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PubMed1998

Gabapentin and carbamazepine affect eye movements and posture control differently: a placebo-controlled investigation of acute CNS side effects in healthy volunteers.

This prospective study examined the effects of the new antiepileptic drug (AED) gabapentin (GBP) compared to the standard AED carbamazepine (CBZ) and placebo (PLA) on eye movements, posture and finger force control in 12 healthy volunteers who received single doses of 600 mg GBP and 400 mg CBZ in a placebo-controlled, double-blind, cross-over, randomized trial. CBZ and GBP reduced almost equally (8% vs. 10%) the mean peak saccade velocity as compared to PLA (P < 0.05). CBZ, but not GBP, significantly prolonged the duration of saccades as compared to placebo (14-24%) (P < 0.05). GBP produced a greater maximal increase of body sway than CBZ with eyes open (P < 0.01) and eyes closed (P < 0.001). CBZ and GBP did not significantly influence control of grip force. CBZ effects were better correlated with plasma levels. Subjective side effects were more pronounced with CBZ than GBP. Although CBZ and GBP cause similar CNS side effects, the effects on eye movements and body sway were different. CBZ predominantly affects saccadic eye movements, whereas GBP had more impact on posture control. Thus, electro-oculography seems to be more appropriate in the detection of CBZ-induced side effects and posturography appears to be more sensitive in the detection of side effects associated with GBP.

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PubMed1998

Gabapentin bioavailability: effect of dose and frequency of administration in adult patients with epilepsy.

UNLABELLED: Gabapentin (GBP) is a non-metabolized antiepileptic drug that is eliminated by renal excretion and displays saturable, dose dependent absorption. The recommended dosing schedule for GBP is t.i.d. At large daily doses, oral bioavailability (F) may be improved by giving the daily dose more frequently. OBJECTIVE: To evaluate whether switching GBP dosage regimen from t.i.d. to q.i.d. results in increased oral bioavailability. METHODS: This study consisted of two parts; a computer simulated pharmacokinetic model and a clinical pharmacokinetic study in nine adult epileptic patients receiving 3600 mg/day and 11 receiving 4800 mg/day. All patients were evaluated during both t.i.d. and q.i.d. regimens. F were determined by calculation of percent of dose excreted unchanged using steady-state 24-h urine collections and were compared using a paired t-test. RESULTS: At 3600 mg/day, mean F following t.i.d. and q.i.d. dosing were 38.7+/-22.1% and 40.0+/-18.9%, respectively (P=0.738). At 4800 mg/day, mean F following t.i.d. and q.i.d. dosing were 29.2+/-16.2% and 35.6+/-17.6%, respectively (P=0.006). DISCUSSION: Good agreement was observed between values from this study and predicted values based on the pharmacokinetic model. Improved GBP F at doses of 3600 mg/day was not achieved with more frequent drug administration, and thus is not warranted. At 4800 mg/day, a 22% increase in F was observed with more frequent drug dosing. CONCLUSION: GBP F may be significantly increased by q.i.d. versus t.i.d. dosing, depending upon dose level. This increase in F however must be balanced against the inconvenience of more frequent dosing. Therapeutic drug level monitoring may aid in the evaluation of such pharmacokinetic maneuvers.

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PubMed2003

Limited efficacy of gabapentin in severe therapy-resistant epilepsies of learning-disabled patients.

Knowledge on the effects of gabapentin (GBP) in learning disabled patients is limited. The objective of this study was to assess antiepileptic efficacy and tolerability of GBP in routine therapy. A retrospective open observational study design was applied. Twenty-nine consecutive residential patients with simple and/or complex partial seizures with or without secondary generalization and with different degrees of learning disability were included. All patients had severe therapy-resistant epilepsy. GBP was administered as add-on therapy. Dosages were progressively increased up to 1600-2400 mg/day (in a number of cases up to 4800 mg/day), in accordance with clinical requirements. The seizure frequency was recorded and compared between a baseline and a treatment period (after 3 months of titration) of 3 months duration each. Only three patients (10.3%) had a reduction of their seizure frequency by 50% or more. No patient became seizure-free. Unwanted side effects, mostly mild and dose-dependent, occurred in 37.9% of all patients. Somnolence and ataxia were the most frequently observed unwanted effects. In two cases hyperphagia/weight increase, and in two other cases edema occurred.We conclude the efficacy of GBP in learning disabled patients with highly therapy-resistant partial seizures is limited.

