Topiramate: a review of preclinical, pharmacokinetic, and clinical data

Idiopathic intracranial hypertension in children: a review and algorithm

This updated review of pediatric idiopathic intracranial hypertension focuses on epidemiology, clinical presentations, diagnostic criteria, evaluation, clinical course, and treatment. General guidelines for the clinical management of idiopathic intracranial hypertension are discussed. A new algorithm outlines an efficient management strategy for the initial diagnostic evaluation of children with signs or symptoms of intracranial hypertension. This algorithm provides a systematic approach to initial evaluation and management, and identifies important decision-making factors. The risk of permanent visual loss with idiopathic intracranial hypertension necessitates a prompt, thorough collaborative approach in the management of patients. Although idiopathic intracranial hypertension has been recognized for over a century, the need remains for prospectively collected data to promote a better understanding of the etiology, risk factors, evaluative methods, and effective treatments for children with this syndrome.

Low energy diet and intracranial pressure in women with idiopathic intracranial hypertension: prospective cohort study

OBJECTIVE

To observe intracranial pressure in women with idiopathic intracranial hypertension who follow a low energy diet.

DESIGN

Prospective cohort study.

SETTING

Outpatient department and the clinical research facility based at two separate hospitals within the United Kingdom.

PARTICIPANTS

25 women with body mass index (BMI) >25, with active (papilloedema and intracranial pressure >25 cm H(2)O), chronic (over three months) idiopathic intracranial hypertension. Women who had undergone surgery to treat idiopathic intracranial hypertension were excluded.

INTERVENTION

Stage 1: no new intervention; stage 2: nutritionally complete low energy (calorie) diet (1777 kJ/day (425 kcal/day)); stage 3: follow-up period after the diet. Each stage lasted three months.

MAIN OUTCOME MEASURE

The primary outcome was reduction in intracranial pressure after the diet. Secondary measures included score on headache impact test-6, papilloedema (as measured by ultrasonography of the elevation of the optic disc and diameter of the nerve sheath, together with thickness of the peripapillary retina measured by optical coherence tomography), mean deviation of Humphrey visual field, LogMAR visual acuity, and symptoms. Outcome measures were assessed at baseline and three, six, and nine months. Lumbar puncture, to quantify intracranial pressure, was measured at baseline and three and six months.

RESULTS

All variables remained stable over stage 1. During stage 2, there were significant reductions in weight (mean 15.7 (SD 8.0) kg, P<0.001), intracranial pressure (mean 8.0 (SD 4.2) cm H(2)O, P<0.001), score on headache impact test (7.6 (SD 10.1), P=0.004), and papilloedema (optic disc elevation (mean 0.15 (SD 0.23) mm, P=0.002), diameter of the nerve sheath (mean 0.7 (SD 0.8) mm, P=0.004), and thickness of the peripapillary retina (mean 25.7 (SD 36.1) micro, P=0.001)). Mean deviation of the Humphrey visual field remained stable, and in only five patients, the LogMAR visual acuity improved by one line. Fewer women reported symptoms including tinnitus, diplopia, and obscurations (10 v 4, P=0.004; 7 v 0, P=0.008; and 4 v 0, P=0.025, respectively). Re-evaluation at three months after the diet showed no significant change in weight (0.21 (SD 6.8) kg), and all outcome measures were maintained.

CONCLUSION

Women with idiopathic intracranial hypertension who followed a low energy diet for three months had significantly reduced intracranial pressure compared with pressure measured in the three months before the diet, as well as improved symptoms and reduced papilloedema. These reductions persisted for three months after they stopped the diet.

Animal models of headache: from bedside to bench and back to bedside

In recent years bench-based studies have greatly enhanced our understanding of headache pathophysiology, while facilitating the development of new headache medicines. At present, established animal models of headache utilize activation of pain-producing cranial structures, which for a complex syndrome, such as migraine, leaves many dimensions of the syndrome unstudied. The focus on modeling the central nociceptive mechanisms and the complexity of sensory phenomena that accompany migraine may offer new approaches for the development of new therapeutics. Given the complexity of the primary headaches, multiple approaches and techniques need to be employed. As an example, recently a model for trigeminal autonomic cephalalgias has been tested successfully, while by contrast, a satisfactory model of tension-type headache has been elusive. Moreover, although useful in many regards, migraine models are yet to provide a more complete picture of the disorder.

Review of topiramate for the treatment of epilepsy in elderly patients

Individuals over 65 years of age experience the new onset of seizures at a prevalence rate of roughly twice that of younger adults. Differences in physiology, need of concomitant medications, and liability for cognitive deficits in this population, make the choice of anticonvulsant drugs especially important. This paper reviews topiramate (TPM), a treatment for many types of seizures, with the above risks in mind. In particular, we discuss efficacy and pharmacokinetics with emphasis on the older patient, and adverse events in both the younger and older adult. With most studies of TPM-induced cognitive deficits having been performed in younger adults and volunteers, we discuss the implications for the older adult. Even in studies of younger individuals, up to 50% discontinue TPM because of intolerable cognitive deficits. Most studies find specific declines in working memory and verbal fluency. In conclusion, we give recommendations for use of this antiepileptic drug in this population.

Emerging drugs for obesity therapy

Central obesity have an important impact on the development of risk factors for coronary heart disease, including dyslipidemia, glucose intolerance, insulin resistance and hypertension. These factors contribute to building cardiovascular (CV) disease as a major cause of death. The approach to obesity therapy should be designed to reduce CV risk and mortality. Diet and lifestyle changes remain the cornerstones of therapy for obesity, but the resultant weight loss is often small and long-term success is uncommon and disappointing. Drug therapy is considered for individuals with a body mass index greater than 30 kg/m(2) or ranging from 25 to 30 kg/m(2) if they have comorbid conditions. Antiobesity agents can be helpful to some patients in achieving and maintaining meaningful weight loss, but yet our pharmaceutical tools are of limited effectiveness considering the magnitude of the problem. At the present, only two drugs, orlistat and sibutramine, are approved for long-term treatment of obesity and promote no more than 5 to 10% of weight loss. Rimonabant, a cannabinoid-1 receptor antagonist, was withdrawn from the market because of concerns about its safety, including risk of suicidal and seizures, although very effective in promoting clinically meaningful weight loss, reduction in waist circumference, and improvements in several metabolic risk factors, rimonabant, a cannabinoid-1 receptor antagonist was withdrawn from the market because it concerns about its safety, including risk of suicidal and seizures. Fortunately, recent fundamental insights into the neuroendocrine mechanisms regulating body weight provide an expanding list of molecular targets for novel, rationally designed antiobesity drugs. In this review, the therapeutic potential of some antiobesity molecules in the development will be analyzed based on an understanding of energy homeostasis.

