Cross-reactive skin eruption with both carbamazepine and oxcarbazepine

Successful Treatment of a Paroxysmal Kinesigenic Dyskinesia Patient with Carbamazepine-Induced Stevens-Johnson Syndrome Using Oxcarbazepine Monotherapy: A Case Report

Paroxysmal kinesigenic dyskinesia (PKD) is a rare condition characterized by abnormal involuntary movements that are precipitated by a sudden movement. PKD is often misdiagnosed with psychogenic movement disorders. Carbamazepine is usually the first choice of medication due to its well-established evidence but could induce Stevens-Johnson syndrome. We report a 21-year-old male patient with PKD referred to our movement disorders clinic after being misdiagnosed with conversion syndrome. PRRT2 gene testing using next-generation sequencing revealed a mutation in c.649dupC p. (Arg217fs). The patient responded well to carbamazepine but had to withdraw the treatment due to carbamazepine-induced Stevens-Johnson syndrome after 3 weeks of medication. Our patient did not respond to trials of levetiracetam and phenytoin but finally responded well to oxcarbazepine. The patient was followed up for 4 years, during which he had no attacks and no side effects. Here, we present a PKD case with carbamazepine-induced Stevens-Johnson syndrome successfully treated with oxcarbazepine despite the risk of cross-reactive skin eruption between these antiepileptics. Careful history taking and examining patient's attacks are crucial to accurate diagnosis and treatment in PKD patients.

Pharmacokinetics and Drug Interaction of Antiepileptic Drugs in Children and Adolescents

Selecting the most appropriate antiepileptic drug (AED) or combination of drugs for each patient and identifying the most suitable therapeutic regimen for their needs is increasingly challenging, especially among pediatric populations. In fact, the pharmacokinetics of several drugs vary widely in children with epilepsy because of age-related factors, which can influence the absorption, distribution, metabolism, and elimination of the pharmacological agent. In addition, individual factors, such as seizure type, associated comorbidities, individual pharmacokinetics, and potential drug interactions, may contribute to large fluctuations in serum drug concentrations and, therefore, clinical response. Therapeutic drug concentration monitoring (TDM) is an essential tool to deal with this complexity, enabling the definition of individual therapeutic concentrations and adaptive control of dosing to minimize drug interactions and prevent loss of efficacy or toxicity. Moreover, pharmacokinetic/pharmacodynamic modelling integrated with dashboard systems have recently been tested in antiepileptic therapy, although more clinical trials are required to support their use in clinical practice. We review the mechanism of action, pharmacokinetics, drug-drug interactions, and safety/tolerability profiles of the main AEDs currently used in children and adolescents, paying particular regard to issues of relevance when treating this patient population. Indications for TDM are provided for each AED as useful support to the clinical management of pediatric patients with epilepsy by optimizing pharmacological therapy.

Human leukocyte antigen genotypes and trial of desensitization in patients with oxcarbazepine-induced skin rash: a pilot study

BACKGROUND

Skin rash associated with specific antiepileptic drugs occurs not infrequently and it usually necessitates discontinuation of the causative drugs. An alternative strategy is to desensitize the individual to the offending drug. We checked the human leukocyte antigen genotypes and conducted a pilot study to investigate the usefulness and safety of desensitization in pediatric patients with skin rash associated with oxcarbazepine.

METHODS

We enrolled 19 patients with epilepsy who had discontinued oxcarbazepine because of skin rash despite an initial good response and then became refractory to other antiepileptic drugs along with an individual with paroxysmal kinesigenic dyskinesia with a similar situation. High-resolution HLA-A and -B genotyping was performed to investigate the genetic risk. The desensitization began with 0.1 mg daily reaching 120 mg on the thirty-first day. Thereafter, the dose was increased at a rate of 12 mg/day.

RESULTS

Nineteen patients completed the desensitization protocol to a target dosage over 2-5 months. Five patients developed itching and erythema during desensitization, but the symptoms disappeared after withholding a dose increment transiently. There were no human leukocyte antigen genotypes relevant to aromatic antiepileptic drug-induced severe hypersensitivity reactions. The seizure frequency was reduced to less than at baseline in 18 individuals.

