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Pharmacologic class: Autonomic nervous system agent
Therapeutic class: Skeletal muscle relaxant (centrally acting)
Pregnancy risk category C
Unclear. Thought to act on spinal cord and subcortical levels of brain, inhibiting multisynaptic reflex arcs responsible for skeletal muscle activity.
Caplets: 500 mg
Tablets: 250 mg, 500 mg
Indications and dosages
➣ Adjunct to rest and physical therapy in treatment of muscle spasms associated with acute, painful musculoskeletal conditions
Adults: 250 to 750 mg P.O. three to four times daily
• Hypersensitivity to drug
• Hepatic impairment
Use cautiously in:
• underlying cardiovascular disease, renal impairment
• children (safety not established).
• If desired, crush tablets and mix contents with food or water.
• Don't withdraw drug abruptly.
CNS: dizziness, drowsiness, light-headedness, malaise, headache, over-stimulation, tremor
GI: nausea, vomiting, constipation, diarrhea, heartburn, abdominal distress, anorexia
GU: orange or purplish-red urine
Hepatic: hepatic dysfunction
Skin: allergic dermatitis, urticaria, erythema, pruritus, petechiae, ecchymosis, angioedema
Other: allergic reactions
Drug-drug. CNS depressants (including antihistamines, antidepressants, opioids, sedative-hypnotics): increased risk of CNS depression
Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, bilirubin: increased levels
Drug-herbs. Chamomile, hops, kava, skullcap, valerian: increased CNS depression
Drug-behaviors. Alcohol use: increased sedation
☞ Stay alert for signs and symptoms of hepatic dysfunction. Withhold drug and notify prescriber if these occur.
• Monitor hepatic enzyme and serum electrolyte levels.
☞ Instruct patient to promptly report yellowing of eyes or skin.
• Caution patient not to consume alcohol during therapy.
• Instruct patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
• Tell patient that drug may turn his urine orange or purplish-red.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above.