Divalproex extended-release versus the original divalproex tablet: results of a randomized, crossover study of well-controlled epileptic patients with primary generalized seizures

Efficacy, Safety, and Retention Rate of Extended-Release Divalproex Versus Conventional Delayed-Release Divalproex: A Meta-Analysis of Controlled Clinical Trials

Purpose: A novel once-daily divalproex-extended release (ER) dose formulation has been developed; this formulation prolongs the therapeutic serum levels of the drug, compared with the twice-daily conventional divalproex-delayed release (DR) formulation. This study aimed to systematically examine and compare the efficacy, safety, and retention rates of the ER divalproex (VPA-ER) and conventional DR divalproex (VPA-DR) formulations.

Methods: Randomized control trials (RCTs) reporting the efficacy, adverse events (AEs), and medication compliance of ER and DR divalproex were searched in online databases, including PubMed, Embase, and Cochrane Library databases, by searching MeSH words and term words. Observational studies with potential biases were excluded. The meta-analysis was performed using Stata 16.0 software.

Findings: Thirteen RCTs, involving 1,028 participants, were included in this meta-analysis. Efficacy, AEs, and drug retention rates were the main study outcomes. According to our study, VPA-ER presented clinically significant benefits compared with the placebo in the population with bipolar disorder (BD) (39.5% versus 27.2%, p < 0.001). A similar efficacy of VPA-ER and VPA-DR in controlling seizures was observed in epilepsy patients (87.4% versus 86.5%, p = 0.769). A significantly lower incidence of AEs was reported in the VPA-ER group than in the placebo group (26.8% versus 34.8%, p = 0.003). By contrast, there was no evidence of difference in safety between VPA-ER and VPA-DR (29.4% versus 30.5%, p = 0.750). In addition, the drug retention rate was significantly lower in the VPA-ER group than in the placebo group (76.0% versus 82.7%, p = 0.020), especially in migraine patients (p = 0.022) and in patients who were treated for fewer than 4 weeks (p = 0.018).

Implications: The efficacy of VPA-ER was significantly superior to that of the placebo treatment, which provided efficacy similar to that of conventional VPA-DR. VPA-ER is well tolerated with a low rate of AEs compared to the placebo. In addition, the acceptable medicine compliance of VPA-ER was conducive to the long-term maintenance treatment of chronic diseases. Although we analyzed open labels and crossover design RCTs, large-scale multicenter studies on the efficacy and medicine compliance of new ER formulations with less AEs are required to validate our conclusion.

Update on Antiepileptic Drugs 2019

PURPOSE OF REVIEW

This article is an update from the article on antiepileptic drug (AED) therapy published in the last Continuum issue on epilepsy and is intended to cover the vast majority of agents currently available to the neurologist in the management of patients with epilepsy. Treatment of epilepsy starts with AED monotherapy. Knowledge of the spectrum of efficacy, clinical pharmacology, and modes of use for individual AEDs is essential for optimal treatment for epilepsy. This article addresses AEDs individually, focusing on key pharmacokinetic characteristics, indications, and modes of use.

RECENT FINDINGS

Since the previous version of this article was published, three new AEDs, brivaracetam, cannabidiol, and stiripentol, have been approved by the US Food and Drug Administration (FDA), and ezogabine was removed from the market because of decreased use as a result of bluish skin pigmentation and concern over potential retinal toxicity.Older AEDs are effective but have tolerability and pharmacokinetic disadvantages. Several newer AEDs have undergone comparative trials demonstrating efficacy equal to and tolerability at least equal to or better than older AEDs as first-line therapy. The list includes lamotrigine, oxcarbazepine, levetiracetam, topiramate, zonisamide, and lacosamide. Pregabalin was found to be less effective than lamotrigine. Lacosamide, pregabalin, and eslicarbazepine have undergone successful trials of conversion to monotherapy. Other newer AEDs with a variety of mechanisms of action are suitable for adjunctive therapy. Most recently, the FDA adopted a policy that a drug's efficacy as adjunctive therapy in adults can be extrapolated to efficacy in monotherapy. In addition, efficacy in adults can be extrapolated for efficacy in children 4 years of age and older. Both extrapolations require data demonstrating that an AED has equivalent pharmacokinetics between its original approved use and its extrapolated use. In addition, the safety of the drug in pediatric patients has to be demonstrated in clinical studies that can be open label. Rational AED combinations should avoid AEDs with unfavorable pharmacokinetic interactions or pharmacodynamic interactions related to mechanism of action.

