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Pharmacologic class: Skeletal muscle relaxant
Therapeutic class: Antispasmodic
Pregnancy risk category C
FDA Box Warning
• With intrathecal form, abrupt withdrawal may cause high fever, altered mental status, exaggerated rebound spasticity, and muscle rigidity; in rare cases, patient progresses to rhabdomyolysis, multisystem failure, and death. To prevent abrupt withdrawal, pay careful attention to programming and monitoring of infusion system, refill scheduling and procedures, and pump alarms. Advise patients and caregivers of importance of keeping scheduled refill visits, and teach about early drug withdrawal symptoms. Give special attention to patients at apparent risk (those with spinal cord injuries at T6 or above, communication problems, or history of withdrawal symptoms from oral or intrathecal baclofen).
Relaxes muscles by acting specifically at spinal end of upper motor neurons
Intrathecal injection: 10 mg/20 ml (500 mcg/ml), 10 mg/5 ml (2,000 mcg/ml)
Tablets: 10 mg, 20 mg
Indications and dosages
➣ Reversible spasticity associated with multiple sclerosis or spinal cord lesions
Adults: Initially, 5 mg P.O. t.i.d. May increase by 5 mg q 3 days to a maximum dosage of 80 mg/day.
Children ages 4 and older: 25 to 1,200 mcg/day by intrathecal infusion; (average is 275 mcg/day); dosage determined by response during screening phase.
➣ Severe spasticity in patients who don't respond to or can't tolerate oral baclofen
Adults: Screening phase-Before pump implantation and intrathecal infusion, give test dose to check responsiveness. Administer 1 ml of 50 mcg/ml dilution over 1 minute by barbotage into intrathecal space. Within 4 to 8 hours, muscle spasms should become less severe or frequent and muscle tone should decrease; if patient's response is inadequate, give second test dose of 75 mcg/1.5 ml 24 hours after first dose. If patient is still unresponsive, may give final test dose of 100 mcg/2 ml 24 hours later. Patients unresponsive to 100-mcg dose aren't candidates for intrathecal baclofen. Following appropriate responsiveness, adjust dosage to twice the screening dose and give over 24 hours. If screening dose efficacy is maintained for 12 hours, don't double the dosage. After 24 hours, increase dosage slowly as needed and tolerated by 10% to 30% daily.
Maintenance therapy-During prolonged maintenance therapy, adjust daily dosage by 10% to 40% as needed and tolerated to maintain adequate control of symptoms. Maintenance dosage ranges from 12 mcg to 2,000 mcg daily.
• Renal impairment
• Seizure disorders
• Elderly patients
• Cerebral palsy
• Tardive dyskinesia
• Trigeminal neuralgia
• Hypersensitivity to drug
• Rheumatic disorders
Use cautiously in:
• renal impairment
• patients who use spasticity to maintain posture and balance
• elderly patients
• pregnant or breastfeeding patients
• Give oral doses with food or milk.
• Dilute only with sterile, preservative-free sodium chloride for injection.
• Know that intrathecal infusion should be performed only by personnel who have been trained in the procedure.
CNS: dizziness, drowsiness, fatigue, confusion, depression, headache, insomnia, hypotonia, difficulty speaking, seizures
CV: edema, hypotension, hypertension, palpitations
EENT: blurred vision, tinnitus, nasal congestion
GI: nausea, vomiting, constipation
GU: urinary frequency, dysuria, erectile dysfunction
Skin: pruritus, rash, sweating
Other: weight gain, hypersensitivity reactions
Drug-drug. CNS depressants: increased baclofen effect
MAO inhibitors: increased CNS depression, hypotension
Tricyclic antidepressants, drugs causing
CNS depression: hypotonia, increased
Drug-diagnostic tests. Alkaline phosphatase, aspartate aminotransferase, glucose: increased levels
Drug-behaviors. Alcohol use: CNS depression
• During intrathecal infusion, check pump often for proper functioning and check catheter for patency.
• Monitor patient's response continually to determine appropriate dosage adjustment.
☞ Observe closely for signs and symptoms of overdose (drowsiness, light-headedness, dizziness, respiratory depression), especially during initial screening and titration. No specific antidote exists. Immediately remove any solution from pump; if patient has respiratory depression, intubate until drug is eliminated.
• Advise patient to take oral dose with food or milk.
• Instruct patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
• Caution patient not to discontinue drug therapy abruptly. Doing so may cause hallucinations and rebound spasticity.
• Advise patient to avoid alcohol and other depressants such as sedatives while taking drug.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and behaviors mentioned above.
baclofenA GABA (gamma-aminobutyric acid) antagonist used to decrease recalcitrant spinal spasticity in patients with multiple sclerosis, spinal-cord injury and possibly also Parkinson’s disease.
Vomiting, weakness, drowsiness, slow breathing, seizures, coma.