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standards of non-Merck sources.
ALERT: U.S. Boxed Warning
The FDA-approved labeling includes a boxed warning. See Warnings/Precautions section and/or refer to product labeling for additional detail.
Medication Safety Issues
Sound-alike/look-alike issues:
Baclofen may be confused with Bactroban®
Lioresal® may be confused with lisinopril, Lotensin®
High alert medication: The Institute for Safe Medication Practices (ISMP) includes this medication (intrathecal administration) among its list of drugs which have a heightened risk of causing significant patient harm when used in error.
Pronunciation
(BAK loe fen)
U.S. Brand Names
Generic Available
Yes: Tablets only
Canadian Brand Names
Pharmacologic Category
Pharmacologic Category Synonyms
Use: Labeled Indications
Treatment of reversible spasticity associated with multiple sclerosis or spinal cord lesions
Orphan drug: Intrathecal: Treatment of intractable spasticity caused by spinal cord injury, multiple sclerosis, and other spinal disease (spinal ischemia or tumor, transverse myelitis, cervical spondylosis, degenerative myelopathy)
Use: Unlabeled/Investigational
Intractable hiccups, intractable pain relief, bladder spasticity, trigeminal neuralgia, cerebral palsy, Huntington's chorea
Pregnancy Risk Factor
C
Lactation
Enters breast milk (small amounts)/compatible
Contraindications
Hypersensitivity to baclofen or any component of the formulation
Warnings/Precautions
Boxed warnings:
• Abrupt withdrawal: See “Other warnings/precautions” below.
Concerns related to adverse effects:
• CNS depression: May cause CNS depression, which may impair physical or mental abilities; patients must be cautioned about performing tasks which require mental alertness (eg, operating machinery or driving).
Disease-related concerns:
• Renal impairment: Use with caution in patients with renal impairment.
• Seizure disorder. Use with caution in patients with a history of seizure disorder.
Special populations:
• Elderly: Use with caution in the elderly; may be more sensitive to adverse CNS effects, especially at higher doses.
Other warnings/precautions:
• Abrupt withdrawal: [U.S. Boxed Warning]: Avoid abrupt withdrawal of the drug; abrupt withdrawal of intrathecal baclofen has resulted in severe sequelae (hyperpyrexia, obtundation, rebound/exaggerated spasticity, muscle rigidity, and rhabdomyolysis), leading to organ failure and some fatalities. Risk may be higher in patients with injuries at T-6 or above, history of baclofen withdrawal, or limited ability to communicate.
Adverse Reactions
>10%:
Central nervous system: Drowsiness, vertigo, psychiatric disturbances, insomnia, slurred speech, ataxia, hypotonia
Neuromuscular & skeletal: Weakness
1% to 10%:
Cardiovascular: Hypotension
Central nervous system: Fatigue, confusion, headache
Dermatologic: Rash
Gastrointestinal: Nausea, constipation
Genitourinary: Polyuria
<1%: Palpitation, chest pain, syncope, euphoria, excitement, depression, hallucinations, xerostomia, anorexia, abnormal taste, abdominal pain, vomiting, diarrhea, enuresis, urinary retention, dysuria, impotence, inability to ejaculate, nocturia, paresthesia, hematuria, dyspnea
Withdrawal reactions have occurred with abrupt discontinuation (particularly severe with intrathecal use).
Drug Interactions
Alcohol (Ethyl): CNS Depressants may enhance the CNS depressant effect of Alcohol (Ethyl). Risk C: Monitor therapy
CNS Depressants: May enhance the adverse/toxic effect of other CNS Depressants. Risk C: Monitor therapy
Ethanol/Nutrition/Herb Interactions
Ethanol: Avoid ethanol (may increase CNS depression).
Herb/Nutraceutical: Avoid valerian, St John's wort, kava kava, gotu kola.
Compatibility
Stable in sterile, preservative free NS.
Compatibility when admixed: Compatible: Morphine.
