Pharmacological and therapeutic properties of valproate: a summary after 35 years of clinical experience

Delta-Sleep-Inducing Peptide Potentiates Anticonvulsive Activity of Valproate against Metaphit-Provoked Audiogenic Seizure in Rats

The effect of delta-sleep-inducing peptide (DSIP) on the anticonvulsive activity of a nonprotective valproate (VPA) dose in a metaphit model of generalized, reflex audiogenic seizures in adult Wistar rats was studied. The animals that received metaphit (10 mg/kg) were exposed to audiogenic stimulation (100 +/- 3 dB, 60 s) at hourly intervals. Metaphit-treated rats displaying seizures in 8 previous tests were i.p. injected with VPA (50 mg/kg) or DSIP (1.0 mg/kg) or their combination. Latency to seizure was behaviorally assessed. The EEGs and power spectra were recorded and analyzed. Neurotoxicity was evaluated by the chimney test. DSIP or VPA alone expressed no significant effect on the latency duration, but their combination significantly prolonged latency to seizure during 6 h after injection, while inducing no significant motor impairment. Neither the applied drugs nor their combination abolished metaphit-provoked EEG epileptiform activity. The results show that DSIP potentiated anticonvulsive effects of a nonprotective VPA dose in a metaphit model of audiogenic seizures without influencing its neurotoxicity.

Diverse mechanisms of antiepileptic drugs in the development pipeline

There is a remarkable array of new chemical entities in the current antiepileptic drug (AED) development pipeline. In some cases, the compounds were synthesized in an attempt improve upon the activity of marketed AEDs. In other cases, the discovery of antiepileptic potential was largely serendipitous. Entry into the pipeline begins with the demonstration of activity in one or more animal screening models. Results from testing in a panel of such models provide a basis to differentiate agents and may offer clues as to the mechanism. Target activity may then be defined through cell-based studies, often years after the initial identification of activity. Some pipeline compounds are believed to act through conventional targets, whereas others are structurally novel and may act by novel mechanisms. Follow-on agents include the levetiracetam analogs brivaracetam and seletracetam that act as SV2A-ligands; the valproate-like agents valrocemide, valnoctamide, propylisopropyl acetamide, and isovaleramide; the felbamate analog flurofelbamate, a dicarbamate, and the unrelated carbamate RWJ-333369; the oxcarbazepine analog licarbazepine, which probably acts as a use-dependent sodium channel blockers, and its prodrug acetate BIA 2-093; various selective partial benzodiazepine receptor agonists, including ELB139, which is a positive allosteric modulator of alpha3-containing GABA(A) receptors. A variety of AEDs that may act through novel targets are also in clinical development: lacosamide, a functionalized amino acid; talampanel, a 2,3-benzodiazepine selective noncompetitive AMPA receptor antagonist; NS1209, a competitive AMPA receptor antagonist; ganaxolone, a neuroactive steroid that acts as a positive modulator of GABA(A) receptors; retigabine, a KCNQ potassium channel opener with activity as a GABA(A) receptor positive modulator; the benzanilide KCNQ potassium channel opener ICA-27243 that is more selective than retigabine; and rufinamide, a triazole of unknown mechanism.

New antiepileptic drugs that are second generation to existing antiepileptic drugs

In the last decade, 10 new antiepileptic drugs (AEDs) have been introduced that offer appreciable advantages in terms of their favourable pharmacokinetics, improved tolerability and lower potential for drug interactions. However, despite the large therapeutic range of old and new AEDs, approximately 30% of the patients with epilepsy are still not seizure free and, consequently, there is a substantial need to develop new AEDs. The new AEDs currently in development can be divided into two categories: drugs with completely new chemical structures such as lacosamide (formally harkoseride), retigabine, rufinamide and talampanel; and drugs that are derivatives or analogues of existing AEDs that can be regarded as second-generation or follow-up compounds of established AEDs. This article focuses on the second category and thus critically reviews the following second-generation compounds: eslicarbazepine acetate or BIA-2-093 and 10-hydroxy carbazepine (carbamazepine derivatives); valrocemide and NPS 1776 (isovaleramide; valproic acid derivatives); pregabalin and XP13512 (gabapentin derivatives); brivaracetam (ucb 34714) and seletracetam (ucb 44212; levetiracetam derivatives); and fluorofelbamate (a felbamate derivative). In addition, a series of valproic acid derivatives that are currently in preclinical stage has also been evaluated because some lead compounds of this series have a promising potential to become new antiepileptics and CNS drugs. For any of these follow-up compounds to become a successful second generation to an existing AED, it has to be more potent, safer and possess favourable pharmacokinetics, including low potential for pharmacokinetic and pharmacodynamic drug interactions.

The influence of old age and enzyme inducing comedication on the pharmacokinetics of valproic acid at steady-state: A case-matched evaluation based on therapeutic drug monitoring data

PURPOSE

To evaluate the influence of aging on the pharmacokinetics of valproic acid (VPA) at steady-state and on the susceptibility of VPA metabolism to enzyme induction by antiepileptic comedication.

METHODS

The database of the therapeutic drug monitoring service of a large neurological hospital was searched to identify patients aged > or = 65 years stabilized on VPA therapy. Apparent VPA oral clearance (CL/F) calculated for each elderly patient was compared with that determined in an equal number of VPA-treated controls aged 20-50 years and matched for gender, body weight and antiepileptic drug (AED) comedication.

RESULTS

A total of 71 elderly patients aged 70.0+/-4.4 years, including 20 receiving enzyme inducing AEDs, was included in the main evaluation. In the absence of enzyme inducing comedication, VPA CL/F in the elderly was similar to that found in non-elderly controls (9.7+/-4.6 versus 10.2+/-4.6mlh(-1)kg(-1)). Elderly patients on enzyme inducing comedication, on the other hand, had lower CL/F values than enzyme induced younger controls (11.7+/-5.4 versus 16.0+/-6.3mlh(-1)kg(-1), p<0.05). Since VPA CL/F is known to increase with increasing dosage, a lower VPA dosage in elderly patients comedicated with enzyme inducers compared with controls may have contributed to differences in CL/F between the two groups.

CONCLUSIONS

In the absence of enzyme inducing comedication, VPA clearance in the elderly was comparable to that observed in controls. VPA clearance in elderly patients receiving enzyme inducing AEDs was lower than in controls, the difference being probably due to an influence of age as well as to the fact that mean VPA dosage was lower in these patients than in controls. Since our measurements of clearance were based on total serum VPA concentrations and VPA binding to plasma proteins is known to be reduced in old age, it is likely that the clearance of unbound, pharmacologically active, VPA was decreased to an important extent in the elderly, presumably as a result of a decline in drug metabolizing capacity.

Myo-inositol enhances teratogenicity of valproic acid in the mouse

BACKGROUND

Valproic acid (VPA) is an anticonvulsant drug that is widely used therapeutically for a variety of neurological conditions. VPA is also well known for its teratogenic potential in both humans and experimental animal models. The typical malformations observed following VPA exposure include neural tube defects (NTDs) and craniofacial and skeletal malformations. Nevertheless, the mechanisms underlying VPA's anticonvulsant efficacy or its teratogenicity remain to be elucidated. It was recently suggested that a relationship exists between VPA exposure and the cellular depletion of myo-inositol (INO). Furthermore, INO has been shown to rescue NTDs in the curly tail mouse. The aim of this study was to investigate the interactions of VPA and INO in the developing embryo.

METHODS

For this purpose, 2 strains of mice were used: SWV/Fnn (known to be sensitive to VPA) and LM/Bc (known to be resistant to VPA-induced NTDs). Pregnant females were randomly assigned to 4 experimental groups: control, VPA (600 mg/kg), INO (400 mg/kg), and VPA plus INO. VPA was injected IP at 8.5 days postcoitum (dpc). INO was administered PO twice a day from 6.5 to 10.5 dpc. At term the dams were killed, the uteri were removed, and all of the general toxicological parameters (number of implants, resorptions, dam weight, and fetus weight) were recorded and statistically analyzed.

RESULTS

Postimplantation loss in the SWV/Fnn strain and NTDs in the LM/Bc strain were significantly increased after the coadministration of VPA and INO.

CONCLUSIONS

This work clearly indicates that INO enhances VPA-induced teratogenicity in the mouse.

