Perspectives on interactions between antiepileptic drugs (AEDs) and antimicrobial agents

In the treatment of seizures and epilepsy associated with central nervous system (CNS) infections, drug–drug interactions may significantly and unexpectedly impact outcome not only of epilepsy but also of the infectious disorders in both emergent and chronic care situations. A case is described in whom, the administration of the antimicrobial agent, meropenem presumably reduced serum valproate concentrations resulting in impaired seizure control. Other situations are reviewed in which interactions between antiepileptic drugs (AEDs) and antimicrobial agents may be of clinical significance. These include: (1) seizure management in individuals with neurocysticercosis, (2) management of seizures in patients with lobar tuberculomas, (3) management of seizures due to cerebral abscess, and (4) management of seizures in HIV-seropositive individuals.     

Diagnosis and treatment of neurocysticercosis

Neurocysticercosis is a parasitic disease caused by the larval (cystic) form of the pork cestode tapeworm, Taenia solium, and is a major cause of acquired seizures and epilepsy worldwide. Development of sensitive and specific diagnostic methods, particularly CT and MRI, has revolutionized our knowledge of the burden of cysticercosis infection and disease, and has led to the development of effective antihelminthic treatments for neurocysticercosis. The importance of calcified granulomas with perilesional edema as foci of seizures and epilepsy in populations where neurocysticercosis is endemic is newly recognized, and indicates that treatment with anti-inflammatory agents could have a role in controlling or preventing epilepsy in these patients. Importantly, neurocysticercosis is one of the few diseases that could potentially be controlled or eliminated-an accomplishment that would prevent millions of cases of epilepsy. This Review examines the rationale for treatment of neurocysticercosis and highlights the essential role of inflammation in the pathogenesis of disease, the exacerbation of symptoms that occurs as a result of antihelminthic treatment, and the limitations of current antihelminthic and anti-inflammatory treatments.     

The effects of antimicrobial and antiepileptic treatment on the outcome of epilepsy associated with central nervous system (CNS) infections

The course and outcome of epilepsy following central nervous system (CNS) infections has been poorly characterized. Likewise, the impact of antimicrobial treatment as well as other preventative and therapeutic interventions on the development of epilepsy following neurological infectious disorders has been insufficiently studied. The CNS infections that can cause epilepsy may be either acute or chronic-recurrent. For most acute infections, for example, viral encephalitis and bacterial meningitis, the effect of specific antimicrobial treatment on the development of epilepsy cannot be studied in a controlled manner due to logistic and ethical reasons. In the specific case of neurocysticercosis (NCC), the risk of seizures in the short term is reduced following either anthelminthic or corticosteroid treatment or both. The effect of anthelminthic treatment on seizure outcome in the long term has not been studied. Finally, treatment with antiepileptic drugs (AEDs) needs to be optimally defined in the case of epilepsy associated with neurological infectious disorders.     

Calcified cysticercotic lesions and intractable epilepsy: a cross sectional study of 512 patients

Background

Neurocysticercosis is a major cause of epilepsy in developing countries and is endemic in Brazil. To test the hypothesis that the aetiological profile of patients with intractable epilepsy in Brazil includes neurocysticercosis, we conducted a cross sectional study investigating the aetiology of intractable epilepsy.

Methods

A total of 512 patients evaluated at the outpatient clinic for intractable epilepsy at the Ribeirão Preto School of Medicine were included in the survey. Medical intractability was determined on the basis of seizure incidence and severity, and response to appropriate epilepsy management. Neuroimaging included brain CT with non‐contrasted and contrasted phases and high resolution MRI. Patients were divided into neurocysticercosis and non‐neurocysticercosis groups according to previous diagnostic criteria.

Results

The most common epileptogenic lesions were mesial temporal sclerosis (MTS; 56.0%), malformations of cortical development (12.1%), and brain tumours (9.9%). Neuroimaging was normal in 8.7% of patients. Calcifications were found in 27% of patients and were significantly more common in patients with MTS than in those without MTS (p<0.001). Isolated neurocysticercosis was found in only eight patients (1.56%).

