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PubMed1997

Tiagabine therapy for complex partial seizures. A dose-frequency study. The Tiagabine Study Group.

OBJECTIVE: To evaluate the efficacy and safety of 2 regimens of tiagabine as add-on therapy for patients with complex partial seizures (CPSs) that are refractory to other treatment. DESIGN: Randomized, double-blind, placebo-controlled, add-on, parallel-group trial with an 8-week baseline period, 12-week experimental period (4 weeks of dose titration and 8 weeks of fixed-dose therapy), and 4-week termination period. SETTING: Twenty-six centers throughout the United States. PATIENTS: Three hundred fifty-one patients were enrolled, 318 were entered in the double-blind period, and 271 completed the study. INTERVENTIONS: Tiagabine, 16 mg 2 times per day (106 patients); tiagabine, 8 mg 4 times daily (105 patients); and placebo (107 patients). The doses of tiagabine were titrated in 3 steps to the fixed dose. MAIN OUTCOME MEASURE: The median change in the 4-week rate of CPSs from baseline to experimental period. RESULTS: The median change from baseline was -1.6 CPSs per 4 weeks in the group of patients who were given tiagabine 2 times per day, and it was -1.2 CPSs in the group of patients who were given tiagabine 4 time per day (P = .06 and P = .02, respectively, compared with placebo). The 4-week seizure frequency was reduced by 50% or more in 31% of the patients who were given tiagabine 2 times per day and in 27% of the patients who were given tiagabine 4 times per day vs 10% of the placebo-treated patients (P < or = .001 for each tiagabine-treated group compared with the placebo group). The most frequent adverse events involved the central nervous system and occurred in comparable proportions in the 3 treatment groups. Similar proportions of patients discontinued the study prematurely for adverse events. CONCLUSIONS: Tiagabine administered 2 and 4 times daily as add-on pharmacotherapy was effective in reducing CPSs in patients with epilepsy whose conditions were refractory to treatment with other antiepileptic agents, and it was well tolerated.

Adolescent↗

PubMed1998

A double-blind, placebo-controlled trial of tiagabine given three-times daily as add-on therapy for refractory partial seizures. Northern European Tiagabine Study Group.

In a multicentre, double-blind, parallel-group, placebo-controlled trial, a three-times daily regimen of tiagabine was evaluated as add-on therapy in 154 adult patients with refractory partial seizures. A total of 77 patients were randomised to treatment in each arm. Tiagabine HCl was titrated from an initial dose of 12-30 mg/day over 4 weeks. During the 12-week fixed-dose period, there was a significant reduction in the median 4-weekly seizure rate for all partial seizures and simple partial seizures (P < 0.05 in each case). Furthermore, the proportion of patients with a reduction of 50% or more in all partial seizures was higher in the tiagabine group than in the placebo group (14 versus 6%), though the difference did not achieve statistical significance. The difference with respect to simple partial seizures was significant (21 versus 6%, P < 0.01). The percentage of patients achieving an increase of at least 50% in the proportion of days free of all partial seizures was significantly greater in the tiagabine group compared to placebo (14 versus 4%, P<0.01). Tiagabine did not appear to influence the plasma concentrations of other concomitant antiepileptic drugs and was generally well tolerated, with most drug-related adverse events being mild or moderate in severity. The most common adverse events were dizziness, asthenia, headache and somnolence. Adverse event incidence was similar between tiagabine and placebo groups, except for dizziness which was more common with tiagabine (29 versus 10%, P < 0.01). Tiagabine had no significant effects on laboratory tests or vital signs. The present study shows that tiagabine, at a dose of 10 mg administered three-times daily, which is at the lower end of the usual recommended dose range (30-50 mg/day, tiagabine base), is generally well tolerated and demonstrates efficacy for the treatment of refractory partial seizures.

Adolescent↗

PubMed1995

Effects of chronic tiagabine treatment on [3H]GABAA, [3H]GABAB and [3H]tiagabine binding to sections from mice brain.