Valproic acid and risk of acute pancreatitis: a population-based case-control study

To examine whether acute pancreatitis is associated with use of valproic acid. Through the population-based hospital discharge registries we identified all patients with an incident hospitalization of acute pancreatitis in the counties of North Jutland (data 1991 to 2003), Aarhus (data 1996 to 2003), and Viborg (data 1998 to 2003), Denmark. From the Danish Civil Registration System, we selected 10 sex-matched and age-matched population controls per case on the basis of risk set sampling. All prescriptions of valproic acid and other antiepileptic drugs within 90 days (present users) or 91 to 365 days (past users) before hospital admission with acute pancreatitis, or index date among controls, were collected from the prescription databases in the counties. We performed conditional logistic regression to estimate the relative risk of acute pancreatitis after exposure to valproic acid or other antiepileptic drugs, adjusting for gallstone diseases, alcohol-related diseases, hyperlipidemia, and hypercalcemia. We included 3083 cases of acute pancreatitis and 30,830 population controls. The adjusted odds ratio (OR) for acute pancreatitis in present users of valproic acid was 1.9 [95% confidence interval (CI), 1.1-3.3); for past users, the adjusted OR was 2.6 (95% CI, 0.8-8.7). For users of other antiepileptic drugs, the corresponding adjusted ORs were 1.6 (95% CI, 1.2-2.2) and 1.8 (95% CI, 1.1-3.0). Use of valproic acid is associated with an elevated relative risk estimate for acute pancreatitis, but it was not materially different from past use or use of other antiepileptic drugs. Therefore, our data challenge the hypothesis that valproic acid is an independent risk factor for acute pancreatitis.

Safety and tolerability of mood-stabilising anticonvulsants in the elderly

The authors review current research on the safety and tolerability of anticonvulsant medications used for individuals over the age of 60 years with affective disorders, agitation and other psychiatric disorders. Three anticonvulsants currently approved in the US for treatment of bipolar affective disorder are reviewed: valproate, lamotrigine and extended-release carbamazepine. The authors discuss the pharmacokinetics, pharmacodynamics, drug-drug interactions and the impact of ageing for each drug. There are few studies of anticonvulsant medications in elderly patients with bipolar disorder or other psychiatric conditions. Therefore, the authors summarise adverse events of greatest prevalence and/or greatest severity based on data derived predominately from studies of geriatric patients with epilepsy and/or other non-psychiatric indications. Guidelines are offered for the safe use of these medications in the elderly, based on research literature.

In vivo synergy between topoisomerase II and histone deacetylase inhibitors: predictive correlates

Histone deacetylase inhibitors (HDACi) are a promising class of anticancer agents, yet the specific biological effects resulting in cell death are still poorly understood and clinically relevant markers of response are not adequately defined. The anticonvulsant valproic acid has recently emerged as an HDACi, and in vitro studies suggested that valproic acid may potentiate cytotoxic agents. We evaluated the pharmacologic and biological effects of valproic acid on histone acetylation, chromatin structure, and DNA damage induced by topoisomerase II inhibitors in mice bearing breast cancer tumors and developed an ex vivo methodology for response prediction using comet assays. The exposure of mice to valproic acid before exposure to epirubicin led to tumor regression when valproic acid was given for 48 hours at concentrations sufficient for histone hyperacetylation, down-regulation of heterochromatin maintenance proteins, and chromatin decondensation. Tumor response was accurately predicted by ex vivo comet moments. Valproic acid did not exacerbate epirubicin-related toxicity. Antitumor effects were not observed with valproic acid alone despite biologically active valproic acid concentrations. These findings suggest that exposure of tumor-bearing mice to valproic acid potentiated the antitumor effects of topoisomerase II inhibitors without enhancing toxicity. The HDACi-induced histone acetylation and modulation of heterochromatin correlated with potentiation of epirubicin-mediated DNA damage. However, these effects did not result in antitumor activity when using a HDACi alone and hence should not be considered a surrogate marker. Ex vivo comet assays may be useful as a predictive tool when tumor cells are limited and serial biopsies are difficult to obtain.

Modulation of cellular radiation responses by histone deacetylase inhibitors

Histone deacetylase (HDAC) inhibitors are emerging as a new class of targeted cancer chemotherapeutics. Several HDAC inhibitors are currently in clinical trials and promising anticancer effects at well-tolerated doses have been observed for both hematologic and solid cancers. HDAC inhibitors have been shown to induce cell-cycle and growth arrest, differentiation and in certain cases apoptosis in cell cultures and in vivo. However, it is known that these compounds induce varying responses in different cells and biological settings, and identifying their precise mechanisms of action is an area of great interest. Important findings are continually expanding our understanding of the cellular effects of HDAC inhibitors and recent studies will be briefly outlined in this review. In addition to their intrinsic anticancer properties, numerous studies have demonstrated that HDAC inhibitors can modulate cellular responses to other cytotoxic modalities including ionizing radiation, ultraviolet radiation and chemotherapeutic drugs. Hence, there is a growing interest in potential clinical use of HDAC inhibitors in combination with conventional cancer therapies. In this review, the interaction of HDAC inhibitors with other anticancer agents is discussed. The focus of the article is on the different mechanisms by which HDAC inhibitors enhance the sensitivity of cells to the effects of ionizing radiation.

Histone deacetylation as a target for radiosensitization

Due to an increase in the understanding of molecular radiobiology, strategies for enhancing tumor radiosensitivity have begun to focus on targeting the molecules and processes that regulate cellular radioresponse. Toward this end, histone acetylation has begun to receive considerable attention as a potential target for radiosensitization. Histone acetylation, which is determined by the competing actions of histone acetylases (HATs) and histone deacetylases (HDACs), plays a role in regulating chromatin structure and gene expression--two parameters that have long been considered determinants of radioresponse. As a means of modifying histone acetylation status, considerable effort has been put into the development of inhibitors of HDAC activity, which is often aberrant in tumor cells. This has led to the generation of a relatively large number of structurally diverse compounds that inhibit HDAC activity and result in histone hyperacetylation, and importantly, are applicable to patient treatment. Whereas a number of these HDAC inhibitors have antitumor activity in preclinical cancer models when delivered as single agents, recent studies have indicated that these compounds also significantly enhance tumor cell radiosensitivity. A structurally diverse set of HDAC inhibitors have been shown to enhance the in vitro radiosensitivity of human tumor cell lines generated from a spectrum of solid tumors. Moreover, HDAC inhibitors increased the radiosensitivity of human tumor xenografts. Although the mechanism responsible for this radiosensitization has not been definitely elucidated, data suggest that inhibiting the repair of radiation-induced DNA damage may be involved. Whereas HDAC inhibitors are currently in clinical trials as single modalities and in combination with chemotherapeutic agents, recent results suggest that these compounds may also enhance the antitumor effectiveness of radiotherapy.

Progress in pharmaceutical development presentation with improved pharmacokinetics: a new formulation for valproate

Successful long-term treatment of patients with epilepsy requires selection of an appropriate antiepileptic regimen, optimal dosing and patient compliance. Recent advances in our understanding of the biological basis of epilepsy and in the choice of treatment options are transforming the global management of these patients. If the achievement of seizure freedom remains the primary goal of any antiepileptic treatment, issues associated with drug acceptability and tolerability, and with quality of life of patients, have gained increasing attention as major determinants of ultimate therapeutic success. Sustained-release formulations of antiepileptic drugs can be very helpful in achieving treatment objectives. Stable serum levels without marked peak-to-trough fluctuations, reduced frequency of dosing and the possibility of dosing flexibility may all improve compliance, patient satisfaction and ultimately quality of life. The efficacy of sodium valproate for the treatment of most types of epilepsy has been demonstrated extensively and this drug remains the mainstay of treatment for many clinical situations. Among the various valproate formulations, extended-release tablets have shown improved patient compliance and satisfaction. However, the tablet size and the limited dosing flexibility could be unsuitable for individualized treatment in special populations such as children, the elderly and patients with swallowing difficulties. A new sustained-release formulation of sodium valproate consisting of tasteless microspheres that can be sprinkled on semi-solid food such as yoghurt or jam has been developed. A stick pack presentation allows individualized dosing and greater convenience.

Valproic acid binding to human serum and human placenta in vitro

The binding characteristics of the antiepileptic agent and teratogen valproic acid for human serum and human placenta were investigated utilizing equilibrium dialysis of the drugs in serum and in homogenates of whole placenta so that the transplacental transfer of the drug could be better defined. A low-capacity, high-affinity binder and a high-capacity, low-affinity binder for valproic acid were found in serum. However, there was only minimal, nonspecific binding of the drug to placenta. It appears that transplacental transfer of valproic acid is not mediated by binding to placenta. It is likely that such transfer occurs by passive diffusion, which may be facilitated by the lipophilicity of the drug and by development of a pH gradient across the placenta. These findings indicate that the placenta is not a depot for valproic acid.

