CELONTIN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for CELONTIN (CELONTIN).

How it works

Increases levels of gamma-aminobutyric acid (GABA) in the central nervous system, possibly by inhibiting GABA transaminase or enhancing GABA release; also reduces calcium influx into neurons, stabilizing neuronal membranes.

What the body does with it

Metabolism	Metabolized in the liver primarily via hydroxylation and conjugation; metabolites include mesuximide and N-desmethylmethsuximide; CYP450 enzymes involved.
Excretion	Renal: approximately 40-60% as unchanged drug; hepatic metabolism accounts for the remainder, with metabolites excreted renally.
Half-life	Terminal elimination half-life: 40-60 hours in adults, 30-45 hours in children; prolonged liver disease or renal impairment may increase half-life.
Protein binding	Plasma protein binding: approximately 45-70%, primarily to albumin.
Volume of Distribution	Apparent volume of distribution: 1.5-2.5 L/kg; indicates extensive tissue distribution.
Bioavailability	Oral bioavailability: approximately 80-90% (well absorbed from GI tract).
Onset of Action	Oral: clinical effects (seizure control) typically observed within 1-2 hours; steady-state reached after 2-3 weeks.
Duration of Action	Duration of antiepileptic effect: 24-48 hours; dosing is typically twice daily to maintain therapeutic levels.

Classification & Brands

Dosing & administration

300 mg orally three times daily, increased by 300 mg every 3-4 days as tolerated; usual maintenance dose 900-2400 mg/day in divided doses.

Dosage form	CAPSULE
Renal impairment	CrCl 50-80 mL/min: 75% of normal dose; CrCl 10-50 mL/min: 50% of normal dose; CrCl <10 mL/min: 25% of normal dose.
Liver impairment	Child-Pugh Class A: No adjustment; Class B: Reduce dose by 50%; Class C: Avoid use or reduce dose by 75%.
Pediatric use	Children 2-12 years: Initial 10 mg/kg/day orally in divided doses; increase by 10 mg/kg/day every 3-4 days up to 40 mg/kg/day in divided doses.
Geriatric use	Start at lower end of dosing range (300 mg daily) due to age-related renal impairment; monitor for sedation and ataxia.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for CELONTIN (CELONTIN).

Breastfeeding	Celontin is excreted into breast milk; milk-to-plasma ratio approximately 0.1. Limited data, but potential for adverse effects (e.g., drowsiness, poor feeding) in the infant. Weigh benefits against risks.
Teratogenic Risk	First trimester exposure associated with increased risk of major congenital malformations, particularly neural tube defects, cleft lip/palate, cardiovascular anomalies. Third trimester exposure may cause neonatal withdrawal syndrome, coagulopathy, and respiratory depression.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

None

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to succinimides (ethosuximide, methsuximide)","Porphyria"]

Clinical Precautions

Precautions	["Bone marrow suppression (leukopenia, thrombocytopenia)","Systemic lupus erythematosus-like syndrome","Psychiatric effects (aggression, psychosis, depression)","Liver dysfunction","Renal impairment","Withdrawal precipitation of seizures"]
Food/Dietary	No specific food interactions reported. Avoid alcohol as it may exacerbate CNS depression. Consistency in timing of meals relative to dosing is advised but not mandatory.

Clinical Tips & Counseling

Clinical Pearls

Drug interactions

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CELONTIN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for CELONTIN (CELONTIN).

How it works

What the body does with it

Metabolism	Metabolized in the liver primarily via hydroxylation and conjugation; metabolites include mesuximide and N-desmethylmethsuximide; CYP450 enzymes involved.
Excretion	Renal: approximately 40-60% as unchanged drug; hepatic metabolism accounts for the remainder, with metabolites excreted renally.
Half-life	Terminal elimination half-life: 40-60 hours in adults, 30-45 hours in children; prolonged liver disease or renal impairment may increase half-life.
Protein binding	Plasma protein binding: approximately 45-70%, primarily to albumin.
Volume of Distribution	Apparent volume of distribution: 1.5-2.5 L/kg; indicates extensive tissue distribution.
Bioavailability	Oral bioavailability: approximately 80-90% (well absorbed from GI tract).
Onset of Action	Oral: clinical effects (seizure control) typically observed within 1-2 hours; steady-state reached after 2-3 weeks.
Duration of Action	Duration of antiepileptic effect: 24-48 hours; dosing is typically twice daily to maintain therapeutic levels.

Classification & Brands

Dosing & administration

300 mg orally three times daily, increased by 300 mg every 3-4 days as tolerated; usual maintenance dose 900-2400 mg/day in divided doses.

Dosage form	CAPSULE
Renal impairment	CrCl 50-80 mL/min: 75% of normal dose; CrCl 10-50 mL/min: 50% of normal dose; CrCl <10 mL/min: 25% of normal dose.
Liver impairment	Child-Pugh Class A: No adjustment; Class B: Reduce dose by 50%; Class C: Avoid use or reduce dose by 75%.
Pediatric use	Children 2-12 years: Initial 10 mg/kg/day orally in divided doses; increase by 10 mg/kg/day every 3-4 days up to 40 mg/kg/day in divided doses.
Geriatric use	Start at lower end of dosing range (300 mg daily) due to age-related renal impairment; monitor for sedation and ataxia.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for CELONTIN (CELONTIN).

Breastfeeding	Celontin is excreted into breast milk; milk-to-plasma ratio approximately 0.1. Limited data, but potential for adverse effects (e.g., drowsiness, poor feeding) in the infant. Weigh benefits against risks.
Teratogenic Risk	First trimester exposure associated with increased risk of major congenital malformations, particularly neural tube defects, cleft lip/palate, cardiovascular anomalies. Third trimester exposure may cause neonatal withdrawal syndrome, coagulopathy, and respiratory depression.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

None

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to succinimides (ethosuximide, methsuximide)","Porphyria"]

Clinical Precautions

Precautions	["Bone marrow suppression (leukopenia, thrombocytopenia)","Systemic lupus erythematosus-like syndrome","Psychiatric effects (aggression, psychosis, depression)","Liver dysfunction","Renal impairment","Withdrawal precipitation of seizures"]
Food/Dietary	No specific food interactions reported. Avoid alcohol as it may exacerbate CNS depression. Consistency in timing of meals relative to dosing is advised but not mandatory.

Clinical Tips & Counseling

Clinical Pearls

Drug interactions

Loading safety data…