(R)-N-(4,4-Bis(3-methyl-2-thienyl)but-3-en-1-yl)nipecotic acid (tiagabine) is a potent inhibitor of gamma-aminobutyric acid (GABA) uptake, which maintains its initial anticonvulsant effects when administered to mice for a prolonged period (21 days). In the present study, mice received chronic (21 days) p.o. administration of tiagabine (15 mg/kg, twice daily) or vehicle alone and the densities of GABAA and GABAB receptors and of [3H]tiagabine recognition sites were measured in several brain regions. The following changes were observed following chronic administration of tiagabine as compared to vehicle: significant reduction (18-37%) in [3H]tiagabine binding in the temporal and entorhinal cortex and in the molecular and granular layer of the cerebellar cortex; increases in the number of GABAA sites (22-44%) in various regions of the frontal cortex, in caudate putamen and in the lateral septum; decreases in the numbers of GABAB sites (18-42%) in the motor cortex, the more dorsal parts of cortex, the anteroventral thalamic nucleus, medial geniculate, superior colliculus and the molecular layer of the cerebellar cortex. Such data suggest that the GABAergic system is differentially modulated in a regional specific manner in response to chronic elevation of the extracellular levels of GABA. The significance of these findings in relation to the reported lack of development of tolerance to the anticonvulsant effects of tiagabine is discussed.

Animals↗

PubMed2004

The pharmacokinetic inter-relationship of tiagabine in blood, cerebrospinal fluid and brain extracellular fluid (frontal cortex and hippocampus).

PURPOSE: Tiagabine is a unique antiepileptic drug with a novel mechanism of action. Whilst some limited data are available as to the peripheral blood pharmacokinetics of tiagabine, data regarding the kinetics of tiagabine in the central brain compartment are very limited. We therefore sought to investigate serum, cerebrospinal fluid (CSF) and frontal cortex and hippocampal extracellular fluid (ECF) kinetic inter-relationship of tiagabine in a freely moving rat model. METHODS: Adult male rats were implanted with either a jugular vein catheter and a cisterna magna catheter for blood and CSF sampling, respectively, or a blood catheter and a microdialysis probe in the hippocampus and frontal cortex (for ECF sampling). Tiagabine was administered intraperitoneal (i.p.) at 20 or 40 mg/kg and blood, CSF and ECF were collected at timed intervals for the measurement of tiagabine concentrations by high performance liquid chromatography. RESULTS: Tiagabine concentrations in blood and CSF rose linearly and dose-dependently and time to maximum concentration (Tmax) was 15 and 29 min, respectively. Mean CSF/serum tiagabine concentration ratios (range, 0.008-0.01) were much smaller than the mean free/total tiagabine concentration ratios in serum (0.045 +/- 0.003). Entry of tiagabine into brain ECF (frontal cortex and hippocampus) was rapid with Tmax values of 31-46 min. Distribution of tiagabine in brain was not brain region specific with values in the frontal cortex and hippocampus being indistinguishable. Whilst elimination from CSF was comparable to that of serum, half-life (t(1/2)) values in ECF were three times longer. CONCLUSIONS: Tiagabine is associated with linear kinetic characteristics and with rapid brain penetration. However, CSF concentrations are not reflective of free non-protein-bound concentrations in serum. The observation that tiagabine elimination from the brain is threefold slower than that seen in blood, may explain as to the relatively long duration of action of tiagabine.

Animals↗

PubMed1998

Tiagabine: a new therapeutic option for people with intellectual disability and partial epilepsy.

Tiagabine exerts its antiepileptic drug (AED) activity by selectively inhibiting the uptake of gamma-aminobutyric acid (GABA) onto the transporter molecules, and thus, increasing extracellular concentrations of GABA in the brain. The absorption and elimination of tiagabine follow linear pharmacokinetics. Tiagabine is metabolized by hepatic cytochrome P450 enzymes and enzyme-inducing AEDs increase tiagabine clearance by 50-65%. Tiagabine has shown no clinically important interactions with other drugs, including oral contraceptives. In the perforant pathway stimulation model of status epilepticus, tiagabine reduced the seizure number and severity, and also prevented the loss of pyramidal cells in the hippocampus as well as alleviated impairment of the spatial memory impairment associated with hippocampal damage. Tiagabine has both antiepileptogenic and anticonvulsant effects in the kindling model of epilepsy. Based on the data from the short- and long-term add-on studies, tiagabine is effective adjunctive therapy for all partial seizure types in adolescents and adults. Conversion to tiagabine monotherapy has been also possible in substantial amount of patients with partial seizures in three trials. Tiagabine is generally well-tolerated. The most common adverse events in controlled studies involve the central nervous system; for example, dizziness, asthenia, nervousness, tremor, depressed mood and emotional lability. Special safety analyses with formal neuropsychological testing suggest that tiagabine does not adversely affect cognition or mood. Tiagabine represents an important new therapeutic option for patients with treatment-refractory partial seizures. The role of tiagabine in the management of partial epilepsy of patients with intellectual disability is especially emphasized since tiagabine has a low side-effect profile in the cognitive area.

