Classifications: central-acting skeletal muscle relaxant; gaba agonist; Therapeutic: skeletal muscle relaxant
Pregnancy Category: C
10 mg, 20 mg tablets; 10 mg, 20 mg orally disintegrating tablets; 50 mcg/mL, 250 mcg/mL ampules
Centrally acting skeletal muscle relaxant. Depresses monosynaptic and polysynaptic afferent reflex activity at spinal cord
level. Baclofen stimulates the GABA receptors, which results in decreased excitatory input into alpha-motor neurons.
Reduces skeletal muscle spasm caused by upper motor neuron lesions.
Symptomatic relief of painful spasms in multiple sclerosis and in the management of detrusor sphincter dyssynergia in spinal
cord injury or disease.
Treatment of trigeminal neuralgia and of tardive dystonia associated with antipsychotic medications, chronic pain.
Pregnancy (category C), coagulopathy, bacteremia, intramuscular or intrathecal administration, subcutaneous administration.
Impaired renal and hepatic function; bipolar disorder, psychosis, schizophrenia, seizure disorders, seizures, stroke, cerebral
palsy, depression, diabetes mellitus, dialysis, head trauma, PKU, epilepsy; thrombocytopenia; psychiatric or brain disorders;
older adults, children <2 y.
Route & Dosage
Adult: PO 5 mg t.i.d., may increase by 5 mg/dose q3d prn (max: 80 mg/d)
Child: PO 27 y, 1015 mg/d divided q8h, may increase by 515 mg/d q3d (max: 40 mg/d); ≥8 y, 1015 mg/d divided q8h, may increase by 515 mg/d q3d (max: 60 mg/d)
Adult: Intrathecal Prior to infusion pump implantation, initiate trial dose of 50 mcg/mL bolus administered in intrathecal space by barbotage
over ≤1 min. Observe patient over next 48 h for significant decrease
in muscle spasm. If response is less than desired, administer second bolus of 75 mcg/1.5 mL and observe 48 h. May
repeat in 24 h with a 100 mcg/2-mL bolus if necessary. Post-implant titration: Use screening dose if response lasted >12 h or double screening dose if response lasted <12 h and administer over 24 h.
After first 24 h, decrease dose by 1030% q24h until desired response achieved. Maintenance doses range from 121500
mcg/d, with most patients maintained on 300800 mcg/d.
- Give with food or milk to avoid GI distress.
- Give by direct intrathecal injection (via lumbar puncture or catheter) over at least 1 min or longer.
- Dilute only with sterile, preservative free NS injection. Baclofen must be diluted to a concentration of 50 mcg/mL when preparing test
- Intrathecal infusion pump: Do not abruptly discontinue as serious adverse effects may develop.
- Store at 15°30° C (59°86° F) in tightly closed container unless otherwise directed.
Adverse Effects (≥1%)CNS: Transient drowsiness,
vertigo, dizziness, weakness, fatigue
, headache, confusion, insomnia; ataxia, loss of seizure control in epileptic patients;
abrupt discontinuation of intrathecal
administration may result in high fever, altered mental status, exaggerated rebound
spasticity, and muscle rigidity, that in rare cases has advanced to rhabdomyolysis, multiple organ-system failure, and death. CV:
Hypotension. Special Senses:
Tinnitus, nasal congestion; blurred vision, mydriasis, nystagmus, diplopia, strabismus, miosis. GI:
, vomiting; mild increases in AST, and alkaline phosphatase, jaundice
Diagnostic Test Interference
Possibility of increases in blood-glucose, serum alkaline phosphatase, and AST levels.
InteractionsDrug: Alcohol, cns depressants
, mao inhibitors
compound CNS depression; baclofen may increase blood glucose
levels, making it necessary to increase dosage of sulfonylureas
Readily from GI tract. Peak:
23 h. Duration:
8 h. Distribution:
Minimal amounts cross blood-brain barrier; crosses placenta; distribution into breast milk unknown. Metabolism:
15% in liver. Elimination:
7085% in urine within 72 h; some elimination in feces. Half-Life:
Assessment & Drug Effects
- Supervise ambulation. Initially, the loss of spasticity induced by baclofen may affect patient's ability to stand or walk.
- Lab tests: Baseline and periodic BP, weight, blood sugar, hepatic function tests, and urine.
- Monitor for adverse neuropsychiatric or genitourinary symptoms that resemble those of the underlying disease. Assess them
carefully and report to the physician.
- Observe carefully for side effects: mental confusion, depression, hallucinations. Older adults are especially sensitive
to this drug.
- Monitor patients with epilepsy closely for possible loss of seizure control.
Patient & Family Education
- Note: CNS depressant effects will be additive to other CNS depressants, including alcohol.
- Monitor blood glucose for loss of glycemic control if diabetic.
- Do not drive or engage in other potentially hazardous activities until the response to drug is known.
- Report adverse reactions to physician. Most can be reduced by decreasing dosage. Incidence of CNS symptoms (drowsiness, dizziness,
ataxia) are reportedly high in patients >40 y of age.
- Do not self-dose with OTC drugs without physician's approval.
- Do not stop this drug unless directed to do so by physician. Drug withdrawal needs to be accomplished gradually over a period
of 2 wk or more. Abrupt withdrawal following prolonged administration may cause anxiety, agitated behavior, auditory and
visual hallucinations, severe tachycardia, acute exacerbation of spasticity, and seizures.