Newer anticonvulsants in the treatment of bipolar disorder

The anticonvulsants valproate and carbamazepine have efficacy in treating acute mania, but their efficacy in treating acute bipolar depression and preventing mood episodes remains uncertain. Despite this, and given their utility and widespread use, both are widely accepted as standard treatments for bipolar disorder. All the newer anticonvulsants that have become available during the last decade have been or are being assessed to determine their efficacy in the treatment of various phases of bipolar disorder. Among the newer anticonvulsants, some appear to have efficacy in treating core bipolar symptoms, while others have efficacy in treating psychiatric comorbidity such as substance abuse or an anxiety disorder. Lamotrigine is the most widely studied and is effective in treating and preventing bipolar depression, and it is the only anticonvulsant approved by the U.S. Food and Drug Administration as a maintenance treatment for bipolar disorder. Other newer anticonvulsants, levetiracetam, oxcarbazepine, phenytoin, and zonisamide offer promise, but further studies are required before they can be recommended for routine use to treat bipolar disorder. Gabapentin and topiramate do not appear to have efficacy in treating acute mania, but their utility in bipolar depression and prevention of mood episodes has not been studied in double-blind trials. Pregabalin has utility in treating generalized anxiety disorder, but it has not been studied in bipolar disorder. Given the success of lamotrigine in treating bipolar disorder, further double-blind controlled trials of the newer anticonvulsants in treating bipolar disorder are warranted. This article summarizes current evidence from trials of anticonvulsants in bipolar disorder and makes recommendations for their clinical use.

Vascular hemichorea/hemiballism and topiramate

Although vascular hemichorea/hemiballism (HC/HB) has been reported to be self-limited, in some cases, it can be irreversible and severely disabling. The standard treatment includes typical and atypical neuroleptics and GABA-mimetic drugs. Topiramate is a new antiepileptic drug possessing a complex mechanism of action, including the enhancement of GABA-mediated inhibition. We describe a 71-year-old patient with HC/HB who markedly improved after topiramate treatment.

Topiramate in the long-term treatment of binge-eating disorder associated with obesity

BACKGROUND

This study assessed the long-term effectiveness and tolerability of topiramate in binge-eating disorder (BED) with obesity.

METHOD

Sixty-one patients with BED (DSM-IV-TR criteria) and obesity enrolled in a 14-week, single-center, randomized, double-blind, placebo-controlled study. Completers (N = 35) were offered participation in a 42-week, open-label extension trial of topiramate. Fifteen patients who received topiramate and 16 patients who received placebo in the double-blind study entered the open-label trial. Topiramate was titrated from 25 mg/day to a maximum of 600 mg/day. The primary endpoint was change from baseline to final visit in weekly binge frequency using the last observation carried forward for all patients who received topiramate. Baseline for patients receiving double-blind topiramate was the beginning of the controlled study; for patients receiving placebo, baseline was the beginning of the open-label trial. Open-label data were gathered from December 1998 to November 2000.

RESULTS

Forty-four patients (31 who received topiramate in the open-label trial plus 13 who received topiramate in the double-blind study only) received at least 1 dose of topiramate; 43 patients provided outcome measures at a median final dose of 250 mg/day. Mean weekly binge frequency declined significantly from baseline to final visit for all 43 patients (-3.2; p < .001), for the 15 patients who received topiramate during the controlled and open-label studies (-4.0; p < .001), and for the 15 patients who received topiramate only during the open-label trial (-2.5; p = .044). Patients also exhibited statistically significant reduction in body weight. The most common reasons for topiramate discontinuation were protocol nonadherence (N = 17) and adverse events (N = 14).

CONCLUSION

Topiramate treatment was associated with enduring improvement in some patients with BED and obesity but was also associated with a high discontinuation rate.

Topiramate treatment of aggression in female borderline personality disorder patients: a double-blind, placebo-controlled study

OBJECTIVE

The goal of this study was to compare the efficacy and safety of topiramate versus placebo in the treatment of aggression in women who meet the criteria for borderline personality disorder.

