How Long Do Muscle Relaxers Stay In Your System? The Hidden Truth


Countless of people are asking: How long do muscle relaxers stay in your system? If you’re one of these individuals, you may be asking this question because you’re scheduled for a drug test, and you don’t want to test positive.

This is because some muscle relaxants could mimic the reaction of tricyclic antidepressants. This will generally test positive in a drug test. In this case, if you come up positive for tricyclic antidepressants, it would be a minus factor for you, especially if you’re in search of employment.

The positive result will indicate that you are prone to depression. An employer will not hire someone, who has the tendency to become depressed.

Therefore, you must know how long the muscle relaxer stays in your system, so you could adjust your job hunting accordingly. This is most especially applicable if you’re on medication with drugs causing muscle relaxation.

Here’s a video about muscle relaxants:

How Long Do Muscle Relaxers Stay in Your System?

The Influencing Factors

The hidden truth is that there are various factors that affect the elimination of the drug from your body. These are:

1. Concentration of The Drug Administered

Additionally, the concentration of the drug taken in must also be considered. The higher the concentration of the drug administered, the longer it stays in your system.

2. Detoxifying and Metabolizing Function of Your Liver

The major functions of the liver are to detoxify and metabolize drugs that enter your body. Thus, if your liver is impaired, the drug will have a long time being metabolized and detoxified, and thus may remain in your system longer than normal.

3. Ability of Your Kidney to Eliminate The Drug and Its Metabolites

Likewise, the major function of the kidneys is to eliminate waste products of metabolism and unwanted toxic substances from your body.

Consequently, when you have an impaired or dysfunctional kidney, drugs that enter your body will have difficulty being excreted, and will remain in your system longer than normal.

4. Weight of The Person

The body mass of the person has to be considered too. The greater the weight or body mass, the quicker the drug can be eliminated from the system.

5. Age and Sex

The speed of elimination of drugs in the elderly is decreased. So, if you’re 50 and above, you should expect a slower elimination of the drug. This is due to the fact that your organs are already ‘old’; you have less efficient organs. Thus, the drug will stay in your system longer.

Usually, males have larger body mass, so the drug is more quickly eliminated from their systems than in women.

6. Frequency and Length of Drug Intake

The frequency and length of intake has also an effect on how long the drug stays in your system.

A person, who takes the drug 3 times a day for 5 days, will eliminate the drug more slowly, than a person, who has taken it once a day for 2 days only.

7. Presence of Drugs That can Interact with The Muscle Relaxer

There are certain drugs that can prevent the elimination of muscle relaxer drugs, so they stay longer in your system. These can be CYP3A4 inhibitors, such as Ritonavir and Chloramphenicol.

Specific Instances That You Must Know

Normal person with intermittent intake of drug (after discontinuance)

In normal persons, without organ impairment, and intermittent intake of muscle relaxers (Examples are Valium, Robaxin, Flexeril and Skelaxin); the drug will stay in your systemic circulation for 5 to 14 days after last dose. Take note that in this case, the intake is intermittent.

The half-life of Flexeril is typically 18 hours, but it’s eliminated from your system after around36 to 42 hours.

Normal person, who are fast metabolizers (after discontinuance)

The drug can be cleared in systemic circulation within a period of 48 to 72 hours. But, to be sure, you may want to extend the number of days, so that the muscle relaxer will be completely excreted from your body.

You have to discontinue completely, the drug as well. Also, hydration could help significantly in eliminating the drug from your system.

Water is a universal solvent, so it can aid your organs in ‘washing’ away drugs that have entered your body. You should drink more than 8 glasses of water per day.

Persons with hepatic and renal dysfunction (after discontinuance)

The elimination of drug is prolonged, so it stays in your system longer than normal. You can expect the drug to stay around 8 to 37 days. This will also depend on the severity of the dysfunction. The more severe the impairment, the longer the drug could be eliminated.


I have answered the question: How long do muscle relaxers stay in your system? As discussed, there are multifarious factors that affect its elimination, so there are many answers. The answer depends on what category you belong to.

Evaluate your body’s physiologic status and determine how many hours will the muscle relaxer stay in your system. Remember to consider all the factors involved.

Do you have similar experiences with other drugs? You could share your thoughts with us.


Hello everyone! I’m glad to have you here. I’m a medical technologist by profession. My second love is writing. So, I’m focusing on providing content to help other people with their health problems. I hope I can be of help to you.

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