Cyclobenzaprine (Flexeril) vs. naproxen (Aleve)

• Cyclobenzaprine and naproxen are used to treat different types of pain in different ways.
• Cyclobenzaprine is a muscle relaxant used with rest and physical therapy for short-term relief of muscle spasms associated with acute painful muscle and skeletal conditions.
• Naproxen is used to relieve mild to moderate pain, inflammation, and fever from various causes.
• Brand names for cyclobenzaprine include Flexeril, Amrix, and Fexmid.
• Brand names for naproxen include Aleve, Anaprox DS, and Naprosyn.
• Cyclobenzaprine and naproxen belong to different drug classes. Cyclobenzaprine is a muscle relaxant and naproxen is a nonsteroidal anti-inflammatory drug (NSAID).
• Side effects of cyclobenzaprine and naproxen that are similar include headaches, dizziness, drowsiness, nausea, constipation, and abdominal pain or discomfort.
• Side effects of cyclobenzaprine that are different from naproxen include dry mouth, fatigue, blurred vision, unpleasant taste, nervousness, confusion, and acid reflux.
• Side effects of naproxen that are different from cyclobenzaprine include rash, ringing in the ears, diarrhea, heartburn, fluid retention, and shortness of breath.

Cyclobenzaprine is a muscle relaxant used together with physical therapy and rest for short-term relief of muscle spasms associated with acute painful musculoskeletal conditions. It is only intended for short-term use of two to three weeks. Cyclobenzaprine works to relieve muscle spasm when the spasm is due to local problems within the muscle and due to problems in the nerves that control the muscles. Research shows that cyclobenzaprine accomplishes its beneficial effect through a complex mechanism within the nervous system, most likely in the brainstem.

Naproxen is a nonsteroidal anti-inflammatory drug (NSAID) used to relieve mild to moderate pain, inflammation, and fever. Other NSAIDs include ibuprofen (Motrin), indomethacin (Indocin), nabumetone (Relafen), and several others. These drugs work by reducing the levels of prostaglandins, chemicals that are responsible for pain, fever, and inflammation. Naproxen blocks the enzyme that makes prostaglandins (cyclooxygenase), resulting in lower concentrations of prostaglandins, and thereby reducing inflammation, pain, and fever.

Cyclobenzaprine

The most common side effects of cyclobenzaprine include:

• Drowsiness
• Dry mouth
• Fatigue
• Headaches
• Dizziness

Other reported side effects include:

• Nausea
• Constipation
• Blurred vision
• Unpleasant taste
• Nervousness
• Confusion
• Acid reflux
• Abdominal pain or discomfort

Possible serious side effects include:

• Seizures
• Abnormal heartbeats
• Stroke
• Heart attacks
• Heat stroke

Abrupt cessation after prolonged therapy may cause withdrawal symptoms such as headaches, nausea, and weakness.

Naproxen

The most common side effects from naproxen are:

• Rash
• Ringing in the ears
• Headaches
• Dizziness
• Drowsiness
• Abdominal pain
• Nausea
• Diarrhea
• Constipation
• Heartburn
• Fluid retention
• Shortness of breath

Other important side effects include:

• Fluid retention
• Blood clots
• Heart attacks
• Hypertension
• Heart failure

Cyclobenzaprine

• The recommended dose of cyclobenzaprine is 5 or 10 mg three times daily using immediate release tablets or 15 or 30 mg once daily using extended release tablets.

Naproxen

• The usual adult dose for pain is 250 mg every 6 to 8 hours or 500 mg twice daily using regular naproxen tablets. The usual dose for Naprelan controlled release tablets is 750 to 1000 mg given once daily. For EC-Naprosyn, the usual dose is 375 to 500 mg twice daily.
• Naproxen should be given with food to reduce upset stomach. The dose for rheumatoid arthritis, osteoarthritis, or ankylosing spondylitis is 500 to 1000 mg every 12 hours. Dysmenorrhea is treated with 250 mg every 6 to 8 hours after an initial dose of 500 mg.

Cyclobenzaprine

• Cyclobenzaprine is chemically related to the tricyclic class of antidepressants -- for example, amitriptyline (Elavil, Endep), nortriptyline (Pamelor). As such, it should not be taken with or within two weeks of any monoamine oxidase inhibitor (MAOI) -- for example, isocarboxazid (Marplan), phenelzine (Nardil), tranylcypromine (Parnate), and procarbazine (Matulane). High fever, convulsions, and even death can occur when these drugs are used together.
• Cyclobenzaprine interacts with other medications and drugs that slow the brain's processes, such as:
  • alcohol
  • barbiturates
  • benzodiazepines -- for example, diazepam (Valium), lorazepam (Ativan)
  • narcotics

Naproxen

Naproxen is associated with several suspected or probable interactions that affect the action of other drugs. The following examples are the most common suspected interactions.

• Naproxen may increase the blood levels of lithium (Eskalith, Lithobid) by reducing the excretion of lithium by the kidneys. Increased levels of lithium may lead to lithium toxicity.
• Naproxen may reduce the blood pressure lowering effects of blood pressure medications. This may occur because prostaglandins play a role in the regulation of blood pressure.
• When naproxen is used in combination with methotrexate (Rheumatrex, Trexall) or aminoglycosides (for example, gentamicin), the blood levels of the methotrexate or aminoglycoside may increase, presumably because the elimination from the body of these drugs is reduced. This may lead to more methotrexate or aminoglycoside-related side effects.
• Individuals taking anticoagulants -- for example, warfarin (Coumadin) -- should avoid naproxen because naproxen also thins the blood, and excessive blood thinning may lead to bleeding.
• Naproxen increases the negative effect of cyclosporine on kidney function and reduces the effect of furosemide (Lasix) and thiazide diuretics because of prostaglandin inhibition.
• Naproxen should be avoided by patients with a history of asthma attacks, hives or other allergic reactions to aspirin or other NSAIDs. If aspirin is taken with naproxen, there may be an increased risk for developing an ulcer.
• Persons who have more than 3 alcoholic beverages per day may be at increased risk of developing stomach ulcers when taking naproxen or other NSAIDs.

Cyclobenzaprine

• There are no adequate studies of cyclobenzaprine in pregnant women. However, studies in animals suggest no important effects on the fetus. Cyclobenzaprine therefore can be used in pregnancy if the doctor considers it necessary.
• It is not known whether cyclobenzaprine is secreted in milk. However, since it is related to the tricyclic antidepressants, some of which are excreted in breast milk, women who are breastfeeding should use caution with this medication.

Naproxen

• NSAIDs may cause a fetal birth defect called ductus arteriosus (early closure of two major blood vessels of the heart and lung) in the third trimester of pregnancy. Therefore, NSAIDs should be avoided during this last part of pregnancy.
• A small amount of naproxen is excreted in breast milk. Because the concentration in breast milk is low, breastfeeding while taking naproxen probably is not harmful to the infant.