METHOD

We conducted a double-blind, placebo-controlled study of topiramate in 29 female subjects (response rate 93.5%) meeting SCID (Structured Clinical Interview for DSM-IV) criteria for borderline personality disorder. The subjects were randomly assigned in a 2:1 ratio to topiramate (N = 21, analysis based on N = 19) or placebo (N = 10). Treatment lasted 8 weeks (November 2003-January 2004). Primary outcome measures were self-reported changes on the anger subscales of the State-Trait Anger Expression Inventory (STAXI).

RESULTS

Significant improvements on 4 subscales of the STAXI (state-anger, trait-anger, anger-out, anger-control) were observed in the topiramate-treated subjects after 8 weeks, in comparison with the placebo group. The difference in improvement in score between the 2 groups for state-anger, trait-anger, and anger-out ranged from 21% to 24%, and the difference for anger-control was -13%. As an exception, a difference of only 8.5% (p < .2) was found on the anger-in subscale. Significantly greater weight loss was observed in the topiramate-treated group than in those treated with placebo (difference in weight loss between the 2 groups: 2.3 kg [5.1 lb] [3.2%]; 95% CI = 1.3% to 4.4%, p < .01). All patients tolerated topiramate well.

CONCLUSIONS

Topiramate appears to be a safe and effective agent in the treatment of anger in women with borderline personality disorder as defined by SCID criteria. Additionally, significant weight loss can be expected.

Synergism between Topiramate and Budipine in Refractory Status Epilepticus in the Rat

PURPOSE

To evaluate the antiepileptic and neuroprotective properties of topiramate (TPM) alone and with coadministration of the N-methyl-D-aspartate (NMDA)-receptor antagonist budipine in a rat model of refractory status epilepticus.

METHODS

Male Sprague-Dawley rats had electrodes implanted into the perforant path and dentate granule cell layer of the hippocampus under halothane anesthesia. Approximately 1 week after surgery, the perforant path of each animal was electrically stimulated for 2 h to induce self-sustaining status epilepticus. Successfully stimulated rats were given intraperitoneally vehicle (n = 6), TPM (20-320 mg/kg; n = 28), budipine (10 mg/kg; n = 5), or budipine (10 mg/kg) and TPM (80 mg/kg; n = 6) 10 min after the end of the stimulation and monitored behaviorally and electroencephalographically for a further 3 h. The animals were killed 14 days later, and histopathology was assessed.

RESULTS

Neither budipine alone nor TPM at any dose terminated status epilepticus. Despite this, TPM resulted in various degrees of neuroprotection at doses between 40 and 320 mg/kg. Coadministration of budipine with TPM terminated the status epilepticus in all rats. This combination also significantly improved the behavioral profile and prevented status-induced cell death compared with control.

CONCLUSIONS

Budipine and TPM are an effective drug combination in stopping self-sustained status epilepticus, and TPM alone was neuroprotective, despite the continuation of seizure activity.

Topiramate Pharmacokinetics in Children with Epilepsy Aged from 6 Months to 4 Years

PURPOSE

To study the pharmacokinetics of topiramate (TPM) at steady state in children younger than 4 years comedicated with other antiepileptic drugs (AEDs).

METHODS

Twenty-two children aged 6 months to 4 years with pharmacoresistant partial or generalized epilepsy were enrolled in an open-label prospective study. Children were assigned to different groups according to comedication with enzyme-inducing AEDs (n = 8), valproic acid (VPA) (n = 6), or other AEDs not known to affect drug metabolism (neutral AEDs, n = 7). One child was receiving treatment with both enzyme-inducing AEDs and VPA. After dose titration, blood samples were collected at steady state just before and 0.5, 1, 1.5, 2, 4, 6, 8, and 12 h after the morning dose of TPM. Pharmacokinetic parameters were determined by a noncompartmental method.

RESULTS

TPM apparent oral clearance (CL/F) was significantly higher in children taking enzyme-inducing AEDs (85.4 +/- 34.0 ml/h/kg) than in those receiving VPA (49.6 +/- 13.6 ml/h/kg) or neutral AEDs (46.5 +/- 12.8 ml/h/kg). Conversely, dose-normalized areas under the plasma TPM concentration curves (0-12 h) were significantly lower in enzyme-induced patients than in patients receiving VPA or other AEDs.

