Gaetano Zaccara

Clinical Pharmacokinetics of Valproic Acid - 1988

SummarySodium valproate (valproic acid) has been widely used in the last decade and is now considered a relatively safe and effective anticonvulsant agent. Recently, several investigators have proposed its use in the treatment of anxiety, alcoholism and mood disorders, although these indications require further clinical studies.Valproic acid is available in different oral formulations such as solutions, tablets, enteric-coated capsules and slow-release preparations. For most of these formulations bioavailability approaches 100%, while the absorption half-life varies from less than 30 minutes to 3 or 4 hours depending on the type of preparation used. Once absorbed, valproic acid is largely bound to plasma proteins and has a relatively small volume of distribution (0.1 to 0.4 L/kg). Its concentration in CSF is approximately one-tenth that in plasma and is directly correlated with the concentration found in tears. At therapeutic doses, valproic acid half-life varies from 10 to 20 hours in adults, while it is significantly shorter (6 to 9 hours) in children.Valproic acid undergoes extensive liver metabolism. Numerous metabolites have been positively identified and there is reasonable evidence that several of them contribute to its pharmacological and toxic actions. In fact, several valproic acid metabolites have anti-convulsant properties, while many of the side effects it may cause (e.g. those related to hyperammonaemia or liver damage) are most often observed in patients previously treated with phenobarbitone. This could indicate that induction of liver enzymes is responsible for the formation of toxic valproic acid metabolites.

Idiosyncratic Adverse Reactions to Antiepileptic Drugs

Summary:  Idiosyncratic drug reactions may be defined as adverse effects that cannot be explained by the known mechanisms of action of the offending agent, do not occur at any dose in most patients, and develop mostly unpredictably in susceptible individuals only. These reactions are generally thought to account for up to 10% of all adverse drug reactions, but their frequency may be higher depending on the definition adopted. Idiosyncratic reactions are a major source of concern because they encompass most life‐threatening effects of antiepileptic drugs (AEDs), as well as many other reactions requiring discontinuation of treatment. Based on the underlying mechanisms, idiosyncratic reactions can be differentiated into (1) immune‐mediated hypersensitivity reactions, which may range from benign skin rashes to serious conditions such as drug‐related rash with eosinophilia and systemic symptoms; (2) reactions involving unusual nonimmune‐mediated individual susceptibility, often related to abnormal production or defective detoxification of reactive cytotoxic metabolites (as in valproate‐induced liver toxicity); and (3) off‐target pharmacology, whereby a drug interacts directly with a system other than that for which it is intended, an example being some types of AED‐induced dyskinesias. Although no AED is free from the potential of inducing idiosyncratic reactions, the magnitude of risk and the most common manifestations vary from one drug to another, a consideration that impacts on treatment choices. Serious consequences of idiosyncratic reactions can be minimized by knowledge of risk factors, avoidance of specific AEDs in subpopulations at risk, cautious dose titration, and careful monitoring of clinical response.

Transcranial magnetic stimulation and epilepsy

Epileptic conditions are characterized by an altered balance between excitatory and inhibitory influences at the cortical level. Transcranial magnetic stimulation (TMS) provides a noninvasive evaluation of separate excitatory and inhibitory functions of the cerebral cortex. In addition, repetitive TMS (rTMS) can modulate the excitability of cortical networks. We review the different ways that TMS has been used to investigate pathophysiological mechanisms and effects of antiepileptic drugs in patients with epilepsy and epileptic myoclonus. The safety of different TMS techniques is discussed too. Finally, we discuss the therapeutic prospects of rTMS in this field.

