Tiagabine Hydrochloride

FDA Drug Information • Also known as: Tiagabine Hydrochloride

Brand Names: Tiagabine Hydrochloride
Dosage Form: TABLET, FILM COATED
Product Type: DRUG FOR FURTHER PROCESSING

Description

DESCRIPTION Tiagabine hydrochloride USP is an antiepilepsy drug available as 2 mg, 4 mg, 12 mg, and 16 mg tablets for oral administration. Its chemical name is (-)-(R)-1-[4,4-Bis(3-methyl-2-thienyl)-3 butenyl]nipecotic acid hydrochloride, its molecular formula is C 20 H 25 NO 2 S 2 HCl, and its molecular weight is 412.01. Tiagabine HCl, USP is a white to off-white powder. It is freely soluble in methanol and in alcohol, soluble in 5% Water in isopropanol, very slightly soluble in chloroform, sparingly soluble in water and practically insoluble in n-Heptane. The structural formula is: Inactive Ingredients Tiagabine hydrochloride tablets contain the following inactive ingredients: Butylated hydroxyanisole, colloidal silicon dioxide, crospovidone, hydrogenated vegetable oil (cottonseed oil), hydroxypropyl cellulose, hypromellose, lactose anhydrous, magnesium stearate, microcrystalline cellulose, pregelatinized starch, stearic acid and titanium dioxide. In addition, individual tablets contain: 2 mg tablets: FD&C yellow No. 6 aluminum lake 4 mg tablets: D&C yellow No. 10 aluminum lake 12 mg tablets: D&C yellow No. 10 aluminum lake and FD&C Blue No. 1 aluminum lake 16 mg tablets: FD&C blue No. 2 aluminum lake tia-str

What Is Tiagabine Hydrochloride Used For?

INDICATIONS AND USAGE Tiagabine hydrochloride tablet is indicated as adjunctive therapy in adults and children 12 years and older in the treatment of partial seizures.

Dosage and Administration

DOSAGE AND ADMINISTRATION General: The blood level of tiagabine obtained after a given dose depends on whether the patient also is receiving a drug that induces the metabolism of tiagabine. The presence of an inducer means that the attained blood level will be substantially reduced. Dosing should take the presence of concomitant medications into account. Tiagabine hydrochloride tablet is recommended as adjunctive therapy for the treatment of partial seizures in patients 12 years and older. The following dosing recommendations apply to all patients taking tiagabine hydrochloride tablets: Tiagabine hydrochloride tablet is given orally and should be taken with food. Do not use a loading dose of tiagabine hydrochloride tablets. Dose titration: Rapid escalation and/or large dose increments of tiagabine hydrochloride tablets should not be used. Missed dose(s): If the patient forgets to take the prescribed dose of tiagabine hydrochloride tablets at the scheduled time, the patient should not attempt to make up for the missed dose by increasing the next dose. If a patient has missed multiple doses, patient should refer back to his or her physician for possible re-titration as clinically indicated. Dosage adjustment of tiagabine hydrochloride tablets should be considered whenever a change in patient’s enzyme-inducing status occurs as a result of the addition, discontinuation, or dose change of the enzyme-inducing agent. Induced Adults and Adolescents 12 Years or Older: The following dosing recommendations apply to patients who are already taking enzyme-inducing antiepilepsy drugs (AEDs) (e.g., carbamazepine, phenytoin, primidone, and phenobarbital). Such patients are considered induced patients when administering tiagabine hydrochloride tablets. In adolescents 12 to 18 years old, tiagabine hydrochloride tablets should be initiated at 4 mg once daily. Modification of concomitant antiepilepsy drugs is not necessary, unless clinically indicated. The total daily dose of tiagabine hydrochloride tablets may be increased by 4 mg at the beginning of Week 2. Thereafter, the total daily dose may be increased by 4 to 8 mg at weekly intervals until clinical response is achieved or up to 32 mg/day. The total daily dose should be given in divided doses two to four times daily. Doses above 32 mg/day have been tolerated in a small number of adolescent patients for a relatively short duration. In adults, tiagabine hydrochloride tablets should be initiated at 4 mg once daily. Modification of concomitant antiepilepsy drugs is not necessary, unless clinically indicated. The total daily dose of tiagabine hydrochloride tablets may be increased by 4 to 8 mg at weekly intervals until clinical response is achieved or, up to 56 mg/day. The total daily dose should be given in divided doses two to four times daily. Doses above 56 mg/day have not been systematically evaluated in adequate and well-controlled clinical trials. Experience is limited in patients taking total daily doses...