CONCLUSIONS

Compared with children not receiving enzyme inducers, children younger than 4 years who receive concomitant enzyme-inducing AEDs need higher doses (milligrams per kilogram) to achieve comparable plasma TPM concentrations.

First BNCT treatment of a skin melanoma in Argentina: dosimetric analysis and clinical outcome

A Phase I/II protocol for treating cutaneuos melanomas with BNCT was designed in Argentina by the Comisión Nacional de Energía Atómica and the medical center Instituto Roffo. The first of a cohort of thirty planned patients was treated on October 9, 2003. This article depicts the protocol-based procedure and describes the first clinical case, treatment regime and planning, patient irradiation, retrospective dosimetric analysis and clinical outcome. Considering the low acute skin toxicity and the complete response in 21 of the 25 subcutaneous melanoma nodules treated, a second irradiation was performed in a different location of the extremity of the same patient. The corresponding clinical outcome is still under evaluation.

Enhanced blood boron concentration estimation for BPA-F mediated BNCT

The blood boron concentration regulates directly the BNCT irradiation time in which the prescribed dose to the patient is delivered. Therefore a proper estimation of the blood boron concentration for the treatment field based on the measured blood samples before irradiation is required. The bi-exponential model fit using Levenberg-Marquardt method was implemented for this purpose to provide the blood boron concentration estimates directly to the treatment data flow during the BNCT procedure. The harmonic mean bi-exponential decay half-lives of the studied patient data (n=28) were 15+/-8 and 320+/-70 min for the faster and slower half-life. The model uncertainty (n=28) was reasonably low, 0.7+/-0.1 microg/g (about 5%). The implemented algorithm provides a robust method for temporal blood boron concentration estimation for BPA-F mediated BNCT. Utilization of the infusion data improves the reliability of the estimate. The overall data flow during the treatment fulfills the practical requirements concerning the BNCT procedure.

Effects of topiramate in adults with Prader-Willi syndrome

Prader-Willi syndrome is a multisystem neurogenetic obesity disorder with behavioral manifestations, including hyperphagia, compulsive behavior, self-injury, and mild to moderate mental retardation. In an 8-week open-label study, we evaluated adjunctive therapy with the anticonvulsant topiramate in 8 adults with Prader-Willi syndrome. Appetite was measured by a 1-hour access to food four times throughout the study and quantified with a visual analogue scale. Topiramate did not significantly change calories consumed, Body Mass Index, or increase self-reported appetite. In addition, there were no significant changes in compulsions. Surprisingly, topiramate treatment resulted in a clinically significant improvement in the self-injury (i.e., skin-picking) that is characteristic of this syndrome. Potential benefits of topiramate for self-injury should be evaluated further in controlled trials.

Management of ejaculation pain with topiramate: a case report

A 39-year-old male presented with penile pain related to ejaculation. No urogenital, infectious, or neurologic diseases were associated with the symptoms. The pain was refractory to conventional analgesics and several neuropathic pain therapies. Oral topiramate was titrated to 75 mg daily, and within a month, the patient's pain improved from 8 to 1 out of 10, which has been maintained for 6 months.

Anticonvulsant drugs in primary headaches prophylaxis

Anticonvulsant drugs have been used in migraine prophylaxis since 1970. In recent years, new antiepileptic medications have given rise to much interest in pain control. Primary headaches prophylaxis is still based on old drugs, and physicians facing these conditions are always prompted to use any new possible choice. Among primary headaches, the most studied drug over last 15 years was divalproex sodium, and many papers showed its efficacy in the treatment of migraine headaches. Valproate is well tolerated and many dosages have been used with success. For the newer drugs, such as gabapentin, lamotrigine or topiramate, evidence is less strong but has been rapidly increasing in the last 5 years. In particular, topiramate has much more evidence of a good efficacy and a safe profile. We review the principal characteristics of their use, according to dosages, lasting of treatments, side effects and significant efficacy.