Valproic acid induces extracellular signal-regulated kinase 1/2 activation and inhibits apoptosis in endothelial cells

The histone deacetylase (HDAC) inhibitor valproic acid (VPA) was recently shown to inhibit angiogenesis, but displays no toxicity in endothelial cells. Here, we demonstrate that VPA increases extracellular signal-regulated kinase 1/2 (ERK 1/2) phosphorylation in human umbilical vein endothelial cells (HUVEC). The investigation of structurally modified VPA derivatives revealed that the induction of ERK 1/2 phosphorylation is not correlated to HDAC inhibition. PD98059, a pharmacological inhibitor of the mitogen-activated protein kinase kinase 1/2, prevented the VPA-induced ERK 1/2 phosphorylation. In endothelial cells, ERK 1/2 phosphorylation is known to promote cell survival and angiogenesis. Our results showed that VPA-induced ERK 1/2 phosphorylation in turn causes phosphorylation of the antiapoptotic protein Bcl-2 and inhibits serum starvation-induced HUVEC apoptosis and cytochrome c release from the mitochondria. Moreover, the combination of VPA with PD98059 synergistically inhibited angiogenesis in vitro and in vivo.

Novel targets for valproic acid: up-regulation of melatonin receptors and neurotrophic factors in C6 glioma cells

Valproic acid (VPA) is a potent anti-epileptic and effective mood stabilizer. It is known that VPA enhances central GABAergic activity and activates the mitogen-activated protein kinase-extracellular signal-regulated kinase (MAPK-ERK) pathway. It can also inhibit various isoforms of the enzyme, histone deacetylase (HDAC), which is associated with modulation of gene transcription. Recent in vivo studies indicate a neuroprotective role for VPA, which has been found to up-regulate the expression of brain-derived neurotrophic factor (BDNF) in the rat brain. Given the interaction between the pineal hormone, melatonin, and GABAergic systems in the central nervous system, the effects of VPA on the expression of the mammalian melatonin receptor subtypes, MT1 and MT2, were examined in rat C6 glioma cells. The effects of VPA on the expression of glial cell line-derived neurotrophic factor (GDNF) and BDNF were also examined. RT-PCR studies revealed a significant induction of melatonin MT1 receptor mRNA in C6 cells following treatment with 3 or 5 mm VPA for 24 h or 5 mm VPA for 48 h. Western analysis and immunocytochemical detection confirmed that the VPA-induced increase in MT1 mRNA results in up-regulation of MT1 protein expression. Blockade of the MAPK-ERK pathway by PD98059 enhanced the effect of VPA on MT1 expression, suggesting a negative role for this pathway in MT1 receptor regulation. In addition, significant increases in BDNF, GDNF and HDAC mRNA expression were observed after treatment with VPA for 24 or 48 h. Taken together, the present findings suggest that the neuroprotective properties of VPA involve modulation of neurotrophic factors and receptors for melatonin, which is also thought to play a role in neuroprotection. Moreover, the foregoing suggests that combinations of VPA and melatonin could provide novel therapeutic strategies in neurological and psychiatric disorders.

Bioequivalence of a new sustained-release formulation of sodium valproate, valproate modified-release granules, compared with existing sustained-release formulations after once- or twice-daily administration

STUDY OBJECTIVE

To compare the pharmacokinetic properties of valproate modified-release (MR) granules with those of two existing valproate sustained-release (SR) formulations to confirm their bioequivalence.

DESIGN

Two randomized, open-label, two-period crossover studies under fasting conditions, and one open-label, randomized, single-dose, three-period crossover study under fasting and nonfasting conditions. Each study had a 7-day washout interval between periods.

SETTING

Three hospitals in France.

SUBJECTS

Healthy male Caucasian volunteers aged 18-35 years (27 subjects in study 1, 24 in study 2, and 24 in study 3).

INTERVENTION

In studies 1 and 2, during two 15-day periods, subjects received either valproate MR granules or an existing valproate SR formulation. In study 3, subjects received only valproate MR granules 500 mg, once with water after a 10-hour fast, once with yogurt after a 10-hour fast, and once 30 minutes after a high-fat morning meal.

MEASUREMENTS AND MAIN RESULTS

Blood samples were collected, and pharmacokinetic parameters of valproic acid were determined for single-dose (studies 1-3) and repeated-dose (studies 1 and 2) administration. The 90% confidence intervals (CIs) for area under the concentration-time curve and maximum concentration (C max ) were in the acceptance limits for bioequivalence (i.e., 90% CI 0.80-1.25) after single and repeated doses of valproate MR granules administered once/day or twice/day. Although time to C max was slightly decreased with valproate MR granules, this difference did not induce a significant difference in terms of C max . Valproate MR granule formulation was bioequivalent with existing SR formulations. High-fat breakfast or yogurt did not modify either the bioavailability or pharmacokinetic profile of valproate MR granules. This formulation was well tolerated. The adverse event profile did not differ among the various regimens.

CONCLUSION

Valproate MR granules, administered once/day or twice/day, may be an attractive alternative to existing SR formulations for patients who have difficulties with swallowing tablets or who favor granules over tablets.

[From the biology of trauma to secondary preventive pharmalogical measures for post-traumatic stress disorders]

Of all the psychological complications that an individual is likely to present with when confronted with an exceptional event, the Post-Traumatic Stress Disorder is characterized by being progressive, frequent, invalidating, strongly associated with comorbidity, and having the tendency to become chronic if it is not detected clinically. By definition, it is threatening and produces an intense fear reaction. The traumatic event is a situation of extreme stress, not only capable of altering the physical and psychological homeostasis of the individual, but is also recognized as determinant in the aetiopathology of complications. The intensity of this distress can be identified clinically and physiologically, and is currently considered as an important risk factor for the development of PTSD later on, together with other pre-, peri- and post-traumatic factors. In fact, the most studied field is the therapeutic approach, in particular drug treatment, of the fully-constituted disorder, although this actually represents tertiary prevention. Even though primary prevention seems to concern Medicine very little, any prospect of performing secondary prevention should begin by rapid identification of the risk or vulnerability factors and should allow a population at risk from developing complications to be defined. Its potential therapeutic impact brings together psychotherapeutic and drug treatment, since it is only this combination that seems able to allow the most favourable clinical outcome to be achieved for an individual, who is confronted by an out-of-the-ordinary event. The aims of secondary prevention strategies are, for example, to reduce the incidence of acute PTSD in patients seen following the event. The benefits for the individual and for the society can easily be measured in terms of the consequences on his/her social, professional and family life, or in terms of cost. The usefulness of this prevention can also be measured by the possible ways that other conditions, comorbid to PTSD, are controlled, such as anxiety disorders, depression and substance abuse, for example. Secondary prevention strategies may also be aimed at determining the therapeutic impact, by preventing or moderating the appearance of an acute stress, or even by contributing in avoiding the onset of chronic PTSD. Psychopharmacology of the immediate and post-immediate disorders, however, remains a field which has been studied very little. Reduction or control of the high, prolonged level of hyperarousal phenomena or hypersensitization of the hypothalamo-pituitary axis, would contribute to the comfort of the individual, and would participate in the prevention of PTSD. Based on current knowledge of the neurobiology of trauma, we look into the existing and potential pharmacological possibilities. Even though benzodiazepines tend to have an important role, knowledge of other drugs and therapeutic groups is rapidly increasing. In this review, we will see that the efficacy of anti-adrenergic drugs and certain other anxiolytics is now well-documented, this opening the door to their use in the future. Other drug groups offer interesting, well-proven approaches, such as serotoninergic drugs, CRF or NPY antagonists, NMDA antagonists, anticonvulsants or other GABAergic agents. In view of this disorder, which represents a true public health problem, we consider that it is now possible to widen the horizons of our drug therapy, in combination with any necessary psychotherapeutic treatment, to reach the heart of the traumatic event, that often upsets the victims, both by the psychological suffering it induces, and the loss of his/her social, family and professional references and support structures.

Histone acetylation and histone deacetylase activity of magnesium valproate in tumor and peripheral blood of patients with cervical cancer. A phase I study

BACKGROUND

The development of cancer has been associated with epigenetic alterations such as aberrant histone deacetylase (HDAC) activity. It was recently reported that valproic acid is an effective inhibitor of histone deacetylases and as such induces tumor cell differentiation, apoptosis, or growth arrest.

METHODS

Twelve newly diagnosed patients with cervical cancer were treated with magnesium valproate after a baseline tumor biopsy and blood sampling at the following dose levels (four patients each): 20 mg/kg; 30 mg/kg, or 40 mg/kg for 5 days via oral route. At day 6, tumor and blood sampling were repeated and the study protocol ended. Tumor acetylation of H3 and H4 histones and HDAC activity were evaluated by Western blot and colorimetric HDAC assay respectively. Blood levels of valproic acid were determined at day 6 once the steady-state was reached. Toxicity of treatment was evaluated at the end of study period.

