Focal (partial) seizures (adjunct): Oral: Note: Do not use a loading dose, rapid titration, and/or increases with large dose increments.
Patients receiving enzyme-inducing AED regimens: Initial: 4 mg once daily for 1 week; may increase by 4 to 8 mg at weekly intervals, based on clinical response, up to 56 mg daily in 2 to 4 divided doses; usual maintenance: 32 to 56 mg/day.
Patients not receiving enzyme-inducing AED regimens: In general, lower doses are required; slower titration may be necessary. 12 mg/day is expected to be comparable to 32 mg/day in patients receiving enzyme-inducing AED regimens, based on clearance data.
Dosage adjustment: Consider dosage adjustment when a change in enzyme-inducing status occurs due to the addition, discontinuation, or dose change of the enzyme-inducing agent. If multiple doses are missed, evaluate if retitration is clinically indicated.
Discontinuation of therapy: Abrupt discontinuation should be avoided given the possibility of increasing seizure frequency, regardless of dose. Tiagabine should be withdrawn gradually over 1 to 6 months unless safety concerns require a more rapid withdrawal (Schachter 2020; Uthman 1998).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
No dosage adjustment necessary.
There are no specific dosage adjustments provided in manufacturer's labeling. However, dosage reduction may be necessary since clearance is reduced in the setting of hepatic impairment.
(For additional information see "Tiagabine: Pediatric drug information")
Focal (partial) seizures; adjunctive therapy:
Note: Do not use loading doses of tiagabine in any patient; do not use a rapid dosage escalation or increase the dose in large increments.
Children ≥12 years and Adolescents:
Patients receiving enzyme-inducing antiseizure drug regimens: Oral: Initial: 4 mg once daily for 1 week, then 8 mg/day in 2 divided doses for 1 week, then increase at weekly intervals in 4 to 8 mg/day increments; administer in 2 to 4 divided doses per day; titrate dose to response; maximum daily dose: 32 mg/day (doses >32 mg/day have been used in select adolescent patients for short periods of time).
Patients not receiving enzyme-inducing antiseizure drug regimens: Oral: The estimated plasma concentrations of tiagabine in patients not taking enzyme-inducing medications is twice that of patients receiving enzyme-inducing antiseizure drug regimens. Lower doses are required; slower titration may be necessary.
Dosage adjustment: Consider dosage adjustment when a change in enzyme-inducing status occurs due to the addition, discontinuation, or dose change of the enzyme-inducing agent. If multiple doses are missed, evaluate if retitration is clinically indicated.
Discontinuation of therapy: There is currently no standard method for the withdrawal of antiseizure medications in pediatric patients. Successful discontinuation of an antiseizure medication is dependent on several factors including but not limited to: Time of seizure freedom, underlying reason for the seizures, neuroimaging abnormalities, underlying neurodevelopmental status, and medication to be withdrawn (including dose, duration of therapy, and other pharmacokinetic/dynamic considerations) (Ayuga Loro 2020). Tiagabine should be withdrawn gradually over several weeks or months. Regardless of dose, abrupt discontinuation should be avoided given the possibility of increasing seizure frequency unless a safety concern requires a more rapid withdrawal.
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
No dosage adjustment necessary.
There are no specific dosage adjustments provided in manufacturer's labeling. However, dosage reduction may be necessary since clearance is reduced in the setting of hepatic impairment.
Refer to adult dosing.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Tablet, Oral, as hydrochloride:
Gabitril: 2 mg [contains fd&c yellow #6 (sunset yellow)]
Gabitril: 4 mg [contains quinoline yellow (d&c yellow #10)]
Gabitril: 12 mg [contains fd&c blue #1 (brilliant blue), quinoline yellow (d&c yellow #10)]
Gabitril: 16 mg [contains fd&c blue #2 (indigotine)]
Generic: 2 mg, 4 mg, 12 mg, 16 mg
Yes
An FDA-approved patient medication guide, which is available with the product information and at http://www.fda.gov/downloads/Drugs/DrugSafety/UCM229203.pdf, must be dispensed with this medication.
Oral: Administer with food.
Oral: Administer with food (to avoid rapid increase in plasma concentrations and adverse CNS effects).
Focal (partial) seizures: Adjunctive therapy in adults and children ≥12 years of age in the treatment of focal (partial) seizures.