CONCLUSION

This study demonstrated 95% efficacy, including 42% seizure-free patients and the favorable tolerability of desensitization to oxcarbazepine in patients with intractable epilepsy and one patient with paroxysmal kinesigenic dyskinesia. Screening for sensitive human leukocyte antigen types and exclusion of severe hypersensitivity reactions should precede desensitization.

Psychiatric medications: adverse cutaneous drug reactions

Psychiatric medications are among the most widely prescribed medications in the United States. Adverse cutaneous drug reactions are associated with psychiatric medications in approximately 2% to 5% of the individuals for whom they are prescribed. Although most adverse cutaneous drug reactions associated with psychotropic medications are benign and easily treated, some can be disfiguring or life-threatening, particularly those associated with the mood stabilizers. Adverse cutaneous drug reactions associated with antidepressants, antipsychotics, and mood stabilizers are reviewed, and important issues that are of concern for the dermatologist who must consider when and how to safely discontinue a psychotropic medication in their patients are presented.

Carbamazepine, HLA-B*1502 and risk of Stevens-Johnson syndrome and toxic epidermal necrolysis: US FDA recommendations

Recently, the USA FDA has made a labeling change to the drug information contained in carbamazepine. Owing to recent data implicating the HLA allele B*1502 as a marker for carbamazepine-induced Stevens-Johnson syndrome and toxic epidermal necrolysis in Han Chinese, the FDA recommends genotyping all Asians for the allele. This allele is seen in high frequency in many Asian populations other than Han Chinese, but there are few data on whether the allele is a marker for this severe outcome in anyone other than Han Chinese. In fact, the association has not been found in Caucasian patients. We review the data that prompted this recommendation, list data for other ethnic groups, both Asian and non-Asian, and briefly discuss the implication of this recommendation for clinical practice.

Anticonvulsant hypersensitivity syndrome: Identification and management

Anticonvulsant hypersensitivity syndrome is a rare and potentially life-threatening delayed-type immune reaction with few proven treatments beyond early recognition and immediate discontinuation of the causative drug. Intravenous immunoglobulin has been shown in some uncontrolled studies to hasten recovery and may prove safer than systemic corticosteroid therapy, which carries a significant risk for increased mortality from sepsis. Identification and counseling of at-risk patients through knowledge of potential drug cross-sensitivity and familial susceptibility may help prevent this dangerous idiosyncratic drug reaction.

Oxcarbazepine in the treatment of bipolar disorder: a review

OBJECTIVE

To review the data on the efficacy of oxcarbazepine (OXC) in bipolar disorder (BD) and to provide recommendations for clinicians on the use of this medication in treating BD.

METHOD

Using the terms oxcarbazepine and bipolar disorder, oxcarbazepine and mania, or oxcarbazepine and bipolar depression, we conducted a computer-aided search of MEDLINE for the years 1950 to 2005.

RESULTS

Case reports, retrospective chart reviews, open prospective studies, and double-blind studies reported the efficacy and effectiveness of OXC in treating BD. The data indicate that OXC has efficacy in treating acute mania and may be a useful add-on in treating acute bipolar depression and in BD prophylaxis. OXC is generally well-tolerated.

CONCLUSION

We recommend using OXC as monotherapy or as add-on therapy in refractory mania, but we recommend it be used predominantly as an add-on treatment for other phases of BD in patients who have not improved with well-established treatments or in patients who have difficulty tolerating adequate dosages.

Chronic neuropathic pain. Mechanisms, diagnosis, and treatment

BACKGROUND

The management of chronic pain represents a significant public health issue in the United States. It is both costly to our health care system and devastating to the patient's quality of life. The need to improve pain outcomes is reflected by the congressional declaration of the present decade as the "Decade of Pain Control and Research," and the acknowledgment in January 2001 of pain as the "fifth vital sign" by the Joint Commission of Healthcare Organizations.