RESULTS

All patients completed the study medication. Mean daily dose for all patients was 1,890 mg. Corresponding means for the doses 20-, 30-, and 40-mg/kg were 1245, 2000, and 2425 mg, respectively. Depressed level of consciousness grade 2 was registered in nine patients. Ten patients were evaluated for H3 and H4 acetylation and HDAC activity. After treatment, we observed hyperacetylation of H3 and H4 in the tumors of nine and seven patients, respectively, whereas six patients demonstrated hyperacetylation of both histones. Serum levels of valproic acid ranged from 73.6-170.49 microg/mL. Tumor deacetylase activity decreased in eight patients (80%), whereas two had either no change or a mild increase. There was a statistically significant difference between pre and post-treatment values of HDAC activity (mean, 0.36 vs. 0.21, two-tailed t test p < 0.0264). There was no correlation between H3 and H4 tumor hyperacetylation with serum levels of valproic acid.

CONCLUSION

Magnesium valproate at a dose between 20 and 40 mg/kg inhibits deacetylase activity and hyperacetylates histones in tumor tissues.

Reduction of affective lability and alcohol use following traumatic brain injury: a clinical pilot study of anti-convulsant medications

OBJECTIVE

A large and under-recognized sub-set of patients suffer both traumatic brain injury (TBI) and alcohol dependence (ADep). This group appears to use alcohol to self-treat affective and anxiety lability following TBI, resulting in new ADep or worsened prior ADep. This study hypothesized that treatment of such patients with mood-stabilizing medications would relieve post-TBI emotional dysregulation and facilitate reduction in alcohol use.

DESIGN

This study reported retrospective medical record data from outpatients in the Substance Abuse Treatment Programme who were treated for labile mood. Medications followed clinical indication and were given in non-blind fashion.

METHOD

Subjects included 18 patients who (1) complained of debilitating affective lability following TBI, (2) described drinking alcohol to ease lability symptoms, (3) met DSM-IV criteria for current ADep and (4) were treated with a mood stabilizing medication.

RESULTS

During 6 weeks of treatment, 16 (89%) achieved abstinence from alcohol. All but two (14/16 or 88%) also showed improvement in their affective and anxiety symptoms.

CONCLUSIONS

These preliminary data are limited by the retrospective collection, clinical impression and non-blinded trial. Nonetheless, the results suggest further investigation of anti-convulsants as potentially useful agents in co-morbid emotional lability and ADep following TBI.

Acute and chronic pain following craniotomy: a review

Postoperative pain is an important clinical problem that has received increasing attention in recent years. However, pain following craniotomy has been a comparatively neglected topic; this review seeks to redress this imbalance. A brief overview of the anatomy of the skull and its linings is given, with particular reference to innervation. The various approaches for craniotomies are classified, with their association with acute and long-term effects on analgesic requirements. A comprehensive search of the literature was undertaken to ascertain the incidence of acute pain post craniotomy and current thoughts on pharmacological management, touching briefly on pre-emptive treatment. Also discussed is the much neglected but nevertheless real incidence of chronic pain following craniotomy and its underlying pathogenesis, prevention and treatment.

Valproic acid, in combination with all-trans retinoic acid and 5-aza-2'-deoxycytidine, restores expression of silenced RARbeta2 in breast cancer cells

Epigenetic silencing of tumor suppressor genes has been established as an important process of carcinogenesis. The retinoic acid (RA) receptor beta2 (RARbeta2) gene is one such tumor suppressor gene often silenced during carcinogenesis. The combined use of histone deacetylase and DNA methyltransferase inhibitors has been shown to reverse the epigenetic silencing of numerous growth regulatory genes. Valproic acid (VPA), which has long been used in the treatment of epilepsy, was shown recently to be an effective histone deacetylase inhibitor that can induce differentiation of neoplastically transformed cells. In this study, we show for the first time that VPA, in combination with RA and the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (Aza-dC), can overcome the epigenetic barriers to transcription of a prototypical silenced tumor suppressor gene, RARbeta2, in human breast cancer cells. Chromatin immunoprecipitation assays show that the combination of VPA, RA, and Aza-dC increases histone acetylation at the silenced RARbeta2 promoter of MCF-7 breast cancer cells. Furthermore, reverse transcription-PCR analyses reveal cell type-specific effects in the actions of VPA on RARbeta2 expression in cultured human breast cancer cells. Finally, we show that VPA, in combination with RA and Aza-dC, inhibits the proliferation of both estrogen receptor alpha-positive (MCF-7) and estrogen receptor alpha-negative (MDA-MB-231) breast cancer cell lines. These data suggest that VPA may ultimately be useful in combination therapies in the treatment of human breast cancers.

Diverse small-molecule modulators of SMN expression found by high-throughput compound screening: early leads towards a therapeutic for spinal muscular atrophy

We have exploited the existence of a second copy of the human SMN gene (SMN2) to develop a high-throughput screening strategy to identify potential small molecule therapeutics for the genetic disease spinal muscular atrophy (SMA), which is caused by the loss of the SMN1 gene. Our screening process was designed to identify synthetic compounds that increase the total amount of full-length SMN messenger RNA and protein arising from the SMN2 gene, thereby suppressing the deleterious effects of losing SMN1. A cell-based bioassay was generated that detects SMN2 promoter activity, on which greater than 550,000 compounds was tested. This resulted in the identification of 17 distinct compounds with confirmed biological activity on the cellular primary assay, belonging to nine different structural families. Six of the nine scaffolds were chosen on the basis of their drug-like features to be tested for their ability to modulate SMN gene expression in SMA patient-derived fibroblasts. Five of the six compound classes altered SMN mRNA levels or mRNA splicing patterns in SMA patient-derived fibroblasts. Two of the compound classes, a quinazoline compound series and an indole compound, also increased SMN protein levels and nuclear gem/Cajal body numbers in patient-derived cells. In addition, these two distinct scaffolds showed additive effects when used in combination, suggesting that they may act on different molecular targets. The work described here has provided the foundation for a successful medicinal chemistry effort to further advance these compounds as potential small molecule therapeutics for SMA.

Drug bioactivation, covalent binding to target proteins and toxicity relevance

A number of therapeutic drugs with different structures and mechanisms of action have been reported to undergo metabolic activation by Phase I or Phase II drug-metabolizing enzymes. The bioactivation gives rise to reactive metabolites/intermediates, which readily confer covalent binding to various target proteins by nucleophilic substitution and/or Schiff's base mechanism. These drugs include analgesics (e.g., acetaminophen), antibacterial agents (e.g., sulfonamides and macrolide antibiotics), anticancer drugs (e.g., irinotecan), antiepileptic drugs (e.g., carbamazepine), anti-HIV agents (e.g., ritonavir), antipsychotics (e.g., clozapine), cardiovascular drugs (e.g., procainamide and hydralazine), immunosupressants (e.g., cyclosporine A), inhalational anesthetics (e.g., halothane), nonsteroidal anti-inflammatory drugs (NSAIDSs) (e.g., diclofenac), and steroids and their receptor modulators (e.g., estrogens and tamoxifen). Some herbal and dietary constituents are also bioactivated to reactive metabolites capable of binding covalently and inactivating cytochrome P450s (CYPs). A number of important target proteins of drugs have been identified by mass spectrometric techniques and proteomic approaches. The covalent binding and formation of drug-protein adducts are generally considered to be related to drug toxicity, and selective protein covalent binding by drug metabolites may lead to selective organ toxicity. However, the mechanisms involved in the protein adduct-induced toxicity are largely undefined, although it has been suggested that drug-protein adducts may cause toxicity either through impairing physiological functions of the modified proteins or through immune-mediated mechanisms. In addition, mechanism-based inhibition of CYPs may result in toxic drug-drug interactions. The clinical consequences of drug bioactivation and covalent binding to proteins are unpredictable, depending on many factors that are associated with the administered drugs and patients. Further studies using proteomic and genomic approaches with high throughput capacity are needed to identify the protein targets of reactive drug metabolites, and to elucidate the structure-activity relationships of drug's covalent binding to proteins and their clinical outcomes.