TiaGABine may be confused with tiZANidine
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified.
>10%:
Central nervous system: Dizziness (27% to 31%), drowsiness (18% to 21%), nervousness (10% to 14%), lack of concentration (7% to 14%)
Gastrointestinal: Nausea (11%)
Infection: Infection (19%)
Neuromuscular & skeletal: Weakness (18% to 23%), tremor (9% to 21%)
Miscellaneous: Accidental injury (21%)
1% to 10%:
Cardiovascular: Vasodilation (2%), chest pain (≥1%), edema (≥1%), hypertension (≥1%), palpitations (≥1%), peripheral edema (≥1%), syncope (≥1%), tachycardia (≥1%)
Central nervous system: Ataxia (5% to 9%), pain (5% to 7%), depression (1% to 7%), insomnia (5% to 6%), confusion (5%), status epilepticus (5%), abnormal gait (3% to 5%), hostility (2% to 5%), memory impairment (4%), paresthesia (4%), speech disturbance (4%), emotional lability (3%), chills (≥1%), depersonalization (≥1%), dysarthria (≥1%), euphoria (≥1%), hallucination (≥1%), hypertonia (≥1%), hypoesthesia (≥1%), hyporeflexia (≥1%), hypotonia (≥1%), malaise (≥1%), migraine (≥1%), myoclonus (≥1%), paranoia (≥1%), personality disorder (≥1%), stupor (≥1%), twitching (≥1%), vertigo (≥1%), agitation (1%), myasthenia (1%)
Dermatologic: Bruise (6%), skin rash (5%), pruritus (2%), alopecia (≥1%), xeroderma (≥1%)
Gastrointestinal: Diarrhea (7% to 10%), vomiting (7%), abdominal pain (5% to 7%), increased appetite (2%), gingivitis (≥1%), stomatitis (≥1%), oral mucosa ulcer (1%)
Endocrine & metabolic: Weight gain (≥1%), weight loss (≥1%)
Genitourinary: Urinary tract infection (5%), abnormal uterine bleeding (≥1%), dysmenorrhea (≥1%), dysuria (≥1%), urinary incontinence (≥1%), vaginitis (≥1%)
Hematologic & oncologic: Lymphadenopathy (≥1%)
Hypersensitivity: Hypersensitivity reaction (≥1%)
Neuromuscular & skeletal: Myalgia (5%), arthralgia (≥1%), hyperkinesia (≥1%), hypokinesia (≥1%), neck pain (≥1%)
Ophthalmic: Amblyopia (9%), nystagmus (2%), visual disturbance (≥1%)
Otic: Otalgia (≥1%), otitis media (≥1%), tinnitus (≥1%)
Respiratory: Flu-like symptoms (6% to 9%), pharyngitis (7% to 8%), increased cough (4%), bronchitis (≥1%), dyspnea (≥1%), epistaxis (≥1%), pneumonia (≥1%)
Miscellaneous: Language problems (2%), cyst (≥1%), diaphoresis (≥1%)
<1%, postmarketing, and/or case reports: Abnormal dreams, abnormal electroencephalogram, abnormal erythrocytes, abnormal hepatic function tests, abnormal pap smear, abnormal stools, abscess, ageusia, altered sense of smell, amenorrhea, anemia, angina pectoris, apathy, aphthous stomatitis, apnea, arthritis, asthma, benign skin neoplasm, blepharitis, blindness, blurred vision, brain disease, breast hypertrophy, bullous dermatitis, bursitis, cellulitis, cerebral ischemia, cholecystitis, cholelithiasis, CNS neoplasm, coma, contact dermatitis, cutaneous nodule, cystitis, deafness, dehydration, delusions, dental caries, dermal ulcer, dysgeusia, dysphagia, dystonia, ECG abnormality, eczema, eructation, esophagitis, exfoliative dermatitis, eye pain, facial edema, fecal incontinence, fibrocystic breast disease, furunculosis, gastritis, gastrointestinal hemorrhage, gingival hyperplasia, glossitis, goiter, halitosis, hematuria, hemiplegia, hemoptysis, hemorrhage, hepatomegaly, hernia, herpes simplex infection, herpes zoster, hiccups, hirsutism, hyperacusis, hypercholesteremia, hyperglycemia, hyperlipemia, hypermenorrhea, hyperreflexia, hyperventilation, hypoglycemia, hypokalemia, hyponatremia, hypotension, hypothyroidism, impotence, increased libido, increased thirst, keratoconjunctivitis, laryngitis, leg cramps, leukopenia, maculopapular rash, mastalgia, melena, movement disorder, muscle spasm, myocardial infarction, neck stiffness, neoplasm, neuritis, nocturia, oral paresthesia, orthostatic hypotension, osteoarthrosis, otitis externa, pallor, paralysis, pelvic pain, periodontal abscess, peripheral neuritis, peripheral vascular