REVIEW SUMMARY

At present, therapeutic options are largely limited to drugs approved for other conditions, including anticonvulsants, antidepressants, antiarrhythmics, and opioids. However, treatment based on the underlying disease state (eg, postherpetic neuralgia, diabetic neuropathy) may be less than optimal, in that 2 patients with the same neuropathic pain syndrome may have different symptomatology and thus respond differently to the same treatment. Increases in our understanding of the function of the neurologic system over the last few years have led to new insights into the mechanisms underlying pain symptoms, especially chronic and neuropathic pain.

CONCLUSIONS

The rapidly evolving symptom- and mechanism-based approach to the treatment of neuropathic pain holds promise for improving the quality of life of our patients with neuropathic pain.

Oxcarbazepine: current status and clinical applications

Oxcarbazepine (OXC) was introduced in 1990 and is now registered in 54 countries worldwide as monotherapy, as add-on treatment for partial seizures, with or without secondarily generalised seizures, and primary generalised tonic-clonic seizures. OXC and its active metabolite, monohydroxy derivative (MHD), block voltage-dependent sodium channels and may effect potassium and calcium channels. In animal models of epilepsy, OXC and MHD have efficacy similar to that of CBZ. There is no evidence for clinically important teratogenicity, mutagenicity or carcinogenicity. OXC has no effect on serum concentrations of hepatically metabolised anti-epileptic drugs (AEDs) and no clinically important interactions with common non-AEDs, other than hormonal contraceptives. MHD has low protein binding and linear pharmacokinetics. Adverse effects (AEs) are usually related to the central nervous system. Approximately three-quarters of patients who experience adverse effects with CBZ improve when switched to OXC, without loss of seizure control. The incidence of rash appears to be less than that expected with CBZ. While hyponatraemia may occur more often with OXC than with CBZ, it is rarely symptomatic. OXC is an effective and safe drug for the treatment of partial-onset and primary generalised tonic-clonic seizures. Placebo- and low-dose controlled double-blind monotherapy studies prove that OXC has anticonvulsant activity and that therapeutic dosages may be obtained with a 24 h titration in hospitalised patients, if necessary. Comparative double-blind trials show that OXC has similar efficacy to VPA, CBZ and PHT, but has advantages compared to those agents in terms of pharmacokinetics, side-effects and tolerability.

What is the evidence that oxcarbazepine and carbamazepine are distinctly different antiepileptic drugs?

Oxcarbazepine (OXC, Trileptal) is a modern antiepileptic drug (AED) used as both monotherapy and adjunctive therapy for the treatment of partial seizures with or without secondary generalization in adults and children above 4 years (USA) or 6 years (Europe) of age. Although OXC has been developed through structural variation of carbamazepine (CBZ) with the intent to avoid metabolites causing side effects, significant differences have emerged between the two drugs. The mechanism of action of OXC involves mainly blockade of sodium currents but differs from CBZ by modulating different types of calcium channels. In contrast to CBZ, which is oxidized by the cytochrome P-450 system, OXC undergoes reductive metabolism at its keto moiety to form the monohydroxy derivative (MHD), which is glucuronidated and excreted in the urine. The involvement of the hepatic cytochrome P-450-dependent enzymes in the metabolism of OXC is minimal. Although it does not prevent interaction with oral contraceptives, it explains why OXC can be more effectively combined with other AEDs such as valproate compared with CBZ. Switching from CBZ to OXC normalized CBZ-associated thyroid and sexual hormone abnormalities and pathological lipid values in small patient samples. OXC is often better tolerated than CBZ and causes fewer rashes than CBZ. Add-on or substitution treatment with OXC was effective in controlled trials even when CBZ did not achieve sufficient seizure control. This constitutes compelling clinical evidence that OXC and CBZ are distinctly different medications. From postmarketing experience in over 1,000,000 patient years, OXC had an advantageous risk-benefit balance also in comparison to other new AEDs. OXC should be preferred over CBZ and other older AEDs because of its proven efficacy and excellent side effect profile in children, adolescents, and adults with partial seizures.