Hiperamonemia secundária ao uso terapêutico de ácido valpróico: relato de caso

O ácido valpróico tem sido amplamente utilizado no tratamento da epilepsia, sendo usualmente bem tolerado, não obstante alguns efeitos colaterais que lhe são atribuídos. Um efeito ainda pouco conhecido é a hiperamonemia, independente da hepatotoxicidade da droga. A hiperamonemia se estabelece no início ou no decurso do tratamento, sendo caracterizada por vômitos, alteração progressiva da consciência, sinais neurológicos focais e aumento na freqüência das crises epilépticas. Descrevemos o caso de menino de seis anos de idade que desenvolveu hiperamonemia pelo uso terapêutico de ácido valpróico. Os exames descartaram aminoacidopatias, acidemias orgânicas e distúrbios do ciclo da uréia, sendo a hipótese de efeito secundário reiterada pela normalização da concentração sangüínea de amônia, após a retirada do medicamento. Os mecanismos da hiperamonemia são discutidos, concluindo-se que o monitoramento da amônia é importante nos pacientes que utilizam o ácido valpróico.

Lamotrigine has an anxiolytic-like profile in the rat conditioned emotional response test of anxiety: a potential role for sodium channels?

RATIONALE

Many anticonvulsants are used in disorders other than epilepsy. For example, lamotrigine is reported to be effective in post-traumatic stress disorder and mania.

OBJECTIVE

We assessed the effects of the anticonvulsants lamotrigine, valproate and carbamazepine in an animal model of anxiety. We assessed a wide range of pharmacological tools to delineate the mechanism of lamotrigine's anxiolytic effect.

METHODS

We assessed these compounds in the rat conditioned emotional response (CER) test of anxiety.

RESULTS

Lamotrigine (30-80 mg/kg) dose-dependently and reproducibly engendered an anxiolytic response in this test, with similar efficacy to benzodiazepines. Carbamazepine (20-40 mg/kg) and riluzole (10 mg/kg), which block Na+ channels by a similar mechanism as lamotrigine, were also anxiolytic. By contrast, valproate (100-600 mg/kg) was inactive and appears to differ in its interaction with Na+ channels. The SSRI paroxetine, the GABA(A) receptor positive modulator propofol, the NMDA antagonists memantine and (+)MK-801, and the Ca2+ channel antagonist nifedipine were all inactive in the CER test, suggesting these mechanisms may not mediate the anxiolytic effect of lamotrigine. More directly, we showed that the anxiolytic effect of lamotrigine could be blocked by co-administering rats with the Na+ channel activator veratrine (0.1 mg/kg). By contrast, neither the Ca2+ channel agonist BAYK8644 (0.5 mg/kg) nor the 5-HT1A or 5-HT(1/2) antagonists WAY100635 (0.3 mg/kg) and metergoline (3 mg/kg), respectively, were able to block the effect.

CONCLUSION

Lamotrigine's anxiolytic effect in the CER test may be mediated via block of Na+ channels, and this may represent a target for the development of novel anxiolytics.

Acute leukemia associated with valproic acid treatment: a novel mechanism for leukemogenesis?

Valproic acid has been previously associated with hematologic toxicity, including a reversible myelodysplasia-like syndrome without chromosomal abnormalities. We now report three cases of acute leukemia with features of secondary leukemia associated with valproic acid therapy: two cases of acute myelogenous leukemia with multilineage dysplasia, one with trisomy 8 and one with monosomy 7, and one case of secondary acute lymphoblastic leukemia with del (7) (q22q34), del (9) (q21.11q22), del (11) (q12q23). One patient had a previous myelodysplastic syndrome while on valproic acid. Valproic acid has been previously shown to be a histone deacetylase inhibitor. Inhibition of histone deacetylase causes a relaxation of chromatin structure and thus increases susceptibility to DNA damage and sensitizes cells to radiation. We propose that valproic acid therapy may lead to secondary leukemia by increasing DNA damage through chronic inhibition of histone deacetylase.

A Case of Hyperammonemic Encephalopathy Secondary to a Combination of Valproic Acid and Topiramate

Purpose

To report a case of hyperammonemic encephalopathy induced by a combination of valproic acid and topiramate.

Case Summary

A 30-year-old male was admitted to our institution after experiencing headaches, decreasing mental capacity and increasing somnolence over the previous 3 days. Past medical history was significant for generalized tonic-clonic seizure disorder and mild mental retardation for which he had been regularly taking valproic acid, topiramate, and lorazepam. The patient was seizure free for the past 9 months prior to his seizure 2 weeks prior to admission. Upon presentation, an electroencephalogram revealed excessive slowing in the left more than right, with a differential consistent with a metabolic encephalopathy, head injury, or postictal state. Laboratory workup revealed a valproic acid level that was slightly elevated, but still within normal limits, at 92.5 mcg/mL (normal = 50 to 100 mcg/mL). Furthermore, the patient's ammonia level was found to be elevated at 72 mcg/dL (normal = 14.7 to 55.3 mcg/dL). On hospital day 3, after discovering these findings, valproic acid was discontinued and lactulose 20 g three times daily was started. Five days after admission, the patient's mental status changes were resolved, and he was discharged with an ammonia level of 57 mcg/dL.

Conclusion

Hyperammonemic encephalopathy is rare, but a serious and sometimes fatal disorder can occur in patients receiving valproic acid therapy. The incidence of hyperammonemia may be increased in patients receiving concomitant valproic acid and topiramate therapy. In patients on valproic acid and topiramate who present with altered mental status, an ammonia level in addition to a serum valproate level should be ascertained to rule out this potentially serious adverse drug reaction.

Computerized Tremor Analysis of Valproate-induced Tremor: A Comparative Study of Controlled-release versus Conventional Valproate

PURPOSE

Valproate (VPA) induces postural tremor in 6-45% of patients. The characteristics of VPA-induced tremor have not yet been quantitatively assessed, and it is not known whether tremor prevalence or severity is affected by VPA formulation (controlled-release CR-VPA vs. conventional VPA). The aim of this study was quantitatively to assess tremor in epilepsy patients receiving VPA and to compare the effects of two VPA formulations (CR-VPA vs. VPA) on tremor severity.

METHODS

In a prospective study, 18 consecutive patients with newly diagnosed focal or generalized epilepsy were assigned to receive alternately either VPA (n=10) or CR-VPA (n=8) monotherapy. Computerized tremor analysis was performed at baseline 1 day before initiating VPA treatment and repeated after a seizure-free period of >or=8 weeks, during which VPA doses had remained stable. Rest and postural tremor were recorded by accelerometry, and surface electromyograms (EMGs) were recorded from the wrist flexors and extensors.

RESULTS

At baseline, the two groups had similar postural tremor amplitudes. At follow-up, the CR-VPA group had remained at the same level, whereas VPA subjects exhibited a significant increase in tremor amplitudes (p<0.05) despite comparable VPA doses and comparable plasma VPA concentrations at the time of tremor testing.

CONCLUSIONS

This is the first study to assess quantitatively VPA-induced tremor by standardized tremor analysis. These results suggest that CR-VPA may cause less tremorigenic activity as compared with standard VPA. The mechanisms underlying this difference are unclear but may include greater peak-trough variation with VPA than with CR-VPA.

Carbamazepine toxicity following Oxybutynin and Dantrolene administration: a case report

OBJECTIVE

To report a case of Carbamazepine toxicity following the administration of Oxybutynin and Dantrolene.

STUDY DESIGN

A case report.

SETTING

The Spinal Rehabilitation Department, Loewenstein Hospital, Raanana, Israel.

METHODS

A patient with C6D tetraplegia who sustained intoxication because of drug interaction is presented. She had been treated by Carbamazepine 1000 mg/day for neuropathic pain for 2 years without clinical or laboratory signs of toxicity. After administration of Oxybutynin concomitantly with an increase in the dose of Dantrolene, she presented the clinical symptoms and laboratory finding of Carbamazepine intoxication. Trying to adjust the treatment to the patient's requirements, Carbamazepine together with Oxybutynin and Dantrolene was readministrated in lower doses.

RESULTS

The combination of these drugs, even small doses, caused toxicity. Adding Dantrolene and Oxybutynin elevated the blood level of Carbamazepine, possibly by inhibition of cytochrome P450.

CONCLUSION

A possible pharmacokinetic interaction between Dantrolene and Oxybutynin should be borne in mind when considering Carbamazepine medication for a patient with a spinal cord lesion.