Adult↗

PubMed2003

Tiagabine for the treatment of generalized anxiety disorder: a randomized, open-label, clinical trial with paroxetine as a positive control.

BACKGROUND: Gamma-aminobutyric acid (GABA) plays a central role in the pathophysiology of anxiety. Tiagabine, a selective GABA reuptake inhibitor, enhances normal GABA tone. This 10-week, randomized, open-label trial evaluated tiagabine in patients with generalized anxiety disorder (GAD), with paroxetine serving as a positive control. METHOD: Adult patients with DSM-IV GAD were randomly assigned to receive either tiagabine or paroxetine. Tiagabine was initiated at 4 mg/day (2 mg morning and evening) during week 1. Between weeks 2 and 6, the dose was individually titrated in 2-mg increments (maximum increase of 4 mg/week) for optimal response to a maximum dose of 16 mg/day (8 mg morning and evening). During weeks 7 through 10, patients received the dosage determined during the titration period. Paroxetine was initiated at 20 mg nightly for the first week and similarly titrated in 10-mg increments to a maximum dose of 60 mg/day. Assessments included the Hamilton Rating Scale for Anxiety (HAM-A), Hospital Anxiety and Depression Scale (HADS), Hamilton Rating Scale for Depression (HAM-D), Pittsburgh Sleep Quality Index (PSQI), and Sheehan Disability Scale (SDS). RESULTS: Forty patients were enrolled (tiagabine, N = 20; paroxetine, N = 20). Mean final doses were tiagabine 10 mg/day (range, 4-16 mg/day) or paroxetine 27 mg/day (range, 20-40 mg/day). Tiagabine and paroxetine significantly reduced anxiety (HAM-A and HADS total and anxiety subscales). Although patients were not diagnosed with a mood disorder, both tiagabine and paroxetine reduced comorbid depressive symptoms (HAM-D total and HADS total and depressive subscale). Tiagabine and paroxetine significantly improved sleep quality (PSQI) and functioning (SDS). Both tiagabine and paroxetine were well tolerated. CONCLUSION: The selective GABA reuptake inhibitor tiagabine and the positive control paroxetine significantly reduced anxiety and comorbid depressive symptoms, improved sleep quality and functioning, and were well tolerated in patients with GAD. Tiagabine may be a therapeutic option for the treatment of anxiety disorders.

Adult↗

PubMed2006

Tiagabine in the maintenance treatment of bipolar disorders.

BACKGROUND: Tiagabine, an anticonvulsant, has been reported to have efficacy in prophylactic treatment of bipolar disorder in case reports and in case series. OBJECTIVES: To review the efficacy and acceptability of tiagabine, relative to placebo, and other agents in the prevention and/or attenuation of episodes of bipolar affective disorder. The efficacy and acceptability of tiagabine were considered in terms of mood symptoms, mortality, general health, social functioning, adverse effects and overall acceptability to patients. SEARCH STRATEGY: The following databases were searched on 13-10-2005. The Cochrane Collaboration Depression, Anxiety and Neurosis Controlled Trials Registers (CCDANCTR-Studies and CCDANCTR-References),The Cochrane Controlled Clinical Trials Register (CCCTR),EMBASE,MEDLINE,LILACS,PsycLIT andPsyndex. Reference lists of relevant papers and major textbooks of affective disorder were examined.Authors, other experts in the field and pharmaceutical companies were contacted for knowledge of suitable published or unpublished trials. Specialist journals and conference proceedings were handsearched. SELECTION CRITERIA: Randomised controlled trials which compare tiagabine with placebo, alternative mood stabilisers or antipsychotics, where the stated intent of intervention was the maintenance treatment of bipolar affective disorder, were sought. Bipolar patients, male and female, of all ages were to be included. DATA COLLECTION AND ANALYSIS: Data were to be extracted from the original reports if they met our inclusion criteria. The main outcomes to be assessed were:(1) The efficacy of tiagabine treatment in preventing or attenuating further episodes of bipolar affective disorder, including its efficacy in rapid cycling disorder.(2) The acceptability of tiagabine treatment to patients.(3) The prevalence of side effects.(4) Mortality, if any, on tiagabine treatment.Outcomes concerning relapse or recurrence were to be analysed excluding data from studies using discontinuation protocols, which were to be analysed separately. Sub-group analyses were to be performed to examine the effects of tiagabine treatment in rapid cycling bipolar disorder and previous mood stabiliser non-responders. Data were to be analysed using Review Manager version 4.2.8. MAIN RESULTS: No randomised controlled trials of tiagabine in the maintenance treatment of bipolar disorder were found. AUTHORS' CONCLUSIONS: There is an insufficient methodologically rigorous evidence base to provide guidance on the use of tiagabine in the maintenance treatment of bipolar disorder. There is a need for randomised controlled trials examining the therapeutic potential of this agent in bipolar disorder, after the nature of reported episodes of syncope or seizure in tiagabine-treated bipolar patients has been established.