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PubMed2003

The absorption of gabapentin following high dose escalation.

Gabapentins (GBP) is structurally similar to GABA yet its mode of action remains uncertain. It is water-soluble and GI tract absorption occurs via the L-amino acid transport system in the proximal small bowel. It has been suggested that this transportation is capacity limited, thus decreasing GBP bioavailability at higher doses. GBP is not protein bound, therefore, salivary levels might be expected to be similar to those in serum; also the drug does not induce hepatic enzymes and is excreted unmetabolised by the kidney. Within the dose-range normally prescribed, it is devoid of pharmacokinetic (PK) drug interactions with all other anti-epileptic drugs. This study assesses two things in patients with epilepsy: (a) bioavailability of higher doses of GBP (1200-4800 mg per day), and (b) the influence of high dose GBP on between-dose serum concentrations of co-prescribed anti-epileptic drugs. After stabilising at each dosage, a sequence of serum and saliva samples were collected within the dosage interval; GBP and co-medication concentrations were determined and the results subjected to PK modelling. Meaned results from 10 patients indicate that GBP continues to be absorbed in a reasonably linear manner relative to dose up to 4800 mg per day. The study also shows that GBP is transported into saliva, however, salivary concentrations are only 5-10% of those in plasma. Furthermore, the results indicate that GBP, in higher than recommended doses, did not change plasma concentrations of lamotrigine, carbamazepine, carbamazepine-epoxide, vigabatrin, primidone, phenobarbitone or phenytoin when added to treatment. It is concluded that larger than recommended doses of GBP can be efficiently absorbed by some patients and also that GBP plasma levels do not fluctuate greatly between dosage intervals, therefore, twice daily dosage is a possibility.

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PubMed2002

Gabapentin treatment of glossopharyngeal neuralgia: a follow-up of four years of a single case.

Glossopharyngeal neuralgia causes intermittent, lancinanting pain, involving the posterior tongue and pharynx, with radiation to deep ear structures. There are different pharmacological therapies which are tried to treat the neuralgia: carbamazepin, phenytoin, diazepam, amytriptyline, phenobarbital, ketamine, and baclofen; there are also surgical treatment proposed in order to cure the neuralgia such as vascular decompression or electrical stimulation of the motor cortex controlateral to the pain area. We report a single case of a patient with glossopharyngeal neuralgia treated with Gabapentin, the first described, who was followed up for four years, who respond completely to the therapy and did not complain from side effects, reducing even the reminiscence of pain during the second cluster of crisis.

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PubMed2000

Gabapentin-induced modulation of interictal epileptiform activity related to different vigilance levels.

OBJECTIVES: Gabapentin (GBP) is a novel antiepileptic drug (AED), currently used as add-on therapy in patients with partial seizures. Similar to other AEDs, little is known about its effects on nocturnal sleep, despite the strict relationship between sleep and epileptic discharges. The aim of our study was to evaluate the effects of chronic therapy with GBP on both nocturnal sleep and on interictal epileptiform abnormalities (IEA) in relation to the different sleep stages. METHODS: Eighteen patients affected by partial seizures resistant to common AEDs were submitted to nocturnal polygraphic recordings under baseline conditions and after 4 months of add-on GBP treatment. RESULTS: We observed a significant increase in unilateral/focal IEA during light NREM sleep and a significant reduction in bilateral/diffuse IEA during wakefulness after sleep onset (WASO) with respect to the baseline condition. A significant increase in REM sleep and slow wave sleep (SWS) associated with a reduction in the number of awakenings and Stage 1 was also observed after GBP chronic therapy. CONCLUSIONS: GBP therapy improves the sleep pattern of epileptic patients and it seems to modulate the expression of IEA with different effects in relation to the various vigilance levels.