disease, petechia, phlebitis, photophobia, polyuria, psoriasis, psychoneurosis, psychosis, pyelonephritis, rectal hemorrhage, renal failure, salpingitis, seizure (in patients with or without underlying seizure disorder), sepsis, sialorrhea, skin carcinoma, skin discoloration, skin photosensitivity, status epilepticus, Stevens-Johnson syndrome, subcutaneous nodule, suicidal ideation, suicidal tendencies, tendinous contracture, thrombocytopenia, thrombophlebitis, urethritis, urinary retention, urinary urgency, urticaria, vaginal hemorrhage, vesiculobullous dermatitis, visual field defect, voice disorder, withdrawal syndrome (seizures with abrupt withdrawal), xerostomia
Hypersensitivity to tiagabine or any component of the formulation
Concerns related to adverse effects:
• CNS depression: May cause CNS depression, which may impair physical or mental abilities; patients must be cautioned about performing tasks which require mental alertness (eg, operating machinery or driving).
• Dermatologic reactions: Severe reactions, including Stevens-Johnson syndrome, although rarely reported, have resulted in fatalities.
• Generalized weakness: Moderately severe to incapacitating generalized weakness has been reported after administration of tiagabine. The weakness resolved in all cases after a reduction in dose or discontinuation of tiagabine.
• Ophthalmic effects: Evidence of residual binding of tiagabine in the retina and uvea after 3 weeks has been observed in animal studies; although not directly measured, melanin binding is suggested. Long-term (up to 1 year) toxicological studies of tiagabine in animals showed no treatment-related ophthalmoscopic changes and macro- and microscopic examinations of the eye were unremarkable. The ability of available tests to detect potentially adverse consequences, if any, of the binding of tiagabine to melanin-containing tissue is unknown, and there was no systematic monitoring for relevant ophthalmological changes during the clinical development of tiagabine. Prescribers should be aware of the possibility of long-term ophthalmologic effects.
• Suicidal ideation: Pooled analysis of trials involving various antiseizure medications (regardless of indication) showed an increased risk of suicidal thoughts/behavior (incidence rate: 0.43% treated patients compared to 0.24% of patients receiving placebo); risk observed as early as 1 week after initiation and continued through duration of trials (most trials ≤24 weeks). Monitor all patients for notable changes in behavior that might indicate suicidal thoughts or depression; notify health care provider immediately if symptoms occur.
Disease-related concerns:
• Hepatic impairment: Use with caution in patients with hepatic impairment.
Concurrent drug therapy issues:
• Enzyme-inducing drugs: Experience in patients not receiving enzyme-inducing drugs has been limited; caution should be used in treating any patient who is not receiving one of these medications (decreased dose and slower titration may be required).
Other warnings/precautions:
• Off-label use: New-onset seizures and status epilepticus have been associated with tiagabine use when taken for off-label indications. Seizures have occurred with doses as low as 4 mg/day and shortly after a dosage increase, even after stable therapy. In most cases, patients were using concomitant medications (eg, antidepressants, antipsychotics, stimulants, opioids). In these instances, the discontinuation of tiagabine, followed by an evaluation for an underlying seizure disorder, is suggested. Use for unapproved indications, however, has not been proven to be safe or effective and is not recommended.
• Withdrawal: Antiseizure medications should not be discontinued abruptly because of the possibility of increasing seizure frequency; therapy should be withdrawn gradually to minimize the potential of increased seizure frequency, unless safety concerns require a more rapid withdrawal.
