Chlorzoxazone (By mouth)


Chlorzoxazone (klor-ZOX-a-zone)

Treats pain and stiffness caused by muscle spasm. This medicine is a muscle relaxer.

Brand Name(s)

Lorzone, Remular-S, Parafon Forte DSC

There may be other brand names for this medicine.

When This Medicine Should Not Be Used

You should not use this medicine if you have ever had an allergic reaction to chlorzoxazone. You should not use if you have had a recent heart attack, heart failure, a heart rhythm disorder, heart block, or hyperthyroidism (overactive thyroid).

How to Use This Medicine


  • Your doctor will tell you how much to take and how often.
  • You may take the tablets whole or you may crush the tablets and mix them with a small amount of food or liquid.

If a dose is missed:

  • Use the missed dose as soon as possible.
  • If it is almost time for your next regular dose, wait until then to use the medicine and skip the missed dose.
  • You should not use two doses at the same time.

How to Store and Dispose of This Medicine

  • Store at room temperature away from heat, moisture, and direct light.
  • Keep all medicine out of the reach of children.

Drugs and Foods to Avoid

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • You should not use this medicine if you have used an MAO inhibitor such as Marplan® or Nardil® within the past 14 days.
  • Unless approved by your doctor, you should not use antidepressants, sleeping pills, tranquilizers, cold and allergy medicine, pain killers, or other muscle relaxants while using chlorzoxazone.
  • Do not drink alcohol while using this medicine.

Warnings While Using This Medicine

  • If you are pregnant or breastfeeding, talk to your doctor before using this medicine.
  • Talk to your doctor before using this medicine if you have kidney or liver disease or glaucoma.
  • You should not use more of this medicine, or use it for longer periods, than your doctor has ordered.
  • This medicine can cause drowsiness or blurred vision. Be careful while driving a car or operating machinery.
  • This medicine can sometimes cause your urine to turn an orange or red color. This is normal.

Possible Side Effects While Using This Medicine

Call your doctor right away if you notice any of these side effects:

  • Skin rash or itching
  • Trouble breathing
  • Swelling of face or tongue
  • Yellowing of eyes or skin
  • Muscle weakness or slurred speech

If you notice these less serious side effects, talk with your doctor:

  • Drowsiness, dizziness, clumsiness
  • Constipation or diarrhea
  • Nausea or vomiting
  • Dry mouth
  • Heartburn or unpleasant taste

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Version Info

  • Last Reviewed on 06/12/2013

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This page was last updated: June 18, 2013

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