Hot water epilepsy and focal malformation of the parietal cortex development

Hot water epilepsy (HWE) refers to a specific type of reflex epilepsy precipitated by the stimulus of bathing in hot water. HWE is considered to be a geographically specific epileptic syndrome since it mainly occurs in the Indian community. Spontaneous seizures may also occur later in life. The seizure pattern includes complex partial attacks. Although the pathogenesis of HWE is still unknown, temporal lobe has been thought to take part in the epileptogenesis. This paper reports on a 4-year-old girl who, at the age of 6 months, experienced complex partial seizures triggered by bathing in hot water. Non-provoked seizures intercritical EEG showed isolated spikes and spike-and-waves in the left parietal region. Brain MRI detected a left parietal focal cortical dysplasia. This is the second patient with HWE in whom a cortical malformation has been observed. The observation present here and data reported in the literature seem to indicate that the sensory cortex might also be involved in triggering seizures precipitated by a bath in hot water. Moreover, the authors believe that MRI examination should be considered for this group of patients.

Topiramate in migraine prevention: evidence-based medicine from clinical trials

The importance of evidence-based medicine is often underestimated when migraine preventive treatments are chosen. Evidence from large, well-conducted, placebo-controlled trials of sufficient duration should be given particular consideration when evaluating the efficacy, tolerability and safety of a medication for a broad range of patients. Pizotifen, propranolol, flunarizine, amitriptyline, divalproex sodium and topiramate have all been evaluated for efficacy in migraine prevention in double-blind, placebo-controlled trials. The largest clinical programme in migraine prevention, studying these or any other agents, was comprised of 2 pivotal trials, as well as other studies, evaluating topiramate for preventive therapy in migraine. Results from these trials indicated that topiramate (100 mg/day) has proven safety and efficacy in migraine prevention. Response rates were high, and onset of action usually occurred within the first month of treatment. Therefore, topiramate has demonstrated safety and represents an effective option in the prevention of migraine, as supported by extensive clinical research.

Topiramate: new indication. Single-agent therapy in refractory epilepsy: for a few patients only

(1) Topiramate is helpful for some adults and children (aged over 4 years) with partial or generalised epilepsy, when combined with an inadequate ongoing treatment. (2) The indications for topiramate have now been extended in France to cover single-agent therapy of refractory epilepsy, from the age of 2 years. (3) A dose-finding study of 48 patients with refractory partial epilepsy suggests that the efficacy of topiramate monotherapy is dose-dependent. In a non comparative trial in 170 patients with refractory partial or generalised epilepsy, 12 patients were able to switch to topiramate alone after a phase of combining topiramate with their ongoing treatment. (4) The licence extension to children over 2 years of age is based solely on the results of previous trials. (5) Two dose-finding studies, and a trial versus a standard antiepileptic in which topiramate was used alone, confirmed that the safety profile of topiramate is similar to that of other antiepileptics, neuropsychological disturbance predominating. (6) Other adverse effects more specific to topiramate include cognitive and language problems, weight loss and reduced appetite, acute myopias sometimes associated with intraocular hypertension, an increased risk of renal lithiasis, reduced sweating with a risk of hyperthermia, and metabolic acidosis. (7) In practice, some patients whose epilepsy is refractory to an optimally administered treatment may improve when topiramate is added; and a small minority of them can gradually discontinue their previous treatment.

Levetiracetam Induces a Rapid and Sustained Reduction of Generalized Spike-Wave and Clinical Absence

BACKGROUND

Levetiracetam (LEV) is a new antiepileptic drug with efficacy in partial-onset seizures. We report a case in which generalized-onset absence seizures responded clinically and electrographically to LEV.

METHODS

We evaluated with continuous video/electroencephalography an adult with generalized-onset seizures given 3 antiepileptic drugs, 1 of which was LEV. Levetiracetam initiation 2 months before admission decreased patient-reported seizures. Interictal electroencephalography revealed generalized 3.5-Hz spike-wave and polyspike-wave discharges. Spike-wave bursts lasting 2 seconds or longer caused a pause in continuous reading aloud, consistent with clinical absence seizures. Levetiracetam was discontinued on admission, lamotrigine was gradually discontinued across 2 days, and topiramate was not changed. One encephalographer counted from video/electroencephalography recordings the number of spike-wave bursts in 1-hour time samples that included wake and sleep time.

RESULTS

Spike-wave bursts increased from 4 to 56 per hour at baseline (4000 mg of LEV per day) to 406 to 914 per hour less than 48 hours after LEV discontinuation. Levetiracetam treatment was restarted, and 3 hours after the first dose of 1000 mg, spike-wave bursts dropped to 135 per hour. Response was sustained during the next 2 days.

