TIAGABINE HYDROCHLORIDE

Clinical safety rating: safe

Animal studies have demonstrated safety

How it works

Tiagabine inhibits GABA reuptake into presynaptic neurons and glial cells by binding to the GAT-1 GABA transporter, thereby increasing synaptic GABA concentrations and enhancing inhibitory neurotransmission.

What the body does with it

Metabolism	Primarily hepatic via CYP3A4, with minor contributions from CYP1A2 and CYP2D6
Excretion	Primarily hepatic metabolism via CYP3A4, with <2% excreted unchanged in urine. 63% of dose excreted in feces, 25% in urine as metabolites.
Half-life	Terminal half-life of 5–8 hours in healthy adults; prolonged to 12–16 hours in hepatic impairment. Reduces with enzyme-inducing co-medications.
Protein binding	96% bound to albumin and alpha-1-acid glycoprotein.
Volume of Distribution	Vd approximately 1 L/kg (range 0.7–1.3 L/kg), indicating widespread distribution into tissues.
Bioavailability	Oral bioavailability approximately 90% following a single dose; food may reduce rate but not extent of absorption.
Onset of Action	Oral: peak effect typically within 1–2 hours; immediate-release formulation reaches peak plasma concentration at ~1 hour.
Duration of Action	Duration of effect 6–10 hours; clinical effects wane with declining plasma levels. Trough concentrations may lose efficacy.

Classification & Brands

Dosing & administration

Initial: 4 mg orally once daily; titrate by 4-8 mg/day at weekly intervals. Maintenance: 32-56 mg/day divided 2-4 times daily. Maximum dose: 56 mg/day.

Dosage form	TABLET
Renal impairment	No adjustment required for mild-to-moderate renal impairment; insufficient data for severe impairment (CrCl <25 mL/min).
Liver impairment	Mild hepatic impairment (Child-Pugh A): reduce initial dose to 2 mg once daily; titrate cautiously. Moderate-to-severe impairment (Child-Pugh B or C): contraindicated.
Pediatric use	Children 12 years and older: same as adult dosing. Safety and efficacy in children <12 years not established.
Geriatric use	Initiate at lower dose (2 mg once daily) and titrate slowly due to increased sensitivity and risk of adverse effects; monitor renal function.

Use during pregnancy

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

Clinical note

Strong CYP3A4 inducers may decrease efficacy Can cause seizures in patients without epilepsy.

Breastfeeding	Unknown if excreted in human milk; M/P ratio not available. Risk to infant cannot be excluded. Due to potential for serious adverse reactions, decision to discontinue breastfeeding or drug should be made based on importance of drug to mother.
Teratogenic Risk	Pregnancy Category C. First trimester: limited human data; animal studies show developmental toxicity at clinically relevant doses. Second and third trimesters: potential for fetal harm; case reports of fetal malformations (e.g., neural tube defects) but causality not established. Use only if benefit outweighs risk.

Warnings & precautions

■ FDA Black Box Warning

None

Side Effect Profile

Common Effects	Dizziness
Serious Effects

Absolute Contraindications

["Hypersensitivity to tiagabine or any component of the formulation"]

Clinical Precautions

Precautions

["New-onset or worsening depression, suicidal ideation","Seizure exacerbation if abruptly discontinued or in nonepileptic patients","CNS depression (dizziness, sedation)","Serious skin reactions (e.g., Stevens-Johnson syndrome)","Status epilepticus in patients with preexisting seizure disorders"]

Clinical Tips & Counseling

Drug interactions

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