Mechanism of Action
Inhibits the transmission of both monosynaptic and polysynaptic reflexes at the spinal cord level, possibly by hyperpolarization of primary afferent fiber terminals, with resultant relief of muscle spasticity
Pharmacodynamics/Kinetics
Onset of action: 3-4 days
Peak effect: 5-10 days
Absorption (dose dependent): Oral: Rapid
Protein binding: 30%
Metabolism: Hepatic (15% of dose)
Half-life elimination: 3.5 hours
Time to peak, serum: Oral: Within 2-3 hours
Excretion: Urine and feces (85% as unchanged drug)
Dosage
Oral (avoid abrupt withdrawal of drug):
Children (unlabeled use): Caution: Pediatric dosing expressed as a daily amount, and NOT in mg/kg. Limited published data in children; the following is a compilation of small prospective studies (Albright, 1996; Milla, 1977; Scheinberg, 2006) and one large retrospective study (Lubsch, 2006):
<2 years: 10-20 mg daily divided every 8 hours; titrate dose every 3 days in increments of 5-15mg/day to a maximum of 40 mg daily
2-7 years: Initial: 20-30 mg daily divided every 8 hours; titrate dose every 3 days in increments of 5-15 mg/day to a maximum of 60 mg daily
?8 years: 30-40 mg daily divided every 8 hours; titrate dose every 3 days in increments of 5-15 mg/day to a maximum of 120 mg daily
Note: Baclofen dose may need to be increased over time. One retrospective analysis (Lubsch, 2006) suggested that increased doses were needed as the time increased from spasticity onset, as age increased, and as the number of concomitant antispasticity medications increased. A small number of patients required daily doses exceeding 200 mg.
Adults: 5 mg 3 times/day, may increase 5 mg/dose every 3 days to a maximum of 80 mg/day
Hiccups (unlabeled use): Usual effective dose: 10-20 mg 2-3 times/day
Intrathecal: Children and Adults:
Test dose: 50-100 mcg, doses >50 mcg should be given in 25 mcg increments, separated by 24 hours. A screening dose of 25 mcg may be considered in very small patients. Patients not responding to screening dose of 100 mcg should not be considered for chronic infusion/implanted pump.
Maintenance: After positive response to test dose, a maintenance intrathecal infusion can be administered via an implanted intrathecal pump. Initial dose via pump: Infusion at a 24-hour rate dosed at twice the test dose. Avoid abrupt discontinuation.
Elderly: Oral (the lowest effective dose is recommended): Initial: 5 mg 2-3 times/day, increasing gradually as needed; if benefits are not seen, withdraw the drug slowly.
Dosing adjustment in renal impairment: May be necessary to reduce dosage in renal impairment, but there are no specific guidelines available
Hemodialysis: Poor water solubility allows for accumulation during chronic hemodialysis. Low-dose therapy is recommended. There have been several case reports of accumulation of baclofen resulting in toxicity symptoms (organic brain syndrome, myoclonia, deceleration and steep potentials in EEG) in patients with renal failure who have received normal doses of baclofen.
Administration: Other
Intrathecal: For screening dosages, dilute with preservative-free sodium chloride to a final concentration of 50 mcg/mL for bolus injection into the subarachnoid space. For maintenance infusions, concentrations of 500-2000 mcg/mL may be used.
Administration: I.V. Detail
pH: 5-7
Test Interactions
Increased alkaline phosphatase, AST, glucose, ammonia (B); decreased bilirubin (S)
Patient Education
Take this drug as prescribed. Do not discontinue this medicine without consulting prescriber (abrupt discontinuation may cause hallucinations). Do not take any prescription or OTC sleep-inducing drugs, sedatives, or antispasmodics without consulting prescriber. Avoid alcohol use. You may experience transient drowsiness, lethargy, or dizziness; use caution when driving or engaging in tasks requiring alertness until response to drug is known. Frequent small meals or lozenges may reduce GI upset.
Intrathecal use: Keep scheduled pump refill visits; abrupt interruption can cause serious withdrawal symptoms. Report increased spasticity, itching, numbness, unresolved insomnia, painful urination, change in urinary patterns, constipation, high fever, or persistent confusion.
Pregnancy precaution: Inform prescriber if you are or intend to become pregnant.