CONCLUSIONS

This case showed a dramatic, rapid effect of LEV discontinuation and reinstitution on generalized spike-wave burst frequency and clinical absence. The effects were independent of reduction of lamotrigine and without change in topiramate doses and occurred in a time course consistent with LEV pharmacokinetics. Levetiracetam may be effective in generalized-onset epilepsy, and randomized, controlled trials are indicated.

Changes in body mass index during long-term topiramate therapy in paediatric epilepsy patients—a retrospective analysis

STUDY OBJECTIVE

To assess the effect of topiramate (TPM) on body mass index (BMI) in paediatric epilepsy patients and to examine predictors of weight loss.

DESIGN

Retrospective, observational study.

SETTING

University clinic epilepsy outpatient department.

SUBJECTS

Patients below age 18 years who received TPM for at least 12 months.

MEASUREMENTS AND MAIN RESULTS

Changes in BMI (kg/m2) standard deviation scores (S.D.S.) from baseline to the follow-up periods of 12, 24 and 36 months were evaluated. The repeated measures t-test for paired samples, revealed significant decreases for BMI S.D.S. at 12 months (P = 0.004; n = 53) and 24 months (P = 0.044; n = 35), but no significant decrease at 36 months (n = 21). Analysis of variance revealed a predictor value of sex for BMI S.D.S. at 12 months (females more likely to lose weight; P = 0.037) and a predictor value of baseline BMI for BMI S.D.S. at 24 months (patients with a higher baseline BMI were more likely to lose weight; P = 0.047).

CONCLUSION

Weight loss is common in paediatric epilepsy patients who receive TPM and is sustained for at least one year. The pattern of weight loss differs according to sex and baseline BMI.

Topiramate in painful diabetic polyneuropathy: findings from three double-blind placebo-controlled trials

OBJECTIVES

To evaluate the efficacy and tolerability of topiramate in patients with painful diabetic polyneuropathy.

MATERIALS AND METHODS

Patients with moderate to extreme pain (0-4 Categorical Pain Scale score > or = 2) were randomized to placebo or topiramate (100, 200, or 400 mg/day) in three similar double-blind trials. The primary efficacy analysis was pain reduction from final visit to baseline in the 100-mm Visual Analog Scale (VAS) for the intent-to-treat populations.

RESULTS

After 18-22 weeks of double-blind treatment, pain reductions were numerically greater with topiramate in two studies but differences between topiramate and placebo in VAS scores or in the secondary efficacy endpoints did not reach statistical significance in any of the three studies. Across all studies, 24% of topiramate-treated patients and 8% of placebo-treated patients discontinued due to adverse events; groups did not differ in the occurrence of serious adverse events.

CONCLUSION

These studies did not find topiramate to be significantly more effective than placebo in reducing pain scores in patients with painful diabetic polyneuropathy. Several design features may have precluded the studies from having sufficient sensitivity to differentiate effective and ineffective treatments. The study design and results are instructive for other investigators designing future clinical studies in neuropathic pain.

Medical and surgical management of idiopathic intracranial hypertension in pregnancy

Idiopathic intracranial hypertension (IIH) is a syndrome of increased intracranial pressure without hydrocephalus or mass lesion with elevated cerebrospinal fluid (CSF) pressure but otherwise normal CSF composition. It has been found that pregnancy occurs in IIH patients at about the same rate as in the general population, that IIH can occur in any trimester of pregnancy, that patients have the same spontaneous abortion rate as the general population, and that the visual outcome is the same as for nonpregnant patients with IIH. Although it is also stated that pregnant patients with IIH should be managed and treated the same way as any other patient with IIH, the use of imaging and drug contraindications do make a difference between the two groups. The treatment has two major goals, which are to preserve vision and to improve symptoms. The medical therapy includes weight control, nonketotic diet, serial lumbar punctures, diuretics, steroids, and certain analgesics. When medical therapy fails, surgical procedures should be considered. The two main procedures are optic nerve sheath fenestration and lumboperitoneal shunt. Anesthetic considerations in the pregnant patient are an additional factor when surgeries are contemplated. It is also noted that therapeutic abortion to limit progression of disease is not indicated and that subsequent pregnancies do not increase the risk of recurrence.