Oxcarbazépine et syndrome DRESS : un cas pédiatrique révélé par une hépatite fulminante

Drug rash with eosinophilia and systemic symptoms (DRESS) syndrome, also called hypersensitivity reaction, is a severe idiosyncratic reaction to drugs, especially to anti-epileptic drugs. Clinical features associate cutaneous eruption, fever, multiple peripheral ganglions, and potentially life-threatening damage of one or more organs. DRESS syndrome is well described in adults treated with aromatic anti-epileptic drugs, such as phenytoin, phenobarbital, and carbamazepine, but also with other drugs. The new anti-epileptic drugs, such as oxcarbazepine also induce various cutaneous eruptions, but with less report of DRESS syndrome. In children, DRESS syndrome is rare and probably underdiagnosed. We report on the case of a 11-year-old girl hospitalised with an acute severe hepatitis revealing an oxcarbazepine-induced DRESS syndrome.

Treating epilepsy in the elderly: safety considerations

The incidence of epilepsy increases with advancing age. Epilepsy in the elderly has different aetiologies from that in younger populations, cerebrovascular disease being the most common condition associated with seizures. Partial seizures are the predominant seizure type in older patients. A diagnosis of epilepsy in the elderly is based mainly on the history and is frequently delayed. In addition, seizure imitators are especially frequent. In many cases ancillary tests for diagnosis may show normal age-related variants, sometimes making results difficult to interpret. Treating epilepsy in the elderly is problematic due to a number of issues that relate to age and comorbidity. The physical changes associated with increasing age frequently lead to changes in the pharmacokinetics of many anticonvulsants. The treatment of epilepsy in the elderly is also complicated by the existence of other diseases that might affect the metabolism or excretion of anticonvulsants and the presence of concomitant medications that might interact with them. Moreover, specific trials of anticonvulsants in the aged population are scarce. General guidelines for treatment include starting at lower doses, slowing the titration schedule, individualising the choice of anticonvulsant to the characteristics of the patient, avoiding anticonvulsants with important cognitive or sedative adverse effects, and where possible, treating with monotherapy.

Oxcarbazepine

Oxcarbazepine is one of the recently introduced anti-epileptic drugs (AEDs) in the US. This drug has demonstrated efficacy as adjunctive therapy in adults and children, and as monotherapy in adults for the treatment of seizures of partial onset. There is also convincing evidence of its efficacy in patients with newly diagnosed and refractory trigeminal neuralgia. In addition, the initial efficacy results of oxcarbazepine in other neuropathic pain conditions and in bipolar disorders are encouraging. In this review, recommendations on the optimal clinical use of oxcarbazepine are given based on its pharmacokinetic profile, efficacy and tolerability in those various conditions.

Efficacy, pharmacology, and adverse effects of antiepileptic drugs

This article discusses the factors involved in the appropriate selection of anticonvulsant medications. The clinical use of commonly used traditional antiepileptic drugs and the newly marketed antiepileptic drugs is discussed. This includes the specific indications for use, adverse effects, and dosing of each drug. Drug interactions, mechanisms of action, and pharmacological properties of each drug is also reviewed.

Induction of hypersensitivity to a previously tolerated antiepileptic drug by a second antiepileptic drug

PURPOSE

To describe the induction of hypersensitivity to one antiepileptic drug (AED) by a second AED.

METHODS

Case report and review of the relevant literature.

RESULTS

A patient is reported who was treated with phenytoin (PHT) for 6 months without adverse effect, but developed a hypersensitivity reaction with rash, fever, elevated liver enzymes, lymphadenopathy, and colitis 6 weeks after the introduction of carbamazepine (CBZ). PHT and CBZ were discontinued. Seizures continued despite treatment with valproic acid and clobazam. A decision was made to cautiously reintroduce PHT. Diffuse skin rash and pharyngitis appeared after two doses of PHT.

