Topiramate on ictal seizure semiology: a quantitative, randomized, low and medium dose-controlled study

Comparative effectiveness of add-on therapy with newer-generation antiepileptic drugs in Bulgarian patients with refractory epilepsy

OBJECTIVES

The objective of this study is to perform an open, prospective study on various aspects of comparative effectiveness of newer-generation antiepileptic drugs as add-on therapy in Bulgarian patients with drug-resistant epilepsy.

METHODS

The study was performed with the participation of 1259 patients with epilepsy who attended the Clinic of Neurology at the University Hospital in Plovdiv, Bulgaria for regular visits and completed diaries about seizure frequency, severity, and adverse events.

RESULTS

Oxcarbazepine was used in 82 patients, topiramate in 120 patients, lamotrigine in 73 patients, levetiracetam in 135 patients, pregabalin in 47 patients, tiagabine in 43 patients, gabapentin in 18 patients, lacosamide in 12 patients, and retigabine in 6 patients. During the first 24 months of study, improvement of seizure severity and frequency was most frequent in patients on treatment with pregabalin and levetiracetam and rarest in those on treatment with oxcarbazepine. The retention rate of patients on pregabalin and tiagabine was significantly lower compared to the retention rate of patients on most of the other antiepileptic drugs. The frequency of adverse events was higher in patients on treatment with tiagabine and pregabalin.

CONCLUSION

Despite some similar characteristics of newer-generation antiepileptic drugs' effectiveness, levetiracetam stands out with better dynamic improvement of seizure severity and frequency and satisfactory tolerability; typical for pregabalin is a very good dynamic improvement of seizure severity and frequency mainly in patients with focal seizures, but a lower tolerability, and the main advantage of oxcarbazepine is a good tolerability, efficacy, however, is less satisfactory.

Influence of levetiracetame on ictal and postictal EEG in patients with partial seizures

To investigate the influence of levetiracetame (LEV) treatment on the interhemispheric seizure pattern propagation and postictal recovery of electroencephalography (EEG) background activity. Twenty-three adult patients (age > 16 years) with pharmacoresistant focal epilepsies presenting at the Epilepsy Center Erlangen for pre-surgical evaluation were enrolled in the study. Those eligible patients receiving only one antiepileptic drugs were recruited to the 48-h baseline phase and, after at least two seizures, were randomized to the 7-day treatment phase with either LEV (n = 11) or placebo (n = 12). All participants were submitted to continuous day-and-night video-EEG monitoring. The daily dose of LEV was 1000 mg (500 mg bid.) on the first treatment day and was increased to 2000 mg (1000 mg bid.) from the second day onward. The EEG changes relating to the time delay of the interhemispheric seizure pattern propagation and to the postictal recovery of the background activity were analysed by computerized video-EEG recording and compared using the non-parameter Mann-Whitney U-exact test (alpha = 0.05). A prolonged latency of the contralateral seizure pattern propagation was observed in the LEV group, whereas a more rapid propagation was observed in the placebo group (P = 0.009). Postictal generalized slowing of the background activity was recorded in 21 patients during the baseline phase. More rapid postictal recovery of the EEG background activity was observed in the LEV, but not in the placebo group (P = 0.03). This study demonstrated that LEV not only prevented the seizure pattern propagation but also helped the speedy recovery of the postictal background activity in the EEG.

Topiramate and its clinical applications in epilepsy

Topiramate, a derivative of the monosaccharide d-fructose, has shown a wide spectrum of antiepileptic efficacy in both animal models and clinical trials. Multiple putative mechanisms of action include voltage-sensitive sodium channel blockade, calcium channel inhibition, increase of potassium conductance, GABA-mediated chloride current increment, glutamate-mediated neurotransmission inhibition and carbonic anhydrase isoenzyme inhibition. In general, the clinical response is maintained in the long-term. The most common side effects include somnolence, fatigue, headache, psychomotor slowing, confusion, difficulty with memory, impaired concentration and attention, speech and language problems and weight loss. If slowly titrated and used at a low-to-medium dosage, it is well tolerated and offers a valid therapeutic option, the relevance of which is comparable to that of the most widely used 'old' antiepileptic drugs. As it is not yet wholly clear which specific epilepsy syndromes may benefit most from topiramate with respect to other drugs, more accurate indications for initial monotherapy would require syndrome-oriented trials and more clinical experience.