SUMMARY

Knowledge of AED pharmacokinetics, efficacy, and tolerability profiles facilitates the choice of appropriate AED therapy for patients with epilepsy.

Extended-release drug formulations for the treatment of epilepsy

INTRODUCTION

Extended-release (ER) preparations are either available or have been tested for several antiepileptic drugs (AEDs). Indeed, they may be helpful in improving efficacy, tolerability, adherence, compared to the corresponding immediate release (IR) preparations available. The use of ER preparations has been advocated in women of childbearing age and is - depending on the drug - especially helpful in patients who are treated in combination with enzyme inducing AEDs as well as in children.

AREAS COVERED

Clinical and pharmacokinetic studies on ER formulations of AEDs were identified by a PubMed literature research. Further references were added from the authors' personal knowledge and from the reference lists of the identified studies. Reviews and expert commentaries were included, where necessary.

EXPERT OPINION

Unfortunately, studies providing direct comparisons of ER and IR formulations of a given drug are only available for a handful of drugs. ER preparations are especially helpful in drugs with a short elimination half-life and concentration-depending efficacy and tolerability.

The Diagnosis and Management of Bipolar I and II Disorders: Clinical Practice Update

Bipolar disorders, including bipolar I disorder (BP-I) and bipolar II disorder (BP-II), are common, potentially disabling, and, in some cases, life-threatening conditions. Bipolar disorders are characterized by alternating episodes of mania or hypomania and depression, or mixtures of manic and depressive features. Bipolar disorders present many diagnostic and therapeutic challenges for busy clinicians. Adequate management of bipolar disorders requires pharmacotherapy and psychosocial interventions targeted to the specific phases of illness. Effective treatments are available for each illness phase, but mood episode relapses and incomplete responses to treatment are common, especially for the depressive phase. Mood symptoms, psychosocial functioning, and suicide risk must, therefore, be continually reevaluated, and, when necessary, the plan of care must be adjusted during long-term treatment. Many patients will require additional treatment of comorbid psychiatric and substance use disorders and management of a variety of commonly co-occurring chronic general medical conditions.

Comparative Absorption Profiles of Divalproex Sodium Delayed-Release Versus Extended-Release Tablets—Clinical Implications

Background:

The distinct absorption characteristics of the conventional enteric-coated, delayed-release (DR) and the novel extended-release (ER) divalproex sodium formulations are not well recognized.

Objective:

To quantitatively and qualitatively differentiate the absorption characteristics of divalproex-DR and -ER formulations.

Methods:

Healthy volunteers (N = 28) received single 1000 mg doses of divalproex-DR and divalproex-ER tablets in a crossover fashion. Noncompartmental and compartmental analyses were used to estimate valproic acid (VPA) pharmacokinetics from the plasma concentration–time profiles determined from intensive blood sampling over 48 hours.

Results:

VPA was not absorbed from divalproex-DR in the first 2 hours (absorption lag-time) after dosing. After VPA release in the intestine, approximately 63% of the dose was absorbed in less than 1 hour, that is, 2.9 hours (mean absorption time) from dosing. Maximum concentration (Cmax) was achieved approximately 4 hours after dosing. VPA absorption was complete (~93% of dose) within 3 absorption half-lives (~4.5 h) post-absorption lag-time, that is, 6–7 hours from dosing. In contrast, VPA absorption from divalproex-ER starts immediately after administration, initially at a modest rate, followed by slow and extended absorption at a constant rate for more than 20 hours; VPA concentrations at 1 and 2 hours were 28% and 40% of Cmax. Approximately 53% of the dose was absorbed within 12 hours (mean absorption time); complete absorption occurred over more than 20 hours without any dose dumping.

Conclusions:

When antihypertensive treatment options are clinically equivalent, prescribers may first consider using a verapamil SR–based strategy, especially in patients with CAD who have no history of depression. VPA absorption from enteric-coated divalproex-DR is rapid following a lag-time of approximately 2 hours and is complete within 6–7 hours of dosing. In contrast, VPA absorption from divalproex-ER starts immediately after administration, but occurs at a slow, approximately constant rate over more than 20 hours.

