache
  • Nervousness
  • Decreased blood pressure

It is recommended not to increase the dose or use the drug longer than prescribed or use it more often. It might increase the risk of side effects rather than ameliorate the condition.

Is Flexeril a Narcotic?

Because of the muscle relaxant properties of Flexeril, it is misconceived as a narcotic or a painkiller among people. Flexeril is actually a specific class of antidepressant called TCA, which acts on the CNS to block certain nerve impulses sent to the brain.

Cyclobenzaprine is an active element in Flexeril and can be addictive as other opioids in the market. There is a tendency to abuse Flexeril. Some people use Flexeril more than necessary to suppress pain or take it along with alcohol. It is also recreationally snorted to feel elated.

The risk remains high for people who use it recreationally or more than prescribed doses for pain relief. The Flexeril overdose can lead to dangerous consequences and some of the serious side effects include:

  • Irregular or fast heartbeat
  • Fluctuations in body temperature
  • Mood and mental changes (confusion, hallucinations)
  • Trouble urinating
  • Seizures/Convulsions

Flexeril is mainly used to help relax the muscles to prevent spasms and reduce pain. It is usually used in combination with rest and physical therapy. Following prescription guidelines may benefit the intended purpose.

Is Flexeril Addictive?

Flexeril is prescribed to alleviate pain and discomfort, and has the tendency to ameliorate sleep, motor function and energy levels in individuals experiencing severe muscle pain. Although Flexeril is considered to be non-addictive, there is reported evidence of possible addiction.

Because of the relaxing effects, people misuse Flexeril by increasing the dosages to get more effects. If used more than the intended period, one can build tolerance to the medication and may require higher doses to attain the same effect. Chronic use of the Flexeril can cause physical dependence and encounter withdrawal symptoms when trying to reduce the dose or stop the medication.

Prescription Flexeril can induce minimal side effects, but if abused can have many adverse effects. Due to its sedating and euphoric effects, some people use it in combination with other substances such as alcohol, sedatives or sedative-hypnotic drugs (CNS depressants), which significantly increases the risk of overdose.

Potential Adverse Effects of Flexeril Abuse

  • Nausea
  • Drowsiness
  • Fatigue
  • Dizziness
  • Dry mouth
  • Blurred vision
  • Increased heart rate
  • Headache
  • Abdominal pain
  • Acid regurgitation
  • Constipation
  • Diarrhea
  • Nervousness
  • Impaired cognitive function
  • Physiological dependence

Overdose can induce severe health issues such as dangerously low blood pressure, seizures, depression, seizures, heart attack and even death in extreme cases.

Signs and Symptoms of Flexeril Overdose

  • Slurred speech
  • Hallucinations
  • Confusion
  • Vomiting
  • Rapid or irregular heartbeats
  • Chest pain
  • Difficulty breathing
  • Extreme drowsiness and dizziness
  • Trouble urinating

Though Flexeril has been reported by the Drug Enforcement Administration to be misused and abused, it has not been classed as a controlled substance.

What is Flexeril Used For?

Flexeril is mostly prescribed to relieve pain, discomfort and stiffness caused by acute injury including sprains and strains. Flexeril is intended to be used only for short periods, approximately two to three weeks, during the healing process.

Flexeril works by relaxing the muscles that are tense and painful due to injury and aids the patient to perform physical exercises that treat the injury. Flexeril also helps the patients to perform normal activities, such as sleeping and working, by suppressing the pain caused by the injury.

Flexeril is usually prescribed as part of a treatment plan, including rest and physical therapy, since the medication itself will not resolve the root cause of the pain and muscle spasms.

There is insufficient evidence regarding the effectiveness of Flexeril in prolonged use since muscle spasms associated with acute, painful musculoskeletal conditions are short-lived and require no specific therapy for longer periods.

Flexeril works by blocking the nerve impulses sent to the brain. It also helps in relaxing certain muscles in the body. It improves pain and range of motion associated with muscle cramps. Flexeril has the propensity to improve sleep as well as energy level in individuals suffering from debilitating muscle pain.

Flexeril Interactions with Other Drugs

Drug interactions may vary with respect to how medications work and/or increase the risk for serious side effects. Changing the dose of medications or stopping/starting without doctor’s approval may also increase the risk of side effects.

