Baclofen
Pronouncation: (BACK-low-fen)Class: Skeletal muscle relaxant, Centrally acting
Trade Names:
Lioresal
- Tablets 10 mg
- Tablets 20 mg
- Intrathecal 0.05 mg/mL (50 mcg/mL)
- Intrathecal 10 mg/20 mL (500 mcg/mL)
- Intrathecal 10 mg/5 mL (2000 mcg/mL)
Gen-Baclofen (Canada)
PMS-Baclofen (Canada)
ratio-Baclofen (Canada)
Pharmacology
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Feedback for Baclofen
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May inhibit transmission of reflexes at spinal level, possibly by action (hyperpolarization) at primary afferent fiber terminals, resulting in relief of muscle spasticity; has CNS depressant properties.
Pharmacokinetics
Absorption
Rapidly and extensively absorbed.
Elimination
Primarily by the kidney in unchanged form.
Indications and Usage
OralTreatment of reversible spasticity resulting from multiple sclerosis. May be of some value in patients with spinal cord injuries and other spinal cord diseases.
IntrathecalTreatment of severe spasticity of spinal cord origin in patients who are unresponsive to or cannot tolerate oral baclofen therapy. Used intrathecally in single bolus test doses; chronic use requires implantable pump.
Unlabeled Uses
OralTherapy for trigeminal neuralgia (tic douloureux); tardive dyskinesia.
IntrathecalCerebral palsy spasticity in children.
Contraindications
Treatment of spasms from rheumatic disorders, stroke, cerebral palsy and Parkinson disease; use of intrathecal form via IV, IM, subcutaneous, or epidural routes.
Dosage and Administration
Adults Initial dosePO 5 mg 3 times daily; may be increased by 5 mg/dose every 3 days as needed to max 80 mg/day (20 mg 4 times daily). Intrathecal Refer to manufacturer's manual for implantable pump.
ScreeningAdults
1 mL of 50 mcg/mL dilution is administered into the intrathecal space by barbotage over 1 min and patient is observed for 4 to 8 h; may be repeated 24 h later with 75 mcg/1.5 mL and 48 h later with 100 mcg/2 mL. Do not give implantable pump to patients not responding to 100 mcg bolus.
ChildrenThe starting screening dose for children is the same as in adult patients (eg, 50 mcg). However, for very small patients, a screening dose of 25 mcg may be tried first.
Postimplant Dose Titration PeriodTo determine the initial total daily dose of baclofen following implant, double the screening dose that gave a positive effect and administer over a 24-h period.
Spasticity of Spinal Cord OriginAdults
Intrathecal After the first 24 h, increase the daily dosage slowly in 10% to 30% increments and only once every 24 h, until desired effect is achieved.
Spasticity of Cerebral OriginAdults
Intrathecal After the first 24 h, increase the daily dose slowly 5% to 15% once every 24 h, until desired clinical effect is achieved.
ChildrenAfter the first 24 h, increase the daily dose slowly 5% to 15% only once every 24 h, until the desired effect is achieved.
Maintenance Therapy for Spasticity of Spinal Cord OriginsVery often the maintenance dose needs to be adjusted during the first few months of therapy while patients adjust to changes in life-style because of the alleviation of spasticity.
AdultsIntrathecal During periodic refills of the pump, the daily dose may be increased 10% to 40%, but no more than 40%, to maintain adequate symptom control. Maintenance dose for long-term continuous infusion has ranged from 12 to 2,003 mcg/day, with most patients adequately maintained on 300 to 800 mcg/day.
Maintenance Therapy for Spasticity of Cerebral OriginVery often the maintenance dose needs to be adjusted during the first few months of therapy while patients adjust to changes in life style because of the alleviation of spasticity.
AdultsIntrathecal During the periodic refills of the pump, the daily dose may be increased 5% to 20%, but no more than 20%. Ranges from 22 to 1,400 mcg/day, with most patients adequately maintained on 90 to 703 mcg/day.
Children less than 12 yr of ageAverage daily dose 274 mcg/day. Requires individual titration. Use the lowest dose with an optimal response.
Children at least 12 yr of ageSame as adult. Determination of the optimal dose requires individual titration. Use the lowest dose with an optimal response.