Therapeutic potential of novel glutamate receptor antagonists in migraine

BACKGROUND

Migraine is a common and disabling neurological disorder. Although the pharmacotherapy of migraine has advanced in parallel with our understanding of the pathophysiology of the disease, there is still a considerable unmet need to find more effective treatments. Migraine pathophysiology involves activation or the perception of activation of the trigeminovascular system. Glutamate, the major excitatory neurotransmitter in the CNS, is implicated in elements of the pathophysiology of the disorder, including trigeminovascular activation, central sensitization and cortical spreading depression.

OBJECTIVE

The aim of this article is to review the potential use of glutamate receptor antagonists as innovative neuronally targeted treatments of migraine.

METHODS

A systematic search of peer-reviewed publications was performed in PubMed on glutamate and migraine/trigeminovascular activation, and important references providing an insight into migraine pathophysiology are included. The results of unpublished trials were obtained from presentations at national and international meetings.

RESULTS/CONCLUSIONS

The preclinical and clinical data argue strongly for a role of glutamatergic receptor activation in migraine. The pharmacology of glutamatergic trigeminovascular responses in brain areas involved in migraine pathophysiology is relevant to the development of new therapies for this disabling condition. Glutamate receptors represent a promising target for a valuable, non-vasoconstrictor, and perhaps more importantly neuronal-specific therapeutic approach to the treatment of migraine.

Paroxysmal hemicrania responding to topiramate

Chronic paroxysmal hemicrania (CPH) is a rare primary headache syndrome, which is classified along with cluster headache and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) as a trigeminal autonomic cephalalgia. CPH is exquisitely responsive to indomethacin, so much so that the response is one of the current diagnostic criteria. The case of a patient with CPH, who had marked epigastric symptoms with indomethacin treatment and responded well to topiramate 150 mg daily, is reported. Cessation of topiramate caused return of episodes, and the response has persisted for 2 years. Topiramate may be a treatment option in CPH.

Topiramate, Pseudotumor Cerebri, Weight-Loss and Glaucoma: An Ophthalmologic Perspective

Approved for the treatment of epilepsy and migraine prophylaxis, topiramate also acts as a carbonic anhydrase inhibitor implying a potential role in the treatment of pseudotumor cerebri (PTC). Topiramate has a propensity to cause anorexia with consequent weight loss, which alone may be curative in PTC. Prescribers must be aware of several reported cases of acute secondary angle-closure glaucoma reported in patients treated with topiramate.

Preventive treatment of migraine: effect on weight

Weight gain is a common side effect of drugs used for headache prevention. Weight gain can adversely affect patient health, exacerbate comorbid metabolic disorders, and encourage noncompliance. Additionally, obesity may promote the chronification of episodic migraine. Few studies have looked specifically at the effect that headache medications have on weight. The practicing physician needs accurate information about important side effects, including weight gain, when selecting appropriate pharmacologic regimens. This article discusses the potential effects the more common headache medications have on weight.

Acute topiramate differentially affects human aggressive responding at low vs. moderate doses in subjects with histories of substance abuse and antisocial behavior

Anticonvulsant drugs have demonstrated efficacy in the management of irritability and aggression in a variety of psychiatric populations. We examined the acute effects of topiramate on aggression using a laboratory model of human aggression (PSAP) in individuals at high risk for aggressive and violent behavior.Twelve subjects, on parole/probation and with an Axis-II personality disorder and/or a substance use disorder, received 100, 200, 300, and 400 mg in an ascending sequence, with intervening placebo doses.Subjects participated 2-3 days per week over 4-6 weeks. Due to cognitive side effects at 300 mg, two subjects only completed through the 200 mg dose. Topiramate produced an inverted U-shaped dose response curve, with increases in aggression peaking at 200 mg and a modest decrease at 400 mg. Statistical analysis revealed a polynomial trend for dose (p=0.001). The observed inverted U-shaped function in aggressive responding is consistent with non-human aggression studies of GABA-A modulators. Acute topiramate doses >400 mg may have anti-aggressive effects, but dose levels in the 200-300 mg range may produce increases in aggression and side effects.

Effect of topiramate on cognitive function and single units from hippocampal place cells following status epilepticus

Topiramate, an antiepileptic drug with multiple mechanisms of action, was assessed as a neuroprotective agent following status epilepticus. We administered topiramate or normal saline chronically beginning 1 hour after cessation of lithium pilocarpine-induced status epilepticus. Control animals not subjected to status epilepticus were also treated with topiramate or normal saline. Following completion of the topiramate treatment, animals were tested in the water maze to assess spatial learning and underwent in vivo single-cell place cell recordings. Spontaneous seizure frequency following status epilepticus in the topiramate-treated rats was similar to that in the rats treated with saline. Following status epilepticus, rats had profound deficits in water maze performance and place cell function. Rats subjected to status epilepticus and treated with topiramate were also severely impaired in the water maze, but performed slightly better than rats treated with saline. Following status epilepticus, topiramate-treated rats did not differ from rats treated with normal saline in the platform switch, a test of prefrontal function. Although place cell firing patterns were similar in both the topiramate- and saline-treated rats, rats treated with topiramate had higher information content scores than rats treated with saline. Topiramate-treated animals had less supragranular sprouting following status epilepticus than nontreated rats. Control animals treated with topiramate did not differ from saline-treated controls on any measures. Taken together, this study shows that topiramate administered following status epilepticus has modest neuroprotective effects.