It is advised not to combine Flexeril with any monoamine oxidase inhibitors (MAOIs) or serotonin-increasing medications since it can be life-threatening. It should be noted that MAO inhibitors should not be taken for at least two weeks before starting treatment with Flexeril.

Central nervous system depressants such as sedatives or hypnotic drugs may also induce adverse reactions when consumed with Flexeril. When consumed Flexeril with alcohol, it can induce extreme drowsiness and exaggerate the side effects of the alcohol.

People with underlying medical conditions such as liver failure/hepatic impairment, thyroid disorder (hyperthyroidism), congestive heart failure, heart block, impaired heart rhythm or heart attack should avoid taking Flexeril since it may increase the intensity of side effects.


Flexeril is not used in long-term treatments since it only decreases pain in the first two or three weeks of usage. Flexeril does not offer any pain-relieving benefits after the initial period of use. Doctors usually prescribe lowest possible effective dose to their patients since overdose is a possibility.

Before taking Flexeril, informing the doctor or pharmacist regarding any allergies or medical conditions is highly recommendable. If already taking medications for any other medical conditions, it is prudent to verify interactions between Flexeril and those drugs with the doctor or pharmacist.

Flexeril may induce dizziness and drowsiness. Consuming alcohol or weed along with Flexeril cause more dizziness and drowsiness. It is usually advised not to drive, operate machinery or do any activities that need alertness.

Older adults may experience more side effects from this drug, especially drowsiness and confusion that can increase the risk of falling as well as constipation or trouble urinating. Flexeril extended-release capsule is not recommended in individuals with mild-to-severe hepatic impairment.

Flexeril should be used only when clearly necessitated during pregnancy. If required postpartum, discussing risks and benefits of the medication with the prescribing doctor would be recommendable.

Flexeril has been found ineffective in treating spasticity related to cerebral/spinal cord disease and pediatric cerebral palsy.

How Long Does Flexeril Stay In Your System?

Flexeril can be detected in the urine specimen from 3 to 8 days after its last use. It can be detected in the blood test and drug test from 3 to 4 days after the last dose and stays in the saliva for up to 36 hours. There are no hair drug tests to screen for Flexeril, and it has not been determined how long it stays in the hair.

How long does it take for cyclobenzaprine to kick in?

After consuming Flexeril, the effects will commence within 20 to 30 minutes providing pain relief and muscle relaxation. It takes approximately 3 to 4 hours for the Flexeril to peak in the body system and the effects to slow down thereafter until it is gone. Thus, the Flexeril effects can last for approximately 4 to 6 hours.

There are two formulations of Flexeril (cyclobenzaprine):

  • Immediate Release:  The immediate-release formulation is generally prescribed three times per day and its effects last for about 4 to 6 hours for muscle pain and spasms. The half-life for the immediate release can range from 8 to 37 hours.
  • Extended Release:  This is usually prescribed twice per day and remains effective for about 12 hours. The half-life for the extended release can range from 32 to 33 hours.

Half-life is the amount of time taken to break down half of the drug by the body. Since Flexeril has a long and variable half-life, it can stay in the body for up to 3 days.

It should also be noted that the maximum dose of Flexeril should not exceed 30 mg per day.

How long does Flexeril stay in your system depends on certain factors

  • Drug Usage:  The amount of drug and frequency of consumption.
  • Metabolic Rate:  Varies among individuals.  If slow metabolizer, the drug will remain in the system for a long.
  • Age:  Old people metabolize slower than young people, so increased chances for the drug to linger longer in the system.
  • Body Mass:  Weight may also slow down metabolism, thus impacting the processing speed of the drug out of the system.
  • Health Condition:  Medical and mental health issues may also contribute to slower processing of the drug out of the system.

Other factors that may also influence how long Flexeril will stay in the system

  • Consumption Method:  Some people crush and snort or chew Flexeril tablets. This can hinder the entailed metabolism and impact the rate at which the drug is processed out of the system.
  • Concurrent Substance Use:  Consuming Flexeril with other drugs or alcohol can exacerbate the effects of each substance and impact drug metabolism.
  • Biological and Genetic Influences:  Age, gender and race can also impact drug metabolism.

Cyclobenzaprine Half-life

The average half-life of Flexeril is 18 hours. The half-life can range anywhere from 8 and 37 hours. This indicates how long it takes for the half-dose of the Flexeril to leave the system.