Antimanic Agents↗

PubMed1998

Tiagabine. A review of its pharmacodynamic and pharmacokinetic properties and therapeutic potential in the management of epilepsy.

Tiagabine is a gamma-aminobutyric acid (GABA) uptake inhibitor which is structurally related to nipecotic acid but has an improved ability to cross the blood-brain barrier. Clinical trials have shown that tiagabine is effective as add-on therapy in the management of patients with refractory partial epilepsy. In short term studies of this indication, tiagabine < or = 64 mg/day for 7 to 12 weeks reduced the complex partial and simple partial seizure frequency by > or = 50% in 8 to 31 and 28.2 to 37% of patients, respectively. Tiagabine appeared to produce a sustained reduction in seizure frequency in studies of up to 12 months' duration. Data from preliminary studies are currently insufficient to confirm the usefulness of tiagabine when used as monotherapy or in the treatment of children with epilepsy. Further studies are, therefore, necessary to more fully elucidate the efficacy of the drug in these settings. Adverse events associated with tiagabine are primarily CNS-related and include dizziness, asthenia, nonspecific nervousness and tremor. Skin rash or psychosis occurred with similar frequencies among tiagabine- and placebo-treated patients. With long term administration (> or = 1 year for many patients), the profile and incidence of adverse events was similar to that for short term therapy. Tiagabine does not appear to affect the hepatic metabolism of other drugs such as carbamazepine and phenytoin. Possible disadvantages of tiagabine include its short plasma elimination half-life, necessitating 2 to 4 times daily administration, and its inducible hepatic metabolism. Thus, tiagabine is a new antiepileptic agent with a novel mechanism of action, which has demonstrated efficacy in the adjunctive treatment of patients with refractory partial epilepsy. Further investigation of the efficacy of tiagabine is expected to provide a clearer definition of its place in the treatment of epilepsy and its relative merits in relation to other antiepileptic drugs.

Animals↗

PubMed2005

Tiagabine reduces ethanol reward in C57BL/6 mice under acute and chronic administration regimens.

Three experiments conducted on male C57BL/6 (B6) mice examined the effects of subcutaneous injections of the GABA uptake inhibitor, tiagabine, on appetitive (lever responding) and consummatory behavior (fountain contacts) of food restricted B6 mice for 12% ethanol and water rewards (Exp-1), and for food reward (Exp-2) delivered on a fixed ratio 4 schedule of reinforcement. Effects of acute injections (1,3,6,9 mgkg) and chronic administration (6,9 mg/kg) was examined. Exp-3 examined tiagabine effects on the voluntary consumption of continuously available 12% ethanol, and on the interactive effects of tiagabine and ethanol on motor activity of non-food restricted B6 mice. Results of Exp-1 and Exp-2 indicated that tiagabine can reduce appetitive behavior for ethanol reward with no evidence of tolerance upon chronic exposure. Tiagabine doses that reduced ethanol reward had less effect on behavior maintained by either water or food, and had no effect on motor activity. In contrast to the absence of tolerance to its effect on appetitive behavior for ethanol, mice rapidly developed tolerance to tiagabine's initial reduction of the consummatory response for ethanol (Exp-1), and the intake of freely available ethanol exceeded pre-tiagabine levels after several daily injections (Exp-3). Importantly, mice developed tolerance to tiagabine's sedative effect after three daily injections and its sedation was not enhanced when combined with ethanol, an effect consistent with the lack of a tiagabine + ethanol interaction previously reported for humans. The results of the experiments suggest that in addition to reducing alcohol withdrawal symptoms, tiagabine might also reduce the potency of ethanol-conditioned cues that drive appetitive behavior for ethanol.

Alcohol Drinking↗

PubMed1994

Quantitative autoradiographic characterization of the binding of [3H]tiagabine (NNC 05-328) to the GABA uptake carrier.