Topiramate and type 2 diabetes: an old wine in a new bottle

Topiramate, a marketed antiepileptic drug, has been used to treat seizures and allied neurological problems since 1999. Recently, a series of newer findings for the use of topiramate have cropped up, which include Type 2 diabetes and obesity. In a series of clinical studies, a subset of neurological patients with Type 2 diabetes mellitus (T2DM) serendipitously showed better glycaemic control when treated with topiramate. It has since been demonstrated that topiramate can act both as an insulin secretagogue and sensitiser in T2DM animal models. Pathogenesis of Type 2 diabetes involves both beta-cell dysfunction and insulin resistance. Therefore, an agent that has dual action (insulin secretagougue and sensitisation) is preferred for T2DM. Topiramate seems to act through multiple mechanisms to ameliorate diabetic symptoms, some of them unknown. Hence, it becomes imperative to discuss its probable modes of action. Topiramate raises new hope as an antidiabetic agent or a potential new chemotype with a better safety profile for the treatment of T2DM.

Serum uric acid and lipid levels while taking topiramate for migraine

OBJECTIVE

Topiramate (TPM) therapies for epilepsy or migraine are long-time therapies with unknown mechanisms and special side effects. TPM influences cholesterol (TC) and lipoprotein serum levels. In addition, TPM may cause uric acid (UA) stone formation.

MATERIAL AND METHODS

Serum UA, TC, and triglyceride (TG) levels were measured in 53 migraine patients receiving TPM and in 44 age- and sex-matched controls. Compared with controls, patients on TPM showed significantly higher UA and nonsignificantly higher TC and TG values. We recorded pre- and posttreatment levels of UA, TC, and TG levels in 23 patients.

RESULTS

We found increased serum levels of UA with TPM use (P < .01). There was a significant and positive correlation between serum UA levels and male gender (P < .01).The changes in serum UA levels before and after TPM treatment differed significantly (P < .01).

CONCLUSION

Our results suggest a need for monitoring serum UA levels in patients receiving TPM. We should perhaps prescribe a low-UA diet and advice to drink much more water in these patients.

Treatment of idiopathic intracranial hypertension: topiramate vs acetazolamide, an open-label study

OBJECTIVES - To assess the efficacy of topiramate in the treatment of idiopathic intracranial hypertension (IIH) and to compare it with acetazolamide. METHODS - Fourty patients diagnosed as IIH and randomly assigned to treatment with either acetazolamide or topiramate were assessed prospectively. Improvement in the visual fields at the end of third, sixth and twelfth months were taken into consideration. RESULTS - The demographic, clinical features and the cerebrospinal fluid (CSF) pressure of the two treatment groups were similar at the beginning of the study. When the follow-up visual field grades were compared with the visual field grades at the beginning of the study in each group a statistically significant improvement was detected with both drugs. When the results of the two treatment groups were compared with each other no statistically significant difference was present. Prominent weight loss was recorded in the topiramate group. CONCLUSIONS - Topiramate seems to be effective in the treatment of IIH. Weight reduction as well as the reduction of the CSF formation is the possible mechanism of action.

Topiramate moderately reduces the motivation to consume alcohol and has a marked antidepressant effect in rats

BACKGROUND

In recent human studies, the anticonvulsant drug topiramate (TPM) has shown efficacy in treating alcohol craving and mood disorders. However, preclinical evidence supporting such effects is surprisingly sparse. Three experiments were conducted here to assess possible anticraving and antidepressant effects of TPM using animal models.

METHODS

In Experiment 1, rats were given 23 weeks ad libitum access to food, water, and either beer (4.44% ethanol v/v) or "near-beer" (a calorie-matched nonalcoholic beer, 0.44% ethanol) in their home cages. They were then restricted to daily 1 hour operant sessions in which they licked for water and either beer or near-beer under a progressive ratio schedule of reinforcement in a lickometer apparatus. The acute effects of TPM on the motivation to consume beer or near-beer were then assessed. The effects of naloxone were also assessed (as a positive control) after TPM testing. In Experiment 2, rats were given 11 weeks of ad libitum home-cage access to food, water, and beer. They then received repeated daily injections of TPM and effects on beer consumption under ad libitum home cage access conditions were monitored. In Experiment 3, the effects of TPM were assessed in the modified Porsolt forced swim test, emergence test, and elevated plus-maze (EPM) using alcohol naïve rats.

RESULTS

Topiramate (10, 20, and 40 mg/kg) significantly reduced the motivation to lick for beer, although the maximal effect was moderate in comparison with naloxone (10 mg/kg). However, naloxone, unlike TPM, also reduced responding for near-beer suggesting an alcohol-specific effect of TPM. In Experiment 2, TPM (40 and 80 mg/kg) tended to transiently reduce alcohol consumption in the home cage under ad libitum access but this effect disappeared with repeated administration of the drug. TPM (10 to 80 mg/kg, given twice over 4 hours before test) produced a robust dose-dependent decrease in immobility and increase in active coping strategies in the forced swim test similar to that seen with desipramine (2 x 20 mg/kg). There were modest anxiolytic effects of TPM on the EPM and emergence tests.

CONCLUSIONS

With acute administration, TPM is moderately effective and relatively selective in reducing the drive to consume alcohol in Wistar rats. This anti-alcohol effect is modest in comparison with naloxone and appears to dissipate under conditions of chronic treatment and ad libitum alcohol access. A marked antidepressant-like effect in the forced swim test and partial anxiolytic effects in other animal models suggests that TPM may be a beneficial treatment for affective disorders. These preliminary results suggest further research is warranted to resolve the mechanisms involved in TPM modulation of both mood and alcohol consumption.