Extended-release formulations of antiepileptic drugs: rationale and comparative value

Extended-release products are designed to prolong the absorption of drugs with short half-lives, thereby allowing longer dosing intervals while minimizing fluctuations in serum drug levels. The relationship between serum drug concentration and clinical effects of antiepileptic drugs (AEDs) can be complex and reducing fluctuations in serum drug levels is not equally advantageous for all AEDs. Extended-release formulations have been shown to be particularly valuable for carbamazepine, whereas for other AEDs advantages, other than prolongation of the dosing interval, have not been clearly demonstrated. Differences in bioavailability may exist between extended-release and immediate-release formulations and among different brands of extended-release products. Therefore, when switching from one formulation to another, careful monitoring of clinical response and attention to the need for dose adjustment are warranted.

Once-daily dosing is appropriate for extended-release divalproex over a wide dose range, but not for enteric-coated, delayed-release divalproex: evidence via computer simulations and implications for epilepsy therapy

Divalproex sodium extended-release (divalproex-ER), administered once-daily, maintains plasma valproic acid (VPA) concentrations for 24h, whereas enteric-coated, delayed-release divalproex sodium (divalproex) requires multiple-daily doses to do the same. We hypothesize that a once-daily divalproex regimen should not be administered to epilepsy patients requiring high total daily doses, e.g., 35.6-56 mg/kg/day, due to the potential for high (>125 mg/L) maximum VPA concentrations (C(max)). We examined the impact of once-daily dosing, divalproex vs. divalproex-ER, on steady-state plasma VPA concentration-time profiles at commonly used doses in monotherapy (uninduced) and polytherapy (hepatic enzyme-induced) virtual adult patients. Only the 1125 mg once-daily divalproex dose had mean C(max)<100mg/L; >or=2000 mg produced mean C(max)>or=125 mg/L. Mean divalproex C(min) was approximately 50 mg/L at two of four doses tested, whereas mean ER C(min) was >73 mg/L at all doses tested. Once-daily divalproex peak-trough fluctuation was 4.4-6.2-fold greater than once-daily divalproex-ER. We predict that excursions beyond the conventional recommended VPA plasma concentration range will commonly occur with high total mg daily doses (>or=2000 mg) of enteric-coated divalproex, if dosed once-daily, potentially producing clinical toxicity. This divalproex formulation should not be dosed once-daily at high total mg daily doses due to this risk. Divalproex-ER is the appropriate formulation for administration on a once-daily basis, especially if large total mg/day doses are required for the control of seizure activity.

Overnight versus progressive conversion of multiple daily-dose divalproex to once-daily divalproex extended release: which strategy is better tolerated by adults with intellectual disabilities?

Divalproex (DVP) delayed release and DVP extended release (DVP ER) are approved by the Food and Drug Administration for bipolar disorder, epilepsy, and migraine prophylaxis. Divalproex ER is given once daily, improving compliance and reducing adverse events. Overnight switch to DVP ER is advised in the package insert but could produce more adverse events in this susceptible population. In this pilot study, we compared tolerability of overnight versus gradual switching to DVP ER in 16 adults with intellectual and developmental disabilities receiving DVP, in 9 for epilepsy and in all 16 for comorbid bipolar disorder. The study design was open with parallel groups. Sixteen subjects with intellectual and developmental disabilities were randomized to overnight or gradual conversion for 4 to 6 days. A blinded rater completed the Multidimensional Observation Scale for Elderly Subjects on days +1, +4, and +8 after the switch began. We found no major differences between the 2 groups at each time point. Neither group of subjects, except for 1 subject in the overnight group, manifested sedation, seizures, worsening of tremor, or gastrointestinal adverse events. One subject in the overnight group manifested acute diarrhea and vomiting, followed by a very brief tonic leg seizure 6 days later. Larger studies are warranted.

