How long does Flexeril stay in your system?

Flexeril, the brand name for the drug cyclobenzaprine, is generally prescribed as a muscle relaxer for short-term use only. It can also be prescribed for other medical issues such as fibromyalgia and depression. The use for these conditions is rare, however. Flexeril treats muscle spasms caused by musculoskeletal conditions that cause pain. In most cases, it is not prescribed for more than ten to twelve days. Its peak effectiveness is within the first few days, but the medication subsides beneficial effects by two weeks.


Flexeril affects the brain within an hour of ingestion, and effects wear off between 12 and 24 hours after taking it. However, the medication does remain in the system after the effects have already subsided. Patients should not take cyclobenzaprine if they already take MAOIs, have heart issues such as arrhythmia or congestive heart failure, or are over 65 years old. Older people and those with liver issues can experience stronger side effects than others.

How long does Flexeril stay in your system?

Flexeril is an extended-release medication that should not be taken for more than three or so weeks. The nature of the drug causes it to accumulate in the body. It can be detected in the system anywhere from a few hours to days after it was last taken. Different types of drug tests will yield different lengths of time. The drug does not show up in standard drug testing – a test specifically for the drug would have to be conducted to detect it.

Saliva tests will detect the drug in your system for 36 hours after use. A blood test will detect the drug at about two hours after ingestion and up to 10 days after the last dose. Urine tests will detect it anywhere from five to 13 days after the drug is taken. Hair-based testing for cyclobenzaprine is not generally used as a reliable test has yet to be developed.

90 Days36 hours10 days5-13 days
Flexeril Detection Times

What does Flexeril treat?

Cyclobenzaprine is normally prescribed to relieve pain, discomfort, and stiffness caused by injury, such as pulled muscles, muscle strain, etc. The medication causes the muscles to relax, thus alleviating the pain, in order for the patient to perform exercise or therapies to treat the injured muscle. It also relieves pain, so patients are able to perform normal daily activities. The medication does not treat the reason for the injury, nor will it repair damaged tissue, but it is used in conjunction with physical therapy and rest in order to heal the muscles affected. It is intended for short-term use.

How does Flexeril work?

Cyclobenzaprine affects the alpha and gamma motor systems in the body. These systems consist of nerve fibers, which send impulses to the muscles in your body, causing them to contract. The drug “tells” the brain and spinal column to send a message to the muscles to relax. This relaxation helps prevent spasms in the muscles, thus reducing pain. Flexeril is to be prescribed to accompany rest and physical therapy and is not intended for long-term use. Because of the nature of how the drug works, it is said to not be habit-forming. It can be abused when taken in combination with other medications that suppress the central nervous system.

Because the drug affects the central nervous system, it can make you drowsy. It also causes feelings of relaxation in higher doses, which may promote possible abuse. If taken in very high doses, it can impair physically and cognitively. Reports of ataxia, a condition in which muscle control is lost, have also been associated with the drug if taken in very high doses.

Factors that can affect how long it is in your system

Any drug will affect different people in different ways based on several factors. The older a person is, the stronger the drug’s effects are on them and the longer it will affect them. Bodyweight will also affect how long Flexeril will stay in your system. The larger a person’s body mass is, the longer it will take to fully eliminate the drug. People with any type of liver impairment will have a hard time eliminating the drug from their body, so that can be a factor to consider. People whose metabolisms are faster than normal will eliminate the drug more quickly, while those with a slower metabolism will eliminate it more slowly. Also, the larger the dose taken and the more frequent the use of the drug will slow its elimination from the body.

Flexeril’s half-life

The half-life of a drug is the amount of time it takes a half dose to leave the system. Cyclobenzaprine has an average half-life of 18 hours. Using that as a starting point, it seems to reason it will take a little more than four days to fully eliminate the drug from the system. However, its half-life can vary from eight to 37 hours, so the amount of time for elimination varies based on that.

What are the side effects of Flexeril?

Common side effects of cyclobenzaprine are fatigue, drowsiness, dizziness, headache, nausea, upset stomach, constipation, and dry mouth. Serious side effects can occur that will require immediate attention by medical professionals. These include:

What are the risks of taking Flexeril?

No one who has a thyroid disorder, a recent heart attack, congestive heart failure, allergy to cyclobenzaprine, a heart rhythm disorder, or anyone under 15 years old should take the drug. It can interact dangerously with some prescription drugs, including:

Cyclobenzaprine can also be dangerous to some with certain medical conditions. These people should avoid it or take a lower dosage. These conditions include:

No studies have been performed to verify the safety of Flexeril for pregnant or breastfeeding mothers. Studies done on pregnant animals have shown no harm to the baby, or fertility problems occur when using the drug. However, patients and their doctors should consider the use of the drug only in extreme cases. Drugs similar to cyclobenzaprine have been found to be present in the breast milk of lactating mothers, so nursing mothers and their doctors should discuss the medication thoroughly before use.

Can you overdose on Flexeril?

There is a risk of abuse of the drug because it produces a feeling of relaxation, but even though it does not produce a high feeling, some people start taking more than their prescribed dosage to increase the relaxed feeling, which can result in an overdose. Overdosing on cyclobenzaprine can produce the following signs:

Overdoses on cyclobenzaprine are more likely to occur when people take it in combination with other drugs, especially drugs that depress the central nervous system. These can include benzodiazepines and alcohol. Though addiction was once thought unlikely to occur, experts now believe the possibility of addiction exists. Someone may be addicted to the drug if they exhibit the following signs:

Those addicted to cyclobenzaprine can experience withdrawal symptoms when they stop the use of the drug, but they are usually not severe. They can include nausea, tiredness, headache, and feeling they need the medication.

How can I detox faster?

Every person will react to the medication differently, and everyone who stops taking it will experience different symptoms for different amounts of time. Factors that will affect a person’s detox symptoms include how much they took, for how long they took it, other substances are taken with it, general health, age, weight, metabolism, and genetics.

Following healthy lifestyle guidelines, such as getting proper sleep, exercise, eating well, and staying hydrated, can help you detox as efficiently as possible from the drug. But there is no evidence that doing so will speed your detox time or shorten the amount of time the drug can be detected in your system.

If you are experiencing detox symptoms after stopping the use of the drug, a doctor can supervise you in an inpatient facility if needed. Treatment for Flexeril abuse generally includes therapy, in which counselors and mental health professionals can provide support and offer suggestions about avoiding relapses and maintaining a sober lifestyle.