How Long Does Flexeril Stay in Your System?

Dr. Manish Mishra, MBBS

Medically Reviewed By: Manish Mishra, MBBS


Flexeril is a brand name for cyclobenzaprine. This muscle relaxant is not included in standard 5-panel and 10-panel drug tests.

However, special tests geared towards finding only cyclobenzaprine can be used. These tests may be necessary for prescription monitoring or in the aftermath of an accident or overdose.

When taking Flexeril, effects occur within an hour of consumption. Effects wear off after about 12-24 hours. But it’s important to remember that the substance remains in your system even after effects wear off. 

In general, Flexeril is typically detectable on a drug test within these periods of time:

  • blood  – up to 3 days
  • saliva – up to 36 hours
  • urine – up to 8 days
  • hair – up to 90 days

Flexeril Half-Life

Cyclobenzaprine has an average elimination half-life of 18 hours. The half-life for the drug can be as low as eight hours and as high as 37 hours. This range includes extended-release versions of the drug. 

In general, it takes about five half-lives for a substance to exit the body. This means that Flexeril could show up in drug tests around four days after the last time taken, or up to about eight days later. 

How Long Does Flexeril Stay in Your Urine?

Urine testing is the most common method of drug testing.

Norcyclobenzaprine is Flexeril’s primary metabolite which is detectable in urine. Urine screenings can usually find evidence of the drug between three and eight days after the last use.

How Long Does Flexeril Stay in Your Hair?

Hair tests generally show patterns of drug use over the 90-day period before the test. Evidence of a drug can be visible about a week after ingestion when there is new hair growth. Hair testing for Flexeril use, however, is rare.

How Long Does Flexeril Stay in Your Blood?

Flexeril reaches peak levels in the blood about seven to eight hours after consumption. So, a test done then would likely produce a positive result. With a long half-life, the drug is detectable in blood for around three days. This window of detection can be longer.

How Long Does Flexeril Stay in Your Saliva?

Oral fluid tests tend to be more expensive than other types of biological samples. Saliva testing for Flexeril is uncommon, and there is little information available about how long the drug is detectable in saliva. But some sources suggest the drug can be found up to around 36 hours after consumption. 

Also, be aware that Flexeril is very similar in structure to tricyclic antidepressants (TCAs). Using Flexeril can trigger a false positive for a TCA.

Factors That Affect How Long Flexeril Stays In Your System

The rate at which the body processes Flexeril is not the same for everyone. How long it lasts in the body depends on various factors, including:

  • frequency of use
  • duration of use
  • dosage
  • presence of other substances
  • metabolism
  • general health
  • age
  • weight
  • genetics

Treatment for Substance Use Disorders

Flexeril is usually prescribed for short-term use over two or three weeks. It isn’t habit-forming but misuse does occur. People also take the drug with other substances in potentially harmful combinations.  

Stopping use may bring about withdrawal symptoms, but they are mild compared to those linked to benzodiazepines. 

If you or someone you know is struggling with a dependence on substances, health professionals can supervise your detox in a safe inpatient setting if necessary. Treatment includes therapy. Counselors provide support, guidance and information to prevent relapses and sustain sobriety.

A happier and more stable life is possible. Contact Bedrock Recovery Center to discuss the best options for you.

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Written by Bedrock Recovery Center Editorial Team

© 2024 Bedrock Recovery Center | All Rights Reserved

* This page does not provide medical advice.

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