Extended-release formulations for the treatment of epilepsy

This review analyses the concept of extended-release (ER) formulations in epilepsy and evaluates ER formulations of carbamazepine, valproic acid and a modified-release (MR) formulation of oxcarbazepine. ER formulations are usually designed to reduce dose frequency and maintain relatively constant or flat plasma drug concentration. It is questionable whether flat plasma concentrations of an antiepileptic drug (AED) improve antiepileptic efficacy compared with fluctuating plasma concentrations. More certainly, they minimise concentration-related adverse effects, and the dosing flexibility and consistency of plasma concentrations may simplify the management of antiepileptic drug therapy. Neurologists would like ER formulations that can be administered once- and/or twice-daily to tailor therapy for the individual patient; however, switching dosage schedules from multiple dosages per day to once daily, although more convenient, will not generally improve therapeutic coverage (maintenance of effective drug concentration in biological fluids and tissue). Pharmacokinetically, the impact of a missed dose is greater the larger the dose and the less frequent the administration. Therefore, the risk of breakthrough seizure is higher during AED once-daily administration than twice-daily administration. Consequently, the increased compliance observed with fewer dosages per day should be weighed against the impact or forgiveness of omitted dose(s) and the shorter 'forgiveness' period associated with once-daily administration. Currently, the trend is to treat patients with epilepsy with ER formulations because of the better compliance, convenience and flat plasma concentration versus time curve. Thus, it seems that the term 'flatter is better' for AED plasma profiles has precipitated in the last 10-15 years among neurologists and epilepsy caregivers, and is being promoted by marketing forces of pharmaceutical companies. Data from the literature support the trend to treat epileptic patients with twice-daily administration of the existing ER formulations of valproic acid and carbamazepine, and oxcarbazepine-MR; however, the author of this article is not convinced that these ER formulations can guarantee a complete therapeutic coverage throughout the 24-hour dosing interval following once-daily administration. Epilepsy is a single-episode disease, and the convenience and possible better compliance associated with once-daily administration must be weighed against the shorter 'forgiveness' period and possible higher risk of breakthrough seizure due to sub-therapeutic plasma levels and/or omitted doses. Data suggest just a small difference in compliance between once- and twice-daily administration, with no significant difference in efficacy. Therefore, the increased compliance following once-daily administration may be counter-productive in minimising the occurrence of sub-therapeutic drug concentrations. Weighing up the advantages and disadvantages for once- versus twice-daily administration of ER formulations in epilepsy leads to a conclusion in favour of twice-daily administration.

Extended-release formulations in epilepsy

In the past years, the extended-release antiepileptic drug formulations have been developed and then approved for the treatment of many types of epilepsy. Among these extended-release formulations of antiepileptic drugs, the main drugs are valproic acid, carbamazepine, and phenytoin. This review analyzes the chemical and structural characteristics of the extended-release formulations of these 3 antiepileptic drugs, analyzing their bioequivalence and the studies about their clinical use. The results of these studies are encouraging and suggest a good tolerability and efficacy of these extended-release formulations, although larger studies are needed.

Progress report on new antiepileptic drugs: a summary of the Eigth Eilat Conference (EILAT VIII)

The Eigth Eilat Conference on New Antiepileptic Drugs (AEDs)-EILAT VII, took place in Sitges, Barcelona from the 10th to 14th September, 2006. Basic scientists, clinical pharmacologists and neurologists from 24 countries attended the conference, whose main themes included a focus on status epilepticus (epidemiology, current and future treatments), evidence-based treatment guidelines and the potential of neurostimulation in refractory epilepsy. Consistent with previous formats of this conference, the central part of the conference was devoted to a review of AEDs in development, as well as updates on marketed AEDs introduced since 1989. This article summarizes the information presented on drugs in development, including brivaracetam, eslicarbazepine acetate (BIA-2-093), fluorofelbamate, ganaxolone, huperzine, lacosamide, retigabine, rufinamide, seletracetam, stiripentol, talampanel, valrocemide, JZP-4, NS1209, PID and RWJ-333369. Updates on felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine and new extended release oxcarbazepine formulations, pregabalin, tiagabine, topiramate, vigabatrin, zonisamide and new extended release valproic acid formulations, and the antiepileptic vagal stimulator device are also presented.

Conventional and sustained-release valproate in children with newly diagnosed epilepsy: a randomized and crossover study comparing clinical effects, patient preference and pharmacokinetics

OBJECTIVE

It has been suggested that sustained-release valproate (VPA) formulations may be more effective and better tolerated than conventional VPA due to better compliance and lower fluctuations in VPA serum concentrations, but comparative trials with conventional VPA in children are scarce. This randomized and crossover trial compared the efficacy (complete control of seizures), the tolerability, and the patient (or parents) preference of conventional VPA twice daily (CVbid) with those of sustained-release chrono VPA twice daily (ChVbid), once daily in the morning (ChVom) or once daily in the evening (ChVoe) in monotherapy.

METHODS

The study was carried out in 48 children (29 girls), aged 5-14 years, with newly diagnosed partial epilepsy (n=26), or idiopathic generalized epilepsy (n=22). The study duration was 16 months (four phases of 4 months each). VPA pharmacokinetics data were also compared in the different regimens. Mean VPA dosage was of approximately 870 mg/day (approximately 22 mg/kg/day) and mean VPA concentration was of approximately 89 mg/l at 12 h post-dose and of 54 mg/l at 24 h post-dose.