Onset of Action of Levetiracetam: A RCT Trial Using Therapeutic Intensive Seizure Analysis (TISA)

OBJECTIVES

To correlate the onset of clinical effects of add-on levetiracetam (LEV) therapy with daily serum LEV concentration, in pharmaco-resistant focal epilepsies, using the TISA method.

METHODS

25 adult patients (aged>6 years) with pharmaco-resistant focal epilepsies undergoing presurgical evaluation at the Epilepsy Center Erlangen were enrolled in the study. Eligible patients on a maximum of one other antiepileptic drug (AED) were recruited into the 48-hour baseline phase. Those who had at least two seizures during this phase were randomized into the seven-day treatment phase, when they received either LEV or placebo, under continuous day-and-night video-EEG monitoring. The starting daily dose of LEV was 500 mg bid, titrated from the second treatment day to 1,000 mg bid. The peak serum concentration of LEV was monitored daily at 8:00 am (one hour after drug administration) for every patient. The number and duration of seizures per 24h (N/24h and D/24h respectively) were investigated.

RESULTS

23 patients completed the study (LEV group n=11 and placebo group n=12). Seven patients in the LEV group and two patients in the placebo group achieved seizure-freedom during the treatment phase. The intergroup comparison of the decrease in N/24h and D/24h from the baseline phase to the treatment phase was in favor of the LEV group (p<0.05). A significant effect of LEV on D/24h was seen as early as the second treatment day (p=0.013), becoming more apparent on the third treatment day (p=0.009).

CONCLUSION

The present study objectively quantified the correlation between the anticonvulsant effects of LEV in focal epilepsies and the peak serum concentration of the drug. For the first time, direct measurement was used to demonstrate the onset of action of LEV to be two days after drug initiation.

Influence of Lamotrigine and Topiramate on MDR1 Expression in Difficult-to-Treat Temporal Lobe Epilepsy

PURPOSE

Overexpression of the multiple drug resistance gene 1 (MDR1) was quantified in brain tissue from Coriaria lactone (CL)-kindled Sprague-Dawley (SD) rats after treatment with lamotrigine (LTG) or topiramate (TPM) and compared with that found in rats treated with carbamazepine (CBZ) and valproate (VPA).

METHODS

Twenty-five CL-kindled SD rats were randomized into five groups (n = 5 for each group) to receive once-daily feeding of CBZ, VPA, TPM, and LTG as the monotherapy equivalent of maximum human adult dosage, or normal saline (NS control) for 1 month. The expression of P-gp in brain tissues of all rats was quantified by using an image analysis and measuring system (Image Pro-plus 4.0). Mean area and mean integrated optical density (mean IOD) of P-gp expression were calculated. In addition, the changes in seizure severity were analyzed via video-camera monitoring.

RESULTS

A significant decrease in the number and duration of seizures with antiepileptic drug (AED) treatment was observed in the TPM and LTG groups. The mean area and mean IOD of P-gp expression were highest in the CBZ group and next highest in the VPA group; much lower values were measured in the TPM and LTG groups, and the lowest in the NS control group (p < 0.05).

CONCLUSIONS

TPM and LTG significantly inhibited seizures in this CL model. The expression of P-gp was not significantly increased by TPM or LTG treatment in this study.

Ketter's hypothesis of the mood effects of antiepileptic drugs coupled to the mechanism of action of topiramate and levetiracetam

Mood-modulating profiles of antiepileptic drugs (AEDs) have been classified by Ketter, Post, and Theodore [Neurology 1999; 53 (5, Suppl. 2) S53-76] into two classes: the first class is assumed to have deactivating effects related to GABA potentiation, and the second class is assumed to have activating effects that are associated with glutamate attenuation. We tested this hypothesis by reviewing the multiple mechanisms of action of topiramate (TPM) and levetiracetam (LEV) together with clinical behavioral side effects of patients who had been treated with TPM and LEV in a tertiary referral center for epilepsy. We found LEV to manifest activating and deactivating side effects equally and TPM to act as a deactivating AED, with tiredness/sleepiness side effects being predominant. TPM, in comparison to LEV, was found to be associated with a high incidence of side effects. Testing the hypothesis of Ketter et al. (1999) the deactivating effects of TPM may be coupled to a predominance of potentiation of GABA, but the oversimplified basis of the model needs to be acknowledged.