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PubMed2000

Gabapentin as add-on therapy in focal epilepsy: a computerized EEG study.

OBJECTIVES: Gabapentin (GBP) possesses a well documented clinical efficacy in those types of focal epilepsy otherwise resistant to conventional antiepileptic drugs (AEDs); on the basis of this, it appears important to investigate the drug effects on the EEG epileptiform and background activity. METHODS: Twenty-five patients with cryptogenic or symptomatic partial epilepsy resistant to conventional AED treatment were included in the study. All patients underwent long-term video-EEG recordings before and after GBP addition (900-1200 mg/day). RESULTS: Quantitative analysis of the interictal EEG paroxysms revealed that GBP had no effect on the rate of occurrence of interictal and ictal EEG abnormalities. GBP was active in delimiting the spatial extent of the interictal spiking activity in those patients who displayed a significant reduction (> or =50%) in seizure occurrence (32% of the patients). EEG background activity recorded under rest condition from 18 out of 25 epileptic patients, before GBP therapy, was characterised by a higher content of the slow spectral components (delta and theta) with respect to control subjects. After GBP addition, the increase of theta relative power was also evident during task performance. CONCLUSIONS: These findings suggest that GBP does not interfere with the generation of interictal EEG spiking while it appears to reduce the susceptibility to seizures concomitantly with a limiting effect on the spiking activity spatial extent. The utilization of GBP in controlling focal seizures is reinforced by the absence of negative influence on cognitive functioning.

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PubMed1996

Add-on gabapentin for refractory seizures in patients with brain tumours.

BACKGROUND: Seizures associated with intracranial neoplasms are occasionally refractory to conventional anti-epileptic drugs. Gabapentin (GBP) is one of several novel anti-epileptic drugs effective as an add-on therapy for intractable seizures but has not been studied in patients with cerebral tumours. PATIENTS AND METHODS: We used GBP in a open-label add-on fashion to treat 14 patients with intractable seizures associated with intracranial tumours including four glioblastomas, four metastases, three recurrent glioblastomas, and one each of anaplastic and low grade astrocytoma and meningioma. GBP was added if optimization of pre-existing therapy failed and was titrated until seizures were controlled. RESULTS: One patient experienced adverse drowsiness. Follow-up ranged from 3-24 weeks during which time 7 patients died from disease progression. Concurrent therapy included dexamethasone in eight, cranial irradiation in four, and radiosurgery in one. Responder rate (number with at least 50% fewer seizures) was 100% and persisted throughout follow-up. Complete resolution of seizures occurred in 8/14 patients. CONCLUSIONS: GBP was well tolerated in patients with brain tumours. Seizure frequency was reduced in all patients and efficacy persisted over time; however, the mechanism of this improvement is unclear. Concurrent therapy, regression of frequency to the mean, and the lack of controls may account for apparent benefit. In addition, because GBP may interact with a leucine-related neuronal binding site we also speculate that this novel mechanism of action may have been enhanced in our patients due to the abnormal blood-brain barrier associated with cerebral tumours. Further investigation and a controlled trial are warranted.

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PubMed1996

The simultaneous estimation of the influx and efflux blood-brain barrier permeabilities of gabapentin using a microdialysis-pharmacokinetic approach.