Topiramate reduces ethanol consumption by C57BL/6 mice

BACKGROUND

Previous reports indicate that topiramate (TPM) might be an effective treatment for alcohol dependence, perhaps due to a decrease alcohol's rewarding effects resulting from inhibition mesocorticolimbic dopamine (DA) release. Additional reports indicate that TPM antagonizes chronic changes induced by alcohol at the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) and kainate receptors. In the present study, a C57BL/6 (B6) murine model (n = 40) was used to evaluate the effect of TPM on the consumption of 12% alcohol over a 21-h period.

METHODS

TPM (0, 10, 30, 90 mg/kg) injected subcutaneously into B6 mice 60 min prior to access to a 12% ethanol solution (v/v) over 8 days produced dose-responsive reduction in consumption during the first 2-h period after injection.

RESULTS

Across the 8 days of treatment ethanol intake (g/kg) for SAL, T10, T30, and T90, respectively, was 1.34, 1.03, 0.72, and 0.67. This reduction appears to require systemically available TPM since it was not statistically supported when assessed over the entire 21-h period of ethanol availability. None of the TPM doses affected food consumption or body weight, and T90 dose did not reduce motor activity either by itself or in combination with ethanol.

CONCLUSIONS

Unlike previous experiments using the same B6 mouse model to assess naltrexone or tiagabine, there was no evidence that mice developed tolerance to the TPM-induced reductions in ethanol consumption. Thus, in the B6 mouse, TPM reduced ethanol intake at doses with no readily apparent adverse side effects, an effect consistent with recent clinical reports. Additional study will be directed toward characterizing TPM as a treatment for alcohol dependence.

Prophylaxis of Hemicrania Continua: Two New Cases Effectively Treated With Topiramate

Hemicrania continua (HC) is an uncommon and under-recognized primary headache disorder characterized by a strictly unilateral continuous headache of moderate intensity with possible exacerbations and associated with ipsilateral autonomic features. HC has generally a prompt and enduring response to indomethacin although 25% to 50% of treated patients develop gastrointestinal side effects. These cases pose a difficult management challenge as no other drug is consistently effective in HC. Recently 2 HC patients responsive to topiramate treatment have been reported. Here we describe 2 more patients effectively treated with topiramate. Neither reported any side effects and one had persisting response for 6 months after drug withdrawal.

Symptom management and supportive care of the patient with brain metastases

The focus of care for patients with brain metastases will always be on therapeutic options such as surgery, radiotherapy, and chemotherapy. However, proper symptom management and supportive care of non-therapeutic issues will be equally as important, including treatment of seizures, use of anticonvulsants, corticosteroids, and gastric acid inhibitors, assessment of swallowing dysfunction, treatment of thromboembolic events, appropriate use, and safe application of anticoagulation, and evaluation of psychiatric issues. Appropriate management of these supportive aspects of patient care will improve overall quality of life and allow the patient and family to more easily concentrate on treatment.

Paroxysmal hemicrania responding to topiramate

Chronic paroxysmal hemicrania (CPH) is a rare primary headache syndrome, which is classified along with cluster headache and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) as a trigeminal autonomic cephalalgia. CPH is exquisitely responsive to indomethacin so much so that the response is one of the current diagnostic criteria. The case of a patient with CPH, who had marked epigastric symptoms with indomethacin treatment and responded well to topiramate 150 mg daily, is reported. Cessation of topiramate caused return of episodes, and the response has persisted for 2 years. Topiramate may be a treatment option in CPH.

The obesity pipeline: current strategies in the development of anti-obesity drugs

This review provides a summary of currently available pharmaceutical therapies for the treatment of obesity, along with an overview of the pipeline of products currently in development, and the key mechanisms on which the major development candidates are based. In particular, the recent increase in understanding of the role of gut peptides in energy homeostasis is highlighted as a promising source of potential future obesity therapies.

Psychopharmacology of topiramate: from epilepsy to bipolar disorder

Topiramate (TPM) is one of the novel antiepileptic drugs and exhibits a wide range of mechanisms of action. Efficacy of TPM has been demonstrated in partial-onset seizures and primary generalized seizures in adults and children, as both monotherapy and adjunctive therapy. More recently, TPM has been proposed as an add-on treatment for patients with lithium-resistant bipolar disorder, especially those displaying rapid-cycling and mixed states. This paper reviews the multiple mechanisms of action and the tolerability profile of TPM in the light of its therapeutic potential in affective disorders. Studies of TPM in bipolar disorder are evaluated, and the efficacy and tolerability issues as a mood stabilizing agent are discussed.

The Effect of Antiepileptic Drugs on Cognition: Patient Perceived Cognitive Problems of Topiramate versus Levetiracetam in Clinical Practice

INTRODUCTION

Neurocognitive complaints may interfere with long-term antiepileptic drug (AED) treatment and are an important issue in clinical practice. Most data about drug-induced cognitive problems are derived from highly controlled short-term clinical trials. We analyzed such cognitive complaints for the two most commonly used AEDs in a clinical setting using patient perceived problems as primary outcome measure.

METHOD

All patients of the epilepsy center Kempenhaeghe that received topiramate (TPM) or levetiracetam (LEV) from the introduction to mid 2004 were analyzed using a medical information system, an automated medical file. Patients were analyzed after 6, 12, and 18 months of treatment.

RESULTS

Four hundred and two patients used either TPM (n = 260) or LEV (n = 142); 18 months retention showed a statistically significant difference, revealing 15% more patients that continued LEV compared to TPM: 18 months retention 46% for TPM and 61% for LEV [F (1.400) = 3.313, p = 0.043]. Neurocognitive complaints accounted for a significant number of drug discontinuations and especially the high frequency of neurocognitive complaints in the first period of TPM treatment appeared to be significant different from LEV [F(2,547) = 3.192, p = 0.042]. In the remaining patients, the difference in neurocognitive complaints was not statistically significant.

CONCLUSION

cognitive complaints are common in TPM treatment and frequently lead to drug withdrawal. The impact of LEV on cognitive function is only mild. This leads to a much higher (15%) drug discontinuation rate for TPM compared to LEV.