CONCLUSIONS

The AED hypersensitivity syndrome has been thought to occur as a consequence of preexisting pharmacogenetic and immunologic abnormalities. Our case demonstrates induction of hypersensitivity to an AED that had been formerly well tolerated, after a hypersensitivity reaction to another AED. This is distinct from simple cross-reactivity between one or more drugs. Such induction of hypersensitivity with AEDs has not been previously described.

Oxcarbazepine for Treatment of Partial Epilepsy: A Review and Recommendations for Clinical Use

Recent trials and extensive postmarketing use confirm the efficacy and safety of oxcarbazepine (OXC) as a first-line treatment for adults and children with simple partial seizures, complex partial seizures, and partial seizures evolving to secondarily generalized seizures. OXC undergoes reductive metabolism at its keto moiety to form 10-hydroxy-10,11-dihydro-10-oxo-5H-dibenz[b,f]azepine-5-carboxamide (MHD), which is glucuronidated and excreted in the urine, with minimal involvement of the hepatic cytochrome P450-dependent enzymes. OXC has some drug interactions, and does not require titration, allowing for better tolerability. Titration for monotherapy and adjunctive therapy of OXC could begin at 150 mg/day and be increased by 150 mg every 2-3 days until the target dose of 900-1200 mg/day is reached. If necessary, one can go faster and start with up to 600 mg/day and titrate with weekly increments up to 600 mg/day if necessary for seizure control. Conversion to monotherapy can be done overnight or gradually. For gradual conversion, use the recommended titration of OXC and withdraw the baseline antiepileptic drugs gradually by 25%, starting at Day 14 or earlier in case of baseline tolerability issues. Consider reducing the dose of the primary antiepileptic drug during adjunctive therapy in case of adverse events or increase the dose of OXC in case of incomplete seizure control. In children OXC should be started at 8-10 mg/kg/day in two or three divided doses. If clinically indicated the dose can then be increased by 10 mg/kg/day in weekly intervals with final doses up to 30-46 mg/kg/day. Dose adjustment may be necessary in very young children (age 2-5 years) and in patients with renal dysfunction, based on renal clearance. However no adjustment of OXC dose is needed in patients with mild to moderate hepatic dysfunction. OXC has a number of advantages which include rapid titration, no need for safety monitoring (except for uncommon and mostly asymptomatic hyponatremia), a low potential for drug-drug interactions (except for those possibly impairing the effectiveness of oral contraceptives and increasing the serum concentration of phenytoin), a rash rate of less than 5%, similar efficacy and similar or better tolerability and safety compared with first-generation antiepileptic drugs. OXC is a valuable alternative to current treatment options.

Adverse reactions to new anticonvulsant drugs

A lack of systematic pharmacoepidemiological studies investigating adverse drug reactions (ADRs) to anticonvulsants makes it difficult to assess accurately the incidence of anticonvulsant-related ADRs. Most of the available information in this regard stems from clinical trial experience, case reports and postmarketing surveillance, sources that are not, by any means, structured to provide precise data on adverse event epidemiology. For various ethical, statistical and logistical reasons, the organisation of structured clinical trials that are likely to provide substantial data on ADRs is extremely difficult. This review concentrates on current literature concerning serious and life-threatening ADRs. As with the older anticonvulsants, the majority of ADRs to newer anticonvulsants are CNS-related, although there are several that are apparently unique to some of these new drugs. Gabapentin has been reported to cause aggravation of seizures, movement disorders and psychiatric disturbances. Felbamate should only be prescribed under close medical supervision because of aplastic anaemia and hepatotoxicity. Lamotrigine causes hypersensitivity reactions that range from simple morbilliform rashes to multi-organ failure. Psychiatric ADRs and deterioration of seizure control have also been reported with lamotrigine treatment. Oxcarbazepine has a safety profile similar to that of carbamazepine. Hyponatraemia associated with oxcarbazepine is also a problem; however, it is less likely to cause rash than carbamazepine. Nonconvulsive status epilepticus has been reported frequently with tiagabine, although there are insufficient data at present to identify risk factors for this ADR. Topiramate frequently causes cognitive ADRs and, in addition, also appears to cause word-finding difficulties, renal calculi and bodyweight loss. Vigabatrin has been reported to cause seizure aggravation, especially in myoclonic seizures. There have been rare reports of other neurological ADRs to vigabatrin, such as encephalopathy, aphasia and motor disturbances. Vigabatrin-induced visual field constriction is the latest and most worrying ADR. Many questions regarding the nature of this potentially serious ADR remain unanswered, as no prospective controlled study examining the phenomenon has been published. Rare cases of behavioural ADRs and IgA and IgG2 deficiency associated with the use of zonisamide have been reported. However, relatively few patients so far have been exposed to this drug, and therefore more postmarketing information is required. The relatively late establishment of aplastic anaemia and hepatic failure as potentially fatal ADRs of felbamate, and of visual field constriction with vigabatrin, should serve as ample reminders that ADRs can appear at any time.