PURPOSE: To determine the apparent bidirectional permeabilities of gabapentin (GBP) across the blood-brain barrier (BBB) using a novel microdialysis-pharmacokinetic approach. METHODS: Rats were administered intravenous infusions of [14C]GBP to achieve clinically relevant steady-state plasma concentrations. Microdialysis was used to monitor GBP concentration in brain extracellular fluid (ECF) in conscious animals. Brain tissue GBP concentration was measured at termination. The BBB influx (CL1) and efflux (CL2) permeabilities of GBP were estimated with a hybrid pharmacokinetic model assuming that transport between intra- and extracellular space was more rapid than transport across the BBB. The time course of GBP concentration in brain tissue was determined independently to validate the model assumption. RESULTS AND CONCLUSIONS: Simulations of the concentration-time course of GBP in brain tissue based on this modeling correlated well with the time-course of brain tissue concentrations determined after intravenous bolus administration and validated this pharmacokinetic-microdialysis approach for estimation of BBB permeabilities. The values for CL1 and CL2 were 0.042 (0.017) and 0.36 (0.16) ml/min.g-brain, respectively, indicating that GBP was more efficiently transported from brain ECF to plasma. The total brain tissue concentration of GBP was significantly higher than the ECF concentration at steady-state due to intracellular accumulation and tissue binding, that if not considered, will lead to underestimated efflux BBB permeability using the tissue homogenate-pharmacokinetic approach.

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PubMed2002

Down-regulation of N-type voltage-activated Ca2+ channels by gabapentin.

1. Although the cellular and molecular mechanisms of the anticonvulsant action of gabapentin (GBP) remain incompletely described, in vitro studies have shown that GBP binds to the alpha2delta subunit of the high voltage-activated (HVA) Ca2+ channels. 2. In this report, we analyzed the effects of GBP on the functional expression of HVA Ca2+ channels in the PC12 cell line model system. Negligible inhibition of Ca2+ channel activity was observed after acute treatment, but a significant decrease in Ca2+ current amplitude was promoted by chronic exposure to GBP. 3. Consistent with this, radioligand binding experiments showed a comparable reduction in the total number of membrane HVA N-type channels after GBP treatment.

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PubMed2002

Gabapentin augmentation therapy in bipolar depression.

BACKGROUND: Gabapentin (GBP) may be useful in bipolar disorders, including as adjunctive therapy for bipolar depression, although controlled studies suggest inefficacy as primary treatment for mania or treatment-resistant rapid cycling. METHODS: We performed a 12-week trial of open GBP (mean dose 1725 mg/day) added to stable doses of mood stabilizers or atypical antipsychotics in 22 (10 women, mean age 38.4 years) depressed (28-item Hamilton Depression Rating Scale (HDRS) > 18] bipolar (10 bipolar I, 12 bipolar II) disorder outpatients. Mean illness duration was 18.6 years, current depressive episode duration was 18.0 weeks. Prospective 28-item HDRS, Young Mania Rating Scale (YMRS) and Clinical Global Impression-Severity (CGI-S) ratings were obtained. RESULTS: Overall, HDRS ratings decreased 53% from 32.5 +/- 7.7 at baseline to 16.5 +/- 12.8 at week 12 (p < 0.0001). Twelve of 22 (55%) patients had moderate to marked improvement (HDRS decrease = 50%) with HDRS decreasing 78% from 27.9 +/- 6.2 to 6.2 +/- 4.5 (p < 0.0001). Eight of 22 (36%) patients remitted (HDRS > or = 8). In non-responders, HDRS decreased from 38.0 +/- 5.4 to 28.9 +/- 6.7 (p = 0.005). Ten of 13 (77%) mild to moderately depressed (baseline HDRS > 18 and <35) patients responded, while only two of nine patients (22%) with severe depression (HDRS > or = 35) responded (p < 0.03). Both groups, however, had similar, statistically significant HDRS decreases. GBP was well tolerated. CONCLUSION: Open adjunctive GBP was effective and well tolerated in patients with mild to moderate bipolar depression. This open pilot study must be viewed with caution, and randomized controlled studies are warranted.

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PubMed1999

An in vitro electrophysiological study on the effects of phenytoin, lamotrigine and gabapentin on striatal neurons.