Role of valproate across the ages. Treatment of epilepsy in adults

A workshop was held in Göteborg in June 2005 to discuss the place of valproate in treating adult epilepsies. Consensus positions were developed on the epilepsy types for which the drug is most suitable and the use of valproate in women of child-bearing age, in men and in patients with psychiatric comorbidity. Valproate was considered to be effective across a broad variety of epilepsy syndromes and seizure types and should be considered a suitable choice for first-line monotherapy of juvenile myoclonic epilepsy and other idiopathic generalized epilepsies. The use of valproate by women of child-bearing age is associated with potential harm to the foetus. A conservative approach to treatment is recommended in these patients whereby alternative antiepileptic drugs should be proposed to women planning pregnancies wherever satisfactory seizure control can be thereby maintained. In cases where valproate is used during pregnancy, either because the pregnancy was unplanned or because alternative treatment options of equivalent efficacy are unavailable, appropriate counselling, precautionary measures and monitoring should be provided. The evidence for an impact of valproate on male reproductive health is equivocal and considerations of male fertility should not be taken into account in deciding whether to prescribe valproate to men. Valproate can be proposed safely to patients with comorbid psychiatric disease or underlying psychiatric vulnerability.

Use of Antiepileptic Drugs in Patients with Kidney Disease

The number of medications used to treat different types of seizures has increased over the last 10-15 years. Most of the newer antiepileptic drugs (AEDs) are likely to be unfamiliar to many nephrologists. For both the older and newer AEDs, basic pharmacokinetic information, recommendations for drug dosing in patients with reduced kidney function or who are on dialysis, and adverse renal and fluid-electrolyte effects are reviewed. Newer AEDs are less likely to have significant drug-drug interactions than older agents, but are more likely to need dosage adjustment in patients with reduced kidney function. The most common renal toxicities of these drugs include metabolic acidosis, hyponatremia, and nephrolithiasis; interstitial nephritis and other adverse effects are less common. Little is known about the clearance of most of the newer AEDs with high-efficiency hemodialyzers or with peritoneal dialysis. Monitoring of drug levels when available, careful clinical assessment of patients taking AEDs, and close collaboration with neurologists is essential to the management of patients taking AEDs.

Comparison of the Effect of Topiramate and Sodium Valporate in Migraine Prevention: A Randomized Blinded Crossover Study

BACKGROUND

Topiramate and sodium valporate are anticonvulsants, demonstrated to be effective as monotherapy for migraine prevention in placebo-controlled trials.

OBJECTIVES

To compare the relative efficacy of topiramate and sodium valporate in the prevention of migraine.

PATIENTS AND METHODS

A 24-week, randomized, double-blind, crossover, clinical trial was conducted from October 2003 to September 2004. A total of 64 patients with migraine headache, aged 14 to 57 years, were randomly allocated to the 2 treatment groups. The first group received topiramate (25 mg daily increment over 1 week to 50 mg) for a total of 2 months. The second group received sodium valporate (200 mg daily increment over 1 week to 400 mg) for 2 months. Response to treatment was assessed at 0, 1, 8, 16, and 24 weeks after start of therapy.

RESULTS

Topiramate appeared to be equivalent in efficacy and safety to sodium valporate. A significant decrease in duration, monthly frequency, and intensity of headache occurred in both groups. Of the 32 patients treated with sodium valporate, the mean standard deviation (SD) of monthly migraine frequency decreased from 5.4 (2.5) to 4.0 (2.8) episode per month, headache intensity from 7.7 (1.2) to 5.8 (1.7) by visual analog scale (VAS), and headache duration from 21.3 (14.6) to 12.3 (10.7) hours (P < .001). Correspondingly, in the 32 patients treated with topiramate, the mean SD of monthly headache frequency decreased from 5.4 (2.0) to 3.2 (1.9) per month, headache intensity from 6.9 (1.2) to 3.7 (1.3), and headache duration from 17.3 (8.4) to 3.9 (2.7) hours (P < .001).

CONCLUSION

This study demonstrates that treatment with topiramate and sodium valporate both significantly reduce migraine headache. This effect of topiramate and sodium valporate has previously been shown to reduce migraine headache, and we postulate that treatment with topiramate and sodium valporate may have a similar benefit.

Clinical experience with topiramate dosing and serum levels in patients with epilepsy

OBJECTIVE

To investigate the relevance of serum topiramate (TPM) levels (SL) monitoring in the clinical management of epileptic patients.

METHODS

Twenty-seven patients with different epileptic syndromes on TPM therapy were studied. TPM was used as add-on in 26 patients, only in one as monotherapy de novo; one case changed from TPM as add-on to TPM monotherapy. The mean follow-up time was 11 months. TPM SL were measured by fluorescence polarization immunoassay.

RESULTS

We analyzed the TPM SL in 43 samples from 27 patients. Mean TPM dose was 3.9mg/kg, mean TPM SL 13.43mumol/l. The mean level to dose ratio (LDR) was 3.63mumol/l/mg/kg. Four patients became seizure-free, all with TPM dosages lower than the mean. Eleven patients had at least 50% seizure reduction. The comedication with enzyme-inducing AED significantly reduced TPM SL and LDR. On the other hand, the influence of valproic acid (VPA) on TPM LDR was not univocal. Indeed, patients younger than 15 years showed SL values lower than the adults did, although not significant.

CONCLUSION

We could not detect a direct relationship between high TPM SL and efficacy neither between high TPM SL and tolerability. However, the data we collected seem to favour the hypothesis that high TPM dosage and SL might be associated to a greater probability to reduce seizure severity.