The kinetic properties and regional distribution of [3H]tiagabine ([3,4-3H]N-[4,4-bis(3-methyl-2-thienyl)but-3-en-1-yl]nipecotic acid) binding to the central GABA uptake carrier was examined in the rat brain using quantitative receptor autoradiography. In slide mounted sections of frontal cortex, the binding of [3H]tiagabine was saturable, reversible and sodium dependent. The kinetics of association and dissociation of [3H]tiagabine were monophasic, and Scatchard transformation of saturation isotherms resulted in a linear plot with a Kd = 58 +/- 7 nM and a Bmax = 58.9 +/- 0.9 pmol/mg protein. The autoradiographic distribution of [3H]tiagabine binding sites in rat brain was heterogeneously distributed. The highest density of [3H]tiagabine binding sites was present in the cerebral cortex, mammillary body, globus pallidus, substantia nigra pars reticulata, hippocampus, dorsal raphé, superior colliculus (outer layer), and cerebellum. The distribution of GABA uptake sites, as measured by [3H]tiagabine binding, in the rat brain is highly consistent with the organization of GABAergic terminals and cell bodies. The present investigation characterized the use of [3H]tiagabine as a novel radioligand for the GABA uptake carrier using quantitative receptor autoradiography. [3H]Tiagabine has several major advantages over the currently utilized radioligand for the GABA uptake carrier [3H]nipecotic acid, in that [3H]tiagabine has an increased affinity, specificity, and is not transported intracellularly via the GABA uptake carrier. These data suggest that [3H]tiagabine represents a novel and highly useful ligand for studying the GABA uptake carrier using quantitative receptor autoradiography.

Animals↗

PubMed1996

Tiagabine prevents seizures, neuronal damage and memory impairment in experimental status epilepticus.

A novel antiepileptic drug, tiagabine ((R)-N-[4,4-di-(3-methylthien-2-yl) but-3-enyl] nipecotic acid hydrochloride), was studied in rats in order to determine its efficacy in preventing seizures, seizure-induced neuronal damage and impairment of spatial memory in the perforant pathway stimulation model of status epilepticus. In pilot experiments, administration of tiagabine (50, 100 or 200 mg/kg/day) with subcutaneously implanted Alzet osmotic pumps led to a dose-dependent increase in tiagabine concentrations in the serum and brain. Two days of tiagabine treatment at a dose range of 50-200 mg/kg/day did not change the levels of gamma-aminobutyric acid (GABA), glutamate or aspartate in cisternal cerebrospinal fluid (CSF) compared to the controls. In the pentylenetetrazol test, the maximal anticonvulsive effect of tiagabine administered via osmotic pumps was achieved already with a dose of 50 mg/kg/day. In the perforant pathway model of status epilepticus, subchronic treatment with tiagabine (Alzet pumps, 50 mg/kg/day) completely prevented the appearance of generalized clonic seizures during stimulation (P < 0.001). In the same rats, tiagabine treatment reduced the loss of pyramidal cells in the CA3c and CA1 fields of the hippocampus (P < 0.05) but not the loss of somatostatin immunoreactive neurons in the hilus. Two weeks after perforant pathway stimulation, the tiagabine-treated rats performed better in the Morris water-maze test than the vehicle-treated rats did (P < 0.001). Our results show that tiagabine treatment reduces the severity of seizures in the perforant pathway stimulation model of status epilepticus. Possibly associated with the reduction in seizure number and severity, tiagabine treatment also reduced seizure-induced damage to pyramidal cells in the hippocampus as well as the impairment of the spatial memory associated with hippocampal damage.

Animals↗

PubMed2002

An open case series on the utility of tiagabine as an augmentation in refractory bipolar outpatients.

BACKGROUND: Tiagabine (Gabitril) is a GABA uptake inhibitor recently introduced in the United States as an adjunctive treatment for partial complex seizures. Three published studies have addressed the use of tiagabine for bipolar disorder (BPD); two described positive results and one negative results. We assessed the efficacy of add-on tiagabine in a larger sample of adult BPD outpatients. METHODS: Twenty-two adult outpatients with DSM-IV diagnosed BPD of some type who were considered unsatisfactory responders to standard medications for BPD were treated in an open fashion with adjunctive tiagabine in a low-dose range. After baseline demographic data and mood state at the time of entry were documented, each patient was monitored clinically for at least 6 months while the dose of tiagabine was adjusted according to the patient's clinical status. The subjects were rated using the clinical global impression-bipolar version scale (CGI-BP). RESULTS: After 6 months, eight (36%) of the patients were responders to tiagabine by CGI-BP rating. The dose range of tiagabine for responders was 1-8 mg per day. All 14 nonresponders had to discontinue tiagabine because of unacceptable but reversible side effects; one nonresponder experienced breakthrough absence seizures. LIMITATIONS: This study was performed in a nonrandom, open naturalistic clinical setting. The sample size was small. CONCLUSIONS: Low-dose tiagabine appears to have mood-stabilizing and antimanic properties as an add-on medication for some adult outpatients who have BPD refractory to standard medications. Tiagabine appears to be safe for most adult BPD outpatients. The results of this preliminary open study await confirmation by double-blind controlled studies.

