Chlorzoxazone is indicated as an adjunct to rest, physical therapy, and other measures for the
relief of discomfort associated with acute, painful musculoskeletal conditions. The mode of action
of this drug has not been clearly identified, but may be related to its sedative properties
Chlorzoxazone does not directly relax tense skeletal muscles in man.

Route of administration: Oral
 Always take Relaxon Forte™ Tablets exactly as your doctor has told you.
 You should check with your doctor if you are not sure.
 The usual adult dosage is one tablet to be taken 3 Times daily.
 If adequate response is not obtained with this dose, it may be increased to 1 ½ tablets (750
mg) three daily. As improvement occurs dosage can usually be reduced.

Serious (including fatal) hepatocellular toxicity has been reported rarely in patients receiving
chlorzoxazone. The mechanism is unknown but appears to be idiosyncratic and unpredictable.
Factors predisposing patients to this rare event are not known. Patients should be instructed to
report early signs and/or symptoms of hepatotoxicity such as fever, rash, anorexia, nausea,
vomiting, fatigue, right upper quadrant pain, dark urine, or jaundice. Chlorzoxazone should be
discontinued immediately and a physician consulted if any of these signs or symptoms develop.
Chlorzoxazone use should also be discontinued if a patient develops abnormal liver enzymes
(e.g., AST, ALT, alkaline phosphatase and bilirubin.)
The concomitant use of alcohol or other central nervous system depressants may have an
additive effect.
Chlorzoxazone should be used with caution in patients with known allergies or with a history of
allergic reactions to drugs. If a sensitivity reaction occurs such as urticaria, redness, or itching of
the skin, the drug should be stopped.
If any symptoms suggestive of liver dysfunction are observed, the drug should be discontinued.

Data pertaining to interaction with other medicinal products and other forms of interaction are
not available in any of the stringent regulatory authorities.

The safe use of chlorzoxazone has not been established with respect to the possible adverse
effects upon fetal development. Therefore, it should be used in women of childbearing potential
only when, in the judgment of the physician, the potential benefits outweigh the possible risks.

Chlorzoxazone should not be taken for drivers (as Chlorzoxazone causes drowsiness).

Chlorzoxazone containing products are usually well tolerated. It is possible in rare instances that
chlorzoxazone may have been associated with gastrointestinal bleeding. Drowsiness, dizziness,
lightheadedness, malaise, or over stimulation may be noted by an occasional patient. Rarely,
allergic-type skin rashes, petechiae, or ecchymoses may develop during treatment.
Angioneurotic edema or anaphylactic reactions are extremely rare. There is no evidence that the
drug will cause renal damage.
Rarely, a patient may note discoloration of the urine resulting from a phenolic metabolite of
chlorzoxazone. This finding is of no known clinical significance
To report any side effect(s):
• Saudi Arabia:
The National Pharmacovigilance and Drug Safety Centre (NPC)
Fax: +966-11-205-7662.
Call NPC at +966-11-2038222,
Exts: 2317-2356-2353-2354-2334-2340.
Toll free phone: 8002490000
E-mail: npc.drug@sfda.gov.sa
Website: www.sfda.gov.sa/npc
• Other GCC States:
− Please contact the relevant competent authority.

Symptoms
Initially, gastrointestinal disturbances such as nausea, vomiting, or diarrhea together with
drowsiness, dizziness, lightheadedness or headache may occur. Early in the course there may be
malaise or sluggishness followed by marked loss of muscle tone, making voluntary movement
impossible. The deep tendon reflexes may be decreased or absent. The sensorium remains
intact, and there is no peripheral loss of sensation. Respiratory depression may occur with rapid,
irregular respiration and intercostal and substernal retraction. The blood pressure is lowered, but
shock has not been observed.

Treatment
Gastric lavage or induction of emesis should be carried out, followed by administration of
activated charcoal. Thereafter, treatment is entirely supportive. If respirations are depressed,
oxygen and artificial respiration should be employed and a patent airway assured by use of an
oropharyngeal airway or endotracheal tube. Hypotension may be counteracted by use of
dextran, plasma, concentrated albumin or a vasopressor agent such as norepinephrine.
Cholinergic drugs or analeptic drugs are of no value and should not be used.

Chlorzoxazone is Oxazol, thiazine, and triazine derivatives Muscle Relaxants, Centrally Acting
Agents with ATC code M03BB03. Chlorzoxazone is a centrally-acting agent for painful
musculoskeletal conditions. Data available from animal experiments as well as human study
indicate that Chlorzoxazone acts primarily at the level of the spinal cord and subcortical areas
of the brain where it inhibits multisynaptic reflex arcs involved in producing and maintaining
skeletal muscle spasm of varied etiology. The clinical result is a reduction of the skeletal
muscle spasm with relief of pain and increased mobility of the involved muscles. Blood levels
of Chlorzoxazone can be detected in people during the first 30 minutes and peak levels may be
reached, in the majority of the subjects, in about 1 to 2 hours after oral administration of
Chlorzoxazone. Chlorzoxazone is rapidly metabolized and is excreted in the urine, primarily in
a conjugated form as the glucuronide. Less than one percent of a dose of Chlorzoxazone is
excreted unchanged in the urine in 24 hours.

1. Route of Elimination
Chlorzoxazone is rapidly metabolized and is excreted in the urine, primarily in a conjugated
form as the glucuronide.

2. Metabolism/Metabolites
Chlorzoxazone is rapidly metabolized in the liver and is excreted in the urine, primarily in a
conjugated form as the glucuronide.
3. Mechanism of Action
Chlorzoxazone inhibits degranulation of mast cells, subsequently preventing the release of
histamine and slow-reacting substance of anaphylaxis (SRS-A), mediators of type I allergic
reactions. Chlorzoxazone also may reduce the release of inflammatory leukotrienes.
Chlorzoxazone may act by inhibiting calcium and potassium influx which would lead to
neuronal inhibition and muscle relaxation. Data available from animal experiments as well as
human study indicate that Chlorzoxazone acts primarily at the level of the spinal cord and
subcortical areas of the brain where it inhibits multisynaptic reflex arcs involved in producing
and maintaining skeletal muscle spasm.

There are no preclinical data of relevance to the prescriber additional to that already covered in
other sections of the SPC.

Microcrystalline Cellulose PH101
 Lactose Anhydrous DC Gr
 Pregelatinised Starch-1500
 Sodium Starch Glycolate
 Colloidal Silicon Dioxide (Aerosil 200)
 Magnesium Stearate
 Docusate Sodium 85% and Sodium Benzoate 15%
 Purified Water

None known.

Do not store above 30°C.
 Keep out of reach and sight of children.

Relaxon Forte 500 mg Tablets is packed in Aluminium-PVC/PVDC Blister pack of 3x10’s.

No special requirements.