Geriatric Considerations
The elderly are more sensitive to the effects of baclofen and are more likely to experience adverse CNS effects at higher doses. Two cases of encephalopathy were reported after inadvertent high doses (50 mg/day and 90 mg/day) were given to elderly patients.
Anesthesia and Critical Care Concerns/Other Considerations
Avoid abrupt withdrawal of the drug; abrupt withdrawal of intrathecal baclofen has resulted in severe sequelae (hyperpyrexia, obtundation, rebound/exaggerated spasticity, muscle rigidity, and rhabdomyolysis), leading to organ failure and some fatalities. Risk may be higher in patients with injuries at T-6 or above, history of baclofen withdrawal, or limited ability to communicate. Elderly are more sensitive to the effects of baclofen and are more likely to experience adverse CNS effects at higher doses.
Dental Health: Effects on Dental Treatment
No significant effects or complications reported
Dental Health: Vasoconstrictor/Local Anesthetic Precautions
No information available to require special precautions
Mental Health: Effects on Mental Status
Drowsiness and insomnia are common; rare reports of depression, euphoria, and hallucinations
Mental Health: Effects on Psychiatric Treatment
Concurrent use with psychotropics may produce additive sedation; concurrent use with MAO inhibitors may potentiate their hypotensive effects
Nursing: Physical Assessment/Monitoring
Assess effectiveness and interactions of other medications patient may be taking. Monitor effectiveness of therapy and adverse reactions at beginning of therapy and periodically with long-term use. Assess knowledge/teach patient appropriate use, interventions to reduce side effects, and adverse symptoms to report.
Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Injection, solution, intrathecal [preservative free]:
Lioresal®: 50 mcg/mL (1 mL); 500 mcg/mL (20 mL); 2000 mcg/mL (5 mL, 20 mL)
Tablet: 10 mg, 20 mg
Pricing: U.S. (www.drugstore.com)
Tablets (Baclofen)
10 mg (30): $9.99
20 mg (30): $15.99
Extemporaneously Prepared
Make a 5 mg/mL suspension by crushing fifteen 20 mg tablets; wet with glycerin, gradually add 45 mL simple syrup in 3 x 5 mL aliquots to make a total volume of 60 mL; refrigerate; stable 35 days
Johnson CE and Hart SM, “Stability of an Extemporaneously Compounded Baclofen Oral Liquid,” Am J Hosp Pharm, 1993, 50:2353-5.
References
Abarbanel J, Herishanu Y, Frisher S, “Encephalopathy Associated With Baclofen,” Ann Neurol, 1985, 17(6):617-8.
Albright AL, “Baclofen in Treatment of Cerebral Palsy,” J Child Neurol, 1996, 11(2):77-83.
Cooke DE and Glasstone MA, “Baclofen Poisoning in Children,” Vet Hum Toxicol, 1994, 36(5):448-50.
Khorasani A and Peruzzi WT, “Dantrolene Treatment for Abrupt Intrathecal Baclofen Withdrawal,” Anesth Analg, 1995, 80(5):1054-6.
Lubsch L, Habersang R, Haase M, et al, “Oral Baclofen and Clonidine for Treatment of Spasticity in Children,” J Child Neurol, 2006, 21(12):1090-2.
May CR, “Baclofen Overdose,” Ann Emerg Med, 1983, 12:171-3.
Milla PJ and Jackson AD, “A Controlled Trial of Baclofen in Children With Cerebral Palsy,” J Int Med Res, 1977, 5(6):398-404.
Roberge RJ, Martin TG, Hodgman M, et al, “Supraventricular Tachyarrhythmia Associated With Baclofen Overdose,” J Toxicol Clin Toxicol, 1994, 32(3):291-7.
Scheinberg A, Hall K, Lam LT, et al, “Ora Baclofen in Children With Cerebral Palsy: A Double-Blind Cross-Over Pilot Study,” J Paediatr Child Health, 2006, 42(11):715-20.
Tan AK and Tan CB, “The Syndrome of Painful Legs and Moving Toes - A Case Report,” Singapore Med J, 1996, 37(4):446-7.
International Brand Names
Lexi-Comp.com
Last full review/revision August 2008
Content last modified August 2008
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