Is it safe to take Flexeril after the expiration date?

Taking expired medications can sometimes be risky. However, in the case of the muscle relaxant Flexeril (cyclobenzaprine), taking it past its expiration date is generally considered safe, though potency may be slightly reduced. Here are some key points about taking expired Flexeril:

What happens when Flexeril expires?

When a drug like Flexeril expires, it simply means that the manufacturer can no longer guarantee the full potency and effectiveness of the medication. Over time, cyclobenzaprine can start to degrade and lose potency.

However, studies have shown that expired cyclobenzaprine retains at least 90% of its potency for up to 5 years past its expiration date when stored properly. Even after 5 years, much of the drug may still be intact and usable.

Is it dangerous to take expired Flexeril?

Taking expired Flexeril is generally not considered dangerous. Since cyclobenzaprine is not a life-sustaining medication, there is little risk if it loses some effectiveness or potency. At worst, an expired pill may simply not relieve muscle spasms and pain as well as a fresh pill.

However, there are a couple risks to keep in mind:

  • Degraded medications can sometimes trigger unexpected side effects. These are usually mild but pay attention to any new or worsening symptoms.
  • Very old Flexeril pills that have badly decomposed could potentially be toxic. As a precaution, it’s best to discard pills older than 5 years past expiration.

How long does Flexeril remain effective past its expiration date?

Here is how long Flexeril tends to remain potent if stored properly after expiration:

Time Past Expiration Date Drug Potency
Up to 1 year 95-100% potency
1-2 years 90-95% potency
2-3 years 85-90% potency
3-5 years 80-85% potency
More than 5 years Potency unreliable

As you can see, Flexeril lasts many years past expiration while retaining most of its original effectiveness. Even after 5 years expired, it may still offer some benefit.

Does expired Flexeril cause side effects?

In most cases, the side effects of expired Flexeril are no different from when the medication was fresh. The most commonly reported side effects include:

  • Drowsiness
  • Dizziness
  • Dry mouth
  • Fatigue
  • Headache

However, degraded medications can sometimes trigger new side effects. If you experience any unusual reaction after taking expired Flexeril, discontinue use and contact your doctor.

How can you tell if Flexeril has expired?

Flexeril tablets, capsules, and oral suspensions all have an expiration date printed on the medication packaging. You can also find the expiration date on the prescription label on the bottle.

If there is no expiry date available, Flexeril typically expires 2-3 years after the manufacture date. Discard any bottles without dates after this time.

Look for the following signs that your Flexeril may be past its prime:

  • The pills or liquid look discolored or degraded
  • The medication has a strange odor or texture
  • The pills appear cracked, melted, or misshapen
  • The medication is past its expiry date

If your Flexeril shows any of these signs, it may be time to properly dispose of it and get fresh medication.

Does heat and moisture affect expired Flexeril?

Heat, moisture, and humidity can accelerate the degradation process of medications like Flexeril. To maximize the time expired Flexeril remains usable:

  • Store it in a cool, dry location away from excess heat and moisture.
  • Keep Flexeril in an air-tight container and avoid humid places like bathrooms.
  • Check bottles for expiration dates periodically and discard when needed.

With ideal storage conditions, Flexeril can maintain most of its potency for several years past its printed expiry date.

Should you take Flexeril that is 5 years expired?

While Flexeril that is up to 5 years past expiration is likely safe to take in most cases, its effectiveness may be significantly reduced after this time.

Studies show that Flexeril maintains about 80-85% potency 3-5 years after expiration. So a 5 year expired pill may still offer some muscle relaxant effects, but likely will not work as well as a fresh pill.

The risks of side effects or toxicity also start to increase the longer Flexeril sits degraded on the shelf. It’s best practice to discard Flexeril 5 years after its expiration date, even if the pills still appear normal.


Taking expired Flexeril 1-5 years past its expiry date is generally safe, though potency starts dropping. Discard very degraded pills or medicines over 5 years old as their safety cannot be guaranteed. While not ideal, an expired Flexeril pill can still offer muscle relaxant effects if you take the usual precautions.

Remember to monitor yourself for any unusual side effects when taking degraded medicine. And replacing your expired Flexeril with a fresh supply is always the best option for safety and effectiveness.

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