An overview of psychotropic drug-drug interactions

The psychotropic drug-drug interactions most likely to be relevant to psychiatrists' practices are examined. The metabolism and the enzymatic and P-glycoprotein inhibition/induction profiles of all antidepressants, antipsychotics, and mood stabilizers are described; all clinically meaningful drug-drug interactions between agents in these psychotropic classes, as well as with frequently encountered nonpsychotropic agents, are detailed; and information on the pharmacokinetic/pharmacodynamic results, mechanisms, and clinical consequences of these interactions is presented. Although the range of drug-drug interactions involving psychotropic agents is large, it is a finite and manageable subset of the much larger domain of all possible drug-drug interactions. Sophisticated computer programs will ultimately provide the best means of avoiding drug-drug interactions. Until these programs are developed, the best defense against drug-drug interactions is awareness and focused attention to this issue.

Efficacy of Topiramate and Valproate in Chronic Migraine

OBJECTIVES

The aim of this study was to compare the efficacy of sodium valproate and topiramate in treating chronic migraine.

METHODS

Forty-nine patients with chronic migraine were randomly assigned to 1 of 2 groups of treatment: 750 mg/day valproate or 75 mg/day topiramate. Efficacy variables were number of days with headache over a 30-day period and changes in Migraine Disability Assessment (MIDAS) scores at 3 months.

RESULTS

At baseline the 2 groups had similar numbers of days with headache and mean MIDAS scores. At the end of the treatment period, a significant reduction in 30-day headache frequency with respect to baseline (P < 0.00001) and a significant reduction in MIDAS scores (P < 0.00001) were recorded in both groups. There were no significant differences in beneficial effects between the 2 drugs.

DISCUSSION

Valproate and topiramate seem to be able to manage successfully chronic migraine without substantial differences in efficacy and tolerability. This affords clear practical advantages-in the event of failure of or intolerance for one treatment, the patient may be switched to the other.

The role of glutamate in anxiety and related disorders

Anxiety, stress, and trauma-related disorders are a major public health concern in the United States. Drugs that target the gamma-aminobutyric acid or serotonergic system, such as benzodiazepines and selective serotonin reuptake inhibitors, respectively, are the most widely prescribed treatments for these disorders. However, the role of glutamate in anxiety disorders is becoming more recognized with the belief that drugs that modulate glutamatergic function through either ionotropic or metabotropic glutamate receptors have the potential to improve the current treatment of these severe and disabling illnesses. Animal models of fear and anxiety have provided a method to study the role of glutamate in anxiety. This research has demonstrated that drugs that alter glutamate transmission have potential anxiolytic action for many different paradigms including fear-potentiated startle, punished responding, and the elevated plus maze. Human clinical drug trials have demonstrated the efficacy of glutamatergic drugs for the treatment of obsessive-compulsive disorder, posttraumatic stress disorder, generalized anxiety disorder, and social phobia. Recent data from magnetic resonance imaging studies provide an additional link between the glutamate system and anxiety. Collectively, the data suggest that future studies on the mechanism of and clinical efficacy of glutamatergic agents in anxiety disorders are appropriately warranted.

High performance liquid chromatographic determination of topiramate in human serum using UV detection

Topiramate has no ultraviolet, visible or fluorescence absorption. Analysis of the drug in human serum has been reported by high performance liquid chromatography (HPLC) with either mass detector or fluorescence detection after precolumn derivatization using 9-fluorenylmethyl chloroformate as fluorescent labeling agent. This study was aimed to validate derivatization and analysis of topiramate in human serum with HPLC using UV detection. The drug was extracted from human serum by liquid-liquid extraction and subjected to derivatization with 9-fluorenylmethyl chloroformate. Analysis was performed on a phenyl column using of spectrophotometer detection operated at wavelength of 264 nm. A mixture of phosphate buffer (0.05M) containing triethylamine (1 ml/l, v/v; pH 2.3) and methanol (28:72, v/v) at a flow rate of 2.5 ml/min was used as mobile phase. No interference was found with endogenous substances. Validity of the method was studied and the method was precise and accurate with a linearity range from 40 ng/ml to 40 microg/ml. The limit of quantification was 40 ng/ml of serum. The correlation coefficient between HPLC methods using fluorescence and UV detections was studied and found to be 0.992.

Effect of topiramate on cognitive function and activity level following neonatal seizures

Topiramate, an antiepileptic drug with a number of mechanisms of action including blockade of AMPA/KA receptor subtypes, was assessed as a neuroprotective agent following seizures. We administered topiramate or saline chronically during and following a series of 25 neonatal seizures. After completion of the topiramate treatment, animals were tested in the water maze for spatial learning and the open field for activity level. Brains were then examined for cell loss and sprouting of mossy fibers. Rats treated with topiramate performed significantly better in the water maze than rats treated with saline. Topiramate treatment also reduced the amount of seizure-induced sprouting in the supragranular region. There were no differences between topiramate- and saline-treated rats in activity level in the open field, swimming speed, or weight gain. These findings show that long-term treatment with topiramate after neonatal seizures changes the long-term consequences of seizures and improves cognitive function.

Effects of topiramate on ethanol and saccharin consumption and preferences in C57BL/6J mice

BACKGROUND

Topiramate has recently been found to be more effective than placebo as an adjunct treatment for alcohol dependence, but it has not yet been investigated in animal models of ethanol consumption. The current experiment examined the effects of topiramate on ethanol drinking in mice using a continuous access, two-bottle choice procedure.

METHOD

C57BL/6J male mice were offered a 10% v/v ethanol solution versus tap water over 4 consecutive days per week. Mice were assigned to topiramate (1-50 mg/kg) or saline groups and received injections before the beginning of the dark phase of the light cycle. Topiramate dose increased over 5 successive weeks (1, 5, 10, 25, and 50 mg/kg). Fluid intake was measured 2, 4, and 23 hr after injection. Body weight and food intake were measured at the time of injection. In a second phase, mice were offered saccharin solutions (0.2 and 2.5% w/v) versus tap water after topiramate (50 mg/kg) or saline injections.