Side Effects (Adverse Reactions)

ADVERSE REACTIONS The most commonly observed adverse events in placebo-controlled, parallel-group, add-on epilepsy trials associated with the use of tiagabine hydrochloride in combination with other antiepilepsy drugs not seen at an equivalent frequency among placebo-treated patients were dizziness/light-headedness, asthenia/lack of energy, somnolence, nausea, nervousness/irritability, tremor, abdominal pain, and thinking abnormal/difficulty with concentration or attention. Approximately 21% of the 2531 patients who received tiagabine hydrochloride in clinical trials of epilepsy discontinued treatment because of an adverse event. The adverse events most commonly associated with discontinuation were dizziness (1.7%), somnolence (1.6%), depression (1.3%), confusion (1.1%), and asthenia (1.1%). In Studies 1 and 2 (U.S. studies), the double-blind, placebo-controlled, parallel-group, add-on studies, the proportion of patients who discontinued treatment because of adverse events was 11% for the group treated with tiagabine hydrochloride and 6% for the placebo group. The most common adverse events considered the primary reason for discontinuation were confusion (1.2%), somnolence (1.0%), and ataxia (1.0%). Adverse Event Incidence in Controlled Clinical Trials: Table 5 lists treatment-emergent signs and symptoms that occurred in at least 1% of patients treated with tiagabine hydrochloride for epilepsy participating in parallel-group, placebo-controlled trials and were numerically more common in the tiagabine hydrochloride group. In these studies, either tiagabine hydrochloride or placebo was added to the patient’s current antiepilepsy drug therapy. Adverse events were usually mild or moderate in intensity. The prescriber should be aware that these figures, obtained when tiagabine hydrochloride was added to concurrent antiepilepsy drug therapy, cannot be used to predict the frequency of adverse events in the course of usual medical practice when patient characteristics and other factors may differ from those prevailing during clinical studies. Similarly, the cited frequencies cannot be directly compared with figures obtained from other clinical investigations involving different treatments, uses, or investigators. An inspection of these frequencies, however, does provide the prescribing physician with one basis to estimate the relative contribution of drug and non-drug factors to the adverse event incidences in the population studied. Table 5: Treatment-Emergent Adverse Event1 Incidence in Parallel-Group, Placebo-Controlled, Add-On Trials (events in at least 1% of patients treated with Tiagabine Hydrochloride and numerically more frequent than in the placebo group) Body System/COSTART Tiagabine Hydrochloride N=494 % Placebo N=275 % Body as a Whole Abdominal Pain 7 3 Pain (Unspecified) 5 3 Cardiovascular Vasodilation 2 1 Digestive Nausea 11 9 Diarrhea 7 3 Vomiting 7 4 Increased Appetite 2 0 Mouth Ulceration 1 0 Musculoskeletal Myasthenia 1 0 Nervous System Dizziness 27 15 Asthenia 20 14 Somnolence 18 15 Nervousness 10 3 Tremor 9 3 Difficulty with Concentration/Attention* 6 2 Insomnia 6 4 Ataxia 5 3 Confusion 5 3 Speech Disorder 4 2 Difficulty with Memory* 4 3 Paresthesia 4 2 Depression 3 1 Emotional Lability 3 2 Abnormal Gait 3 2 Hostility 2 1 Nystagmus 2 1 Language Problems* 2 0 Agitation 1 0 Respiratory System Pharyngitis 7 4 Cough Increased 4 3 Skin and Appendages Rash 5 4 Pruritus 2 0 1 Patients in these add-on studies were receiving one to three concomitant enzyme-inducing antiepilepsy drugs in addition to tiagabine hydrochloride or placebo. Patients may have reported multiple adverse experiences; thus, patients may be included in more than one category. *COSTART term substituted with a more clinically descriptive term. Other events reported by 1% or more of patients treated with tiagabine hydrochloride but equally or more frequent in the placebo group were: accidental injury, chest pain, constipation, flu syndrome, rhinitis,...