Substrate of CYP3A4 (major); Note: Assignment of Major/Minor substrate status based on clinically relevant drug interaction potential
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the Lexicomp drug interactions program by clicking on the “Launch drug interactions program” link above.
Alcohol (Ethyl): CNS Depressants may enhance the CNS depressant effect of Alcohol (Ethyl). Risk C: Monitor therapy
Alizapride: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Azelastine (Nasal): May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Blonanserin: CNS Depressants may enhance the CNS depressant effect of Blonanserin. Management: Use caution if coadministering blonanserin and CNS depressants; dose reduction of the other CNS depressant may be required. Strong CNS depressants should not be coadministered with blonanserin. Risk D: Consider therapy modification
Brexanolone: CNS Depressants may enhance the CNS depressant effect of Brexanolone. Risk C: Monitor therapy
Brimonidine (Topical): May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Bromopride: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Bromperidol: May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Buprenorphine: CNS Depressants may enhance the CNS depressant effect of Buprenorphine. Management: Consider reduced doses of other CNS depressants, and avoiding such drugs in patients at high risk of buprenorphine overuse/self-injection. Initiate buprenorphine at lower doses in patients already receiving CNS depressants. Risk D: Consider therapy modification
Cannabinoid-Containing Products: CNS Depressants may enhance the CNS depressant effect of Cannabinoid-Containing Products. Risk C: Monitor therapy
Chlormethiazole: May enhance the CNS depressant effect of CNS Depressants. Management: Monitor closely for evidence of excessive CNS depression. The chlormethiazole labeling states that an appropriately reduced dose should be used if such a combination must be used. Risk D: Consider therapy modification
Chlorphenesin Carbamate: May enhance the adverse/toxic effect of CNS Depressants. Risk C: Monitor therapy
CNS Depressants: May enhance the adverse/toxic effect of other CNS Depressants. Risk C: Monitor therapy
CYP3A4 Inducers (Strong): May decrease the serum concentration of TiaGABine. Risk C: Monitor therapy
Daridorexant: May enhance the CNS depressant effect of CNS Depressants. Management: Dose reduction of daridorexant and/or any other CNS depressant may be necessary. Use of daridorexant with alcohol is not recommended, and the use of daridorexant with any other drug to treat insomnia is not recommended. Risk D: Consider therapy modification
Desmopressin: Hyponatremia-Associated Agents may enhance the hyponatremic effect of Desmopressin. Risk C: Monitor therapy
DexmedeTOMIDine: CNS Depressants may enhance the CNS depressant effect of DexmedeTOMIDine. Management: Monitor for increased CNS depression during coadministration of dexmedetomidine and CNS depressants, and consider dose reductions of either agent to avoid excessive CNS depression. Risk D: Consider therapy modification
Difelikefalin: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Dimethindene (Topical): May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Doxylamine: May enhance the CNS depressant effect of CNS Depressants. Management: The manufacturer of Diclegis (doxylamine/pyridoxine), intended for use in pregnancy, specifically states that use with other CNS depressants is not recommended. Risk C: Monitor therapy
Droperidol: May enhance the CNS depressant effect of CNS Depressants. Management: Consider dose reductions of droperidol or of other CNS agents (eg, opioids, barbiturates) with concomitant use. Risk D: Consider therapy modification
Esketamine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Flunarizine: CNS Depressants may enhance the CNS depressant effect of Flunarizine. Risk X: Avoid combination
Flunitrazepam: CNS Depressants may enhance the CNS depressant effect of Flunitrazepam. Management: Reduce the dose of CNS depressants when combined with flunitrazepam and monitor patients for evidence of CNS depression (eg, sedation, respiratory depression). Use non-CNS depressant alternatives when available. Risk D: Consider therapy modification
Gemfibrozil: May increase the serum concentration of TiaGABine. Both total and unbound concentrations may be increased. Risk C: Monitor therapy
HydrOXYzine: May enhance the CNS depressant effect of CNS Depressants. Management: Consider a decrease in the CNS depressant dose, as appropriate, when used together with hydroxyzine. Increase monitoring of signs/symptoms of CNS depression in any patient receiving hydroxyzine together with another CNS depressant. Risk D: Consider therapy modification
Kava Kava: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Kratom: May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Lemborexant: May enhance the CNS depressant effect of CNS Depressants. Management: Dosage adjustments of lemborexant and of concomitant CNS depressants may be necessary when administered together because of potentially additive CNS depressant effects. Close monitoring for CNS depressant effects is necessary. Risk D: Consider therapy modification
