How Long Do Muscle Relaxers Stay In Your System: What to Know About Drug Testing

Last Updated: May 2, 2024

David Levin Reviewed by David Levin
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Muscle relaxant drugs are commonly prescribed to people who report symptoms that may include spasms, cramps, and similar events. Even though these medications have some contraindications and muscle relaxants adverse effects, studies have shown that they are prescribed to approximately 18.5% of patients with back pain problems, with COX-2 inhibitors and NSAIDs also being common prescription options. Many people want to know how long the chemicals in these medicines would remain in their systems.

Furthermore, for some individuals who recently started their treatment, the common questions are: how do muscle relaxers work , how long does it take for muscle relaxers to kick in and do muscle relaxers show up on a drug test? Let’s take a look at factors controlling muscle relaxants mechanisms of action, how long these drugs stay in the system, their half-life and how to flush muscle relaxers out of your system safely.

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Do Muscle Relaxers Show up on a Drug Test?

The common question is, will muscle relaxers show up on a drug test? Understanding how certain long drugs stay in the system is important. While this may not be such a big concern with all-natural muscle relaxers, it is important to consider these factors when using a pharmaceutical product. Despite the fact that muscle relaxers can be addictive, they are not specifically tested. Some people still want to know how long the medication will remain in their system and for how long they will test positive for specific chemicals.

Below is a guide that provides further details of different muscle relaxants, as well as the time they generally stay in the body and remains detectable:

Baclofen 72 hours for regular doses 48 hours (Up to 10 days with high doses) 48 to 72 hours
Flexeril Up to 10 days 4 to 4 days 3 to 10 days
Soma 24 hours 2-3 days, Variable (Chronic / Acute) up to 4 hours

So, do muscle relaxers show up on a drug test? No, they don’t. This is because they are not classified as illicit substances and so they won’t be an aim of a regular drug test, but specific tests can detect them. Weed and muscle relaxers are a risky combination as they both amplify the effects of the other. Similarly, drinking on muscle relaxers is a bad idea; the reason being that alcohol is a depressant which causes the body to relax. Naturally, these drugs cause a feeling of relaxation, drowsiness, and this can become intense when one drinks.

Half-Life Of Muscle Relaxers

Whether using muscle relaxers medication to treat back pain or muscle-related pain symptoms affecting a different part of the body, many patients do want to know how long does it take for muscle relaxers to work. One useful way of providing an overview of the time that a drug will remain active in the body is to consider its half-life.

There are a number of different options that people can use when they suffer from muscle-related symptoms. It is possible to choose an OTC muscle relaxant or rather opt for a prescription one instead, depending on the severity of the pain. Since there are different types of these medicines on the market, it is essential to take note of the fact that the half-life of each may differ.

Check the names of prescription muscle relaxers, along with the average half-life of each:

Meprobamate 10 hours (Chronic use: up to 48 hours)
Cyclobenzaprine Eight hours to 36 hours (Average: 18 hours)
Vecuronium 70 minutes
Atracurium 20 minutes
Rapacuronium 10 minutes to 20 minutes
Mivacurium 10 minutes to 20 minutes
Metocurine 50 minutes

The half-life of muscle relaxers for fibromyalgia, injury, back pain, and other conditions that lead to muscle-related symptoms, helps to provide a more accurate overview of how a dosage should be calculated for a specific individual.

What Influences The Period Of Muscle Relaxers Staying In The System?

When it comes to considering how long do muscle relaxers stay in the system, it is essential to note that there is no specific time frame that can be mentioned here. While it is useful to consider the half-life of a drug, there are many other factors that ultimately have an impact on how long the chemicals will remain in the system of a person. Only when a person considers all of these factors it would be possible to gain a more accurate overview of how long the drug will remain in the system.

One of the main factors that will impact the period during which the muscle relaxer’s chemicals will remain in the body is the specific type of drug that was used. There is a significant variety of these medicines that a person can use – and each has its own muscle relaxant side effects, half-life period, as well as the time that the body will take to expel the chemical completely.

The dosage that the person takes will also have an impact. The greater the dose, the longer it takes for the body to get rid of all the chemicals that it was introduced to.

Apart from these factors, there are a couple of other factors that should also be considered when trying to determine how long a specific type of muscle relaxant would remain within the system:

  • Sex plays a role, as there is a difference in how liver enzymes process medication in men and women.
  • Age is another factor that plays a part in providing an overview of the period during which the muscle relaxant would remain in a person’s system. As the body ages, there is a reduction in kidney function, as well as liver function.
  • Weight and the percentage of body fat also plays a part. A larger person may require a higher dose for the drug to work effectively.
  • The general well-being of a person also plays a role. A person with existing conditions that affect their kidneys, as well as their liver, may have impaired functionality in terms of how drugs are metabolized.
  • Drinking on muscle relaxers is also known to be responsible for prolonged staying in the system.