Administration, Oral↗

PubMed1997

Comparison of the preclinical anticonvulsant profiles of tiagabine, lamotrigine, gabapentin and vigabatrin.

Tiagabine is a novel antiepileptic drug which has clinical efficacy against complex refractory and myoclonic seizures. The anticonvulsant mechanism of action of tiagabine results from its blockade of neuronal and glial GABA-uptake, thereby increasing GABA levels in the synaptic cleft. Here we present a comparison of the preclinical anticonvulsant profile of tiagabine with that of lamotrigine, gabapentin and vigabatrin in the following tests (all antiepileptic drugs were administered i.p.): seizures induced by pentylentetrazol (PTZ), 6,7-dimethoxy-4-ethyl-b-carboline-3-carboxylate (DMCM) and maximal electroshock (MES); sound induced seizures in DBA/2 mice and finally acute amygdala kindled seizures. Tiagabine was the most potent drug in antagonizing tonic convulsions induced by PTZ, DMCM and sound induced seizures in DBA/2 mice with ED50 values of 2, 2 and 1 mumol/kg, respectively, followed by lamotrigine with ED50 values of 9, 43 and 6 mumol/kg, respectively. Gabapentin and vigabatrin had ED50 values in the same tests of 185, 452, 66 mumol/kg and 2322, > 7740, 3883 mumol/kg, respectively. Tiagabine was the only drug capable of blocking PTZ-induced clonic convulsions (ED50 = 5 mumol/kg), an effect seen at low but not high doses of tiagabine. Lamotrigine was the only drug which antagonized tonic convulsions in the MES test (ED50 = 36 mumol/kg). Therapeutic index (TI) of antiepileptic drugs in NMRI- and DBA/2-mice ranked with decreasing TI lamotrigine > gabapentin > vigabatrin > tiagabine. All drugs reduced the generalized seizures in amygdala kindled rats, but tiagabine and gabapentin furthermore attenuated afterdischarge duration of amygdala kindled seizures. However, an ED50 value against amygdala kindled focal seizures was only obtained for tiagabine (36 mumol/kg). The data here presented show that tiagabine, lamotrigine, gabapentin and vigabatrin possess different preclinical anticonvulsant profiles which is of relevance to the clinical anticonvulsant profiles of the drugs.

Acetates↗

PubMed2006

Effect of tiagabine on sleep in elderly subjects with primary insomnia: a randomized, double-blind, placebo-controlled study.

SUBJECT OBJECTIVE: This study further evaluated the effects of tiagabine on sleep in elderly subjects with primary insomnia. METHODS: Elderly subjects (aged 65-85 years) meeting DSM-IV-TR criteria for primary insomnia were randomly assigned to receive tiagabine 2, 4, 6, or 8 mg or placebo on 2 consecutive nights. Efficacy was assessed using standard polysomnography and a postsleep questionnaire. Additional assessments included the Assessment of Daily Functioning, Digit Symbol Substitution Test (for residual effects), and visual analog scale (for sleepiness/alertness). RESULTS: A total of 207 subjects were randomly assigned to study medication (tiagabine: 2 mg, n = 43; 4 mg, n = 38; 6 mg, n = 45; 8 mg, n = 43; placebo, n = 38). Tiagabine did not significantly effect wake after sleep onset, latency to persistent sleep, or total sleep time compared with placebo (P > .05). Significant increases in Stage 3+4 sleep (i.e., slow-wave sleep) were found for tiagabine 4, 6, and 8 mg versus placebo, with a corresponding significant decrease in Stage 1 sleep (P < .05). At 6 and 8 mg, tiagabine also significantly reduced the number of awakenings and increased the ratio of Stage 3+4/(Stage 1 +wake after sleep onset). In general, there were no significant effects on subjects' ratings of sleep or daily functioning with tiagabine 2, 4, and 6 mg versus placebo. These 3 doses had tolerability profiles comparable with that of placebo and were not associated with significant residual effects or reduced alertness. The 8-mg dose, however, significantly decreased subjective total sleep time and refreshing quality of sleep, as well as daily functioning. This dose was associated with troublesome adverse events, significant residual effects, and reduced alertness. CONCLUSIONS: In elderly subjects with primary insomnia, tiagabine did not have a significant effect on wake after sleep onset, latency to persistent sleep, total sleep time, or the subjective rating of sleep. Tiagabine 4, 6, and 8 mg significantly increased slow-wave sleep, with a corresponding significant decrease in Stage 1 sleep. Tiagabine was generally well tolerated, with doses of less than 6 mg having tolerability profiles generally similar to that of placebo. The 8-mg dose, however, was associated with troublesome adverse events, residual effects, and reduced alertness.