Recent advances in the pharmacotherapy of alcoholism

Alcoholism is a devastating illness that leads to great societal losses. Despite significant health consequences, there are few medically based treatments for alcoholism. During the past decade, a better understanding of the neuroscientific underpinnings of addiction has led to the use of novel pharmacotherapeutic treatments for alcoholism. In particular, there have been new developments in the understanding of the involvement of the dopamine, opiate, serotonin, gamma-aminobutyric acid, and glutamate neurotransmitter systems in the pathophysiology of alcohol withdrawal, alcohol dependence, and in subtypes of individuals with alcoholism. In this article, new developments in the pharmacotherapy of alcohol dependence will be reviewed. In particular, the use of anticonvulsants in alcohol withdrawal and protracted abstinence syndromes will be discussed. Data on naltrexone, acamprosate, and topiramate will be highlighted. In addition, data concerning the use of serotonin reuptake inhibitors in subtypes of alcoholism and the use of combination pharmacotherapy will be reviewed.

Oral topiramate reduces the consequences of drinking and improves the quality of life of alcohol-dependent individuals: a randomized controlled trial

BACKGROUND

Topiramate, a fructopyranose derivative, was superior to placebo at improving the drinking outcomes of alcohol-dependent individuals.

OBJECTIVES

To determine whether topiramate, compared with placebo, improves psychosocial functioning in alcohol-dependent individuals and to discover how this improvement is related to heavy drinking behavior.

DESIGN

Double-blind, randomized, controlled, 12-week clinical trial comparing topiramate vs placebo for treating alcohol dependence (1998-2001).

PARTICIPANTS

One hundred fifty alcohol-dependent individuals, diagnosed using the DSM-IV.

INTERVENTIONS

Seventy-five participants received topiramate (escalating dose of 25 mg/d to 300 mg/d), and 75 had placebo and weekly standardized medication compliance management.

MAIN OUTCOME MEASURES

Three elements of psychosocial functioning were measured: clinical ratings of overall well-being and alcohol-dependence severity, quality of life, and harmful drinking consequences. Overall well-being and dependence severity and quality of life were analyzed as binary responses with a generalized estimating equation approach; harmful drinking consequences were analyzed as a continuous response using a mixed-effects, repeated-measures model.

RESULTS

Averaged over the course of double-blind treatment, topiramate, compared with placebo, improved the odds of overall well-being (odds ratio [OR] = 2.17; 95% confidence interval [CI], 1.16-2.60; P =.01); reported abstinence and not seeking alcohol (OR = 2.63; 95% CI, 1.52-4.53; P =.001); overall life satisfaction (OR = 2.28; 95% CI, 1.21-4.29; P =.01); and reduced harmful drinking consequences (OR = -0.07; 95% CI, -0.12 to -0.02, P =.01). There was a significant shift from higher to lower drinking quartiles on percentage of heavy drinking days, which was associated with improvements on all measures of psychosocial functioning.

CONCLUSIONS

As an adjunct to medication compliance enhancement treatment, topiramate (up to 300 mg/d) was superior to placebo at not only improving drinking outcomes but increasing overall well-being and quality of life and lessening dependence severity and its harmful consequences.

Pharmacologic treatment of the catastrophic epilepsies

Treatment of the catastrophic epilepsies [infantile spasms (IS), Lennox-Gastaut syndrome (LGS), and progressive myoclonic epilepsy (PME)] remains a challenge to clinicians. For IS, adrenocorticotropic hormone has traditionally been the drug of choice in the United States but may be associated with serious side effects in some patients. Vigabatrin has shown promise in treating IS patients, particularly those with tuberous sclerosis. However, the drug is associated with visual field loss and is not commercially available in the United States. Newer antiepilepsy drugs (AEDs), such as zonisamide, topiramate (TPM), and lamotrigine (LTG), may be useful in patients with IS. Although LTG, TPM, and felbamate are approved in the United States for the treatment of LGS, the overall effectiveness of therapy in patients with LGS is poor. For PME, valproate is a first-line treatment. Zonisamide and levetiracetam also show promise. Supplementation with certain cofactors to correct deficiencies and increase mitochondrial function may be useful in some patients with PME, but response to such therapy is not well documented. Advances in our understanding of the etiologies, mechanisms, and genetics underlying the catastrophic epilepsies may facilitate more effective pharmacologic interventions.

