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Pronunciation:

(BAK loe fen)

U.S. Brand Names:

Lioresal®

Generic Available:

Yes: Tablets only

Canadian Brand Names:

Apo-Baclofen®; Gen-Baclofen; Lioresal®; Liotec; Nu-Baclo; PMS-Baclofen

Use:

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:

Use with caution in patients with seizure disorder or impaired renal function. 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.

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%: Palpitations, 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).

Overdosage/Toxicology:

Symptoms of overdose include vomiting, muscle hypotonia, salivation, drowsiness, coma, seizures, and respiratory depression. Atropine has been used to improve ventilation, heart rate, blood pressure, and core body temperature. Treatment is symptom-directed and supportive.

For toxicity following intrathecal administration: For adults, administer physostigmine 2 mg I.M. or I.V. (not to exceed 1 mg/minute). For pediatric patients, administer physostigmine 0.02 mg/kg I.M. or I.V. (not to exceed 0.5 mg/minute). Consider withdrawal of 30-40 mL of CSF to reduce baclofen concentration. Abrupt withdrawal of intrathecal baclofen has resulted in severe sequelae (hyperpyrexia, obtundation, muscle rigidity, and rhabdomyolysis)

Drug Interactions:

Increased effect: Opiate analgesics, benzodiazepines, hypertensive agents

Increased toxicity: CNS depressants and ethanol (sedation), tricyclic antidepressants (short-term memory loss), clindamycin (neuromuscular blockade), guanabenz (sedation), MAO inhibitors (decrease blood pressure, CNS, and respiratory effects)

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:

2-7 years: Initial: 10-15 mg/24 hours divided every 8 hours; titrate dose every 3 days in increments of 5-15 mg/day to a maximum of 40 mg/day

8 years: Maximum: 60 mg/day in 3 divided doses

Adults: 5 mg 3 times/day, may increase 5 mg/dose every 3 days to a maximum of 80 mg/day

Hiccups: Adults: Usual effective dose: 10-20 mg 2-3 times/day

Intrathecal:

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: It is 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:

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

Test Interactions:

Increased alkaline phosphatase, AST, glucose, ammonia (B); decreased bilirubin (S)

Patient Education:

Take this drug as prescribed. Do not discontinue 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.

Nursing Implications:

Epileptic patients should be closely monitored; supervise ambulation; avoid abrupt withdrawal of the drug

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

Dosage Forms:

Injection, solution, intrathecal [preservative free] (Lioresal®): 50 mcg/mL (1 mL); 500 mcg/mL (20 mL); 2000 mcg/mL (5 mL)

Tablet: 10 mg, 20 mg

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.

International Brand Names:

Alpha-Baclofen® (NZ); Apo-Baclofen® (CA, NZ, SG); Baclofen AWD® (DE, RO); Baclofen® (CZ, GB, HU, PL, RO, RU); Baclofen dura® (DE); Baclofen Pharmadica® (TH); Baclofen-ratiopharm® (DE, LU); Baclon® (FI); Baclopar® (FI, IE); Baclosal® (IL, TH); Baclospas® (GB); Baklofen NM® (DK); Baklofen NM Pharma® (SE); Baklofen® (NO); Balgifen® (GB); Clofen® (AU); Colmifen® (CY); DBL Baclofen® (AU); Gabalon® (JP); Gen-Baclofen (CA); Lebic® (DE); Lioresal® (AR, AT, AU, BE, BR, CA, CH, DE, DK, ES, FI); Liorésal® (FR); Lioresal® (GB, HK, HR, HU, ID, IE, IL, IN, IT, LU, MT, NL, NO, NZ, PT, RO, SE, SG, TH, TR, ZA); Lioresyl® (CL); Liotec (CA); Norton-Baclofen® (ZA); Nu-Baclo (CA); Pacifen® (NZ); PMS-Baclofen (CA)

References

Abarbanel J, Herishanu Y, Frisher S, "Encephalopathy Associated With Baclofen,"Ann Neurol, 1985, 17(6):617-8.

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.

May CR, "Baclofen Overdose,"Ann Emerg Med, 1983, 12:171-3.

Muller-Schwefe G and Penn RD, "Physostigmine in the Treatment of Intrathecal Baclofen Overdose. Report of Three Cases,"J Neurosurg, 1989, 71(2):273-5.

Roberge RJ, Martin TG, Hodgman M, et al, "Supraventricular Tachyarrhythmia Associated With Baclofen Overdose,"J Toxicol Clin Toxicol, 1994, 32(3):291-7.

Tan AK and Tan CB, "The Syndrome of Painful Legs and Moving Toes...A Case Report,"Singapore Med J, 1996, 37(4):446-7.

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