We performed intracellular recordings from a rat corticostriatal slice preparation in order to compare the electrophysiological effects of the classical antiepileptic drug (AED) phenytoin (PHT) and the new AEDs lamotrigine (LTG) and gabapentin (GBP) on striatal neurons. PHT, LTG and GBP affected neither the resting membrane potential nor the input resistance/membrane conductance of the recorded cells. In contrast, these agents depressed in a dose-dependent and reversible manner the current-evoked repetitive firing discharge. These AEDs also reduced the amplitude of glutamatergic excitatory postsynaptic potentials (EPSPs) evoked by cortical stimulation. However, substantial pharmacological differences between these drugs were found. PHT was the most effective and potent agent in reducing sustained repetitive firing of action potentials, whereas LTG and GBP preferentially inhibited corticostriatal excitatory transmission. Concentrations of LTG and GBP effective in reducing EPSPs, in fact, produced only a slight inhibition of the firing activity of these cells. LTG, but not PHT and GBP, depressed cortically-evoked EPSPs increasing paired-pulse facilitation (PPF) of synaptic transmission, suggesting that a presynaptic site of action was implicated in the effect of this drug. Accordingly, PHT and GBP, but not LTG reduced the membrane depolarizations induced by exogenously-applied glutamate, suggesting that these drugs preferentially reduce postsynaptic sensitivity to glutamate released from corticostriatal terminals. These data indicate that in the striatum PHT, LTG and GBP decrease neuronal excitability by modulating multiple sites of action. The preferential modulation of excitatory synaptic transmission may represent the cellular substrate for the therapeutic effects of new AEDs whose use may be potentially extended to the therapy of neurodegenerative diseases involving the basal ganglia.

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PubMed2003

Tiagabine synergistically interacts with gabapentin in the electroconvulsive threshold test in mice.

Polytherapy, based on the rational combining of antiepileptic drugs (AEDs), is required for patients with drug-resistant epilepsy. In such cases, the combinations of AEDs usually offer a significant enhancement of their protective effects against seizures. There has appeared a hypothesis that combining two AEDs, influencing the same neurotransmitter system, results in the potentialization of their anticonvulsant effects. For corroborating this hypothesis, a pharmacological character of interaction between tiagabine (TGB) and gabapentin (GBP)-two novel AEDs affecting the GABA-ergic system, in the maximal electroshock seizure threshold (MEST)-test in mice was evaluated. TGB at the dose of 4 mg/kg and GBP at 75 mg/kg significantly raised the electroconvulsive threshold. Further, using the isobolographic calculations, TGB was coadministered with GBP at three fixed-ratios (1 : 3, 1 : 1, and 3 : 1) of their respective protective drug doses. All examined combinations of TGB with GBP exerted supra-additive (synergistic) interactions against MEST-induced seizures in mice. The interaction index, describing the strength and magnitude of interaction, ranged between 0.25 and 0.50 indicating supra-additivity. Adverse (neurotoxic) effects were evaluated in the chimney (motor performance) and the step-through, light-dark passive avoidance (long-term memory) tests in mice. The examined combinations of TGB with GBP did not affect the motor coordination, except for the fixed-ratio of 1 : 1, at which significant impairment of motor performance was observed. Moreover, all combinations selectively impaired the acquisition of the task in the passive avoidance test, having no impact on consolidation and retrieval in the long-term memory test. The pain threshold test revealed that the observed disturbances in the passive avoidance testing resulted presumably from the antinociceptive activity of these AEDs in combinations. After lengthening the exposing time to the direct current stimulus in the passive avoidance test from 2 to 6 s, the acquisition of the task, in animals receiving the combinations of TGB and GBP was not impaired. Neither the plasma, nor brain concentrations of GBP were affected by TGB application, so pharmacokinetic events that might negatively influence the observed effects are not probable. Results of this study clearly indicate that the activation of the same neurotransmitter system (GABA-ergic) leads to a synergistic interaction. The pain threshold test is a very good paradigm for screening the antinociceptive properties of AEDs, which may disturb the long-term memory testing in animals. Combinations of TGB with GBP (very promising from a preclinical point of view) should be clinically verified for elaborating the most effective treatment regimen in patients with intractable seizures.