RESULTS

By intention in treatment there were no significant differences in efficacy (73%, 83%, 77% and 75%, respectively) or in adverse reaction frequency (56%, 58%, 67% and 46%, respectively). There were significant differences, however, in patient (or parents) preference, the order being ChVoe (31%) > ChVom (25%) > CVbid (17%) > ChVbid (8%). The mean VPA serum concentration fluctuation between 4 h and 0 h post-morning-dose was nonsignificantly lower after CVbid than after ChVbid. Fluctuation was significantly higher after ChVom than after CVbid or ChVbid. The mean VPA serum concentration difference between 12 h and 24 h post-dose was approximately 40 mg/l.

CONCLUSION

Although our results should be confirmed by a larger study, they suggest that the efficacy and tolerability of chrono valproate is similar to that of conventional valproate, and that the main advantage is the once-daily administration.

Does It Really Matter When a Blood Sample for Valproic Acid Concentration is Taken Following Once-Daily Administration of Divalproex-ER?

Divalproex sodium extended-release (divalproex-ER) is a novel formulation intended for once-daily oral administration, either morning or evening. Questions have risen concerning the optimal time for obtaining a blood sample for valproic acid (VPA) concentration in relation to the dose. Trough sampling is easily achieved just before a morning daily dose, but the best time to sample after an evening daily dose is unclear, because collecting a blood sample 21 to 24 hours later may be limited by the operational hours of the laboratory. This investigation provides practical guidance regarding blood sample timing. Steady-state plasma VPA concentration-time profiles from 5 published divalproex-ER studies (healthy subjects and epilepsy patients) were analyzed. The concentration-time profile for each subject/patient was expressed as a percentage of his/her trough concentration and summary statistics computed. Typically, when taking divalproex-ER once daily in the morning, a blood sample collected 21 to 24 hours later is expected to have a concentration within 3% of the trough value. Conversely, for divalproex-ER dosed once-daily in the evening, for example 8 PM, a blood draw 12 to 15 hours later (ie, 8 to 11 AM) will give a plasma VPA concentration value that is 18% to 25% higher, on average, than the trough value. However, waiting longer, (for example 18 to 21 hours, ie 2 to 5 PM) will result in concentration values that are merely 3% to 13% higher than trough values, which may provide acceptable information for monitoring purposes. The greatest deviation from trough VPA concentration occurs around the peak, that is 3 to 15 hours after a once-daily divalproex-ER dose; sampling during this time period is recommended only if a clinical need exists to test for a higher VPA concentration. Despite the apparent smoothness of the VPA concentration-time profile after a once-daily divalproex-ER dose, the timing of the blood sample does matter and impacts the proper interpretation of the VPA concentration.

Conversion from delayed-release sodium valproate to extended-release sodium valproate: initial results and long-term follow-up

OBJECTIVE

The goal of our study was to evaluate clinical and serum valproic acid concentration changes in patients following overnight conversion from delayed-release sodium valproate (VPA-DR) to the same daily dosage of extended-release sodium valproate (VPA-ER).

METHODS

Epilepsy patients on VPA-DR were offered the chance to convert to VPA-ER. Thirty patients were converted to twice-daily dosing and 11 were converted to once-daily dosing. Trough levels of valproic acid were measured prior to the change and 2 weeks after conversion. Short-term and long-term clinical data were evaluated.

RESULTS

Patients successfully converted from VPA DR to VPA-ER. No significant difference in percentage change in serum trough valproic acid level was observed when comparing dosing frequency of VPA-DR, total daily dosage of VPA, conversion to once-daily versus twice-daily VPA-ER, or presence of enzyme-inducing agents. Mean seizure count per month prior to conversion was 3.35 versus 3.29 following conversion. Improvements in tremor, weight gain, and nausea/vomiting were noted.

CONCLUSIONS

Overnight conversion to VPA-ER was well tolerated by all patients. Long-term results were favorable, with 77.5% of patients remaining on drug. Seizure counts and adverse events remained the same or were improved in both short-term and long-term evaluations. Dosing of VPA-ER either once-daily or twice-daily is acceptable.