A new approach in anti-epileptic drug evaluation

Presurgical trials with video-electroencephalogram (EEG) monitoring for a couple of days provide the possibility to objectively and quantitatively analyze seizure activity during different drug treatments. Patients are provided with the optimal medical care and safety precautions when hospitalized. Hereby a method used in the antiepileptic drug (AED) trials called therapeutic intensive seizure analysis (TISA) has been recently introduced, by which AED efficacy on seizure activity can be objectively quantified by using continuous video-EEG monitoring. This could be used not only as a supplement to the traditional evaluation of AEDs' efficacy by treatment failure designs in large groups, but also can provide early individual information on the changes of seizure activity of each patient during the therapy. Data from TISA studies suggest that secondarily generalized tonic-clonic seizures (SGTCs) mostly occur in patients with a SGTC history after withdrawal of AED. The first 3 days of titration of a newly introduced AED was important for efficacy assessment; with a low risk of SGTCs. By using the TISA method an early recognition of first effects of a new AED on seizure activity and neuropsychological changes is possible, which can be correlated to serum concentration levels in a small sample size. The essentials of the proposed modification to the conventional presurgical trial are: (1) a complete withdrawal of AEDs should be avoided, if possible and (2) a titration phase limited to 3 days is suggested, using a condensed evaluation setting including the TISA method, serum concentration and neuropsychological monitoring. In addition long-term effects can be evaluated by repeated video-EEG monitoring.

Efficacy and tolerability of the new antiepileptic drugs, II: Treatment of refractory epilepsy: report of the TTA and QSS Subcommittees of the American Academy of Neurology and the American Epilepsy Society

PURPOSE

To assess the evidence demonstrating efficacy, tolerability, and safety of seven new antiepileptic drugs (AEDs) [gabapentin (GBP), lamotrigine (LTG), topiramate (TPM), tiagabine (TGB), oxcarbazepine (OXC), levetiracetam (LEV), and zonisamide (ZNS)] in the treatment of children and adults with refractory partial and generalized epilepsies.

METHODS

A 23-member committee, including general neurologists, pediatric neurologists, epileptologists, and doctors in pharmacy, evaluated the available evidence based on a structured literature review including MEDLINE, Current Contents, and Cochrane Library for relevant articles from 1987 to March 2003.

RESULTS

All of the new AEDs were found to be appropriate for adjunctive treatment of refractory partial seizures in adults. GBP can be effective for the treatment of mixed seizure disorders, and GBP, LTG, OXC, and TPM for the treatment of refractory partial seizures in children. Limited evidence suggests that LTG and TPM also are effective for adjunctive treatment of idiopathic generalized epilepsy in adults and children, as well as treatment of the Lennox-Gastaut syndrome.

CONCLUSIONS

The choice of AED depends on seizure and/or syndrome type, patient age, concomitant medications, and AED tolerability, safety, and efficacy. The results of this evidence-based assessment provide guidelines for the prescription of AEDs for patients with refractory epilepsy and identify those seizure types and syndromes for which more evidence is necessary.

A kindling model of pharmacoresistant temporal lobe epilepsy in Sprague-Dawley rats induced by Coriaria lactone and its possible mechanism

PURPOSE

The aim of this study was to develop a new animal model of pharmacoresistant temporal lobe epilepsy (TLE) by repeated intramuscular injection of Coriaria lactone (CL) at subthreshold dosages and to explore the mechanisms that might be involved.

METHODS

Healthy male Sprague-Dawley rats (n = 160) were randomized into four groups during the kindling process: three groups (n = 50 for each group) received CL injection at subthreshold dosages (1.25, 1.5, and 1.75 mg/kg, respectively), and ten received normal saline (NS) injection as a control group. The maximal human adult dosage of carbamazepine (CBZ), valproate (VPA), and phenytoin (PHT) was administered as monotherapy to different groups of kindled rats for 1 month (n = 20 for each group). Changes in EEG recording, seizure number, intensity (expressed as grade 1-5 according to Racine stage), and duration, including spontaneous seizures during different interventions, were compared. The expression of P-170, a multiple drug resistance gene (MDR1) encoding P-glycoprotein, was measured in brain samples from different groups of experimental rats by using an image analysis and measurement system (ImagePro-Plus 4.0).