Enhancement ofin vitro andin vivo tumor cell radiosensitivity by valproic acid

Valproic acid (VA) is a well-tolerated drug used to treat seizure disorders and has recently been shown to inhibit histone deacetylase (HDAC). Because HDAC modulates chromatin structure and gene expression, parameters considered to influence radioresponse, we investigated the effects of VA on the radiosensitivity of human brain tumor cells grown in vitro and in vivo. The human brain tumor cell lines SF539 and U251 were used in our study. Histone hyperacetylation served as an indicator of HDAC inhibition. The effects of VA on tumor cell radiosensitivity in vitro were assessed using a clonogenic survival assay and gammaH2AX expression was determined as a measure of radiation-induced DNA double strand breaks. The effect of VA on the in vivo radioresponse of brain tumor cells was evaluated according to tumor growth delay analysis carried out on U251 xenografts. Irradiation at the time of maximum VA-induced histone hyperacetylation resulted in significant increases in the radiosensitivity of both SF539 and U251 cells. The radiosensitization was accompanied by a prolonged expression of gammaH2AX. VA administration to mice resulted in a clearly detectable level of histone hyperacetylation in U251 xenografts. Irradiation of U251 tumors in mice treated with VA resulted in an increase in radiation-induced tumor growth delay. Valproic acid enhanced the radiosensitivity of both SF539 and U251 cell lines in vitro and U251 xenografts in vivo, which correlated with the induction of histone hyperacetylation. Moreover, the VA-mediated increase in radiation-induced cell killing seemed to involve the inhibition of DNA DSB repair.

Ethosuximide and valproate display high efficacy against lindane-induced seizures in mice

Both lindane (gamma-hexachlorocyclohexane), an organochlorine ectoparasiticide and pentylenetetrazol, used as a model of experimental epilepsy, produce convulsive seizures resulting from the blockade of the gamma-aminobutyric acid (GABAA) receptor. In the present study we established the protective effects of ethosuximide and valproate against seizures induced by lindane and compared them with the well-known protective effects of these drugs against pentylenetetrazol-induced seizures in mice. Both ethosuximide and valproate afforded complete and dose-dependent protection against seizures induced by lindane. However, the potencies of these drugs were lower than those obtained against pentylenetetrazol seizures. Nevertheless, the protective efficacy of ethosuximide and valproate against experimentally induced lindane seizures may suggest possible efficacy of these drugs against seizures in lindane-poisoned patients.

Lamotrigine versus valproic acid as first-line monotherapy in newly diagnosed typical absence seizures: an open-label, randomized, parallel-group study

PURPOSE

To compare the efficacy of lamotrigine (LTG) and valproic acid (VPA) in newly diagnosed children and adolescents with typical absence seizures.

METHODS

A randomized, open-label parallel-group design was used. After undergoing an awake video-EEG recording, which included one to two trials of 3 min of hyperventilation and intermittent photic stimulation, eligible patients were randomized to receive LTG or VPA. LTG was initiated at a daily dose of 0.5 mg/kg for 2 weeks in two divided doses, followed by 1.0 mg/kg/day for an additional 2 weeks. Thereafter, doses were increased in 1-mg/kg/day increments every 5 days until seizures were controlled, intolerable adverse effects occurred, or a maximum dose of 12 mg/kg/day had been reached. VPA was equally uptitrated according to clinical response, starting at 10 mg/kg and increasing by 5 mg/kg/24 h every 3 days, if required, to a maximum of 30 mg/kg/day in three divided doses. Patients were seen in the clinic every month for < or = 12 months. The primary efficacy end point at each visit was seizure freedom, defined as lack of clinically observed seizures since the previous visit and lack of electroclinical seizures during ambulatory 24-h EEG testing and a video-EEG session with hyperventilation.

RESULTS

Thirty-eight children (17 boys, 21 girls), aged from 3 to 13 years (mean, 7.5 years), all newly diagnosed with childhood or juvenile typical absence seizures, were enrolled. After 1 month of treatment, 10 (52.6%) of 19 children taking VPA and one (5.3%) of 19 taking LTG were seizure free (p = 0.004). By the 3-month follow-up, 12 (63.1%) children taking VPA and seven (36.8%) taking LTG were controlled (p = 0.19). After 12 months, 13 children taking VPA (dose range, 20-30 mg/kg/day; mean serum level, 76.8 mg/L; range, 51.4-91 mg/L) and 10 taking LTG (dose range, 2-11 mg/kg/day; mean serum level, 8.1 mg/L; range, 1.1-18 mg/L) were seizure free (p = 0.51). Side effects were mostly mild and transient and were recorded in two (10.6%) children treated with VPA and in six (31.8%) treated with LTG.

CONCLUSIONS

Both VPA and LTG can be efficacious against absence seizures, although VPA shows a much faster onset of action, at least in part because of its shorter titration schedule.

Encephalopathy and myoclonus triggered by valproic acid

In recent years, the use of valproic acid (VPA) as a mood-stabilizing agent has continuously increased. Although VPA usually is well tolerated, its use in combination with other psychotropic compounds might bear an elevated risk of adverse reactions. Here, we present the case of a 42-year-old male suffering from treatment-resistant psychotic depression, who was prescribed VPA additionally to lithium, clomipramine, flupentixol and risperidone. By doing so, he developed myoclonus, tremor and encephalopathy with sedation and marked EEG background slowing. Most notably, these side effects occurred in the presence of normal VPA and ammonia serum concentrations. On VPA discontinuation, all symptoms vanished and EEG normalized. We thus suggest that direct VPA-induced encephalopathy in the absence of ammonemia does exist, in this case probably facilitated by psychotropic polypharmacy.

Increased human cytomegalovirus replication in fibroblasts after treatment with therapeutical plasma concentrations of valproic acid

Valproic acid (2-propylpentanoic acid, VPA), an effective inhibitor of histone deacetylases (HDAC) is used for the treatment of epilepsia. In this study, structure-activity relationships for the action of structurally modified VPA derivatives on human cytomegalovirus (HCMV) replication and HDAC inhibition were defined. Pretreatment of human foreskin fibroblasts with VPA (0.125-1mM) caused a concentration-dependent increase of HCMV immediate early and antigen late antigen expression. Structure-activity relationships of VPA derivatives for HCMV stimulation were compared to those for teratogenic action and those for HDAC inhibition. Side chain elongation and introduction of a triple bond in 4-position of the other chain caused teratogenicity, stimulated HCMV replication, and increased HDAC inhibition, as demonstrated by enhanced levels of acetylated histones. Teratogenic VPA derivatives with a branched chain in 3-position as well as a non-teratogenic anticonvulsive active VPA derivative did not stimulate HCMV or accumulation of acetylated histones. This demonstrates a strict correlation between inhibition of HDAC and increased HCMV replication.

Treatment of the metabolic disturbances caused by antipsychotic drugs: focus on potential drug interactions

The risk of excessive bodyweight gain, glucose dysregulation and hyperlipidaemia is differentially increased by conventional and atypical antipsychotic drugs. Switching or combining agents may be sufficient in some cases, but in many instances additional drug treatment will be required. This includes oral antidiabetics, insulin and agents to treat hyperlipidaemia, hypertension and platelet dysfunction, among others. Numerous pharmacokinetic and pharmacodynamic interactions with the antipsychotics are possible, although few have been tested in formal studies. After reviewing the literature, the authors provide preliminary guidelines to assist clinicians in drug selection for this complex and fragile clinical population.

Characterization of the anticonvulsant profile of valpromide derivatives

The antiepileptic activity of nine derivatives of valpromide is discussed. They comply with a pharmacophore model that establishes the essential structural and electronic features responsible for the protection against the MES test. The model results from the comparison of 17 structures, using density functional methodologies combined with an active analog approach. The derivatives of valpromide have been tested for anticonvulsant activity in mice. These compounds displayed a phenytoin-like profile, being active in the MES test and inactive in the PTZ test. 4-(Valproylamido)benzenesulfonamide is the most active compound, with an ED(50) of 53 micromol/kg and no neurotoxicity at doses up to 1000 micromol/kg. The pharmacological behavior of the drugs points to a sodium channel blocking effect as one of the associated mechanisms. This mechanism was tested positive for N-ethylvalpromide through its competition with the binding of [(3)H]batrachotoxin-A-20 alpha-benzoate to the voltage-dependent sodium channels from rat brain synaptosomes.

Valproate therapy and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease was defined recently as another symptom of insulin resistance. Continuous therapy with valproate can result in increased body weight and insulin resistance, but no data are yet available on a possible relationship between valproate and nonalcoholic fatty liver disease. We here demonstrate in abdominal ultrasound investigations that characteristics of fatty liver disease were present in 61% of valproate-treated patients as compared with 23% receiving carbamazepine therapy.