Every-12-hour administration of extended-release divalproex in patients with epilepsy: impact on plasma valproic acid concentrations

Extended-release divalproex sodium (divalproex-ER) biopharmaceutics after every-12-hour (q12h) administration was compared with that of once-daily divalproex-ER and conventional divalproex given every 6 hours (q6h) in a multiple-dose (14-day), randomized, three-period crossover design study in 24 patients with epilepsy concomitantly receiving enzyme-inducing antiepileptic medication(s). Plasma valproic acid (VPA) minimum concentration (Cmin) for divalproex-ER q12h was higher than the once-daily divalproex-ER Cmin (P=0.043). Once-daily divalproex-ER Cmin values were not different from those for divalproex q6h, suggesting that adequate trough steady-state concentrations are maintained with once daily dosing, despite enzyme-inducing comedication. The degree of peak-trough fluctuation (DFL, calculated as (Cmax-Cmin)/Cavg) in VPA concentration was less with both q12h (35.2% less) and once-daily (16.9% less) divalproex-ER regimens compared with q6h divalproex (P0.024). The DFL for divalproex-ER dosed as a q12h regimen was 22% less than that for once-daily divalproex-ER (P=0.02). The DFL in VPA concentration with divalproex-ER can be minimized with once-daily administration and more so with q12h administration, compared with conventional enteric-coated divalproex taken q6h.

Successful Initiation of Combined Therapy with Valproate Sodium Injection and Divalproex Sodium Extended-release Tablets in the Epilepsy Monitoring Unit

PURPOSE

Patients in epilepsy monitoring units (EMUs) often require aggressive initiation or reinitiation of therapy before discharge. We developed a simple dosing scheme using valproate sodium injection (VPA-IV) and divalproex sodium extended-release (VPA-ER) tablets to minimize the time required for initiation of therapy, without increasing the likelihood of seizures and adverse effects.

METHODS

We identified 42 patients in the EMU, naïve to VPA-IV and VPA-ER, for whom one of the discharge AEDs included divalproex sodium. On the day of discharge, patients were loaded with 20 mg/kg VPA-IV at 6 mg/kg/min, followed by approximately 20 mg/kg VPA-ER within 1 h. The discharge daily dose of VPA-ER was identical to the dose given after the IV load. We assessed tolerability and seizure occurrence during infusion, at 1 h, 4 h, and 1 week after discharge.

RESULTS

All patients tolerated the VPA-IV dose followed by VPA-ER. Four patients reported mild nausea, and two patients reported mild dizziness within 4 h. No seizures or significant changes in heart rate or blood pressure occurred within 4 h, and all patients were discharged the same day. All patients denied systemic complaints at 1 week, and five had seizures during the week after discharge. All patients had improved seizure frequencies at the end of the first week.

CONCLUSIONS

VPA-IV is well tolerated and convenient for rapid loading in the EMU. When promptly followed by VPA-ER, seizure control remains excellent.

Rapid oral loading of extended release divalproex in patients with acute mania

BACKGROUND

Oral loading with the delayed release formulation of divalproex sodium is widely used for the treatment of patients with acute mania and produces rapid attainment of therapeutic serum levels. Recently, an extended release formulation of divalproex sodium (divalproex ER) was approved for treatment of migraine headaches. This formulation may be a useful treatment option for patients with acute mania.

METHOD

A retrospective review of medical records was conducted on 14 inpatients with acute mania whose treatment included initiation of divalproex ER at a dose of 30 mg kg(-1) day(-1) in a single dose. Doses, serum levels and side effects associated with this treatment were recorded from the medical records of these patients.

RESULTS

The average dose of divalproex ER was 2034 mg day(-1) (range, 1500-3000 mg day(-1)). Two of the 14 patients (14%) had documented side effects, none of which were severe. The average level obtained on day 3 after initiation of divalproex ER treatment was 93.2 mug ml(-1) (range, 47-136 mug ml(-1)), and in all but three patients valproate levels at this time point were within the therapeutic range of 50-125 mug ml(-1). In no case was divalproex ER discontinued due to a perceived lack of efficacy.

CONCLUSION

The results suggest that divalproex ER can be safely administered by oral loading in inpatients with acute mania and that using a standard loading protocol can result in therapeutic serum levels in most patients in 3 days or less.

Extended-release Divalproex in Child and Adolescent Outpatients with Epilepsy

PURPOSE

To determine whether valproic acid [divalproex (DVP)] extended-release, administered at a higher proportionate once-daily dosage, can be safely substituted for delayed-release or sprinkle in pediatric patients with epilepsy.