Conclusions

These data suggest that neurocysticercosis is an uncommon cause of intractable epilepsy, even in an endemic region such as Brazil, and that it may only represent a coexistent pathology. However, an analysis of our findings reveals that neurocysticercosis was more common in patients with MTS. This finding could suggest either that there is a cause‐effect relationship between MTS and neurocysticercosis, or that MTS and neurocysticercosis co‐vary with a missing variable, such as socio‐economic status.     

Some common issues in the use of antiepileptic drugs

Since 1993, eight new antiepileptic drugs (AEDs) have become available in the United States for the treatment of epilepsy: felbamate, gabapentin, lamotrigine, topiramate, tiagabine, levetiracetam, oxcarbazepine, and zonisamide. Of the older AEDs, six continue to be widely used: phenobarbital, phenytoin, primidone, ethosuximide, carbamazepine, and valproate. As a result, there is a relatively large number of alternative AEDs for the treatment of any given type of epilepsy. This has been particularly beneficial for patients with generalized epilepsies, both idiopathic and symptomatic. Given the wide availability of effective agents, the toxicity and pharmacokinetic profile of an AED have become major factors in the selection process. A number of common clinical situations may benefit from the abundance of AEDs. Chronic toxicity observed with some of the older AEDs such as osteoporosis, gingival hyperplasia, or alterations in reproductive endocrine function may be avoided with the use of the newer agents. The obese patient with epilepsy may benefit from the use of AEDs such as topiramate or zonisamide, which have a tendency to produce weight loss. In patients with a history of drug-induced skin rash, AEDs such as valproate, gabapentin, topiramate, tiagabine, and levetiracetam carry a lower risk of cross-reactivity. In patients sensitive to cognitive dysfunction, drugs with a favorable profile include gabapentin, tiagabine, lamotrigine, oxcarbazepine, and levetiracetam. A more favorable pharmacokinetic profile is observed in the majority of the newer AEDs in contraposition to the classic agents. Good absorption, linear kinetics, and low drug-drug interaction potential make these drugs easier to use. The newer AEDs are eliminated through different combinations of liver metabolism and direct renal excretion, thus providing a wider variety of choices in patients with failure of one of these organs. Some specific problems have been found with some of the newer AEDs. Hyponatremia, known to occur rarely with carbamazepine use, appears to be more common with oxcarbazepine. Felbamate has been associated with a high incidence of aplastic anemia and liver failure and should be used exceptionally. Acute angle closure glaucoma has been observed with the use of topiramate. This complication occurs early in the course of therapy and reverses rapidly with discontinuation of the drug, so physician and patient awareness of this problem is very important. In this article several common clinical situations in the management of patients with epilepsy are presented in the form of case studies. These cases illustrate some current aspects of the use of the AEDs and will give some guidelines to help the treating physician in the increasingly complex process of AED selection.     

Drug selection for the newly diagnosed patient: When is a new generation antiepileptic drug indicated?

Abstract. Treatment options in epilepsy have increased dramatically since the early 1990s with the introduction of nine new generation antiepileptic drugs (AEDs) (felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, tiagabine, topiramate, vigabatrin and zonisamide). This makes drug selection much more complicated and challenging. This review discusses drug selection in patients with newly diagnosed epilepsy and in particular the role of new AEDs in this population. The choice of treatment should always be based on a careful comparison of the risk-benefit ratio for the different treatment options and the outcome of such evaluation may be different in patients with new onset compared with chronic epilepsy. Efficacy, tolerability and safety are the main criteria for selection of AEDs and any first line drug for patients with newly diagnosed epilepsy must have demonstrated satisfactory efficacy as monotherapy in that patient population. So far, of the new AEDs only lamotrigine, oxcarbazepine and topiramate have documentation sufficient to be granted licence for use as monotherapy in most European countries. Because the new generation AEDs have failed to demonstrate improved effectiveness as monotherapy, old generation AEDs such as carbamazepine and valproate remain drugs of first choice for partial and generalised seizures, respectively. However, there are special situations and populations where a new AED may be a reasonable first line drug. These include vigabatrin in West syndrome associated with tuberous sclerosis, lamotrigine as alternative to valproate in idiopathic generalised seizures in women of childbearing potential and lamotrigine for the treatment of epilepsy in the elderly population. The role of the new generation AEDs is likely to become more prominent as more experience is gained.     