RESULTS

Results revealed that high topiramate doses (25 and 50 mg/kg) increased water intake and decreased ethanol preference. Compared with saline controls, topiramate produced dose-dependent, bidirectional effects on ethanol dose, with 25 mg/kg of topiramate increasing ethanol dose at 4 and 23 hr after injection but 50 mg/kg topiramate decreasing ethanol dose at 2 hr after injection. During saccharin exposure, topiramate decreased saccharin preference (for 2.5% w/v saccharin solution) and marginally increased water intake but did not directly alter intake of the saccharin solutions. Topiramate had no effects on body weight or daily food intakes.

CONCLUSIONS

Topiramate reduced ethanol preference in C57BL/6J mice, but this effect was primarily attributable to elevated water intake. Topiramate also reduced saccharin preference, likely through marginally significant increases in water intake. Increases in water intake and bidirectional effects of topiramate on ethanol dose complicate conclusions with regard to the effects of topiramate on ethanol reward.

Comparison of sulfamate and sulfamide groups for the inhibition of carbonic anhydrase-II by using topiramate as a structural platform

This paper examines the relative effectiveness of sulfamate and sulfamide groups for the inhibition of carbonic anhydrase-II (CA-II). Topiramate (1) and its sulfamide analogue 4, and 4,5-cyclic sulfate 6 and its sulfamide analogue 5, were compared for inhibition of human CA-II. A colorimetric assay, based on the pH shift that accompanies hydration of carbon dioxide, and an esterase assay were used. For these bioisosteric pairs, 1/4 and 6/5, the sulfamate compound was markedly more potent than its sulfamide counterpart. A similar, large difference in potency was also observed for the sulfamate/sulfamide pairs 14/15 and 16/17. These results indicate that the sulfamide moiety is not particularly suitable for obtaining potent carbonic anhydrase inhibition. A discussion of this structure-activity relationship with respect to the interactions of 1 and 6 with CA-II from published X-ray data is presented. A metabolic acidosis study was performed in rats with 1, 4, 6, and 2, and the results are discussed with respect to the degree of inhibition of CA-II in vivo.

Review of the use of Topiramate for treatment of psychiatric disorders

BACKGROUND: Topiramate is a new antiepileptic drug, originally designed as an oral hypoglycaemic subsequently approved as anticonvulsant. It has increasingly been used in the treatment of numerous psychiatric conditions and it has also been associated with weight loss potentially relevant in reversing weight gain induced by psychotropic medications. This article reviews pharmacokinetic and pharmacodynamic profile of topiramate, its biological putative role in treating psychiatric disorders and its relevance in clinical practice. METHODS: A comprehensive search from a range of databases was conducted and papers addressing the topic were selected. RESULTS: Thirty-two published reports met criteria for inclusion, 4 controlled and 28 uncontrolled studies. Five unpublished controlled studies were also identified in the treatment of acute mania. CONCLUSIONS: Topiramate lacks efficacy in the treatment of acute mania. Increasing evidence, based on controlled studies, supports the use of topiramate in binge eating disorders, bulimia nervosa, alcohol dependence and possibly in bipolar disorders in depressive phase. In the treatment of rapid cycling bipolar disorders, as adjunctive treatment in refractory bipolar disorder in adults and children, schizophrenia, posttraumatic stress disorder, unipolar depression, emotionally unstable personality disorder and Gilles de la Tourette's syndrome the evidence is entirely based on open label studies, case reports and case series. Regarding weight loss, findings are encouraging and have potential implications in reversing increased body weight, normalisation of glycemic control and blood pressure. Topiramate was generally well tolerated and serious adverse events were rare.

A retrospective assessment of topiramate in children and adolescents with pervasive developmental disorders

An open-label retrospective study was conducted to assess the effectiveness and tolerability of topiramate in children and adolescents with pervasive developmental disorders (PDD). Topiramate is a novel antiepileptic drug approved as an adjunctive treatment for seizure disorders. A retrospective chart review was conducted in an outpatient clinic specialized in treating individuals with developmental disabilities, to identify all children and adolescents with PDD who received topiramate. Patients were included if concomitant medications remained unchanged. Treatment response was assessed using the Global Improvement item of the Clinical Global Impressions scale (CGI-GI), based on a review of medical records and the Conners Parent Scale (CPS), as completed by parents. Fifteen patients were identified (12 male, 3 female; age = 14.7 +/- 3.3 years), including 11 patients with autistic disorder, 2 patients with Asperger's disorder, and 2 patients with PDD not otherwise specified (PDD, NOS). Eight patients (4 patients with autistic disorder, 2 patients with Asperger's disorder, and 2 patients with PDD, NOS) were judged to be responders, as defined by a score of 1 or 2 on the CGI-GI. Treatment duration was 25 +/- 16 weeks, and the mean dose was 235 +/- 88 mg. Differences between baseline and the end-of-trial period were observed in the following CPS subscales: conduct, hyperactivity, and inattention. No differences were noted in the psychosomatic, learning, and anxiety subscales. Three patients discontinued topiramate because of side effects, with 2 patients experiencing cognitive difficulties and 1 patient a skin rash. Topiramate may be beneficial for treating secondary symptoms of PDD, and prospective openlabel studies and double-blind, placebo-controlled studies to assess its efficacy and safety are needed.

Role of Topiramate for the Treatment of Painful Diabetic Peripheral Neuropathy

OBJECTIVE

To review the possible role of topiramate for the treatment of neuropathic pain and, specifically, the pain of diabetic peripheral neuropathy.

DATA SOURCES

Clinical studies and abstracts were identified by using PubMed (January 1966--October 2003), Ovid (January 1966--December 2003), and International Pharmaceutical Abstracts (January 1970--December 2003) and by reviewing bibliographies of published studies. Key search terms included pain, peripheral neuropathy, diabetes, and topiramate. English-language studies were identified, as were pertinent references from these articles.

DATA SYNTHESIS

Published data are limited on the successful use of topiramate in the treatment of neuropathic pain syndromes, and only three prospective studies evaluated the effectiveness of topiramate in diabetic peripheral neuropathy. In addition, the use of topiramate to treat diabetic neuropathic pain syndromes successfully may be limited by patients' inability to tolerate the adverse effects associated with the agent.