Preclinical profile of combinations of some second-generation antiepileptic drugs: an isobolographic analysis

PURPOSE

The need for an efficacious treatment of patients with intractable seizures is urgent and pressing, because approximately 30% of epilepsy patients worldwide are still inadequately medicated with current frontline antiepileptic drugs (AEDs). This study sought to determine the interactions among some newer AEDs [topiramate (TPM), felbamate (FBM), oxcarbazepine (OXC), and lamotrigine (LTG)] in the maximal electroshock-induced seizures (MES) and chimney test (motor performance) in mice, by using the isobolographic analysis.

METHODS

Evaluation of the anticonvulsant and acute adverse (neurotoxic) effects in mice produced by the AEDs in combinations at the fixed ratios of 1:3, 1:1, and 3:1 allowed the assessment of their preclinical profile and the determination of benefit indices (BIs) for all individual combinations.

RESULTS

Combinations of TPM+FBM at the fixed ratios of 1:3, 1:1, and 3:1 offered supraadditive (synergistic) interactions against electroconvulsions and subadditivity (antagonism) in terms of acute neurotoxic effects in the chimney test (BIs ranged between 1.90 and 2.59, the best combinations from a preclinical point of view). The examined combinations of TPM+OXC also were advantageous due to synergistic interactions in the MES, and additivity in terms of acute neurotoxic effects produced by the AEDs (BIs ranged between 1.35 and 1.71). In contrast, OXC+FBM exerted subadditive (antagonistic) interactions in the MES test and additive interactions in terms of acute motor impairment of animals (BIs ranged between 0.53 and 0.71). The worst combination was observed for OXC+LTG, at the fixed ratio of 1:1, displaying subadditivity (antagonism) against electroconvulsions and supraadditivity (synergy) with respect to neurotoxicity (BIs, 0.43). The remaining combinations of OXC+LTG tested (i.e., 1:3 and 3:1) exerted additivity in the MES test and supraadditivity in the chimney test (BIs 0.54 and 0.49, respectively). None of the studied AEDs affected the brain concentrations of other AEDs, so the existence of any pharmacokinetic interactions to be responsible for the observed effects is improbable.

CONCLUSIONS

Based on the current preclinical data, the pharmacological profile of combinations of TPM+FBM and TPM+OXC evaluated with isobolography was beneficial and might be worth recommendation to further clinical practice. In contrast, utmost caution is required during the use of OXC+FBM or OXC+LTG in clinical practice, because of the high risk of neurotoxic adverse effect appearance.

A pilot trial of topiramate for the treatment of cocaine dependence

BACKGROUND

Both GABAergic and glutamatergic neurons appear to be important modulators of the brain reward system and medications that affect GABA and glutamatergic neurotransmission may reduce the rewarding properties of cocaine and reduce cocaine craving. Topiramate, an anticonvulsant, raises cerebral GABA levels, facilitates GABAergic neurotransmission and inhibits glutametergic activity at AMPA/kainite receptors. Thus, it may be useful for treating cocaine dependence.

METHODS

The efficacy of topiramate for cocaine dependence was tested in a 13-week, double-blind, placebo-controlled pilot trial (n = 40). Topiramate was titrated gradually over 8 weeks to a dose of 200 mg daily. The primary outcome measure was cocaine abstinence verified by twice weekly urine benzoylecgonine tests (UBT).

RESULTS

Eighty-two percent of subjects completed the trial. Analysis of the UBT using a GEE model showed that after week 8, when the dose titration was completed, topiramate-treated subjects were more likely to be abstinent from cocaine compared to placebo-treated subjects (Z = 2.67, P = 0.01). Topiramate-treated subjects were also more likely to attain 3 weeks of continuous abstinence from cocaine (chi2 = 3.9, d.f. = 1, P = 0.05).

CONCLUSION

Topiramate may be effective for the treatment of cocaine dependence.