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(me-tax -a-lone) ,


(trade name)


Therapeutic: skeletal muscle relaxants
Pregnancy Category: UK


Muscle spasm associated with acute painful musculoskeletal conditions (with rest and physical therapy).


Skeletal muscle relaxation, probably as a result of CNS depression.

Therapeutic effects

Skeletal muscle relaxation.


Absorption: Well absorbed following oral administration.
Distribution: Unknown.
Metabolism and Excretion: Mostly metabolized by the liver; metabolites excreted in urine.
Half-life: 2–3 hr.

Time/action profile

PO1 hr2 hr4–6 hr


Contraindicated in: Hypersensitivity;Significant hepatic/renal impairment;History of drug-induced hemolytic anemia or other anemia.
Use Cautiously in: Hepatic impairment;History of seizures; Obstetric / Lactation / Pediatric: Pregnancy, lactation or children ≤12 yr (safety not established); Geriatric: Appears on Beers list. Poorly tolerated due to anticholinergic effects.

Adverse Reactions/Side Effects

Central nervous system

  • drowsiness (most frequent)
  • dizziness (most frequent)
  • confusion
  • headache
  • irritability
  • nervousness


  • nausea (most frequent)
  • anorexia
  • dry mouth
  • GI upset
  • vomiting


  • urinary retention


Drug-Drug interaction

↑ CNS depression with other CNS depressants including alcohol, antihistamines, opioid analgesics, and sedative/hypnotics.Concomitant use of kava-kava, valerian, or chamomile can ↑ CNS depression.


Oral (Adults) 800 mg 3–4 times daily.

Availability (generic available)

Tablets: 800 mg Cost: Generic — $409.39 / 100

Nursing implications

Nursing assessment

  • Assess for pain, muscle stiffness, and range of motion before and periodically during therapy.
  • Geriatric: Assess geriatric patients for anticholinergic effects (sedation and weakness).
  • Lab Test Considerations: Monitor hepatic function tests closely in patients with pre-existing liver damage.
    • May cause false-positive Benedict’s tests.

Potential Nursing Diagnoses

Acute pain (Indications)
Impaired bed mobility (Indications)
Risk for injury (Side Effects)


  • Provide safety measures as indicated. Supervise ambulation and transfer.
  • Oral: Administer 3–4 times daily.

Patient/Family Teaching

  • Instruct patient to take medication as directed. Take missed doses within 1 hr; if not, return to regular dosing schedule. Do not double doses.
  • Encourage patient to comply with additional therapies prescribed for muscle spasm (rest, physical therapy, heat).
  • Medication may cause dizziness, drowsiness, and blurred vision. Advise patient to avoid driving and other activities requiring alertness until response to drug is known.
  • Instruct patient to make position changes slowly to minimize orthostatic hypotension.
  • Advise patient to avoid concurrent use of alcohol and other CNS depressants while taking this medication.
  • Instruct patient to notify health care professional if skin rash or yellowish discoloration of the skin or eyes occurs.
  • Emphasize the importance of routine follow-up exams to monitor progress.

Evaluation/Desired Outcomes

  • Decreased musculoskeletal pain and muscle spasticity.
    • Increased range of motion.
Drug Guide, © 2015 Farlex and Partners


A centrally acting muscle relaxant.
Adverse effects
Nausea, vomiting, gastrointestinal upset, drowsiness, dizziness, headache, irritability, rash, pruritus, leukopenia, haemolytic anaemia, jaundice.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.
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Elan had sued King after it withdrew from the agreed sale when US regulators began probing alleged patent irregularities over Skelaxin - the investigation was dropped earlier this month.
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King agreed in January to buy the US and Puerto Rican rights to the muscle relaxant Skelaxin and sleep aid Sonata for $850m.
However, the US company indicated last week the sale might not go ahead after it emerged that regulators in the US were probing claims that Elan unfairly blocked genetic competition regarding Skelaxin.
Sales of King's muscle relaxant Skelaxin, which also faces competition from a new drug, fell by about $1 million.
The US Food and Drug Administration approved a supplemental new drug application for two new treatments - the 800 milligramme strength Skelaxin tablet and a new drug application for tizanidine hydrochloride in capsule form.
Chief executive officer Donal Geaney said its key products continued powerful performance with revenues for Skelaxin, 51 per cent, and Maxiprime 112 per cent.
The launches of other key first-to-file products in the United States included metaxalone (Skelaxin, King Pharmaceuticals Inc.) and amoxicillin-clavulunate potassium ER (Augmentin ER, GlaxoSmithKline PLC).
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rights to muscle relaxant Skelaxin, the subject of the Federal Trade Commission investigation, as well as Sonata, a sleep aid.