Cyclobenzaprine vs. Norco: What's the Difference?

What is Cyclobenzaprine? What is Norco?

Cyclobenzaprine is a muscle relaxant used with rest and physical therapy for short-term relief up to two or three weeks only of muscle spasms associated with acute painful muscle and skeletal conditions. Cyclobenzaprine relieves muscle spasm when the spasm is due to problems in the muscle itself and not problems in the nerves controlling the muscles. Cyclobenzaprine seems to achieve its helpful effect through a complex mechanism within the nervous system, probably in the brainstem.

Norco (hydrocodone acetaminophen) is a combination of a narcotic pain-reliever and a cough suppressant, similar to codeine, and a non-narcotic analgesic (pain reliever) and antipyretic (fever reducer) prescribed for moderate to moderately severe pain. The hydrocodone in Norco blocks the receptors on nerve cells in the brain that give rise to the sensation of pain. The acetaminophen in Norco works by elevating the threshold to pain, that is, in order for pain to be felt, greater stimulation of the nerves responsible for the sensation of pain is necessary. It reduces fever through its action on the temperature-regulating center of the brain.

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What are the side effects of cyclobenzaprine and Norco?

Cyclobenzaprine

The most common side effects of cyclobenzaprine include:

Other reported side effects include:

Possible serious side effects include:

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

Norco

Common side effects of hydrocodone/acetaminophen are:

  • lightheadedness,
  • dizziness,
  • sedation,
  • nausea, and
  • vomiting.

Other important side effects include:

  • drowsiness,
  • constipation, and
  • spasm of the ureter, which can lead to difficulty in urinating.

Hydrocodone can impair thinking and the physical abilities required for driving or operating machinery. Hydrocodone can depress breathing, and should be used with caution in elderly, debilitated patients and in patients with serious lung disease.

Hydrocodone may be habit-forming. Mental and physical dependence can occur but are unlikely when used for short-term pain relief.

Acetaminophen can cause severe liver failure if excessive amounts are used and when combined with chronic alcohol use or other drugs that also impair liver function.

What is the dosage of cyclobenzaprine vs. Norco?

Cyclobenzaprine

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

Norco

The usual dose for adults is 1 to 2 tablets or capsules (hydrocodone 2.5 to 10 mg; acetaminophen 300 to 750 mg) every 4 to 6 hours or 15 mL of liquid every 4 to 6 hours as needed.

What drugs interact with cyclobenzaprine and Norco?

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 (MAO) inhibitor, 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

Norco

Patients receiving other narcotics, antihistamines, antipsychotics, antianxiety agents, or other CNS depressants (including alcohol) concomitantly with NORCO may exhibit an additive CNS depression. When combined therapy is contemplated, the dose of one or both agents should be reduced.

The use of MAO inhibitors or tricyclic antidepressants with hydrocodone preparations may increase the effect of either the antidepressant or hydrocodone.

Drug/Laboratory Test Interactions

Acetaminophen may produce false-positive test results for urinary 5-hydroxyindoleacetic acid.

Are cyclobenzaprine and Norco safe to use while pregnant or breastfeeding?

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 physician feels that it is 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, caution is advised in using this medication in women who are breastfeeding.

Norco

There are no adequate studies of hydrocodone and acetaminophen in pregnant women.

Hydrocodone/acetaminophen is excreted in breast milk, and, therefore should be used cautiously by nursing mothers.

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Summary

Cyclobenzaprine (Flexeril) and Norco (hydrocodone acetaminophen) are used to treat pain. Cyclobenzaprine is mainly used with rest and physical therapy for short-term relief of muscle spasms associated with acute painful muscle and skeletal conditions. Norco is prescribed for moderate to moderately severe pain of various causes. Brand names for cyclobenzaprine include, Amrix, and Fexmid.

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Medically Reviewed on 6/5/2019
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