Warnings and Precautions

WARNINGS Seizures in Patients Without Epilepsy: Post-marketing reports have shown that tiagabine hydrochloride use has been associated with new onset seizures and status epilepticus in patients without epilepsy. Dose may be an important predisposing factor in the development of seizures, although seizures have been reported in patients taking daily doses of tiagabine hydrochloride as low as 4 mg/day. In most cases, patients were using concomitant medications (antidepressants, antipsychotics, stimulants, narcotics) that are thought to lower the seizure threshold. Some seizures occurred near the time of a dose increase, even after periods of prior stable dosing. The tiagabine hydrochloride dosing recommendations in current labeling for treatment of epilepsy were based on use in patients with partial seizures 12 years of age and older, most of whom were taking enzyme-inducing antiepileptic drugs (AEDs; e.g., carbamazepine, phenytoin, primidone and phenobarbital) which lower plasma levels of tiagabine hydrochloride by inducing its metabolism. Use of tiagabine hydrochloride without enzyme-inducing antiepileptic drugs results in blood levels about twice those attained in the studies on which current dosing recommendations are based (see DOSAGE AND ADMINISTRATION). Safety and effectiveness of tiagabine hydrochloride have not been established for any indication other than as adjunctive therapy for partial seizures in adults and children 12 years and older. In nonepileptic patients who develop seizures while on tiagabine hydrochloride treatment, tiagabine hydrochloride should be discontinued and patients should be evaluated for an underlying seizure disorder. Seizures and status epilepticus are known to occur with tiagabine hydrochloride overdosage (see OVERDOSAGE). Suicidal Behavior and Ideation: Antiepileptic drugs (AEDs), including tiagabine hydrochloride, increase the risk of suicidal thoughts or behavior in patients taking these drugs for any indication. Patients treated with any AED for any indication should be monitored for the emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior. Pooled analyses of 199 placebo-controlled clinical trials (mono- and adjunctive therapy) of 11 different AEDs showed that patients randomized to one of the AEDs had approximately twice the risk (adjusted Relative Risk 1.8, 95% CI:1.2, 2.7) of suicidal thinking or behavior compared to patients randomized to placebo. In these trials, which had a median treatment duration of 12 weeks, the estimated incidence rate of suicidal behavior or ideation among 27,863 AED-treated patients was 0.43%, compared to 0.24% among 16,029 placebo-treated patients, representing an increase of approximately one case of suicidal thinking or behavior for every 530 patients treated. There were four suicides in drug-treated patients in the trials and none in placebo-treated patients, but the number is too small to allow any conclusion...

Drug Interactions

Drug Interactions In evaluating the potential for interactions among co-administered antiepilepsy drugs (AEDs), whether or not an AED induces or does not induce metabolic enzymes is an important consideration. Carbamazepine, phenytoin, primidone, and phenobarbital are generally classified as enzyme inducers; valproate and gabapentin are not. Tiagabine hydrochloride is considered to be a non-enzyme inducing AED (see PRECAUTIONS, General, Use in Non-Induced Patients ). The drug interaction data described in this section were obtained from studies involving either healthy subjects or patients with epilepsy. Effects of Tiagabine Hydrochloride on other Antiepilepsy Drugs (AEDs): Phenytoin: Tiagabine had no effect on the steady-state plasma concentrations of phenytoin in patients with epilepsy. Carbamazepine: Tiagabine had no effect on the steady-state plasma concentrations of carbamazepine or its epoxide metabolite in patients with epilepsy. Valproate: Tiagabine causes a slight decrease (about 10%) in steady-state valproate concentrations. Phenobarbital or Primidone: No formal pharmacokinetic studies have been performed examining the addition of tiagabine to regimens containing phenobarbital or primidone. The addition of tiagabine in a limited number of patients in three well-controlled studies caused no systematic changes in phenobarbital or primidone concentrations when compared to placebo. Effects of other Antiepilepsy Drugs (AEDs) on Tiagabine Hydrochloride: Carbamazepine: Population pharmacokinetic analyses indicate that tiagabine clearance is 60% greater in patients taking carbamazepine with or without other enzyme-inducing AEDs. Phenytoin: Population pharmacokinetic analyses indicate that tiagabine clearance is 60% greater in patients taking phenytoin with or without other enzyme-inducing AEDs. Phenobarbital (Primidone): Population pharmacokinetic analyses indicate that tiagabine clearance is 60% greater in patients taking phenobarbital (primidone) with or without other enzyme-inducing AEDs. Valproate: The addition of tiagabine to patients taking valproate chronically had no effect on tiagabine pharmacokinetics, but valproate significantly decreased tiagabine binding in vitro from 96.3 to 94.8%, which resulted in an increase of approximately 40% in the free tiagabine concentration. The clinical relevance of this in vitro finding is unknown. Interaction of Tiagabine Hydrochloride with Other Drugs: Cimetidine: Co-administration of cimetidine (800 mg/day) to patients taking tiagabine chronically had no effect on tiagabine pharmacokinetics. Theophylline: A single 10 mg dose of tiagabine did not affect the pharmacokinetics of theophylline at steady state. Warfarin: No significant differences were observed in the steady-state pharmacokinetics of R-warfarin or S-warfarin with the addition of tiagabine given as a single dose. Prothrombin times were not affected by tiagabine. Digoxin: Concomitant administration of tiagabine did not affect the...

Contraindications

CONTRAINDICATIONS Tiagabine hydrochloride is contraindicated in patients who have demonstrated hypersensitivity to the drug or its ingredients.