Incidence and predictors of acute symptomatic seizures after stroke

Objective: To assess incidence and predictors of acute symptomatic seizures in a prospective cohort of patients with first stroke. Methods: Patients with first stroke hospitalized in 31 Italian centers were recruited. Relevant demographic data, disease characteristics, and risk factors were collected. Acute symptomatic seizures (≤7 days) were recorded and correlated to age, gender, family history of epilepsy, and vascular risk factors. Results: A total of 714 patients (315 women, 399 men; age 27–97 years) were enrolled. A total of 609 (85.3%) had cerebral infarction (32 cerebral infarction with hemorrhagic transformation [CIHT]) and 105 (14.7%) primary intracerebral hemorrhage (PIH). A total of 141 (19.7%) had a large lesion (>3 cm) and 296 (41.5%) cortical involvement. Twelve patients reported family history of seizures. Forty-five patients (6.3%) presented acute symptomatic seizures, 24 with cerebral infarction (4.2%), 4 with CIHT (12.5%), and 17 (16.2%) with PIH. In multivariate analysis, compared to cerebral infarction, PIH carried the highest risk (odds ratio [OR] 7.2; 95% confidence interval [CI] 3.5–14.9) followed by CIHT (OR 2.7; 95% CI 0.8–9.6). Cortical involvement was a risk factor for PIH (OR 6.0; 95% CI 1.8–20.8) and for CI (OR 3.1; 95% CI 1.3–7.8). Hyperlipidemia (OR 0.2; 95% CI 0.03–0.8) was a protective factor for IPH. Conclusion: The incidence of acute symptomatic seizures is the highest reported in patients with first stroke with prospective follow-up. Hemorrhagic stroke and cortical lesion were independent predictors of acute symptomatic seizures. Hyperlipidemia was a protective factor for hemorrhagic stroke.

Slow Repetitive TMS for Drug-resistant Epilepsy: Clinical and EEG Findings of a Placebo-controlled Trial

Summary:  Purpose: To assess the effectiveness of slow repetitive transcranial magnetic stimulation (rTMS) as an adjunctive treatment for drug‐resistant epilepsy.

Modulation of interhemispheric inhibition by volitional motor activity: an ipsilateral silent period study

Brief interruption of voluntary EMG in a hand muscle by focal transcranial magnetic stimulation (TMS) of the ipsilateral primary motor cortex (M1), the so‐called ipsilateral silent period (ISP), is a measure of interhemispheric motor inhibition. However, little is known about how volitional motor activity would modulate the ISP. Here we tested in 30 healthy adults to what extent and under what conditions voluntary activation of the stimulated right M1 by moving the left hand strengthens interhemispheric inhibition as indexed by an enhancement of the ISP area in the maximally contracting right first dorsal interosseous (FDI). Left index finger abduction, already at low levels of contraction, significantly enhanced the ISP compared to left hand at rest. Even imagination of left index finger movement enhanced the ISP compared to rest or mental calculation. This enhancement occurred in the absence of motor‐evoked potential amplitude modulation in the left FDI, thus excluding a non‐specific contribution from an increase in right M1 corticospinal excitability. Contraction of the left extensor indicis, but not contraction of more proximal left upper limb or left or right lower limb muscles also enhanced the ISP. A reaction time experiment showed that the ISP enhancement developed at a late stage of movement preparation just before or at movement onset. Interhemispheric inhibition of the motor‐evoked potential as tested by a bifocal paired‐pulse TMS protocol and thought to be mediated via a neuronal circuit different to the ISP was not enhanced when tested under identical motor task conditions. Finally, ISP enhancement by contraction of the left FDI correlated inversely with EMG mirror activity in the right FDI during phasic abductions of the left index finger. Our findings strongly suggest that voluntary M1 activation by real or imagined movement of the contralateral hand increases interhemispheric motor inhibition of the opposite M1. This phenomenon shows substantial topographical, temporal and neuronal circuit specificity, and has functional significance as it probably plays a pivotal role in suppressing mirror activity.

The adverse event profile of pregabalin: A systematic review and meta-analysis of randomized controlled trials

Purpose:  Despite the widespread use of antiepileptic drugs (AEDs) across different neurologic and psychiatric disorders, no study has systematically reviewed all available randomized controlled trials (RCTs) of a given AED to fully uncover its tolerability profile.