RESULTS

A total of 70 (46.7%) rats were fully kindled with a median of 15 (seven to 20) CL injections. Electrocorticogram (ECoG) including hippocampal (EHG) monitoring revealed the temporal lobe origins of epileptiform potentials, which were consistent with the behavioral changes observed. Spontaneous seizures occurred with frequency and diurnal patterns similar to those of human TLE. The antiepileptic drugs (AEDs) tested lacked a satisfactory seizure control. The maximal P-170 expression was in the kindled rats with AED treatment; the next highest was in the kindled rats without AED intervention. Nonkindled SD rats with CL injection also had increased P-170 expression compared with control SD rats.

CONCLUSIONS

The study provided a simple and stable animal TLE kindling model with pharmacoresistant properties. The pharmacoresistance observed in the kindled rats to CBZ, VPA, and PHT at maximal human adult dosages together with the increased P-170 expression was a distinct feature of this model. This model might be used in further investigations of the mechanisms involved in pharmacoresistant TLE and for developing new AEDs.

Anticonvulsant drugs differentially suppress individual ictal signs: A pharmacokinetic/pharmacodynamic analysis in the cortical stimulation model in the rat

Antiepileptic drugs can suppress seizures completely, but they may also modify the appearance of drug-resistant seizures. In this study, the effects of three antiepileptic drugs on a seizure pattern were assessed by means of population pharmacokinetic/pharmacodynamic (PK/PD) modeling, yielding estimates of baseline response, EC50, and Hill slope. Lamotrigine did not affect eye closure, although it did suppress the other ictal signs in a concentration-dependent fashion. Midazolam suppressed forelimb clonus less potently than the other ictal signs; the same was observed for tiagabine with respect to eye closure. This study shows that ictal component analysis (ICA) in combination with PK/PD modeling may facilitate drug selection and dose optimization. The application of ICA is not restricted to a single seizure type or anticonvulsant drug and can be used to identify drug combinations that have a complementary action.

Clinical effects of topiramate against secondarily generalized tonic--clonic seizures

OBJECTIVE

Intensive and quantitative evaluation of the duration, intensity and frequency of tonic and clonic signs of secondarily generalized tonic-clonic seizures (GTCS) in patients with pharmacoresistant partial seizures during topiramate (TPM) treatment.

METHODS

Thirty patients suffering from refractory partial seizures with secondarily GTCS undergoing presurgical evaluation were randomized into a low dosage (100 mg daily) and a parallel medium dosage (200 mg daily) group of TPM add-on medication (15 patients for each group). Study phases included a 3 days baseline video-EEG phase, a 10 days TPM titration phase without video-EEG and a 3 days TPM dose maintenance phase with video-EEG. During the baseline and the dose maintenance phase seizures were recorded using video-EEG monitoring and the following parameters were measured for each recorded secondarily generalized tonic and clonic signs: duration (lasting seconds), intensity (on a 0-3 scale), frequency (numbers per 24 h).

RESULTS

A total of 46 complex partial seizures with secondarily generalized tonic-clonic signs during the baseline phase and 20 during the dose maintenance phase were intensively analyzed. More patients in the medium dosage group than in the low dosage groups were free from secondarily GTCS during the dose maintenance phase (nine vs. two, P<0.05). Intergroup comparison suggested that the duration of all tonic signs decreased more in the medium dosage group computing the reduction from baseline to the dose maintenance phase (P<0.05). There were statistically more significant reductions in the duration and intensity of clonic signs in the medium dosage group (P<0.05).

CONCLUSION

TPM has an early dose-dependant effect on secondarily GTCS in patients with pharmacoresistant partial seizures.

SHORT COMMUNICATION

The present study intensively analyzed the duration, intensity, and frequency of secondarily generalized tonic and clonic signs in patients with pharmacoresistant partial seizures. The quantitative data suggested that TPM had a robust early inhibitory effect on secondarily generalized tonic-clonic signs; effects were more prominent in the medium dosage group (200 mg daily) than in the low dosage group (100 mg daily).