Pharmacotherapy of epilepsy: new armamentarium, new issues.

Since 1990 there have been over ten antiepileptic drugs (AEDs) approved for the therapy of epilepsy. These agents have a new spectrum of efficacy and novel adverse effects, some totally unexpected. They also represent an enormous escalation of costs. Few have been subjected to head-to-head comparisons in monotherapy against established AEDs. The aim of therapy is to eliminate rather than to reduce seizure manifestations. Many traditional agents have been phased out due to poor tolerability. New epilepsy syndromes and genetic contributions to epilepsy have been refined. Special considerations apply to various classes of sufferers such as the elderly, women of childbearing age, and sufferers with concomitant disorders, treated with medications capable of drug interactions. There is a recognition of the value of slow introduction, a preference for monotherapy, recognition of the effects of AEDs on hormones and reproductive function and effects on the fetus exposed to AEDs in utero, comprising physical malformations and effects on cognitive development. A balance between efficacy and safety is pivotal, as every preference about the initial pharmacotherapy of epilepsy and subsequent polytherapy has its protagonists. With improvement in diagnostic techniques and new therapeutic modalities it is likely that in the future, pharmacogenomics and an understanding of pharmacoresistance may influence drug selection for individual patients with epilepsy.     

Antiepileptic drugs and memory

Impaired memory is among the most common complaints of patients with epilepsy. Multiple factors contribute to memory impairment in patients with epilepsy. Thus, delineation of the effects of antiepileptic drugs (AEDs) on memory in clinical populations faces methodological difficulties. Further, subjective perception of memory problems by patients is influenced by mood. However, there is evidence from animal and healthy volunteer studies supporting an independent potential for AEDs to impair memory. Differential AED effects on memory have been observed, and AED effects may interact with focal brain lesions. Memory impairment from AEDs is a greater concern at the age extremes, although the effects of AEDs, especially the newer agents, have not been thoroughly studied in these populations. Well-controlled studies are needed to understand the underlying mechanisms and to further delineate the magnitude and relative effects of AEDs on memory.     

Antiepileptic Drugs in Pediatric Practice

Summary: Several factors characterize the current medical treatment of epilepsy during childhood. Children do not present the same types of seizures or epilepsies as adults, and certain epilepsy syndromes are seen only during childhood. Accordingly, the choice of antiepileptic drugs (AEDs) may differ in children. In addition, certain medical therapies, such as ACTH or pyridoxine, are used only in children. It is also common practice to prescribe AEDs in children for indications that are "off-label," such as the treatment of partial-onset seizures with car-bamazepine before the age of 6 years. The natural history of epilepsy and the risk for seizure recurrence may be different in the pediatric age range, and this may influence the decision to institute chronic prophylactic therapy in children. Similar considerations may apply to the decision to discontinue AED therapy. The pharmacokinetics of several AEDs are age-dependent, and dosages are more variable among patients. The adverse effects of AEDs may be age-dependent, and the pattern of exacerbation of certain seizures by AEDs may be different in children. In addition, several new AEDs are now available, or are about to be released, and the preferential sequence of AEDs of choice in children with epilepsy will need to be reassessed as experience grows and as the results of comparative studies become available.     

Epileptic fits and epilepsy in the elderly: general reflections, specific issues and therapeutic implications

Seizures and epilepsy are commonly encountered in the elderly. Diagnosis is not always straightforward as reliable history is often difficult to obtain and EEG findings can be non-specific. When to treat and how may be difficult choices as adequate studies in elderly are rather scarce. Treatment should be based on careful assessment and comparison of risk/benefit profiles of various anti-epileptic drugs (AEDs) in this specific elderly population. Since most AEDs are effective in terms of seizure control in the elderly, the choice of treatment is often determined by tolerability, pharmacokinetic profile and drug interactions of AEDs. As recently introduced AEDs have a better safety profile compared to older agents it seems logical to initiate treatment in the frail elderly patient with those more modern AEDs. In this review some distinctive clinical features of epilepsy in the elderly are discussed in three sections (general issues, special issues and selected treatment options with special reference to medicinal treatment).