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PubMed2001

AUStralian study of titration to effect profile of safety (AUS-STEPS): high-dose gabapentin (neurontin) in partial seizures.

PURPOSE: To evaluate the safety, tolerability, efficacy, and impact on quality of life of gabapentin (Neurontin; GBP) as adjunctive therapy in patients with refractory partial seizures. METHODS: AUS-STEPS was an open-label, multicenter, prospective study in patients experiencing partial seizures who were inadequately controlled with one to three concurrent antiepileptic drugs (AEDs). GBP treatment was titrated to a maximum of 4,800 mg/day, over a treatment period of 24 weeks, to achieve an efficacious and tolerable dosage. Efficacy was assessed by seizure-frequency data. Quality of life was evaluated by using the QOLIE-10 questionnaire, and safety was assessed by adverse-event reports and clinical laboratory findings. RESULTS: A total of 176 patients received treatment with GBP, with 174 evaluable for intention-to-treat (ITT) efficacy analysis. A reduction of >50% in overall seizure frequency was observed in 93 patients (53%). There was a small (4.6%) overall improvement in QOLIE-10 score. The most frequent adverse events were dizziness (31%), fatigue (29%), somnolence (27%), headache (21%), and ataxia (20%), with no major increase seen in adverse events necessitating discontinuation as the dose of GBP was titrated upward. CONCLUSIONS: This study indicates that patients with partial epilepsy may be effectively treated with GBP at dosages of < or =4,800 mg/day, without altering the safety profile of the drug.

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PubMed2001

Anticonvulsant efficacy of gabapentin on kindling in the immature brain.

The anticonvulsant and motor effects of gabapentin (GBP) were evaluated in rat pups aged 16-17 days. Fourteen-day-old rat pups received an implanted stimulating electrode in the amygdala unilaterally. Kindled seizures were produced on day 16 of life by repeatedly applying an electrical current stimulus to the amygdala electrode. Animals received kindling stimulation until they achieved three consecutive generalized convulsions. On day 17, rat pups received one of four doses of GBP 10, 25, 50, or 100 mg/kg. After receiving GBP, rat pups again received electrical stimulation to the amygdala electrode to determine the extent to which GBP prevented the kindled seizure. Anticonvulsant effects were found at doses as low as 10 mg/kg. A separate group of naïve rats received GBP to determine the motor effects of each treatment dose. Impaired motor performance, quantified as time on a balance beam, occurred at doses of >or=50 mg/kg. In summary, our data indicate that in immature rats, GBP exerts an anticonvulsant effect against kindled seizures at doses that do not significantly impair motor performance.

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PubMed2001

Comparative cognitive effects of carbamazepine and gabapentin in healthy senior adults.

PURPOSE: This study compared the cognitive effects of carbamazepine (CBZ) and gabapentin (GBP) in healthy senior adults by using a randomized, double-blind crossover design. METHODS: Thirty-four senior adults were randomized to receive one of the two drugs followed by a 5-week treatment period. A 4-week washout phase preceded initiation of the second drug. Antiepileptic drugs (AEDs) were titrated to target doses of either CBZ (800 mg/day) or GBP (2,400 mg/day). Primary outcome measures were standardized neuropsychological tests of attention/vigilance, psychomotor speed, motor speed, verbal and visual memory, and the Profile of Mood State (POMS), yielding a total of 17 variables. Each subject received cognitive testing at predrug baseline, end of first drug phase, end of second drug phase, and 4 weeks after completion of the second drug phase. RESULTS: Fifteen senior adults (mean age, 66.5 years; range, 59-76 years) completed the study. Seniors completing the study did not differ significantly from noncompleting seniors in terms of demographic features or baseline cognitive performances. Fifteen of the 19 seniors not completing the study dropped out while receiving CBZ. Adverse events were frequently reported for both AEDs, although they were more common for CBZ. Mean serum levels for the completers were within midrange clinical doses (CBZ, 6.8 microg/ml; GBP, 7.1 microg/ml). Significant differences between CBZ and GBP were found for only one of 11 cognitive variables, with better attention/vigilance for GBP, although the effect was modest. Performances on the nondrug average were significantly better on 45% of cognitive variables compared with CBZ and 36% compared with GBP. The overall pattern of means favored GBP over CBZ on 15 of 17 (p < 0.001), nondrug over CBZ on 17 of 17 (p < 0.0000), and nondrug over GBP on eight of 17 (NS). CONCLUSIONS: Mild cognitive effects were found for both AEDs compared with the nondrug average condition. The magnitude of difference between the two AEDs across the cognitive variables was modest. Self-reported mood was not significantly affected by either AED. However, overall tolerability and side-effect profile of CBZ were poorer than those of GBP in senior adults at doses and titration rates reported in this study.

