Cyclobenzaprine, commonly prescribed under the brand name Flexeril, is a prescription skeletal muscle relaxant used primarily to treat muscle spasms. It’s one of the most widely used medications for musculoskeletal pain and is prescribed under a few additional brand names including Amrix, Fexmid, and FusePaq Tabradol.
At low doses, cyclobenzaprine can also be prescribed as an off-label treatment for insomnia.
As a central nervous system (CNS) depressant, cyclobenzaprine works by blocking pain sensations sent from the brain, helping to relax muscles and relieve tension. It’s structurally similar to tricyclic antidepressants, though not used as an antidepressant treatment itself.
Because of its effect on the brain, cyclobenzaprine can cause sleepiness and impair judgment. That’s why it’s important to know your dosage, understand how long the effects last, and how long it stays in your system.
See What is cyclobenzaprine used for? for more information around its effects and usage.
How long does cyclobenzaprine (10 mg) last in your system?
The effects of cyclobenzaprine last between four to six hours when taking the immediate-release formula. However, it can stay in your system much longer than that.
With a half-life ranging from 8 to 37 hours for immediate-release and between 32 and 33 hours for extended-release, cyclobenzaprine can potentially stay in the body for up to three days. It accumulates and, if dosed three times a day, can reach steady-state within 3-4 days. This is the point at which the amount entering your bloodstream is equal to the amount being eliminated.
Half-life — the length of time it takes for half of the drug to be broken down by the body.
Steady state — the rate of the drug entering your body equals the rate as the drug leaving your body
While 10 mg is a common dosage, cyclobenzaprine can often be effective in lower doses. It’s also recommended for night-time use due to its drowsiness effects.
As always, if you have any questions about your cyclobenzaprine dosage, it’s best to consult with your doctor.
Factors that impact the metabolism of cyclobenzaprine
Everyone metabolizes drugs differently, which means the effects and total duration of medication can range from person to person and, in some cases, even day to day.
A few known factors that can impact how cyclobenzaprine is metabolized include:
- Kidney damage/decreased liver function — cyclobenzaprine is excreted through the kidneys, so those with kidney damage or decreased liver function may not process the drug as quickly.
- Age—Flexeril is metabolized more slowly in the elderly and is more likely to cause adverse side effects, including hallucinations, confusion, and cardiac events.
- Taking other medications — taking cyclobenzaprine with taking cyclobenzaprine with other medications, including antidepressants, antipsychotics, and analgesics (“painkillers”), can also interfere with its metabolization. Often, this leads to an increase in both severity and duration of the drug’s effects.
How long it takes to start feeling the effects
Cyclobenzaprine’s onset varies depending on how it’s taken and whether it’s an immediate release or extended release formula.
- Immediate-release — begins to work within an hour of being ingested, with some effects starting within 20 to 30 minutes.
- Extended-release — patients typically start to feel effects within 60 to 90 minutes.
When is cyclobenzaprine at its peak?
The time of peak concentration varies depending on the formulation of cyclobenzaprine.
If taking a single dose of extended-release formula, the average peak time is around 7 hours. For immediate-release cyclobenzaprine, peak time is around 4 hours.
How long does Cyclobenzaprine make you sleepy for?
Sleepiness is a common side effect of cyclobenzaprine and other muscle relaxers. This can last for 4 to 6 hours with immediate-release tablets. During this time, it’s recommended to avoid drinking alcohol, operating machinery, driving, or any high performing tasks.
How long before bed should I take Cyclobenzaprine?
Because cyclobenzaprine has a long half life, our doctors say the earlier, the better.
It’s recommended to take your dose 1 to 2 hours before bed, which will decrease your chances of experiencing side effects the next day. After taking it, you should be prepared for sleep, not driving home from work or preparing a hot meal.
Do muscle relaxers make you tired the next day?
The mild sedative effect of muscle relaxers make them great for sleep, but it can also make you tired the next day. This depends on dosage, which can affect how long your next day drowsiness lasts and how severe it is.
In general, the lower the dose, the less likely it will be that you experience next-day drowsiness. For the 5 mg dosage we typically prescribe for sleep, this effect is rarely observed when taken as prescribed.
How far apart can you take Cyclobenzaprine 10 mg?
It’s recommended not to exceed three doses of cyclobenzaprine per day, dosed every ~6-8 hours.
The best way to know how often you should be taking cyclobenzaprine is to consult your doctor and follow the directions as prescribed.
When taking cyclobenzaprine for better sleep, our doctors advise taking a lower dosage of no more than 5 mg per night to avoid next-day drowsiness.