Aged↗

PubMed2005

The selective GABA reuptake inhibitor tiagabine for the treatment of generalized anxiety disorder: results of a placebo-controlled study.

OBJECTIVE: To evaluate the efficacy and tolerability of tiagabine, a selective gamma-aminobutyric acid (GABA) reuptake inhibitor, in adults with generalized anxiety disorder (GAD). METHOD: This 8-week, randomized, double-blind, multicenter, placebo-controlled study enrolled patients with GAD (DSM-IV). Tiagabine was initiated at 4 mg/day and then flexibly dosed twice a day to a maximum dose of 16 mg/day. Study drug was tapered after week 8 in decrements of 2 mg every other day. Efficacy assessments included the Hamilton Rating Scale for Anxiety (HAM-A) and Sheehan Disability Scale. Adverse events, sexual functioning, and change in depressive symptoms were monitored. Data were collected from May 2003 to January 2004. RESULTS: A total of 266 patients (tiagabine, N = 134; placebo, N = 132) were included in safety analyses; 260 patients (tiagabine N = 130; placebo N = 130) were included in efficacy analyses. Tiagabine reduced symptoms of GAD according to the observed case and mixed models repeated-measures (MMRM) analyses but not the primary last-observation-carried-forward (LOCF) analysis. At final visit, the reduction from baseline in mean HAM-A total score was 11.8 for tiagabine, compared with 10.2 for placebo (LOCF analysis, p = .27). In a post hoc MMRM analysis, a significant difference in the mean reduction in HAM-A total score over the efficacy evaluation period was found, favoring tiagabine over placebo (p < .01). Tiagabine had an early onset of effect, as shown by significant reduction from baseline in mean HAM-A total score compared with placebo at week 1 (observed cases, p < .05). Tiagabine was generally well tolerated and not associated with changes in sexual functioning or depressive status. Symptoms of a discontinuation syndrome during taper were not observed. CONCLUSION: The primary LOCF analysis was negative; however, results from the observed case and MMRM analyses suggest that tiagabine may be a useful treatment option for adult patients diagnosed with GAD. These findings warrant further evaluation in randomized clinical studies.

Adult↗

PubMedDate not supplied

Effect of combined administration of ethanol and tiagabine on rabbit EEG.

Tiagabine is a new generation antiepileptic drug, a specific inhibitor of gamma-aminobutiric acid (GABA) reuptake from the synaptic space to neurons and glia. Central effect of ethanol is mainly connected with its effect on GABAergic, glutamatergic, serotonergic and opioid transmission. The mechanism of tiagabine effect suggests that it may alleviate the rewarding effect of ethanol, which can be applied in the treatment of addiction. There are only a few studies discussing interactions of tiagabine and ethanol. In this study we have decided to examine interaction of ethanol with tiagabine by the use of pharmaco-EEG method. The influence of tiagabine on the effect of ethanol on EEG of rabbits (midbrain reticular formation, hippocampus, frontal cortex) was tested. Tiagabine was administered at a single dose (5 and 20 mg/kg) (po) or repeatedly twice a day at a total dose of 5 mg/kg for 14 days. Ethanol was injected (iv) at a dose of 0.8 g/kg 60 min after tiagabine treatment. Ethanol caused an increase in the slow frequencies (0.5-4 Hz) in the recording, as well as a marked decrease of the fastest frequencies (30-45 and 13-30 Hz in cortex). Tiagabine leads to changes in rabbit EEG-recording suggesting their depressant-effect on the central nervous system (CNS) (increase in slow and decrease in fast frequencies). They are less pronounced after repeated doses, which may indicate the adaptative changes in the receptors. A single dose of tiagabine markedly increases the effect of ethanol on rabbit EEG, which indicates a synergistic inhibitory effect of these agents on the CNS. Repeated doses of tiagabine decrease the sensitivity of the hippocampus to the effect of ethanol, which may be important for the treatment of addictions.