Metabolism of a new antiepileptic drug, N-methyl-tetramethylcyclopropanecarboxamide, and anticonvulsant activity of its metabolites

N-methyl-tetramethylcyclopropanecarboxamide (MTMCD) is a new antiepileptic drug (AED) structurally related to valproic acid (VPA) that has a broad spectrum of anticonvulsant activity including models of therapy-resistant epilepsy. The purpose of this study was to identify in vivo metabolites of MTMCD that could contribute to its anticonvulsant efficacy. The metabolism of MTMCD was studied in mice, in human liver microsomes (HLM), and in recombinant human CYP isoforms with focus on formation of the hydroxylation product, N-hydroxymethyl-tetramethylcyclopropanecarboxamide (OH-MTMCD) and the N-demethylation product tetramethylcyclopropanecarboxamide (TMCD). The anticonvulsant activity of MTMCD's metabolites was evaluated in the maximal electroshock (MES), subcutaneous metrazole (s.c. Met), and in the 6Hz model in mice. In mice, OH-MTMCD was identified as a phase I metabolite of MTMCD and detected in plasma and brain after administration of MTMCD. In human liver microsomes MTMCD was biotransformed to OH-MTMCD but not to TMCD. Chemical inhibition studies suggested that MTMCD hydroxylation is mainly mediated by CYP 2A6 and CYP 2C19, which was confirmed using cDNA-expressed P450 isozymes. OH-MTMCD was a broad-spectrum anticonvulsant and possessed significant anticonvulsant activity in mouse models of partial and generalized seizures (ED50 values 75-220mg/kg), but was less potent than MTMCD. As OH-MTMCD was also present at lower concentrations than MTMCD in mouse brain, it is likely that MTMCD itself and not one of its metabolites is responsible for its activity in therapy-resistant epilepsy.

Antiepileptic Drug Treatment of Nonconvulsive Seizures Induced by Experimental Focal Brain Ischemia

Nonconvulsive seizures (NCSs) after traumatic and ischemic brain injury are often refractory to antiepileptic drug therapy and are associated with a decline in patient outcome. We recently characterized an in vivo rat model of focal brain ischemia-induced NCS and here sought to evaluate potential pharmacological treatments. Electroencephalographic activity was recorded continuously for 24 h in freely behaving rats subjected to permanent middle cerebral artery occlusion (MCAo). Rats were treated with an antiepileptic drug from one of seven different drug classes at ED(50) and 2x ED(50) doses (as reported in other rat seizure models), delivered as a single i.v. injection 20 min post-MCAo. Vehicle-treated rats (n = 9) had an 89% incidence of NCS with an average number of NCS of 8.6 +/- 1.9. The latency to onset of NCS was 32.5 +/- 3.4 min post-MCAo with an average duration of 49.1 +/- 8.2 s/event. The high doses of ethosuximide, gabapentin, fos-phenytoin, and valproate significantly reduced the incidence of NCS (11, 14, 14, and 38%, respectively), whereas midazolam, phenobarbital, and dextromethorphan had no significant effect at either dose. Across treatment groups, there was a low but significant correlation between the number of NCS events per animal and volume of brain infarction (r = 0.352). Antiepileptic drug therapy that prevented the occurrence of NCS also reduced mortality from 26 to 7%. Based on combined effects on NCS, infarction, neurological recovery, and mortality, ethosuximide and gabapentin were identified as having the best therapeutic profile.

Adaptive and maladaptive psychobiological responses to severe psychological stress: implications for the discovery of novel pharmacotherapy

Post-traumatic stress disorder (PTSD) is one of the few DSM-IV diagnoses contingent upon a psychosocial stressor. In this context, there is an urgent need to acquire a better understanding of both the adaptive and maladaptive psychobiological responses to traumatic stress. Preclinical investigators have utilized a variety of animal models to identify the behavioral and neurobiological features of the organism's response to stress. However, given the complexity of the healthy and pathological human response to physiological and psychological stress, the extent to which the animal data is immediately transferable to human remains to be fully determined. This review draws upon preclinical and clinical literature to examine the transformation of an adaptive human stress response into a maladaptive and debilitating mental disorder. An integrative psychobiological model for PTSD is presented, linking psychological processes and behavioral patterns with current findings in neurocircuitry, neurochemistry and psychophysiology. The implications of this model for the discovery of novel pharmacological approaches to the treatment of severe psychological distress are discussed.

Treatment of partial seizures in childhood : an overview

The treatment of partial seizures in children is based on the use of first generation and recently introduced antiepileptic drugs as well as nonpharmacological treatments such as the ketogenic diet, vagus nerve stimulation and surgical therapy. The present review discusses the efficacy and tolerability of different treatment options for partial seizures in childhood. Few adjunctive or monotherapy, placebo-controlled or comparative trials of the first-generation antiepileptic drugs and some of the more recently introduced antiepileptic drugs have been performed in children. This can be explained by the fact that it is only relatively recently (1989) that the International League against Epilepsy proposed that randomised, controlled trials be included among the required criteria for assessing the efficacy and tolerability of an antiepileptic agent. This led to controlled, comparative trials among older antiepileptic drugs (phenobarbital, phenytoin, carbamazepine and valproic acid), both in adults and in paediatric patients, being performed relatively 'late', based on when these drugs were first introduced. Carbamazepine and valproic acid may still be considered as first-line antiepileptic therapies for children with partial seizures. Phenobarbital and phenytoin are mostly considered as last choice drugs because of their adverse event profiles. The new generation of antiepileptic agents has added to the first- and second-line treatment options for paediatric partial seizures. To date, there are sufficient data to support the clinical use of some of the recently introduced antiepileptic drugs (e.g. oxcarbazepine, topiramate, gabapentin and lamotrigine) as adjunctive or first-line monotherapy. Because of the risk of visual field constriction with vigabatrin, the use of this drug is currently limited to patients refractory to other medications. Tiagabine, felbamate, levetiracetam and zonisamide have been shown to be effective in adults with partial seizures; however, at present there are not yet enough data on the efficacy of these drugs in children to support consideration of their use as either first-line or add-on therapy in this patient population, although controlled studies are expected shortly. Furthermore, the use of felbamate is considerably limited by rare, but severe, hepatic and haematological toxicity. Controlled trials for paediatric partial seizures are still lacking for the ketogenic diet and vagus nerve stimulation, though they may represent, in given patients, useful adjunctive alternative treatments for refractory partial seizures. In conclusion, further trials are needed to determine an optimal sequence of first- and second-line therapies and to establish whether other newer antiepileptic drugs merit consideration as initial therapy in children with partial seizures.

What Is the Best Strategy for Converting from Twice-Daily Divalproex to a Once-Daily Divalproex ER Regimen?

OBJECTIVE

To examine if, during conversion from conventional divalproex to once-daily divalproex extended-release (ER) tablets, plasma valproic acid (VPA) concentrations in the first 48 hours after conversion are maintained within the accepted therapeutic range (50-100 mg/L).

METHODS

Four distinct 12-hourly (q12h) divalproex to once-daily divalproex ER conversion strategies were explored: immediate, delayed, stepwise and mixed conversion. These strategies were each used in simulations for hypothetical adult patients being treated under different conditions: monotherapy (uninduced, at 1500 mg/day divalproex ER) and polytherapy on enzyme-inducing co-medications (induced, at 3000 and 4500 mg/day divalproex ER).

RESULTS

The proportion of uninduced patients expected to have minimum VPA concentrations (C(min)) >50 mg/L was 90% for immediate, 83% for stepwise and 82% for mixed-conversion strategies; only 52% undergoing a delayed-conversion strategy had C(min) >50 mg/L. More importantly, 33% of induced patients under-going delayed conversion to 3000 mg/day divalproex ER maintained an adequate VPA C(min). Maximum VPA concentrations (C(max)) attained after conversion to divalproex ER are unlikely to rise beyond the steady-state C(max) observed with divalproex q12h regimens with any conversion strategy tested in uninduced or induced patients. Marked perturbation in VPA concentration is not likely when converting to once-daily divalproex ER 'all-at-once' 12 hours after the last divalproex q12h dose. Stepwise and mixed-conversion strategies do not offer any advantage; delayed conversion may produce a large drop in VPA concentration.

CONCLUSIONS

An ideal conversion strategy for q12h divalproex to once-daily divalproex ER appears to be an immediate conversion 12 hours after the last divalproex q12h dose; it causes the least perturbation in plasma VPA, even for patients required to take high divalproex ER doses.

Valproate-induced neural tube defects in folate-binding protein-2 (Folbp2) knockout mice

BACKGROUND

Folate is an important B vitamin that is transported into cells by way of folate-binding proteins and transporters. Folate-binding protein-2 nullizygous (Folbp2(-/-)) mice develop normally; however, we have found them to be more susceptible to the teratogenic effects of arsenate exposure than wild-type control mice.