Recommendations of the Italian League Against Epilepsy Working Group on Generic Products of Antiepileptic Drugs

Summary:  The availability of generic products of antiepileptic drugs (AEDs) has been increasing in recent years. In view of the importance of the issue, the Italian League against Epilepsy (LICE) set up an ad hoc working group whose task was to assess available evidence on the efficacy and safety of generic AEDs in the treatment of epilepsy and to produce recommendations on their use. A careful review of the literature revealed no adequately powered randomized controlled trials that assessed the risk/benefit ratio of generic substitution. Although there have been reports of loss or worsened seizure control, or appearance of adverse events, following the switch from brand products to generics, a critical assessment of the evidence generally does not allow us to establish a cause–effect relationship between the switch and a change in clinical status. Overall, the working group concluded that generic AEDs meeting current regulatory criteria for bioequivalence represent a valuable choice in the management of epilepsy by allowing a substantial reduction of treatment costs, particularly in patients initiating monotherapy or adjunctive treament and in those with persistent seizures. The working group considered that in patients who achieved seizure freedom a modest change in plasma drug levels, which may occasionally occur even after substitution of products that meet bioequivalence criteria, could in rare cases lead to seizure breakthrough. Therefore, generic substitution is not recommended in patients who achieved seizure remission. Switches between a particular generic and another generic should also be preferably avoided. Finally, sustained‐release AED formulations should not be used interchangeably with immediate‐release brand or generic products. Patients need to be informed about the stringent criteria that currently govern the approval of generic products and about the implications of the use of generic AEDs, and their opinion should be taken into consideration at the time of prescribing.

Behavioral and Psychological Symptoms in Alzheimer’s Disease: Frequency and Relationship with Duration and Severity of the Disease

The occurrence of behavioral and psychological symptoms of dementia (BPSD) is currently recognized as an important aspect of Alzheimer’s disease (AD). We evaluated the frequency and severity of BPSD with the Neuropsychiatric Inventory across the various degrees and phases of the disease in 50 consecutive AD outpatients. Apathy, aberrant motor activity, dysphoria and anxiety were the symptoms most frequently reported by the caregivers, ranging in the whole study sample from 46 to 74%. A clear trend towards increasing frequency with the severity of disease was found for delusions, hallucinations and aberrant motor activity. A major effect of the duration of the disease was found in the probability of developing hallucinations and aberrant motor activity. Apart from hallucinations, all BPSD were present starting from a mild degree of dementia. A better understanding of the global spectrum of BPSD in AD is warranted in order to improve the allocation of health resources toward the treatment of dementia.

Central nervous system adverse effects of new antiepileptic drugs: A meta-analysis of placebo-controlled studies

OBJECTIVE Systematic review and meta-analysis of the most frequent treatment-emergent central nervous system adverse events (CNS AEs) of new antiepileptic drugs (AEDs) from double-blind, add-on, placebo-controlled studies conducted in adult epileptic patients and identification of dose-adverse effect relationships. METHODS Trial reports found by searching Medline and journals. Outcome was the number of patients complaining of treatment-emergent CNS AEs. Sixteen predefined CNS AEs were considered. Risk differences (RDs) were calculated for individual studies and summary statistics estimated using the random effect model. Predefined CNS AEs in patients treated with active drug (broken down into dose levels) or placebo were extracted and the RDs (95% CI) for CNS AEs were calculated. RESULTS Thirty-six suitable studies identified. No meta-analysis was possible for oxcarbazepine and tiagabine (only one study each included). For these drugs RDs were calculated from single studies. Gabapentin was significantly associated with somnolence 0.13 (0.06-0.2) and dizziness 0.11 (0.07-0.15); lamotrigine with dizziness 0.11 (0.05-0.17), ataxia 0.12 (0.01-0.24) and diplopia 0.12 (0.00-0.24); levetiracetam with somnolence 0.06 (0.01-0.11); pregabalin with somnolence 0.11 (0.07-0.15), dizziness 0.22 (0.16-0.28), ataxia 0.10 (0.06-0.14) and fatigue 0.04 (0.01-0.08); topiramate with somnolence 0.09 (0.04-0.14), dizziness 0.06 (0.00-0.11), cognitive impairment 0.14 (0.06-0.22) and fatigue 0.06 (0.01-0.12); zonisamide with somnolence 0.06 (0.02-0.11) and dizziness 0.06 (0.00-0.12). The dose-response relationship was analysed only for those CNS AEs significantly associated with the AED. CONCLUSIONS No comparison between drugs was possible. One CNS AE was significantly more frequent for levetiracetam, two for zonisamide and gabapentin, three for lamotrigine and four for pregabalin and topiramate.