Animals↗

PubMed1995

Postischemic inhibition of GABA reuptake by tiagabine slows neuronal death in the gerbil hippocampus.

The neuroprotective effects of enhancing neuronal inhibition with a gamma-aminobutyric acid (GABA) uptake inhibitor were studied in gerbil hippocampus following transient ischemia. We used in vivo microdialysis to determine a suitable dosing regimen for tiagabine (NNC328) to elevate extracellular levels of GABA within the hippocampus. In anesthetized (normothermic) gerbils, tiagabine (45 mg/kg, i.p.) selectively elevated extracellular GABA levels 450% in area CA1 of the hippocampus. In gerbils subjected to cerebral ischemia via 5-min bilateral carotid occlusion, extracellular GABA levels increased 13-fold in area CA 1 returning to baseline within 30-45 min. When tiagabine was injected 10 min following onset of reperfusion, GABA levels remained elevated (200-470%) for 90 min. In addition, tiagabine significantly reduced the ischemic-induced elevation of glutamate levels in area CA1 during the postischemic period when GABA levels were elevated. There was no effect of postischemic tiagabine on aspartate or six other amino acids. Using the same dosing regimen, we evaluated the degree of neuroprotection in the hippocampus of gerbils 4 and 21 days after ischemia. Tiagabine decreased body temperature a maximum of 2.7 degrees C beginning 30 min into reperfusion and lasting 90 min. In untreated gerbils sacrificed 4 and 21 days after ischemia, there was severe necrosis (99%) of the pyramidal cell layer in area CA1. Whereas tiagabine significantly protected the CA1 pyramidal cell layer in ischemic gerbils at 4 days (overt necrosis confined to about 17% of area CA1), the protection diminished significantly 21 days postischemia. When normothermia was maintained both during and after ischemia in a separate group of tiagabine-treated animals, approximately 77% of the CA1 pyramidal cell layer was necrotic at 4 days. Based on these findings, we suggest that 1) tiagabine slows the development of hippocampal degeneration following ischemia, and 2) that mild, postischemic hypothermia is responsible, in large part, for the neuroprotective actions of this drug. We conclude that the histological outcome after administration of cerebral neuroprotectants should be assessed following long-term survival.

Animals↗

PubMed1994

Lack of tolerance to the anticonvulsant effects of tiagabine following chronic (21 day) treatment.

The anticonvulsant, and side effect, profile of the gamma-aminobutyric acid (GABA) uptake inhibitor (R)-N-(4,4-di-(3-methylthien-2-yl)but-3-enyl) nipecotic acid hydrochloride (tiagabine) was examined in mice following chronic (21 day) administration. Twenty-four hours following the discontinuation of the 21 days' treatment with twice daily administration of vehicle or tiagabine at 15 or 30 mg/kg p.o., an ED50 for tiagabine was determined for the anticonvulsant effect, the rotarod performance, the traction response and the inhibition of locomotor activity in the animals treated with vehicle only, and in the groups previously treated with 15 or 30 mg/kg p.o. of tiagabine. There was no significant decrease in the anticonvulsant efficacy of acutely administered tiagabine (ED50 for inhibition of methyl 6,7-dimethoxy-4-ethyl-beta-carboline-2-carboxylate (DMCM)-induced seizures of 1.7 +/- 0.4, 1.9 +/- 0.3, and 2.0 +/- 0.50 mg/kg i.p., respectively). However, there was a significant decrease in the ability of acutely administered tiagabine to impair rotarod performance (ED50 of 5.9 +/- 1.2, 14 +/- 1.9 and 21 +/- 2.7 mg/kg i.p., respectively), inhibit a traction response (ED50 of 10 +/- 1.6, 23 +/- 3.0 and 34 +/- 4.6 mg/kg i.p., respectively), and to inhibit exploratory locomotor activity (ED50 of 13 +/- 23, 19 +/- 2.6 and 28 +/- 38 mg/kg i.p. respectively). Following the discontinuation of chronic tiagabine administration there was no change in pentylenetetrazol (PTZ) seizure threshold, animal weight or gross behavior, suggesting the lack of a behavioral withdrawal syndrome. The production of tolerance to the sedative and ataxic effects, but not the anticonvulsant effects, of tiagabine suggests that tiagabine may be a useful agent for the long-term treatment of epilepsy.

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