Tiagabine

Respiratory depression was seen in a number of patients, including children, in the context of seizures. May cause a potentially dangerous rash that may develop into Stevens Johnson syndrome, an extremely rare but potentially fatal skin disease.

Limited data are available on the hepatotoxicity of tiagabine. In clinical trials, therapy with tiagabine was not associated with an increased frequency of serum aminotransferase elevations or liver toxicity. No individual case reports of liver injury from tiagabine have been published and its use has not been associated with hypersensitivity syndromes or autoimmunity. However, its overall use has been limited.

Symptoms most often accompanying tiagabine 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, coma, ataxia, confusion, somnolence, drowsiness, impaired speech, agitation, lethargy, myoclonus, spike wave stupor, tremors, disorientation, vomiting, hostility, and temporary paralysis. Respiratory depression was seen in a number of patients, including children, in the context of seizures.

/HUMAN EXPOSURE STUDIES/ The long-term effects of tiagabine monotherapy on cognition and mood were evaluated in adult patients with chronic partial epilepsy in a 48-week, open-label extension period that followed an 8-week, double-blind, titration study. Cognitive function was evaluated using neuropsychological evaluations that measured learning and memory, general intellectual ability, attention and mental speed, and reaction speed. Mood was assessed using a Finnish modification of the Profile of Mood States. Of the 34 patients who entered the open-label extension period, 18 successfully continued long-term monotherapy and underwent neuropsychological evaluation at 48 weeks of tiagabine monotherapy. The mean daily dose of tiagabine monotherapy at the end of open-label treatment was 19.7 mg/day (range, 5-35 mg/day). Tiagabine monotherapy did not adversely affect cognitive function. No significant changes in mood were observed. The median number of seizures was 2 (range, 0-71), and 8 patients (44%) were seizure-free during the 48 weeks of open-label tiagabine treatment. The results of this small open-label extension study indicate that patients with chronic partial epilepsy who were successfully converted to long-term tiagabine monotherapy demonstrated no adverse effects on cognitive function or mood.

/SIGNS AND SYMPTOMS/ Symptoms most often accompanying /tiagabine/ 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, coma, ataxia, confusion, somnolence, drowsiness, impaired speech, agitation, lethargy, myoclonus, spike wave stupor, tremors, disorientation, vomiting, hostility, and temporary paralysis. Respiratory depression was seen in a number of patients, including children, in the context of seizures.

/SIGNS AND SYMPTOMS/ /Acute intoxication/: Agitation, severe; ataxia, severe (clumsiness or unsteadiness); confusion, severe; hostility; impaired consciousness (coma); lethargy (sluggishness; mental depression; myoclonus (severe muscle twitching or jerking); precipatation of a tonic-clonic seizure (increased seizures); somnolence, severe (drowsiness); speech problems, severe; weakness.

/CASE REPORTS/ There have been as many as 10 cases of sudden unexpected deaths during the clinical development of tiagabine among 2531 patients with epilepsy (3831 patient-years of exposure). This represents an estimated incidence of 0.0026 deaths per patient-year. This rate is within the range of estimates for the incidence of sudden and unexpected deaths in patients with epilepsy not receiving /tiagabine/ (ranging from 0.0005 for the general population with epilepsy, 0.003 to 0.004 for clinical trial populations similar to that in the clinical development program for /tiagabine/, to 0.005 for patients with refractory epilepsy). The estimated SUDEP rates in patients receiving /tiagabine/ are also similar to those observed in patients receiving other antiepilepsy drugs, chemically unrelated to /tiagabine/, that underwent clinical testing in similar populations at about the same time.

For more Human Toxicity Excerpts (Complete) data for TIAGABINE (9 total), please visit the HSDB record page.

Drug-Induced Liver Injury Severity and Toxicity (DILIst)

tiagabine

DILI Negative

Oral

DOI:10.1016/j.drudis.2019.09.022

/LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity/ In rats, a study of the potential carcinogenicity associated with tiagabine HCl administration showed that 200 mg/kg/day for 2 years resulted in small, but statistically significant increases in the incidences of hepatocellular adenomas in females and Leydig cell tumors of the testis in males. The significance of these findings relative to the use of /tiagabine/ in humans is unknown. The no effect dosage for induction of tumors in this study was 100 mg/kg/day (17 to 50 times the exposure at the MRHD). No statistically significant increases in tumor formation were noted in mice at dosages up to 250 mg/kg/day.