Pregnancy and Breastfeeding

Pregnancy: Tiagabine has been shown to have adverse effects on embryo-fetal development, including teratogenic effects, when administered to pregnant rats and rabbits at doses greater than the human therapeutic dose. An increased incidence of malformed fetuses (various craniofacial, appendicular, and visceral defects) and decreased fetal weights were observed following oral administration of 100 mg/kg/day to pregnant rats during the period of organogenesis. This dose is approximately 16 times the maximum recommended human dose (MRHD) of 56 mg/day, based on body surface area (mg/m 2 ). Maternal toxicity (transient weight loss/reduced maternal weight gain during gestation) was associated with this dose, but there is no evidence to suggest that the teratogenic effects were secondary to the maternal effects. No adverse maternal or embryo-fetal effects were seen at a dose of 20 mg/kg/day (3 times the MRHD on a mg/m 2 basis). Decreased maternal weight gain, increased resorption of embryos and increased incidences of fetal variations, but not malformations, were observed when pregnant rabbits were given 25 mg/kg/day (8 times the MRHD on a mg/m 2 basis) during organogenesis. The no effect level for maternal and embryo-fetal toxicity in rabbits was 5 mg/kg/day (equivalent to the MRHD on a mg/m 2 basis). When female rats were given tiagabine 100 mg/kg/day during late gestation and throughout parturition and lactation, decreased maternal weight gain during gestation, an increase in stillbirths, and decreased postnatal offspring viability and growth were found. There are no adequate and well-controlled studies in pregnant women. Tiagabine should be used during pregnancy only if clearly needed. To provide additional information regarding the effects of in utero exposure to tiagabine hydrochloride, physicians are advised to recommend that pregnant patients taking tiagabine hydrochloride enroll in the NAAED Pregnancy Registry. This can be done by calling the toll free number...

Overdosage

OVERDOSAGE Human Overdose Experience: Human experience of acute overdose with tiagabine hydrochloride is limited. Eleven patients in clinical trials took single doses of tiagabine hydrochloride up to 800 mg. All patients fully recovered, usually within one day. The most common symptoms reported after overdose included somnolence, impaired consciousness, agitation, confusion, speech difficulty, hostility, depression, weakness, and myoclonus. One patient who ingested a single dose of 400 mg experienced generalized tonic-clonic status epilepticus, which responded to intravenous phenobarbital. From post-marketing experience, reports of overdose involving tiagabine hydrochloride alone have included cases in which patients required intubation and ventilatory support as part of the management of their status epilepticus. Overdoses involving multiple drugs, including tiagabine hydrochloride, have resulted in fatal outcomes. Symptoms most often accompanying tiagabine hydrochloride overdose, alone or in combination with other drugs, have included: seizures including status epilepticus in patients with and without underlying seizure disorders, nonconvulsive status epilepticus, respiratory arrest, coma, loss of consciousness, ataxia, dizziness, confusion, somnolence, drowsiness, impaired speech, aggression, agitation, lethargy, myoclonus, spike wave stupor, encephalopathy, amnesia, dyskinesia, tremors, disorientation, psychotic disorder, vomiting, hostility, and temporary paralysis. Respiratory depression was seen in a number of patients, including children, in the context of seizures. Management of Overdose: There is no specific antidote for overdose with tiagabine hydrochloride. If indicated, elimination of unabsorbed drug should be achieved by emesis or gastric lavage; usual precautions should be observed to maintain the airway. General supportive care of the patient is indicated including monitoring of vital signs and observation of clinical status of the patient. Since...

How Supplied

HOW SUPPLIED Tiagabine hydrochloride tablets are available in four dosage strengths. 2 mg light orange-peach colored, round shaped, biconvex film-coated tablets debossed with “MT” on one side and “3” on the other side, are available in bottles of 30 (NDC 72205-084-30). 4 mg yellow colored, round shaped, biconvex film-coated tablets debossed with “MT” on one side and “4” on the other side, are available in bottles of 30 (NDC 72205-085-30). 12 mg green colored, capsule shaped, biconvex film-coated tablets debossed with “MT” on one side and “5” on the other side, are available in bottles of 30 (NDC 72205-086-30). 16 mg blue colored, capsule shaped, biconvex film-coated tablets debossed with “MT” on one side and “6” on the other side, are available in bottles of 30 (NDC 72205-087-30). Recommended Storage: Store at 20° to 25°C (68° to 77°F). [See USP Controlled Room Temperature]. Protect from light and moisture.

About This Information

This drug information is sourced from FDA-approved labeling via the openFDA database. It is intended for educational and reference purposes only. This is not medical advice. Always consult your healthcare provider before making decisions about medication. Drug information may be updated by the FDA; check with your pharmacist for the most current information.

What are side effects?

Side effects are unwanted reactions that can occur when taking a medication. They range from mild (headache, nausea) to severe (allergic reactions, organ damage). Not everyone experiences side effects, and severity varies. Report any concerning side effects to your doctor.

What are drug interactions?

Drug interactions occur when a medication is affected by another drug, food, or supplement. Interactions can make medications less effective or cause dangerous side effects. Always tell your doctor about all medications and supplements you take.