TIAGABINE HYDROCHLORIDE
Clinical safety rating: safe
Animal studies have demonstrated safety
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.
| 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. |
| Molecular Weight | 375.9 |
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. |
| 1st trimester | Tiagabine is not recommended during the first trimester due to potential teratogenic effects based on animal studies; human data are limited. |
| 2nd trimester | Use only if clearly needed; may be associated with fetal harm; limited human data suggest possible developmental toxicity. |
| 3rd trimester | Avoid use in third trimester as neonatal withdrawal or sedation may occur; use only if benefit outweighs risk. |
Clinical note
Strong CYP3A4 inducers may decrease efficacy Can cause seizures in patients without epilepsy.
| Placental transfer | Tiagabine crosses the placenta in animals; human data are insufficient to quantify extent, but likely moderate transfer due to low molecular weight and lipophilicity. |
| Breastfeeding | Tiagabine is excreted into breast milk in low concentrations. Limited data suggest no adverse effects in breastfed infants, but caution is advised, especially in neonates or preterm infants. Monitor for sedation or poor feeding. |
■ FDA Black Box Warning
None
| Common Effects | Dizziness |
| Serious Effects |
Hypersensitivity to tiagabine or any component of the formulationSevere hepatic impairment (Child-Pugh class C)
| 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 |
| Food/Dietary | Tiagabine should be taken with food to slow absorption and reduce central nervous system side effects. There are no known specific food restrictions, but alcohol may exacerbate CNS depression and should be avoided. Grapefruit juice is not reported to interact significantly with tiagabine. |
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) |
| 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. |
| Fetal Monitoring | Monitor maternal liver function, complete blood count, and drug levels (if available) regularly. Observe for maternal CNS depression, dizziness, or suicidal ideation. Fetal monitoring: serial ultrasound for growth, amniotic fluid volume, and anatomy. |
| Fertility Effects | Animal studies: no clear impairment of fertility observed. Human data: limited. No confirmed effects on spermatogenesis or menstrual cycle; theoretical risk of hormonal alterations due to GABAergic effects. |
| Clinical Pearls | Tiagabine is a selective GABA reuptake inhibitor used as adjunctive therapy for partial seizures. It is not effective for absence seizures and may exacerbate them. Due to rapid absorption and short half-life, dosing should be administered with food to reduce peak concentrations and minimize adverse effects such as dizziness, somnolence, and confusion. Tiagabine is highly protein-bound and can be displaced by other highly bound drugs (e.g., valproate). Slow titration is essential to reduce CNS side effects. Abrupt discontinuation should be avoided to prevent withdrawal seizures. Also, tiagabine has been associated with non-convulsive status epilepticus, especially in patients with a history of spike-wave discharges. |
| Patient Advice | Take tiagabine exactly as prescribed, usually three to four times daily with food to decrease side effects. · Do not stop taking this medication suddenly, as it may cause withdrawal seizures. · Avoid driving or operating heavy machinery until you know how tiagabine affects you, as it may cause dizziness or drowsiness. · Notify your doctor if you experience confusion, weakness, or new seizure types (e.g., staring spells). · Inform all healthcare providers that you are taking tiagabine, as it may interact with other medications. · Store tiagabine at room temperature away from moisture and heat. |