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Baclofen

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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.

U.S. BRAND NAMES — Lioresal®

PHARMACOLOGIC CATEGORY
Skeletal Muscle Relaxant

DOSING: ADULTS
Spasticity:
Oral: 5 mg 3 times/day, may increase 5 mg/dose every 3 days to a maximum of 80 mg/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-hourly rate dosed at twice the test dose. Avoid abrupt discontinuation.

Hiccups (unlabeled use): Oral: 10-20 mg 2-3 times/day

DOSING: PEDIATRIC — Spasticity:

(For additional information see “Baclofen: Pediatric drug information”)

Oral (avoid abrupt withdrawal of drug) (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 5-15 mg/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.

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Intrathecal: Refer to adult dosing.

DOSING: 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: RENAL IMPAIRMENT — May be necessary to reduce dosage; no specific guidelines have been established

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.

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

DOSAGE FORMS: CONCISE
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

GENERIC EQUIVALENT AVAILABLE — Yes: Tablets only

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.

COMPATIBILITY — Stable in sterile, preservative free NS.

Compatibility when admixed: Compatible: Morphine.

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

ADVERSE REACTIONS SIGNIFICANT
>10%:
Central nervous system: Drowsiness, vertigo, dizziness, psychiatric disturbances, insomnia, slurred speech, ataxia, hypotonia
Neuromuscular & skeletal: Weakness

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1% to 10%:
Cardiovascular: Hypotension
Central nervous system: Fatigue, confusion, headache
Dermatologic: Rash
Gastrointestinal: Nausea, constipation
Genitourinary: Polyuria

<1% (Limited to important or life-threatening): Chest pain, dyspnea, dysuria, enuresis, hematuria, impotence, inability to ejaculate, nocturia, palpitation, syncope, urinary retention; withdrawal reactions have occurred with abrupt discontinuation (particularly severe with intrathecal use). CONTRAINDICATIONS — Hypersensitivity to baclofen or any component of the formulation WARNINGS / PRECAUTIONS
Boxed warnings: Abrupt withdrawal: .

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.

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

Methotrimeprazine: CNS Depressants may enhance the CNS depressant effect of Methotrimeprazine. Methotrimeprazine may enhance the CNS depressant effect of CNS Depressants. Management: Reduce dosage of CNS depressant agents by 50% with initiation of concomitant methotrimeprazine therapy. Further CNS depressant dosage adjustments should be initiated only after clinically effective methotrimeprazine dose is established. Risk D: Consider therapy modification

ETHANOL / NUTRITION / HERB INTERACTIONS
Ethanol: Avoid ethanol (may increase CNS depression).

Herb/Nutraceutical: Avoid valerian, St John’s wort, kava kava, gotu kola.

PREGNANCY RISK FACTOR — C (show table)

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LACTATION — Enters breast milk (small amounts)/compatible

PRICING — (data from drugstore.com)
Tablets (Baclofen)
10 mg (30): $9.99
20 mg (30): $15.99

CANADIAN BRAND NAMES — Apo-Baclofen®; Gen-Baclofen; Lioresal®; Liotec; Nu-Baclo; PMS-Baclofen

INTERNATIONAL BRAND NAMES — Alpha-Baclofen (NZ); Alpha-Clofen (AU); Bac
lan (KP); Baclo (AU); Baclofen (PL); Baclofen-ratiopharm (LU); Baclofene (FR); Baclon (FI, TW); Baclopar (IE); Baclosal (IL, TH); Bacofen (KP); Baklofen (DK, NO); Clofen (AU, MY); Curofen (KP); Diafen (UY); Espast (PE); Liobac (TH); Lioresal (AE, AR, AT, AU, BB, BD, BE, BF, BG, BH, BJ, BM, BR, BS, BZ, CH, CI, CL, CY, CZ, DE, DK, EG, ES, ET, FI, FR, GB, GH, GM, GN, GR, GY, HK, HN, HR, HU, ID, IE, IL, IN, IQ, IR, IT, JM, JO, JP, KE, KP, KW, LB, LR, LU, LY, MA, ML, MR, MU, MW, MY, NE, NG, NL, NO, OM, PH, PK, PT, PY, QA, RU, SA, SC, SD, SE, SG, SL, SN, SR, SY, TH, TN, TR, TT, TW, TZ, UG, VE, YE, ZA, ZM, ZW); Lioresyl (CN); Lyflex (GB, IE); Onelaxant-R (PH); Pacifen (NZ, TW); Solofen (TW); Spinax (TW); Stelax (AU, HK)

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)

PATIENT INFORMATION

(For additional information see “Baclofen: Patient drug information”)
Intrathecal: It is important not to miss scheduled appointments for refills. Contact prescriber immediately if symptoms of withdrawal occur (high fever, confusion, increased spasticity, or muscle rigidity).

Oral: Take with food or milk; abrupt withdrawal after prolonged use may cause anxiety, hallucinations, tachycardia, or spasticity. May cause drowsiness and impair coordination and judgment.

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