METHODS

Patients between ages 6 and 17 years with stable epilepsy taking DVP were randomized to 7 days of either DVP delayed-release/sprinkle (at the usual daily dose taken before study entry) or extended-release DVP (daily dose, 8% to 25% higher than their usual dose), and then (crossed over to) 7 days of the comparator formulation. Patient's clinical status was evaluated at a screening visit and on days 8 and 15, and with telephone follow-up 1 month after study completion.

RESULTS

No statistically significant difference in mean plasma VPA levels measured at the end of treatment was observed: 99, 92, and 103 mug/ml with the delayed-release tablets (n = 4), the sprinkle formulation (n = 11), and the extended-release tablets (n = 16), respectively. Seizure-control rates were stable during patients' use of the extended-release formulation. None of the study patients experienced a treatment-related adverse event.

CONCLUSIONS

The total daily dose for patients taking the delayed-formulation may need to be increased by < or = 20% when they are switched to the extended-release formulation. When switching from sprinkles to the extended-release formulation, individual variability must be considered. In patients who have VPA levels near the very high end of the therapeutic range (>100 microg/ml), it may be more prudent to make only minor modifications to the total daily dose during conversion and then to individualize the DVP extended-release dose based on plasma levels.

Clinical comparison of extended-release divalproex versus delayed-release divalproex: pooled data analyses from nine trials

Divalproex sodium is an effective anticonvulsant, antimanic, and migraine prophylaxis agent. Recently, a new extended-release (ER) formulation of divalproex sodium has become available, which allows for once-daily dosing and provides prolonged therapeutic serum levels. Using data pooled from nine open-label trials involving 321 epilepsy and psychiatry patients, we compared the efficacy and tolerability of divalproex ER with preceding treatment with the older delayed-release (DR) formulation, based on patient reports and analysis by McNemar's test for within-subject paired data. Divalproex ER was associated with superior tolerability with less frequent tremor, weight gain, and gastrointestinal complaints (all P<0.001), but not less hair loss. Divalproex ER also yielded improved seizure control and greater improvement of psychiatric symptoms, and was greatly preferred by patients over divalproex DR. Although the results of the current analyses must be considered highly tentative due to the open-label nature of the trials included, the findings do suggest broad clinical superiority of the new ER preparation.

Progress report on new antiepileptic drugs: a summary of the Seventh Eilat Conference (EILAT VII)

The Seventh Eilat Conference on New Antiepileptic Drugs (AEDs) (EILAT VII) took place in Villasimius, Sardinia, Italy from the 9th to 13th May 2004. Basic scientists, clinical pharmacologists and neurologists from 24 countries attended the conference,whose main themes included advances in pathophysiology of drug resistance, new AEDs in pediatric epilepsy syndromes, modes of AED action and spectrum of adverse effects and a re-appraisal of comparative responses to AED combinations. Consistent with previous formats of this conference, the central part of the conference was devoted to a review of AEDs in development, as well as updates on second-generation AEDs. This article summarizes the information presented on drugs in development, including atipamezole, BIA-2-093, fluorofelbamate, NPS 1776, pregabalin, retigabine, safinamide, SPM 927, stiripentol, talampanel,ucb 34714 and valrocemide (TV 1901). Updates on felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, tiagabine,topiramate, vigabatrin, zonisamide, new oral and parenteral formulations of valproic acid and SPM 927 and the antiepileptic vagal stimulator device are also presented.

Single unprovoked seizures

Unprovoked seizures are common, affecting approximately 4% of the population by age 80. Only approximately 30% to 40% of patients with a first seizure will have a second unprovoked seizure (ie, epilepsy). Treatment with antiepileptic drugs (AEDs) should not be initiated unless the diagnosis of a seizure is firm. Decisions regarding treatment of single unprovoked seizures must balance seizure recurrence risk, the potential impact of a recurrent seizure, the likelihood of adverse effects of treatment, and patient preference. Risk factors for seizure recurrence include a history of remote neurologic insult, epileptiform abnormalities on electroencephalogram, focal structural lesion on neuroimaging, and family history of epilepsy. Adult patients with these risk factors have a recurrence risk of 60% to 70% and usually should be treated with an AED to prevent seizure recurrence. Without risk factors, the recurrence risk is 20% to 30%, and treatment depends on individual risk-to-benefit ratios and patient preference. Treatment of a first unprovoked seizure is often not necessary in childhood, especially if the seizure is part of a benign self-limited syndrome, such as benign Rolandic epilepsy of childhood. Treatment with an AED reduces the risk of seizure recurrence after a single unprovoked seizure. This must be balanced against the risk of adverse effects of AEDs. Treatment of the first seizure does not appear to affect the long-term prognosis of epilepsy. The choice of an AED should be guided by the seizure type and likely epilepsy syndrome diagnosis. Monotherapy is preferable. Standard AED options include phenytoin, carbamazepine, valproate, and phenobarbital. The newer AED, including gabapentin, lamotrigine, topiramate, oxcarbazepine, levetiracetam, and zonisamide, have good efficacy, favorable pharmacokinetic profiles, and often fewer adverse effects, supporting their use early in treatment. Not all of the newer AEDs are approved for use as monotherapy. Patients with single seizures should be counseled about seizure first aid and general safety measures, including precautions regarding swimming alone, engaging in high-risk activities, driving, possible seizure precipitation by photic stimuli (in generalized epilepsy), sleep deprivation, and alcohol.