Costs of drug treatment in Parkinson's disease

Parkinson's disease (PD) has a major socioeconomic impact on society. The chronic, progressive course of the disease, which often leads to severe disability, results in high expenses for the medical resources used for treatment, care, and rehabilitation of patients as well as reduced or lost productivity as a result of illness or premature death. In Great Britain, it has been estimated that the National Health Service spends up to 383 million pound sterling (1992) annually for the care of PD. This emphasizes the importance of assessing the costs related to this disease. A detailed knowledge of the cost allocation would provide a solid basis on which health care priorities can be rationally set. Next to hospitalization, drug treatment accounts for the highest expense for direct medical costs of PD. Therefore, this analysis focuses on the costs of drug treatment for PD. The cost analysis was based on a retrospective study of 409 patients with PD who were seen over a 1-year period in our movement disorders clinic. The cost of therapy varied considerably depending on the severity of the condition (assessed in the "off" phase), the incidence of motor fluctuations, and the type of PD. In the early stage of the disease (Hoehn and Yahr stage I [HY I]), mean daily costs for therapy were DM (German marks) 6.60, which increased in later stages of the disease (HY V) to DM 22.00. If rare cases requiring continuous subcutaneous apomorphine infusion were included, mean daily costs of patients in HY V rose to DM 32.50 (the mean daily costs of subcutaneous apomorphine-treated patients in HY V: DM 74.30). Patients with motor fluctuations accounted for higher costs (DM 16.50) compared with those without motor fluctuations (DM 7.80). With respect to the three subtypes of PD, the mean daily expenditure was DM 7.00 for the tremor-dominant type, DM 12.40 for the akinetic-rigid type, and DM 10.80 for the mixed type. In the group of 409 PD patients included in this analysis, the average daily expenditure for drug treatment totaled DM 10.70 per patient (including patients on subcutaneous apomorphine).

Newer anti-epileptic drugs

During the past few years, a number of drugs have been added to the anti-epileptic arsenal. This review focusses on five of these drugs which have undergone extensive trials: Vigabatrin, Lamotrigine, Gabapentin, Felbamate and Oxcarbazepine. Some of these antiepileptic drugs appear to be helpful for treatment of catastrophic childhood epilepsies. Vigabatrin appears promising in children with infantile spasms who do not respond to ACTH or Prednisolone. Children with Lennox-Gastaut syndrome may respond to treatment with Lamotrigine or Vigabatrin. Gabapentin and vigabatrin have proved to be effective in refractory partial seizures. Oxcarbazepine, a ketoderivative of carbamazepine, is as effective as Carbamazepine but has a better safety profile. Lesser neurotoxicity and fewer drug interactions is another advantage with these drugs. However monitoring is required to determine the long term safety with their usage. These drugs have a definite role in childhood epilepsies refractory to conventional antiepileptic drugs.