General Advice
- Administer with milk or food to avoid GI upset.
- Dilute intrathecal medication per manufacturer's instructions.
Storage/Stability
OralDo not store above 86°F.
IntrathecalDo not store above 86°F. Do not freeze. Do not heat sterilize.
Drug Interactions
CNS depressantsMay cause increased sedative effects.
Morphine (epidural)May cause hypotension and dyspnea.
Laboratory Test Interactions
May cause false elevation of AST, alkaline phosphatase, or blood glucose.
Adverse Reactions
Cardiovascular
Hypotension; palpitations; chest pain.
CNS
Drowsiness; weakness in lower extremities; dizziness; seizures; headache; numbness; euphoria; depression; confusion; lethargy; insomnia; hallucinations; paresthesia; asthenia; anxiety; agitation.
Dermatologic
Pruritus; rash.
EENT
Tinnitus; blurred vision; taste disorder; nasal congestion.
GI
Nausea; vomiting; dry mouth; constipation; diarrhea; abdominal pain; anorexia.
Genitourinary
Urinary frequency; enuresis; dysuria; impotence.
Respiratory
Dyspnea; pneumonia; hypoventilation.
Miscellaneous
Hypotonia; slurred speech; muscle pain; ankle edema; excessive perspiration; weight gain; back pain.
Precautions
WarningsIntrathecalAbrupt discontinuation has resulted in high fever, altered mental status, exaggerated rebound spasticity, and muscle rigidity that in rare cases advances to rhabdomyolysis, multiple organ system failure and death. Give special attention to patients at apparent risk (eg, spinal cord injuries at T-6 or above, communication difficulties, history of withdrawal symptoms from oral or intrathecal baclofen). |
Pregnancy
Category C .
Lactation
Excreted in breast milk.
Children
Safety of oral baclofen in children younger than 12 yr of age and of intrathecal baclofen in children younger than 4 yr of age has not been established.
Renal Function
Administer with caution. Dosage reduction may be necessary.
Intrathecal use
Only specially trained personnel should administer baclofen intrathecally because of potentially life-threatening CNS depression, CV collapse, or respiratory failure.
Epilepsy and psychotic disorders
Use with caution because of potential exacerbations.
Fatalities
Fatalities occurred in premarketing trials of intrathecal baclofen; baclofen's role in these deaths is unknown.
Infection
Patients should be infection-free before screening trial with baclofen intrathecal.
Stroke
Baclofen has not significantly benefited patients with stroke; these patients also have poor drug tolerance.
Overdosage
Symptoms
Vomiting, muscular hypotonia, muscle twitching, drowsiness, accommodation disorders, coma, respiratory depression, seizures (oral); drowsiness, lightheadedness, dizziness, somnolence, respiratory depression, seizures (intrathecal).
Patient Information
- Instruct patient to take drug exactly as prescribed. If dose is missed it should be taken within 1 h. Warn patient not to double up on doses.
- Explain that full effectiveness of drug may not occur until several weeks after initiation of drug therapy.
- Warn patient not to discontinue medication abruptly. Explain that hallucinations or seizures may occur.
- Instruct patient to avoid intake of alcoholic beverages or other CNS depressants.
- Teach patient to avoid sudden position changes to prevent orthostatic hypotension.
- Caution diabetic patient that false elevation of blood glucose may occur. Instruct patient to monitor blood glucose carefully.
- Instruct patient to report the following symptoms to health care provider: dizziness, nausea, hypotension, urinary frequency, retention, painful urination, headache, seizures, weakness.
- Advise patient that drug may cause drowsiness, and to use caution while driving or performing other tasks requiring mental alertness.
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More Baclofen resources:
Baclofen - Includes detailed dosage instructions.
Lioresal Intrathecal Intrathecal-Systemic - Includes detailed dosage instructions.
Muscle Spasm, Migraine Prevention, Trigeminal Neuralgia, Hiccups, Alcohol Withdrawal, Cerebral Spasticity, Cervical Dystonia, Chronic Spasticity, Periodic Limb Movement Disorder, Huntington's Disease, Neuralgia
