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How Long Does Flexeril Stay in Your Body?

How Long Does Flexeril Stay in Your Body?

Flexeril stays in your body for anywhere from 5 days to slightly more than 2 weeks (16 days). The factors that determine this length of time include how much of it you have taken and how often, your metabolic rate and how speedy it is, your age and general health levels, and your body mass. A slimmer person with a faster metabolism will eliminate the drug faster if taking the same amount at the same time.

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More generally, yay for pharmacology. Here in the 21st century we have such a wide array of safe and reliable medications available to us to get relief from so many different conditions. Pain is the most common of the ailments that nearly all of suffer from time and time. Whether it’s pain from a chronic or degenerative condition, or incidental pain from taking a fall or twisting an ankle, it’s a condition that would be awfully unpleasant to endure without medication. Flexeril is an effective pain relief medication, and now you have the answer for how long does Flexeril stay in your body.

These same people who want to know they’re taking a proven safe pain medication may also want to know of the side effects of Flexeril. The good news here is that there’s nothing in the formulation of Flexeril that would be a cause for concern if were to remain in the body for any extended period of time. There’s also very little in the way of side effects of Flexeril that you would need to concern yourself with.

We’ll take a detailed look at Flexeril here, and detail what makes it a good choice for relief from all the pain that often comes with living an active, full life or more simply from the bad luck we all have from time to time. Plus, in the interest of keeping this engaging we’ll start by asking how many of you know where the term for one of the most common muscles strains – the ‘charley horse’ – comes from?

Read on, and you’ll also learn why it has that name!

Why Flexeril?

Muscle pain is one thing, but muscle spasms are another. While pain can usually be connected to some specific incident that caused it, the reason why you’re having muscle spasms can be less clear. Muscles are built to contract, and they do all the time. But they’re also supposed to relax after contracting. When they contract but don’t relax – or don’t relax enough – then you’ve got a muscle spasm.

Flexeril is best suited for short-term relief of muscle spasms stemming from painful muscle and skeletal conditions. It works by blocking nerve impulses and pain sensations that would otherwise be sent to the brain.

The recommended dosage for Flexeril is 5 or 10mg taken 3 times daily. A prescribing physician will let you know that Flexeril is only for short-term use, up to 2 or 3 weeks at the most.


There’s how long does Flexeril work for, and how long does Flexeril stay in your body. Two different questions, and we’ve already determined that Flexeril stays in your body for anywhere from 5 to 16 days. After you take the medication it typically starts to work within 20 to 30 minutes, then providing relief from muscle pain and muscle spasms for 6 hours on average.

Side Effects of Flexeril

It’s fair to say that Flexeril is a safe drug, and like all others available for dispensing from pharmacies it’s been approved by the US FDA (Food and Drug Administration). People suffering from muscle pain or muscle spasms can go ahead and use Flexeril without concern provided it’s been prescribed by their physician and they take it exactly as directed.

That said, the noted possible side effects of Flexeril can be divided into 2 categories. Serious and not-so-serious.

Serious side effects of Flexeril include:

  • Fast or irregular heartbeats
  • Chest pain or pressure
  • Pain that spreads to your jaw or shoulder
  • Sudden numbness or weakness, particularly on one side of the body
  • Slurred speech
  • Balance problems

Not-so-serious side effects of Flexeril include:

  • Drowsiness or tiredness
  • Headache or dizziness
  • Dry mouth
  • Upset stomach
  • Nausea
  • Constipation

Another consideration here is medications that may interact with Flexeril. These include bupropion, meperidine, tramadol and verapamil, plus medications for treating Parkinson’s disease, stomach acid and ulcers, and overactive bladder. 

The Story Behind The ‘Charley Horse’

This definitely has nothing to do with how long does Flexeril stay in your body, but those of you who are familiar with a charley horse might be interested to start here by learning that charley horses don’t always occur with leg muscles. They can actually occur in any muscle, but they’re most common in the legs.

The standard defining symptom for a charley horse is uncontrollable muscle contractions, and such Flexeril is an excellent choice as a charley horse treatment medication.

But enough about that, we promised to share where the term charley horse came from and that’s exactly what we will do. The name dates all the way back to the 1880s, and what we can be certain is that it actually comes from baseball slang originating in the great city of Chicago. What’s not certain is which of the two sources of the name is the correct one, or maybe it’s a combination of both.

The first one is that Charley was the name of a horse that pulled the roller at White Sox ballpark in the later part of the 19th century. He was a ‘lame’ horse, meaning he had mobility issues and didn’t move very well. That may be where the name comes from, but it’s also possible that it’s a different story.

The White Sox had a pitcher back then named Charley Radbourne (note the spelling, not Charlie as it is nearly always spelled), and his team nickname was Old Hoss. During a game way back then he developed a leg muscle injury, and people around the team started to call these types of injuries a Charley Horse.

Interesting stuff, and while it of course has nothing to do how long does Flexeril stay in your body it’s something you likely would never have guessed when it comes to where that name came from.


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IMPORTANT NOTE: The above information is intended to increase awareness of health information and does not suggest treatment or diagnosis. This information is not a substitute for individual medical attention and should not be construed to indicate that use of the drug is safe, appropriate, or effective for you. See your health care professional for medical advice and treatment.


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