For instance, if the half-life is 8 hours, then the drug will be completely eliminated from the body within 2 days. If the half-life is 37 hours, it will be fully eliminated in approximately 8.5 days. For most people, it usually takes between 4 and 5 days to completely eliminate the drug.

If you are addicted to the drug, the elimination period might take more than the estimated time period.

How Long Does Flexeril Stay in Urine?

Flexeril can be detected in urine from 3 to 8 days. Employers generally don’t test for Flexeril.  Since the molecular structure of Flexeril resembles TCA, it is frequently misidentified on urine tests.

Flexeril can be tested if there is a direct reasoning to abuse it, but won’t be tested randomly in most of the cases.

How Long Does Flexeril Stay in Blood?

Flexeril stays in the blood for up to 10 days after the last use. It can be detected within 3 to 4 hours of ingestion.  The half-life of Flexeril is between 8 to 32 hours and builds up in the system over time, which is difficult to predict.

On average, Flexeril can be detected in the blood test for up to 3.75 days after use based on the drug’s half-life, drug usage, and various other factors.

Blood tests are not commonly employed to screen for Flexeril. In the case of a workplace accident or reasonable suspicion, the employer can order blood tests to check if the employee in question was under the influence of any specific drug.

How Long Does Flexeril Stay in Saliva?

Flexeril stays in the saliva for up to 36 hours after use; however, depending on the degree of usage, the detection window may be stretched out to two days. Swab tests do not screen for Flexeril, but random swab tests may be ordered in workplace accidents or reasonable suspicion while on Flexeril.

How Long Does Flexeril Stay in Hair?

Though Flexeril gets eliminated from the body within 72 hours, traces of Flexeril can be found in hair for about 90 days after use. This also depends on the length of the hair and other factors. A hair test rarely applies for Flexeril testing.

Liver and kidney functions also can impact the duration of Flexeril in the system. People with the liver disorder may experience reduced isoenzyme function leading to the prolongation of substance excretion and thereby lengthening the duration of cyclobenzaprine in the body.

Do Muscle Relaxers Show Up on a Drug Test?

In general, muscle relaxers might not show up on a drug test. There is no specific drug test that detects the abuse of muscle relaxers. But it might show positive results for some antidepressants that might show up on your 10-panel or 12-panel drug test. 

There is no evidence or proven results that a 5-panel drug test might show positive results for muscle relaxers like Carisoprodol, Chlorzoxazone, Dantrolene, etc.  

Prescribed usage of muscle relaxers might not affect your drug test results. But some people may use muscle relaxers for pleasurable feelings during pain without a prescription. This might lead to muscle relaxer addiction or overdose. 

According to, muscle relaxants may cause CNS (Central Nervous System) depression in older patients, and most of the muscle relaxants are on the BEERS list, causing sedation, the risk for falls and fractures, etc.

Will cyclobenzaprine show up on a drug test? Maybe. Let's learn more about Flexeril (cyclobenzaprine) and does it show up on a drug test.

Does Flexeril Show Up On A Drug Test?

No. Flexeril does not show up on a standard drug test. Most companies conduct a standard 5 panel drug test, and Flexeril will not show up.

But, if you are subjected to a drug test and have been taking Flexeril,  you may come out positive for TCA (antidepressants). 

TCA is a class of drugs used to treat anxiety, eating disorders and depression. The TCA assays reportedly have had higher rate of false positives. Drugs and/or metabolites that mimic chemical structures of TCA yield false-positive TCA results.

Overdose of Flexeril may show positive for benzodiazepine drugs which might show up in a 10-panel drug test. So people taking Flexeril should disclose their medication prescription to their employer and the tester before taking the drug test.

If an employee shows signs of drowsiness and disorientation, which imposes safety risk may undergo a drug test specifically for cyclobenzaprine.

How long do the effects of Flexeril last?

The length of time Flexeril shows up on a drug screening depends on the type of drug test done, frequency and amounts of drug taken, metabolism, age, weight, height, and genetics. Lifestyle and exercise habits may also influence. These factors differ from person to person, and some people may have longer or shorter drug detoxification processes.

Urine drug screen immunoassay is a quick and affordable method for detecting the presence of drugs of abuse. On the initial drug screen, there may be cross-reactions with other analytes, potentially causing a false-positive result. These false-positive results are generally considered presumptive until confirmed by an alternate test method.