Clobazam, oxcarbazepine, tiagabine, topiramate, and other new antiepileptic drugs

Clinical investigators recently have studied at least 21 new antiepileptic drugs (AEDs) in people with epilepsy. This review briefly examines 15 of these new AEDs: clobazam (CLB), dezinamide, flunarizine (FNR), loreclezole, milacemide (MLM), MK-801, nafimidone, ORG-6370, oxcarbazepine (OCBZ), progabide (PGB), ralitoline, stiripentol, tiagabine (TGB), topiramate (TPM), and zonisamide (ZNS). CLB, PGB, and TGB represent agents that act on the GABA system, and MLM acts on the glycine system. MK-801 and ZNS (in part) are excitatory amino acid antagonists, and FNR is a calcium-channel antagonist. OCBZ is a keto analogue of carbamazepine, which is not metabolized to the epoxide and may have fewer side effects. The remaining agents are novel compounds with a variety of suspected mechanisms. TPM appears especially effective for intractable partial seizures but has a high incidence of cognitive side effects. None of these new AEDs is useful for all patients with inadequate seizure control or ongoing toxicity. The role of each will require further clinical study and experience.

Newer antiepileptic drugs. Towards an improved risk-benefit ratio

Epilepsy is one of the most common neurological disorders. Even though existing antiepileptic drugs can render 80% of newly diagnosed patients seizure free, a significant number of patients have chronic intractable epilepsy causing disability with considerable socioeconomic implications. There is, therefore, a need for more potent and effective antiepileptic drugs and drugs with fewer adverse effects, particularly CNS effects. Drugs for the treatment of partial seizures are particularly needed. With major advances in our understanding of the basic neuropathology, neuropharmacology and neurophysiology of epilepsy, numerous candidate novel antiepileptic drugs have been developed in recent years. This review comparatively evaluates the pharmacokinetics, efficacy and adverse effects of 12 new antiepileptic drugs namely vigabatrin, lamotrigine, gabapentin, oxcarbazepine, felbamate, tiagabine, eterobarb, zonisamide, remacemide, stiripentol, topiramate and levetiracetam (ucb-L059). Of the 12 drugs, vigabatrin, lamotrigine and gabapentin have recently been marketed in the UK. Five of these new drugs have known mechanisms of action (vigabatrin, lamotrigine, tiagabine, oxcarbazepine and eterobarb), which may provide for a more rational approach to the treatment of epilepsy. Oxcarbazepine, remacemide and eterobarb are prodrugs. Vigabatrin, gabapentin and topiramate are more promising on the basis of their pharmacokinetic characteristics in that they are excreted mainly unchanged in urine and not susceptible to significant pharmacokinetic interactions. In contrast, lamotrigine, felbamate and stiripentol exhibit significant drug interactions. Essentially, all the drugs are effective in partial or secondarily generalised seizures and are effective to varying degrees in other seizure types. Particularly welcome is the possible effectiveness of zonisamide in myoclonus and felbamate in Lennox-Gastaut syndrome. In relation to adverse effects, CNS effects are observed with all drugs, however, gabapentin, remacemide and levetiracetam appear to exhibit least. There is also the possibility of rational duotherapy, using drugs with known mechanisms of action, as an additional therapeutic approach. The efficacy of these 12 antiepileptic drug occurs despite the fact that candidate antiepileptic drugs are evaluated under highly unfavourable conditions, namely as add-on therapy in patients refractory to drug management and with high seizure frequency. Thus, whilst candidate drugs which do become licensed are an advance in that they are effective and/or are associated with less adverse effects than currently available antiepileptic drugs in these patients, it is possible that these drugs may exhibit even more improved risk-benefit ratios when used in normal clinical practice.

Clinical experience with oxcarbazepine

Controlled studies of oxcarbazepine (OCBZ) and the largest of the open studies of OCBZ were reviewed. The overall results indicated that OCBZ has the same clinical effect as carbamazepine (CBZ) but causes fewer adverse effects. Studies of allergic toxicity seem to indicate that OCBZ may be tolerated in the majority of patients developing allergy towards CBZ. We concluded that OCBZ is a drug of first choice for the treatment of epilepsy.