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PubMed2002

Gabapentin increases slow-wave sleep in normal adults.

PURPOSE: The older antiepileptic drugs (AEDs) have a variety of effects on sleep, including marked reduction in rapid-eye-movement (REM) sleep, slow-wave sleep (SWS), and sleep latency, and an increase in light sleep. The effects of the newer AEDs on sleep are unknown. Our purpose was to study the effect of gabapentin (GBP) on sleep. METHODS: Ten healthy adults and nine controls were the subjects of this study. All underwent baseline and follow-up polysomnography (PSG) and completed sleep questionnaires. After baseline, the treated group received GBP titrated to 1,800 mg daily. Polygraphic variables and Epworth Sleepiness Scale (ESS) scores, a subjective measure of sleep propensity, were compared by using the Wilcoxon signed rank test. RESULTS: Nine of the treated subjects achieved the target dose; one was studied with 1,500 mg daily because of dizziness experienced at the higher dose. GBP-treated subjects had an increase in SWS compared with baseline. No difference in the ESS or other polygraphic variables was observed. However, a minor reduction in arousals, awakenings, and stage shifts was observed in treated subjects. CONCLUSIONS: GBP appears to be less disruptive to sleep than are some of the older AEDs. These findings may underlie the drug's therapeutic effect in the treatment of disorders associated with sleep disruption.

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PubMed2002

Effects of gabapentin and carbamazepine on the EEG and cognition in healthy volunteers.

PURPOSE: Antiepileptic drug (AED) therapy can be associated with neurotoxic side effects including cognitive dysfunction. Objective methods for detection of neurotoxicity in individual patients would be useful. We studied the effects of gabapentin (GBP) and carbamazepine (CBZ) on neurophysiologic and cognitive/behavioral measures in healthy volunteers. METHODS: In a 12-week, randomized, double-blind, parallel-group study of CBZ and GBP in healthy volunteers, 23 subjects completed the protocol. All achieved the target dose of 1,200 mg CBZ or 3,600 mg GBP. A structured EEG for quantitative analysis and a cognitive test battery were administered before AED therapy and again after 12 weeks of therapy. Test-retest differences were compared with those of 72 untreated control subjects. RESULTS: Both CBZ and GBP significantly decreased the peak frequency of the posterior (alpha) rhythm, with CBZ exerting a greater effect. Ten CBZ and six GBP subjects exceeded the 95% confidence interval (CI) for an individual. Cognitive tests revealed AED vs. control group effects for two of seven measures (Digit Symbol, Stroop) and all subjective measures. However, few subjects exceeded the 95% CI for any objective test. Differences between CBZ and GBP were not significant. Greater EEG slowing was associated with greater subjective neurotoxicity and poorer test-retest performance on a cognitive test summary measure. CONCLUSIONS: Prolonged CBZ and GBP therapy induced EEG slowing that correlated with cognitive complaints and often exceeded the confidence interval for individual subjects. Quantitative EEG measures may be useful in the objective determination of AED-related neurotoxicity.

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