Tiagabine Hydrochloride

Absorption

Bioavailability

Well absorbed; absolute bioavailability is about 90%.1

Rapidly absorbed following oral administration, with peak plasma concentration usually occurring in approximately 45 minutes.1

Food

Food does not affect extent of absorption but delays time to peak plasma concentrations to 2.5 hours.1 5 13

Distribution

Plasma Protein Binding

96% (mainly albumin and α1-acid glycoprotein).1

Elimination

Metabolism

Undergoes extensive hepatic metabolism, principally via CYP3A4.1 5 6

Elimination Route

Excreted in feces (63%) and in urine (25%) mainly as metabolites; approximately 2% is excreted unchanged.1

Half-life

7–9 hours.1 5 6 13 11

Decreases to 2–5 hours in patients receiving an anticonvulsant that induces hepatic microsomal enzymes (e.g., carbamazepine, phenobarbital, phenytoin, primidone).1 5 6 13 11

Special Populations

In patients with moderate hepatic impairment (Child-Pugh class B), clearance of unbound tiagabine was reduced by about 60%. 1 Dosage adjustment may be needed.1 (See Hepatic Impairment under Dosage and Administration.)

Pharmacokinetics similar in those with normal renal function (Clcr >80 mL/minute), mild, moderate, or severe renal impairment (Clcr 40–80, 20–39, or 5–19 mL/minute, respectively), and those undergoing dialysis.1

In children 3–10 years of age receiving hepatic enzyme-inducing anticonvulsants, clearance is similar to that found in adults receiving these anticonvulsants (e.g., carbamazepine, phenytoin).1 In children receiving non-inducing anticonvulsants (e.g., valproate), clearance is increased compared with adults not receiving a hepatic enzyme-inducing agent.1

Storage

Oral

20–25°C.1 Protect from light and moisture.1