A study of the safety, efficacy, and tolerability of switching from the standard delayed release preparation of divalproex sodium to the extended release formulation in patients with schizophrenia

OBJECTIVE

To assess the safety, efficacy, and tolerability of switching from a multiple dose preparation of divalproex sodium delayed release (DR) to once-daily dosing with divalproex sodium extended release (ER) in patients with schizophrenia already receiving the standard DR formulation.

METHOD

Thirty subjects with schizophrenia were switched from divalproex DR to a 4-week open-label treatment trial of the ER formulation. Baseline plasma levels of valproate were obtained 12 hours postdose. Patients were converted from divalproex DR to ER on a 1.0:1.0 mg basis (rounded up to the nearest 500-mg increment) if baseline valproate plasma levels were > or =85 microg/mL; otherwise, the conversion rate was 1.0:1.2 mg rounded up. Measured at baseline and end point were the Brief Psychiatric Rating Scale and the Udvalg for Kliniske Undersogelser Side Effect Rating Scale. End point plasma levels were obtained at both 12 and 24 hours postdose.

RESULTS

Patients who switched from divalproex DR to ER had a small (and probably clinically insignificant) improvement noted on the total Brief Psychiatric Rating Scale at end point (mean change +/- SD = -2.3 +/- 5.4; t = -2.2538; df = 28; P = 0.0322) and on the Udvalg for Kliniske Undersogelser (mean change+/- SD = -2.2+/- 4.1; t = -2.7361; df = 26; P = 0.0111). Baseline and end point trough plasma levels were 80.1 +/- 20.4 and 73.1 +/- 24.2 microg/mL, respectively. Patients who converted on a 1.0:1.0 mg basis had lower end point valproate trough plasma levels than at baseline but did not experience deterioration on their psychopathology. For all patients, end point valproate peak and trough plasma levels were statistically significantly different (t = -3.8706; df = 27; P = 0.0006), but these differences were small in magnitude (mean +/- SD = 14.6 +/-19.6 microg/mL). Seven patients experienced spontaneously reported adverse events, but none required early termination from the protocol.

CONCLUSIONS

Switching to a once-daily formulation of ER divalproex can be accomplished without a deterioration in psychopathology. The ER formulation of divalproex sodium appears well tolerated. A parallel group design will be necessary to confirm these findings.

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.

Progress report on new antiepileptic drugs: a summary of the Sixth Eilat Conference (EILAT VI)

The Sixth Eilat Conference on New Antiepileptic Drugs (AEDs) took place in Taormina, Sicily, Italy from 7th to 11th April, 2002. Basic scientists, clinical pharmacologists and neurologists from 27 countries attended the conference, whose main themes included dose-response relationships with conventional and recent AEDs, teratogenic effects of conventional and recent AEDs, update on clinical implications of AED metabolism, prevention of epileptogesis, and seizure aggravation by AEDs. According to tradition, the central part of the conference was devoted to a review of AEDs in development, as well to updates on AEDs, which have been marketed in recent years. This article summarizes the information presented on drugs in preclinical and clinical development, including carabersat (SB-204269), CGX-1007 (Conantokin-G), pregabalin, retigabine (D-23129), safinamide, SPD421 (DP-VPA), SPM 927, talampanel and valrocemide (TV 1901). Updates on fosphenytoin, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, tiagabine, topiramate, vigabatrin, zonisamide, new formulations of valproic acid, and the antiepileptic vagal stimulator device are also presented.