Generic Flexeril

Cyclobenzaprine is a muscle relaxant. It works by blocking nerve impulses (or pain sensations) that are sent to your brain.

Cyclobenzaprine is used together with rest and physical therapy to treat skeletal muscle conditions such as pain or injury.

Cyclobenzaprine may also be used for purposes not listed in this medication guide.

Important Information

You should not use cyclobenzaprine if you have an allergy to the medication, a certain type of thyroid disorder (hyperthyroidism), heart block, congestive heart failure, a heart rhythm disorder, or you have recently had a heart attack.

Do not use cyclobenzaprine if you have taken an MAO inhibitor in the past 14 days, such as isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, or tranylcypromine.

Cyclobenzaprine Pregnancy Warnings

US FDA pregnancy category: B

Embryofetal development in rats and rabbits given approximately 3 and 15 times, respectively, the maximum recommended human dose (MRHD) was not adversely effected. Dams receiving this drug at doses 3 times or more the MRHD during pregnancy and lactation, had pups with decreased body weight and survival. There are no adequate and controlled studies in pregnant women.

US FDA pregnancy category B: Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women.
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Cyclobenzaprine Breastfeeding Warnings

This drug has been shown to be excreted in rat milk and achieve concentrations in the milk which are 50% of those in the rat maternal plasma. As this drug is closely related to the tricyclic antidepressants, some of which are known to be excreted in human milk, use caution especially when other drugs that cause sedation are used simultaneously.

Caution is recommended.

Cyclobenzaprine Levels and Effects while Breastfeeding

Summary of Use during Lactation

Amounts of cyclobenzaprine in milk appear to be very small and two infants apparently tolerated the drug in milk well. If cyclobenzaprine is required by the mother, it is not a reason to discontinue breastfeeding. Monitor the infant for (drowsiness, adequate weight gain, and developmental milestones), especially in neonates and preterm infants and when using combinations of sedating drugs.

Drug Levels

Maternal Levels. Two mothers were taking chronic cyclobenzaprine therapy. One mother was taking 5 mg once daily for temporomandibular joint pain and the other mother was taking 10 mg twice daily for fibromyalgia pain. Each collected milk at 0, 1, 2, 4, 6, 8 and 12 hours after a dose. After the 5 mg dose, the peak milk level was 6.6 mcg/L and the average level was 2.2 mcg/L. After the 10 mg dose, the peak milk level was 24.5 mcg/L and the average level was 10.3 mcg/L. These amounts resulted in the respective infant dosages of 0.3 mcg/kg and 0.7 mcg/kg daily. In both cases, the weight-adjusted dosage was 0.5% of the maternal dosage.

Infant Levels. Relevant published information was not found as of the revision date.

Effects in Breastfed Infants

Two mothers were taking chronic cyclobenzaprine therapy. One mother was taking 5 mg once daily for temporomandibular joint pain and the other mother was taking 10 mg twice daily for fibromyalgia pain. The latter mother was also taking unspecified antidepressants, levothyroxine, zolpidem, alprazolam and famotidine. Both mothers were breastfeeding their infants (extent not stated). Neither infant had any noticeable adverse reaction such as sedation.[1]

A search was performed of the shared database of all U.S. poison control centers for the time period of 2001 to 2017 for calls regarding medications and breastfeeding. Of 2319 calls in which an infant was exposed to a substance via breastmilk, 7 were classified as resulting in a major adverse effect, and one of these involved cyclobenzaprine. A 16-day-old infant was exposed to cyclobenzaprine, acetaminophen and oxycodone in breastmilk. The infant was admitted to the hospital in a noncritical care unit for bradycardia, hypotension, and respiratory arrest. The dosages and extent of breastfeeding were not reported and the infant survived.

Effects on Lactation and Breastmilk

Relevant published information was not found as of the revision date.

Before taking this medicine

You should not use cyclobenzaprine if you are allergic to it, or if you have:

• hyperthyroidism;
• heart block, heart rhythm disorder, congestive heart failure; or
• if you have recently had a heart attack.

Cyclobenzaprine is not approved for use by anyone younger than 15 years old.

Do not use cyclobenzaprine if you have taken an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, and tranylcypromine.

Some medicines can interact with cyclobenzaprine and cause a serious condition called serotonin syndrome. Be sure your doctor knows if you also take stimulant medicine, opioid medicine, herbal products, or medicine for depression, mental illness, Parkinson’s disease, migraine headaches, serious infections, or prevention of nausea and vomiting. Ask your doctor before making any changes in how or when you take your medications.

To make sure cyclobenzaprine is safe for you, tell your doctor if you have:

• thyroid disease;
• liver disease;
• glaucoma;
• enlarged prostate; or
• problems with urination.

It is not known whether cyclobenzaprine will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

It may not be safe to breast-feed while using this medicine. Ask your doctor about any risk.

Older adults may be more sensitive to the effects of this medicine.

Cyclobenzaprine is usually taken taken for up to 2 or 3 weeks. Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose.

Follow your doctor’s dosing instructions very carefully.

Swallow the capsule whole and do not crush, chew, break, or open it.

Call your doctor if your symptoms do not improve after 3 weeks, or if they get worse.

Store at room temperature away from moisture, heat, and light.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose of cyclobenzaprine can be fatal.

Overdose symptoms may include severe drowsiness, vomiting, fast heartbeats, tremors, agitation, or hallucinations.

What should I avoid while taking cyclobenzaprine?

Avoid driving or hazardous activity until you know how this medicine will affect you. Your reactions could be impaired.

Avoid drinking alcohol. Dangerous side effects could occur.

Cyclobenzaprine side effects

Get emergency medical help if you have signs of an allergic reaction to cyclobenzaprine: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using this medicine and call your doctor at once if you have:

• fast or irregular heartbeats;
• chest pain or pressure, pain spreading to your jaw or shoulder; or
• sudden numbness or weakness (especially on one side of the body), slurred speech, balance problems.

Seek medical attention right away if you have symptoms of serotonin syndrome, such as: agitation, hallucinations, fever, sweating, shivering, fast heart rate, muscle stiffness, twitching, loss of coordination, nausea, vomiting, or diarrhea.

Serious side effects may be more likely in older adults.

Common cyclobenzaprine side effects may include:

• drowsiness, tiredness;
• headache, dizziness;
• dry mouth; or
• upset stomach, nausea, constipation.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Using cyclobenzaprine with other drugs that make you drowsy can worsen this effect. Ask your doctor before using opioid medication, a sleeping pill, a muscle relaxer, or medicine for anxiety or seizures.

Tell your doctor about all your other medicines, especially:

• MAO inhibitors, such as isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, or tranylcypromine;
• Any antidepressant or anxiety medications;
• bupropion (Zyban, for smoking cessation or Wellbutrin, for depression);
• meperidine;
• tramadol;
• verapamil;
• cold or allergy medicine that contains an antihistamine (Benadryl and others);
• medicine to treat Parkinson’s disease;
• medicine to treat excess stomach acid, stomach ulcer, motion sickness, or irritable bowel syndrome;
• medicine to treat overactive bladder; or
• bronchodilator asthma medication.

This list is not complete. Other drugs may interact with cyclobenzaprine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

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