Do not take muscle relaxers before consulting a physician as they can be addictive, especially when used for a long time. This also reveals the risk of having withdrawal symptoms if one suddenly stops taking the medication after a long period of use. It is usually best to reduce dosage successively rather than stopping abruptly. The symptoms of withdrawal may include anxiety, insomnia, vomiting, and others. It is recommended to seek professional medical treatment at this point.

How Do Muscle Relaxers Work?

There are various categories of medication, and each muscle relaxants mechanism of action is restricted to a specific location in the body. So, how do muscle relaxers work? They relieve contractions, tense muscles, and stiffness in the tissues, and this is done in different ways.

There are two categories of muscle relaxants that work a bit differently in the body:

  • neuromuscular blockers
  • spasmolytics or antispasmodics

The neuromuscular blockers interfere with chemical transmissions at the endplates. They don’t affect the CNS, while the spasmolytics are known to ease muscular tension by interacting with GABA receptors as an agonist and acting on the CNS in a wide variety of neurological disorders ensuing hyperpolarization of neurons.

Contractions stemming from the brain and spinal cord. Some muscle relaxers work specifically on the central nervous system, which directly affects the brain and the spinal cord. Some of these types of medication include Methocarbamol, Baclofen, and Tizanidine.

Contractions in the muscles. Medications such as dantrolene restrict themselves to relieving muscular stress. Its restriction to the muscular tissue makes it one of the safest relaxers with fewer side effects, unlike those that have a direct impact on the CNS. This is why a physician will most likely prescribe this drug as the first choice.

The mechanism of action of skeletal muscle relaxants in classed with the spasmolytics. Other tissue-related mechanisms are neuromuscular, such as muscle relaxers for menstrual cramps.

How Do Muscle Relaxers Work

How Long Does It Take For Muscle Relaxers To Work?

From the moment one ingests a pill, the most common question is usually: how long does it take for muscle relaxers to work? There are factors that may be responsible for either delayed or immediate potency but generally, the time it takes for muscle relaxers to kick in may hinge on differentials such as weight, body fat, and others.

So, how long do muscle relaxers take to work? It takes about 30 minutes or more after it is ingested.  Peak efficacy may linger around 2 to 4 hours. When one ingests the drug orally, it disintegrates and enters the bloodstream where it is then distributed to various tissues, organs, and CNS.  The progression might take up to 30 minutes before results may be experienced.

How long do muscle relaxers last? In many cases, they may last about 12 hours or more. In some cases, delayed efficacy may be due to numerous factors that only a medical doctor can understand. At this point, it is inadvisable to take more doses of the medication, since it may result in muscle relaxants overdose. Intravenous drugs are usually administered by means of an injection directly into the veins. It is the shortest route for taking them because it goes directly into the bloodstream and becomes effective in less than 10 minutes.

Always Consult Your Doctor: How to Flush Muscle Relaxers out of Your System Safely

Even though several suggestions have been made that certain claim drugs can be flushed out of the system safely, it should be noted that these drugs have a specific half-life and their elimination will be affected by a number of factors related to the medication, as well as the patient being treated.

The specific time it would take to get a muscle relaxer completely eliminated from the system depends on the drug. Some might only be detectable in the system for a period of two days, while others can be found for as long as a month.

Still, there are a few tips that might be worth a try. Hydrating the body thoroughly with about three liters of water per day could be a good way to speed up the elimination process of the chemicals that are in the body. Some have also suggested that cranberry juice, in addition to the water, can be helpful to clear out the chemicals faster. Exercise is yet another potential option that may be utilized. Furthermore, avoiding foods that could slow down metabolism is also an important step to take when trying to eliminate these drugs from the body at an accelerated rate.

When the use of muscle relaxers do become a problem, a person might require a professional detoxification procedure to get rid of the chemicals in their system. Professional addiction treatment can be provided to the person. This would usually include a program in a drug rehab that assists in reducing withdrawal symptoms, while also enabling the person to stop their habit of potentially abusing these muscle relaxants.

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Page Sources

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  4. Landy, S., Altman, C. A., & Xie, F. (2011). Time to Recovery in Patients With Acute Painful Musculoskeletal Conditions Treated With Extended-Release or Immediate-Release Cyclobenzaprine. Advances in therapy, 28(4), 295-303.
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Published on: August 14th, 2019

Updated on: May 2nd, 2024


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