Lisuride: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Lofexidine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Magnesium Sulfate: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Mefloquine: May diminish the therapeutic effect of Antiseizure Agents. Mefloquine may decrease the serum concentration of Antiseizure Agents. Management: Mefloquine is contraindicated for malaria prophylaxis in persons with a history of seizures. If antiseizure drugs are being used for another indication, monitor antiseizure drug concentrations and treatment response closely with concurrent use. Risk D: Consider therapy modification
Methotrimeprazine: CNS Depressants may enhance the CNS depressant effect of Methotrimeprazine. Methotrimeprazine may enhance the CNS depressant effect of CNS Depressants. Management: Reduce the usual dose of CNS depressants by 50% if starting methotrimeprazine until the dose of methotrimeprazine is stable. Monitor patient closely for evidence of CNS depression. Risk D: Consider therapy modification
Metoclopramide: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
MetyraPONE: Antiseizure Agents may diminish the diagnostic effect of MetyraPONE. Management: Consider alternatives to the use of the metyrapone test in patients taking antiseizure agents. Risk D: Consider therapy modification
MetyroSINE: CNS Depressants may enhance the sedative effect of MetyroSINE. Risk C: Monitor therapy
Mianserin: May diminish the therapeutic effect of Antiseizure Agents. Risk C: Monitor therapy
Minocycline (Systemic): May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Olopatadine (Nasal): May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Opioid Agonists: CNS Depressants may enhance the CNS depressant effect of Opioid Agonists. Management: Avoid concomitant use of opioid agonists and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug. Risk D: Consider therapy modification
Orlistat: May decrease the serum concentration of Antiseizure Agents. Risk C: Monitor therapy
Orphenadrine: CNS Depressants may enhance the CNS depressant effect of Orphenadrine. Risk X: Avoid combination
Oxomemazine: May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Oxybate Salt Products: CNS Depressants may enhance the CNS depressant effect of Oxybate Salt Products. Management: Consider alternatives to this combination when possible. If combined, dose reduction or discontinuation of one or more CNS depressants (including the oxybate salt product) should be considered. Interrupt oxybate salt treatment during short-term opioid use Risk D: Consider therapy modification
OxyCODONE: CNS Depressants may enhance the CNS depressant effect of OxyCODONE. Management: Avoid concomitant use of oxycodone and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug. Risk D: Consider therapy modification
Paraldehyde: CNS Depressants may enhance the CNS depressant effect of Paraldehyde. Risk X: Avoid combination
Perampanel: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Piribedil: CNS Depressants may enhance the CNS depressant effect of Piribedil. Risk C: Monitor therapy
Pramipexole: CNS Depressants may enhance the sedative effect of Pramipexole. Risk C: Monitor therapy
Procarbazine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Ropeginterferon Alfa-2b: CNS Depressants may enhance the adverse/toxic effect of Ropeginterferon Alfa-2b. Specifically, the risk of neuropsychiatric adverse effects may be increased. Management: Avoid coadministration of ropeginterferon alfa-2b and other CNS depressants. If this combination cannot be avoided, monitor patients for neuropsychiatric adverse effects (eg, depression, suicidal ideation, aggression, mania). Risk D: Consider therapy modification
ROPINIRole: CNS Depressants may enhance the sedative effect of ROPINIRole. Risk C: Monitor therapy
Rotigotine: CNS Depressants may enhance the sedative effect of Rotigotine. Risk C: Monitor therapy
Rufinamide: May enhance the adverse/toxic effect of CNS Depressants. Specifically, sleepiness and dizziness may be enhanced. Risk C: Monitor therapy
Suvorexant: CNS Depressants may enhance the CNS depressant effect of Suvorexant. Management: Dose reduction of suvorexant and/or any other CNS depressant may be necessary. Use of suvorexant with alcohol is not recommended, and the use of suvorexant with any other drug to treat insomnia is not recommended. Risk D: Consider therapy modification
Thalidomide: CNS Depressants may enhance the CNS depressant effect of Thalidomide. Risk X: Avoid combination
Trimeprazine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Valerian: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Zolpidem: CNS Depressants may enhance the CNS depressant effect of Zolpidem. Management: Reduce the Intermezzo brand sublingual zolpidem adult dose to 1.75 mg for men who are also receiving other CNS depressants. No such dose change is recommended for women. Avoid use with other CNS depressants at bedtime; avoid use with alcohol. Risk D: Consider therapy modification
Food reduces the rate but not the extent of absorption. Management: Administer with food.