CONCLUSIONS

Topiramate has been used successfully in relieving the pain of various neuropathies, including painful diabetic peripheral neuropathy. Randomized controlled trials that specifically focus on the use of topiramate in patients with painful diabetic peripheral neuropathy are needed to confirm the initial findings in case reports, abstracts, and small clinical trials that have focused on treating numerous neuropathic pain syndromes, including diabetic peripheral neuropathy.

Effect of topiramate on seizures and respiratory dysrhythmia in Rett syndrome

Rett syndrome, a neurodevelopmental disorder, manifests in the first few years of life with developmental arrest, stereotyped behaviors, and respiratory abnormalities. Seizures occur in 70 to 80% of patients. Clinical drug trials have not demonstrated the superiority of any specific antiepilepsy drug. We report our experience with topiramate in eight patients with Rett syndrome. Topiramate was initiated as monotherapy in two patients and as adjunctive therapy in six patients. Seven patients had improved seizure control. Respiratory abnormalities improved by 50 to 75% in two patients and by 20 to 50% in two others. In our cohort, seven of eight patients showed improvement in seizure control and/or respiratory abnormalities on topiramate. Topiramate was well tolerated. The effect of topiramate, a broad-spectrum drug, could be due to its gamma-aminobutyric acid (GABA)ergic and glutaminergic effects, both systems thought to be disordered in Rett syndrome.

Topiramate in clinical practice: long-term experience in patients with refractory epilepsy referred to a tertiary epilepsy center

For the treatment of patients with chronic refractory epilepsies, information about the long-term efficacy and safety profile of any new antiepileptic drug is crucial. Topiramate has been proven to be effective in patients with refractory chronic partial epilepsies in short-term controlled clinical trials, but the long-term retention, long-term efficacy, and long-term side-effect profile have not been sufficiently investigated. We analyzed all patients who had been treated with topiramate in the Epilepsy Centre Kempenhaeghe from the introduction of the drug in the spring of 1993 up to a final assessment point in mid-2002. In total, 470 patients were identified. The data show that the clinical dose achieved was about 200mg/day, reached after approximately 6 months of treatment. Further dose escalation in the survivors was slow, with a mean dose of about 300 mg/day after 24 months of treatment. Mean titration dose is 25mg/week, but titration strategy is mostly individual and responds to patient complaints. With respect to seizure frequency, 10-15% of the patients were seizure-free at the 6-month evaluation; 4 patients achieved a 2-year remission. Retention rate was 53% after 1 year, 45% after 2 years, 38% after 3 years, and 30% after 4 years. At 4 years, almost 70% of the patients had discontinued topiramate. The main reason was adverse events, which accounted for about 65% of the discontinuations. Behavioral side effects were dominant, with mental slowing (27.6%), dysphasia (16.0%), and mood problems (agitation: 11.9%) being the most frequently reported side effects. In about 10% of the patients side effects led to discontinuation despite the obvious favorable effects on seizure frequency. Comparisons between the patients who discontinued topiramate treatment and those who continued topiramate showed that discontinuation was associated with comedication (vigabatrin and lamotrigine). Our conclusion is that TPM is associated with a high incidence of side effects in clinical practice, affecting long-term retention. Meaningful prognostic factors that may help us in clinical decision making, i.e., to prevent the side effects or to help us identify those at risk, have not been found.

Special considerations in the treatment of patients with bipolar disorder and medical co-morbidities

BACKGROUND: The pharmacological treatment of bipolar disorder has dramatically improved with multiple classes of agents being used as mood-stabilizers, including lithium, anticonvulsants, and atypical antipsychotics. However, the use of these medications is not without risk, particularly when a patient with bipolar disorder also has comorbid medical illness. As the physician who likely has the most contact with patients with bipolar disorder, psychiatrists must have a high index of suspicion for medical illness, as well as a basic knowledge of the risks associated with the use of medications in this patient population. METHODS: A review of the literature was conducted and papers addressing this topic were selected by the authors. RESULTS AND DISCUSSION: Common medical comorbidities and treatment-emergent illnesses, including obesity, diabetes mellitus, dyslipidemia, cardiac disease, hepatic disease, renal disease, pulmonary disease and cancer are reviewed with respect to concomitant use of mood stabilizers. Guidance to clinicians regarding effective monitoring and treatment is offered. CONCLUSIONS: Mood-stabilizing medications are necessary in treating patients with bipolar disorder and often must be used in the face of medical illness. Their safe use is possible, but requires increased vigilance in monitoring for treatment-emergent illnesses and effects on comorbid medical illness.

Daytime Sleepiness in Epilepsy Patients Receiving Topiramate Monotherapy

PURPOSE

Limited research has focused to date on objective neurophysiological evaluation of daytime sleepiness in patients treated with newer antiepileptic drugs (AEDs), especially when used as monotherapy. This study was aimed at assessing occurrence of daytime sleepiness in newly diagnosed, drug-naïve patients with partial epilepsy receiving initial topiramate (TPM) monotherapy.

METHODS

Daytime vigilance was assessed in 14 consecutive, newly diagnosed and never medicated adult patients with focal epilepsy, receiving monotherapy with TPM. At baseline and 2 months after slowly titrated therapy with TPM, 200 mg/day, patients underwent the Multiple Sleep Latency Test (MSLT), visual simple and choice reaction times (VRT), and self-rated their own degree of sleepiness with the Epworth Sleepiness Scale. A group of 14 age- and gender-matched healthy volunteers served as controls.

RESULTS

At baseline, mean daytime sleep latencies on the MSLT were comparable in patients and in controls. Two months after TPM monotherapy, MSLT scores did not significantly change in patients as compared with pretreatment values. Accordingly, subjective daytime sleepiness and VRTs, which were comparable in controls and in untreated patients at baseline, did not change in patients after TPM monotherapy.

CONCLUSIONS

Study results suggest that an initial short-course monotherapy with TPM, 200 mg/day, does not impair daytime vigilance in newly diagnosed adult patients with partial seizures.