GABLOFEN
Clinical safety rating
cautionComprehensive clinical and safety monograph for GABLOFEN (GABLOFEN).
GABLOFEN (baclofen) is a GABA-B receptor agonist that reduces spinal reflex transmission and inhibits excitatory neurotransmitter release.
| Metabolism | Hepatic metabolism via deamination; minor CYP450 involvement. Approximately 15% is metabolized; 85% excreted unchanged in urine. |
| Excretion | Renal: 70-80% unchanged; biliary/fecal: <5% as metabolites. Total clearance 2.5-3.0 L/h. |
| Half-life | Terminal half-life 5-7 hours; clinically relevant for dosing interval of every 6-8 hours. |
| Protein binding | 30-35% bound to albumin. |
| Volume of Distribution | 0.5-0.8 L/kg; indicates distribution into extracellular fluid and tissues. |
| Bioavailability | Oral: 70-90%; intrathecal: near 100% (direct CSF delivery). |
| Onset of Action | Oral: 1-2 hours; intrathecal bolus: 0.5-1 hour; continuous intrathecal infusion: 4-8 hours to steady state. |
| Duration of Action | Oral: 4-8 hours; intrathecal bolus: 4-12 hours; continuous infusion: sustained while infused. |
| Molecular Weight | 213.66 |
10 mg orally three times daily, may increase by 10 mg/day every 3 days to a maximum of 80 mg/day (20 mg four times daily).
| Dosage form | INJECTABLE |
| Renal impairment | GFR > 60 mL/min: no adjustment; GFR 30-60 mL/min: reduce dose by 50%; GFR < 30 mL/min: avoid use. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use. |
| Pediatric use | Age 2-16 years: initial 5 mg orally twice daily, increase by 5 mg/day every 3 days to maximum 40 mg/day (10 mg four times daily) for weight < 50 kg; for weight ≥ 50 kg, use adult dosing. |
| Geriatric use | Initial 5 mg orally twice daily, increase slowly; maximum 40 mg/day; monitor for sedation and dizziness. |
| 1st trimester | Data limited; potential teratogenicity in animal studies; avoid unless clearly needed. Risk of neural tube defects, congenital heart defects, and cleft palate. |
| 2nd trimester | Risk of fetal growth restriction and neurodevelopmental effects; use only if benefit outweighs risk. |
| 3rd trimester | Risk of neonatal withdrawal syndrome (irritability, hypotonia, seizures) and sedation; avoid near term due to risk of floppy infant syndrome. |
Clinical note
Comprehensive clinical and safety monograph for GABLOFEN (GABLOFEN).
| Placental transfer | Crosses placenta; achieves fetal concentrations approximately 30-80% of maternal levels. |
| Breastfeeding | Enters breast milk in low concentrations; monitor infant for sedation, poor feeding, and hypotonia. Avoid if possible or use lowest effective dose. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | First trimester: Limited data; animal studies show increased risk of neural tube defects and skeletal abnormalities at supratherapeutic doses. Second and third trimesters: Risk of fetal growth restriction, oligohydramnios, and neonatal withdrawal syndrome (hypertonia, tremors, seizures) if used chronically. Avoid in all trimesters unless benefit outweighs risk. |
| Fetal Monitoring | Maternal: Vital signs, liver function tests, renal function, and signs of CNS depression. Fetal: Ultrasound for growth and amniotic fluid volume (every 4-6 weeks), fetal heart rate monitoring after 24 weeks gestation. Neonatal: Monitor for withdrawal syndrome (irritability, hypertonia, seizures) for 48-72 hours postpartum. |
| Fertility Effects | In animal studies, high doses caused decreased spermatogenesis and reduced fertility. Human data limited; no clinically significant effects on male or female fertility reported at therapeutic doses. |
■ FDA Black Box Warning
Abrupt discontinuation of intrathecal baclofen may precipitate severe withdrawal reactions including hyperpyrexia, altered mental status, rebound spasticity, and rhabdomyolysis, which can be life-threatening. Pump failure or dosage error may cause overdose or withdrawal.
| Serious Effects |
Hypersensitivity to baclofenSevere renal impairment (CrCl <30 mL/min)Active psychotic disorder
| Precautions | Withdrawal reactions after abrupt cessation; renal impairment requiring dose adjustment; sedation and dizziness impairing ability to drive/operate machinery; increased risk of seizures in epileptic patients; exacerbation of psychotic disorders; respiratory depression when combined with CNS depressants. |
| Food/Dietary | No significant food interactions. Alcohol should be avoided due to additive CNS depressant effects. Grapefruit juice has no known interaction with baclofen. |
| Clinical Pearls | GABLOFEN is a brand name for baclofen, a GABAB receptor agonist used for spasticity. Sudden withdrawal can cause serious hyperpyrexia, rigidity, and seizures; taper over 1-2 weeks. Renal dose adjustment required (creatinine clearance <30 mL/min: decrease dose or extend interval). Monitor for drowsiness, dizziness, and muscle weakness, especially when initiating therapy. For intrathecal use, pump refill intervals must be strict to avoid withdrawal. |
| Patient Advice | Do not stop taking Gablofen suddenly; a gradual dose reduction is needed to avoid serious withdrawal reactions. · Avoid alcohol and other CNS depressants (e.g., benzodiazepines, opioids) as they increase sedation and respiratory depression risk. · May cause dizziness, drowsiness, or blurred vision; avoid driving or operating heavy machinery until you know how the drug affects you. · Take with food if gastrointestinal upset occurs. · Report any signs of infection at the pump site (pain, redness, swelling) if using intrathecal formulation. · Store at room temperature away from moisture and heat. |
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