Adverse events were observed in animal reproduction studies. Information specific to the use of tiagabine in pregnancy is limited (Leppik 1999; Neppe 2000).
Patients exposed to tiagabine during pregnancy are encouraged to enroll themselves into the North American Antiepileptic Drug (NAAED) Pregnancy Registry by calling 1-888-233-2334. Additional information is available at www.aedpregnancyregistry.org.
It is not known if tiagabine is excreted into breast milk. Information specific to the use of tiagabine while breast-feeding is limited (Neppe, 2000). According to the manufacturer, tiagabine should be used in breast-feeding women only when the benefits outweigh the potential risks.
Seizure frequency, liver function tests (periodically), suicidality (eg, suicidal thoughts, depression, behavioral changes)
A therapeutic range for tiagabine plasma concentrations has not been established. Because of the potential for pharmacokinetic interactions between tiagabine and drugs that induce or inhibit hepatic metabolizing enzymes, it may be useful to obtain plasma levels of tiagabine before and after changes are made in the therapeutic regimen. A tentative target trough concentration of 20 to 200 ng/mL (53.2 to 532 nmol/L) has been suggested (Hiemke 2018).
The exact mechanism by which tiagabine exerts antiseizure activity is not definitively known; however, in vitro experiments demonstrate that it enhances the activity of gamma aminobutyric acid (GABA). It is thought that the binding of tiagabine to the GABA uptake carrier inhibits the uptake of GABA into presynaptic neurons, allowing an increased amount of GABA to be available to postsynaptic neurons; based on in vitro studies, tiagabine does not inhibit the uptake of dopamine, norepinephrine, serotonin, glutamate, or choline
Absorption: Rapid (45 minutes), well absorbed (>95%); prolonged with food.
Distribution: Note: Vd values are more similar between children and adults when expressed as L/m2 (Gustavson 1997); Mean Vd:
Children 3 to 10 years: 2.4 L/kg.
Adults: 1.3 to 1.6 L/kg.
Protein binding: 96%, primarily to albumin and alpha-1 acid glycoprotein.
Metabolism: Hepatic via CYP (primarily 3A4): undergoes enterohepatic recirculation.
Bioavailability: Oral: Absolute: ~90%; diurnal effect: Trough concentrations and AUC are lower in the evening versus morning.
Half-life elimination:
Children 3 to 10 years: Mean: 5.7 hours (range: 2 to 10 hours); receiving enzyme-inducing AEDs: Mean: 3.2 hours (range: 2 to 7.8 hours).
Adults: 7 to 9 hours; receiving enzyme-inducing AEDs: 2 to 5 hours.
Time to peak, plasma: Fasting state: 45 minutes.
Excretion: Feces (63%); urine (25%); 2% as unchanged drug; primarily as metabolites.
Clearance: Note: Clearance values are more similar between children and adults when expressed as mL/minute/m2 (Gustavson 1997).
Children 3 to 10 years: 4.2 ± 1.6 mL/minute/kg.
Children 3 to 10 years receiving enzyme-inducing AEDs: 8.6 ± 3.3 mL/minute/kg.
Adults: 1.9 ± 0.5 mL/minute/kg.
Adults receiving enzyme-inducing AEDs: 6.3 ± 3.5 mL/minute/kg.
Hepatic impairment: Clearance of unbound drug is decreased by ~60%.
Hepatic function impairment: Moderate hepatic impairment (Child-Pugh class B) caused a 60% decrease in the Cl of unbound tiagabine.
Tablets (Gabitril Oral)
2 mg (per each): $14.29
4 mg (per each): $14.29
12 mg (per each): $18.48
16 mg (per each): $24.19
Tablets (tiaGABine HCl Oral)
2 mg (per each): $7.93
4 mg (per each): $7.93
12 mg (per each): $11.51
16 mg (per each): $15.08
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