In general, Cyclobenzaprine might show up in 

  • Blood test for up to 10 days.
  • Urine test for 3 to 4 days.
  • Saliva test for 2 to 7 days.

Here is some further information to know more about Flexeril addiction.

Flexeril Addiction

Individuals abuse Flexeril in order to feel relaxed, elated, or sedated. High doses can produce anticholinergic effects by changing the neurotransmitter activities in the brain. Chronic Flexeril use leads to physical dependence, and withdrawal symptoms may be experienced if used chronically in high doses.

Indications of Flexeril addiction include

  • Consuming Flexeril longer than prescribed
  • Frequently taking it if not required
  • Needing higher drug doses to elicit the same effects
  • Misrepresenting symptoms to acquire Flexeril prescriptions
  • Always using Flexeril
  • Unable to stop Flexeril
  • Changes in behavior, physical appearance, and hygiene

Flexeril Withdrawal and Treatment

Flexeril is given as a short-term treatment of acute conditions related to the musculoskeletal system. It is typically used along with rest and physical therapy to treat injuries. It is also used off-label to treat fibromyalgia. It is a CNS depressant and has similar effects to TCA.

Even though Flexeril is not a controlled substance, it can potentially be abused or habit-forming because of its euphoric effects and feelings of pleasant relaxation. Regular use of Flexeril can cause the brain to get accustomed to its effects. One may experience withdrawal symptoms if one attempted to suddenly stop the Flexeril.

Many people might experience mild withdrawal symptoms such as headache, drowsiness, nausea, malaise and discomfort after the last dose of Flexeril. Symptoms usually peak for about 2 to 4 days, though some people may experience it for up to 1 to 2 weeks.

More severe withdrawal symptoms can include hallucinations and seizures. Inpatient treatment program along with detoxification can help manage discomfort associated with withdrawal symptoms. Patients can then transition into the actual treatment program phase after detox. Supervised detoxification programs will not be necessary in most cases and treatment can be taken on an outpatient basis.

Inpatient and outpatient rehabilitation programs typically include cognitive behavioral therapy to teach coping skills that are required for long-term recovery as well as reduce the risk of relapse by providing assistance throughout the process.

Flexeril Detoxification/Treatment

Flexeril (cyclobenzaprine) detox for mild withdrawal symptoms can be dealt at home. However, there may be situations where professional Flexeril detox is necessary. Flexeril is often abused along with alcohol, sedatives or opioids. Individuals who misuse Flexeril and other substances can receive assistance through professional medical detoxification programs since there can be severe withdrawal symptoms from other substances too.

Depending on the drug and period of usage, there are various treatment options available to help overcome drug dependence. Professional Flexeril detox program is also available for individuals with underlying psychological disorders.

Rehab programs are also available where people can stay in a safe, sober environment for an extended period of time before returning to a least protected environment. People can choose to enroll either in a residential rehab program or an outpatient rehab program after detox.

A Residential Drug Rehab Program provides comfortable, safe, gender-specific, sober living environments. Patients enrolled live in the rehab center throughout the program with treatment facilities at the same location. They have structured daily schedule including meals, meditation, process groups, individual therapy sessions, etc., which patients adhere to. The residential programs are ideal for people with severe addictions and for people who have relapsed once or several times before.

An Outpatient Drug Rehab Program has more flexibleness. Individuals who are working or going to school or taking care of their family members at home can schedule sessions according to their convenience. Outpatient programs are scheduled two to three times a week, facilitated by professional addiction treatment staff in a group environment and patients work through recovery materials.

The cost of rehab programs will greatly vary depending on the chosen program. Most rehab programs accept medical insurance and there are other payment alternatives to help reduce the treatment cost.

Addiction can be overcome with continued treatment and recovery support. There are aftercare programs if people choose to continue their treatment. Aftercare program offers extended assistance to people convalescing from Flexeril addiction as well as other substance abuse problems through recuperative support programs.

Aftercare organizes group meetings facilitated by trained professionals. These are sometimes organized along with NA or AA support group meetings as well. People discuss about their struggles and success in addiction recovery as well as work collectively aiming towards sustained, long-term sobriety.

Flexeril can be an effective way to deal with debilitating pain associated with muscle injuries, but it is important to bear in mind that abuse of any drug is life-threatening and may develop into serious addiction.

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