METHODS

In the current study, we wanted to extend our findings and test the hypothesis that Folbp2(-/-) mice are more susceptible to the teratogenic effects of valproic acid (VPA), a commonly used antiepileptic drug that is known to induce neural tube defects (NTDs) in both humans and laboratory animals.

RESULTS

Folbp2(-/-) mice had higher VPA-induced frequencies of embryonic lethality and exencephaly than did the wild-type control mice during folate supplementation and a control diet, respectively. All other differences in response between the two genotypes were short of reaching statistical significance. Folate supplementation of wild-type, but not Folbp2(-/-) dams reduced embryonic lethality of VPA-treated wild-type embryos compared to the folate-deficient diet.

CONCLUSIONS

Unlike our previous findings with arsenate, enhanced susceptibility of Folbp2(-/-) mice to in utero VPA exposure was demonstrated in some dietary folate regimens. Thus, our data indicate a relatively frail relationship between Folbp2 and VPA-induced NTDs.

Valproic acid increases SMN levels in spinal muscular atrophy patient cells

Spinal muscular atrophy (SMA) is an inherited motor neuron disease caused by mutation of the telomeric copy of the survival motor neuron gene (SMN1). Although a centromeric copy of the survival motor neuron gene (SMN2) is retained in all patients with SMA, it differs from SMN1 at a critical nucleotide such that the majority of SMN2 transcripts lack exon 7 and encode an unstable, truncated protein. Here, we show that valproic acid increases levels of exon 7-containing SMN transcript and SMN protein in type I SMA patient-derived fibroblast cell lines. Valproic acid may increase SMN levels both by activating the SMN promoter and by preventing exon 7 skipping in SMN transcripts. Valproic acid and related compounds warrant further investigation as potential treatment for SMA.

Antiepileptic drug-induced pharmacodynamic aggravation of seizures: does valproate have a lower potential?

Thirty-five years since its introduction into clinical use, valproate (valproic acid) has established itself as one of the most widely used antiepileptic drugs (AEDs). In recent years, there has been a growing awareness of the potential aggravation of seizure disorders by AEDs. Such aggravation may be due to a variety of factors that include a paradoxical pharmacodynamic effect. In order to address this important safety aspect of AED treatment, we reviewed all available published evidence in search of factors related to seizure aggravation during valproate therapy. We analysed the 20 available publications, which outline about 99 case reports (in some papers, the exact number was not specified) of aggravation of seizures associated with valproate. Almost all of these cases occurred in a specific clinical context known to be linked to seizure aggravation, such as overdose, encephalopathy, hepatopathy or metabolic disorders. However, we found no consistent evidence of pure pharmacodynamic aggravation in the absence of any of the above quoted factors. In view of the large number of patients treated worldwide with valproate, the number of reported cases of seizure aggravation in patients taking the drug in the literature is low. Conditions in which worsening of seizures as a result of valproate use may occur are well known and often avoidable. Thus, unlike most AEDs, including the newer ones, valproate appears to have a very low potential for pharmacodynamic paradoxical seizure aggravation. This knowledge is in accordance with long-standing clinical experience and practice.

Compliance and satisfaction with switching from an immediate-release to sustained-release formulation of valproate in people with epilepsy

OBJECTIVE

The goal of our work was to assess compliance and patient satisfaction with switching from sodium valproate to Depakine Chrono in patients with epilepsy.

METHODS

Clinical, demographic, and behavioral details assessing compliance and satisfaction were collected using self-completion questionnaires at the time of inclusion in the study and 3 months after the inclusion day.

RESULTS

Data were collected from 2031 respondents from eight European countries. There were significant differences between time 1 and time 2 of the study in seizure frequency, reported side effects, compliance, and patient satisfaction.

CONCLUSION

Findings suggest that switching from sodium valproate to Depakine Chrono results in an increase in seizure-free rates, a reduction in reported side effects, an improvement in the level of compliance, and a modest improvement in patient satisfaction.

Teratogenicity of valproate conjugates with anticonvulsant activity in mice

Valproic acid (VPA) is an effective antiepileptic medication, the use of which in females of childbearing age is complicated by its ability to induce birth defects, including neural tube defects (NTDs), in exposed embryos. In experimental settings, VPA reproducibly induces NTDs in laboratory animals such as the highly inbred SWV/Fnn mice. In search of new, efficacious derivatives of VPA that lack toxicity, the conjugates of VPA with amantadine (VPA-AMA) and N-3-aminopropyl-2-pyrrolidinone (VPA-PYR) have been synthesized and evaluated for their anticonvulsant activity. In the present study, the authors evaluated the teratogenicity potential of VPA-AMA and VPA-PYR using a well-established mouse model for antiepileptic drug teratogenicity. All tested compounds were injected intraperitoneally to pregnant dams on gestational day 8.5, and the fetuses examined on day 18.5. At the highest dose tested (3.61 mmol/kg), VPA-PYR was maternally lethal, whereas VPA-AMA induced excessive embryonic lethality. At a dose of 2.20 mmol/kg, VPA-PYR was not teratogenic to the exposed embryos; VPA-AMA induced NTDs in 8.2% of embryos, VPA caused 5.5% NTDs. 0.80 mmol/kg amantadine induced NTDs in 2.2% of the exposed fetuses. In conclusion, VPA-AMA has a comparable teratogenicity as does VPA, and it is proposed that the teratogenicity of VPA-AMA is due to the parent compound. Additional studies are needed to fully define and understand the structure-teratogenicity relationships of VPA analogues.

Epilepsy: from consensus to daily practice

Most clinicians would accept that epilepsy treatment should begin with monotherapy, and in the majority of cases this is the preferred drug maintenance option. The clinical choice of one antiepileptic drug (AED) over another should be based on firm evidence of efficacy and tolerability as evaluated in comparative monotherapy studies and pharmacokinetics. This paper presents the findings of evidence-based reviews of AED monotherapy in patients newly diagnosed with epilepsy. The main study was conducted in the United Kingdom and investigated the clinical evidence supporting AEDs used as first-line monotherapy. In this paper the general treatment recommendations will focus on valproate, one of the mainstay drugs used in the fight against epilepsy. Finally, with these recommendations in mind, the principles behind AED drug selection in clinical practice will be discussed. Factors for consideration that impact on AED decision-making include: seizure and syndrome diagnosis, AED tolerability profiles, patient characteristics and pharmacokinetic/pharmacodynamic AED interactions.

Search for a common mechanism of mood stabilizers

Manic-depression, or bipolar affective disorder, is a prevalent mental disorder with a global impact. Mood stabilizers have acute and long-term effects and at a minimum are prophylactic for manic or depressive poles without detriment to the other. Lithium has significant effects on mania and depression, but may be augmented or substituted by some antiepileptic drugs. The biochemical basis for mood stabilizer therapies or the molecular origins of bipolar disorder is unknown. One approach to this problem is to seek a common target of all mood stabilizers. Lithium directly inhibits two evolutionarily conserved signal transduction pathways. It both suppresses inositol signaling through depletion of intracellular inositol and inhibits glycogen synthase kinase-3 (GSK-3), a multifunctional protein kinase. A number of GSK-3 substrates are involved in neuronal function and organization, and therefore present plausible targets for therapy. Valproic acid (VPA) is an antiepileptic drug with mood-stabilizing properties. It may indirectly reduce GSK-3 activity, and can up-regulate gene expression through inhibition of histone deacetylase. These effects, however, are not conserved between different cell types. VPA also inhibits inositol signaling through an inositol-depletion mechanism. There is no evidence for GSK-3 inhibition by carbamazepine, a second antiepileptic mood stabilizer. In contrast, this drug alters neuronal morphology through an inositol-depletion mechanism as seen with lithium and VPA. Studies on the enzyme prolyl oligopeptidase and the sodium myo-inositol transporter support an inositol-depletion mechanism for mood stabilizer action. Despite these intriguing observations, it remains unclear how changes in inositol signaling underlie the origins of bipolar disorder.

Anticonvulsant-induced dyskinesia

Anticonvulsant-induced dyskinesia (AID) is an underdiagnosed side effect of many anticonvulsants that may take place during initial or chronic treatment at normal or toxic drug levels. The occurrence of AID subjects the patient to another medical condition and may prompt an extensive work-up. Similarities with other drug-induced dyskinesias and some animal studies suggest that dopaminergic dysfunction in the basal ganglia is pivotal in the occurrence of dyskinesia. Clinical presentation and outcomes are variable; however, in most cases, dyskinesias respond well to anticonvulsant withdrawal. Enhancing the awareness of AID is important in light of the recent development of many new anticonvulsants and their wider clinical use.