Generic Name: cyclobenzaprine (sye-kloe-BEN-za-preen)
Brand Names: Flexeril®
Classification: Muscle Relaxant
Issue Date: 1984

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

Cyclobenzaprine is used to treat pain, tenderness, and limited motion caused by muscle spasms. This medication is used together with rest and physical therapy for short-term treatment (2 to 3 weeks).

Take this medication exactly as it was prescribed for you. Do not take the medication in larger amounts, or take it for longer than recommended by your doctor.

Take each dose with a full glass of water. This medication is usually taken three times each day for a period of 2 to 3 weeks. Do not use cyclobenzaprine for longer than 3 weeks unless your doctor has told you to.

Do not stop taking cyclobenzaprine suddenly if you have been taking it for longer than 1 week. Stopping suddenly may cause nausea, headache and general discomfort.

This medication can cause you to have unusual results with certain medical tests. Tell any doctor who treats you that you are using cyclobenzaprine.

Store cyclobenzaprine at room temperature away from moisture and heat.

Do not take cyclobenzaprine if you have used an MAO inhibitor such as:

• isocarboxazid (Marplan®)
• tranylcypromine (Parnate®)
• phenelzine (Nardil®)
• selegiline (Eldepryl®, Emsam®)

within the past 14 days. Serious, life-threatening side effects can occur if you take cyclobenzaprine before the MAO inhibitor has cleared from your body.

Do not use cyclobenzaprine if you have recently had a heart attack, or if you have:

• Heart Rhythm Disorder
• Congestive Heart Failure
• Heart Block
• Overactive Thyroid

Before using this medication, tell your doctor if you have:

• Problems with Urination
• Enlarged Prostate
• Glaucoma
• Liver Disease

If you have any of these conditions, you may not be able to use cyclobenzaprine, or you may need a dosage adjustment or special tests during treatment.

This medication is not expected to be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment.

It is not known whether cyclobenzaprine passes into breast milk or if it could harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

Do not give this medication to a child younger than 12 years old.

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

Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at the next regularly scheduled time. Do not take extra medicine to make up the missed dose.

Seek emergency medical attention if you think you have used too much of this medicine. An overdose of cyclobenzaprine can be fatal.

Symptoms of a cyclobenzaprine overdose may include:

• drowsiness
• fast heartbeat
• tremors or shaking
• slurred speech
• confusion
• nausea
• vomiting
• hallucinations (seeing things)
• chest pain
• seizure (convulsions)

Cyclobenzaprine can cause side effects that may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be awake and alert. Avoid using other medicines that make you sleepy such as:

• cold medicine
• pain medication
• muscle relaxers
• medicine for seizures, depression or anxiety

They can add to sleepiness caused by cyclobenzaprine.

Avoid drinking alcohol, which can increase some of the side effects of cyclobenzaprine.

Side Effects

Get emergency medical help if you have any of these signs of an allergic reaction:

• hives
• difficulty breathing
• swelling of your face, lips, tongue, or throat

Stop using cyclobenzaprine and call your doctor at once if you have any of these SERIOUS side effects:

• Fast, Pounding, or Uneven Heartbeats
• Chest Pain or Heavy Feeling, Pain Spreading to the Arm or Shoulder, Nausea, Sweating, General Ill Feeling
• Sudden Numbness or Weakness, Especially on One Side of The Body
• Sudden Headache, Confusion, Problems with Vision, Speech, or Balance
• Feeling Light-Headed, Fainting
• Confusion, Weakness, Lack of Coordination
• Nausea, Stomach Pain, Low Fever, Loss of Appetite
• Dark Urine, Clay-Colored Stools, Jaundice (yellowing of the skin or eyes)
• Seizure (convulsions)
• Unusual Thoughts or Behavior, Hallucinations (seeing things)
• Easy Bruising or Bleeding, Unusual Weakness

Continue using cyclobenzaprine and talk with your doctor if you have any of these less serious side effects:

• Dry Mouth, Increased Thirst
• Blurred Vision
• Drowsiness, Dizziness, Tired Feeling
• Feeling Nervous or Irritable
• Heartburn, Loss of Appetite, Stomach Pain, Nausea, Vomiting
• Muscle Weakness
• Diarrhea, Constipation, Gas
• Sore Throat, Cold Symptoms

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.

Before taking cyclobenzaprine, tell your doctor if you are using any drugs that make you sleepy such as:

• alcohol
• cold medicine
• pain medication
• muscle relaxers
• medicine for seizures, depression or anxiety

Medications that can increase drowsiness caused by cyclobenzaprine include:

• amitriptyline (Elavil®)
• citalopram (Celexa®)
• clomipramine (Anafranil®)
• desipramine (Norpramin®)
• escitalopram (Lexapro®)
• fluoxetine (Prozac®, Sarafem®)
• fluvoxamine (Luvox®)
• imipramine (Tofranil®)
• nortriptyline (Pamelor®)
• paroxetine (Paxil®)
• sertraline (Zoloft®)
• meperidine (Demerol®)
• morphine (MS Contin, MSIR®)
• propoxyphene (Darvon®, Darvocet®)
• hydrocodone (Lorcet®, Vicodin®)
• oxycodone (Percocet®, Percodan®)
• fentanyl (Duragesic®)
• codeine (Tylenol3®)
• prescription cough medicines
• phenobarbital (Solfoton®, Luminal®)
• amobarbital (Amytal®)
• secobarbital (Seconal®)
• chlorpromazine (Thorazine®)
• fluphenazine (Prolixin®)
• mesoridazine (Serentil®)
• perphenazine (Trilafon®)
• prochlorperazine (Compazine®)
• thioridazine (Mellaril®)
• trifluoperazine (Stelazine®)
• diazepam (Valium®)
• alprazolam (Xanax®)
• lorazepam (Ativan®)
• clorazepate (Tranxene®)

If you are using any of these drugs, you may not be able to use cyclobenzaprine, or you may need dosage adjustments or special tests during treatment.

There may be other drugs not listed that can affect cyclobenzaprine. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.