/LABORATORY ANIMALS: Developmental or Reproductive Toxicity/ Studies of male and female rats administered dosages of tiagabine HCl prior to and during mating, gestation, and lactation have shown no impairment of fertility at doses up to 100 mg/kg/day. This dose represents approximately 16 times the maximum recommended human dose (MRHD). Lowered maternal weight gain and decreased viability and growth in the rat pups were found at 100 mg/kg, but not at 20 mg/kg/day (3 times the MRHD).

/LABORATORY ANIMALS: Developmental or Reproductive Toxicity/ 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.

/LABORATORY ANIMALS: Developmental or Reproductive Toxicity/ 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) during organogenesis. The no effect level for maternal and embryo-fetal toxicity in rabbits was 5 mg/kg/day (equivalent to the MRHD).

For more Non-Human Toxicity Excerpts (Complete) data for TIAGABINE (7 total), please visit the HSDB record page.

While data specific to tiagabine were not located(SRC, 2007), the literature suggests that some pharmaceutically active compounds originating from human and veterinary therapy are not eliminated completely in municipal sewage treatment plants and are therefore discharged into receiving waters(1). Wastewater treatment processes often were not designed to remove them from the effluent(2). Selected organic waste compounds may be degrading to new and more persistent compounds that may be released instead of or in addition to the parent compound(2).

7-9 hours

... The average elimination half-life for tiagabine in healthy subjects ranged from 7 to 9 hours. The elimination half-life decreased by 50 to 65% in hepatic enzyme-induced patients with epilepsy compared to uninduced patients with epilepsy.

Its half-life is about 8 hrs but is shortened by 2 to 3 hrs when coadministered with hepatic enzyme-inducing drugs such as phenobarbital, phenytoin, or carbamazepine.

Tiagabine is likely metabolized primarily by the 3A isoform subfamily of hepatic cytochrome P450.

Although the metabolism of tiagabine has not been fully elucidated, in vivo and in vitro studies suggest that at least two metabolic pathways for tiagabine have been identified in humans: 1) thiophene ring oxidation leading to the formation of 5-oxo-tiagabine; and 2) glucuronidation. The 5-oxo-tiagabine metabolite does not contribute to the pharmacologic activity of tiagabine.

Based on in vitro data, tiagabine is likely to be metabolized primarily by the 3A isoform subfamily of hepatic cytochrome P450 (CYP 3A), although contributions to the metabolism of tiagabine from CYP 1A2, CYP 2D6 or CYP 2C19 have not been excluded.

Tiagabine is likely metabolized primarily by the 3A isoform subfamily of hepatic cytochrome P450. Route of Elimination: Approximately 2% of an oral dose of tiagabine is excreted unchanged, with 25% and 63% of the remaining dose excreted into the urine and feces, respectively, primarily as metabolites. Half Life: 7-9 hours

Z80I64HMNP

TIAGABINE

Established Pharmacologic Class [EPC] - Anti-epileptic Agent

Physiologic Effects [PE] - Decreased Central Nervous System Disorganized Electrical Activity

Tiagabine is an Anti-epileptic Agent. The physiologic effect of tiagabine is by means of Decreased Central Nervous System Disorganized Electrical Activity.

Drugs used to prevent SEIZURES or reduce their severity.

Compounds that suppress or block the plasma membrane transport of GAMMA-AMINOBUTYRIC ACID by GABA PLASMA MEMBRANE TRANSPORT PROTEINS.

Tiagabine is nearly completely absorbed (>95%).

Approximately 2% of an oral dose of tiagabine is excreted unchanged, with 25% and 63% of the remaining dose excreted into the urine and feces, respectively, primarily as metabolites.

109 mL/min [Healthy subjects]

Absorption of tiagabine is rapid, with peak plasma concentrations occurring at approximately 45 minutes following an oral dose in the fasting state. Tiagabine is nearly completely absorbed (>95%), with an absolute oral bioavailability of about 90%. A high fat meal decreases the rate (mean T max was prolonged to 2.5 hours, and mean C max was reduced by about 40%) but not the extent (AUC) of tiagabine absorption.

The pharmacokinetics of tiagabine are linear over the single dose range of 2 to 24 mg. Following multiple dosing, steady state is achieved within 2 days.

Tiagabine is 96% bound to human plasma proteins, mainly to serum albumin and alpha1-acid glycoprotein over the concentration range of 10 ng/mL to 10,000 ng/mL. While the relationship between tiagabine plasma concentrations and clinical response is not currently understood, trough plasma concentrations observed in controlled clinical trials at doses from 30 to 56 mg/day ranged from <1 ng/mL to 234 ng/mL.