Review of new antiepileptic drugs (AEDs)

Somatic comorbidity of epilepsy in the general population in Canada

PURPOSE

There is a notion that people with epilepsy have substantial and often unrecognized comorbidity of chronic conditions. However, most studies focus on selected patient groups; population-based studies are scarce. We compared the prevalence of chronic somatic conditions in people with epilepsy with that in the general population using Canadian, nationwide, population-based health data.

METHOD

We examined epilepsy-specific and general population health data obtained through two previously validated, independently performed, door-to-door Canadian health surveys, the National Population Health Survey (NPHS, N = 49,000) and the Community Health Survey (CHS, N = 130882), which represent 98% of the Canadian population. The prevalence of epilepsy and 19 other chronic conditions was ascertained through direct inquiry from respondents about physician-diagnosed illnesses. Weighted prevalence, prevalence ratios (PR), and 95% confidence intervals were obtained for the entire population and for males and females separately. Multivariate analyses assessed the strength of association of comorbid conditions with epilepsy as compared with the general population.

RESULTS

People with epilepsy had a statistically significant higher prevalence of most chronic conditions than the general population. Conditions with particularly high prevalence in epilepsy (prevalence ratio > or = 2.0) include stomach/intestinal ulcers (PR, CHS 2.5, NPHS 2.7), stroke (PR, CHS 3.9, NPHS 4.7), urinary incontinence (PR, CHS 3.2, NPHS 4.4), bowel disorders (PR, CHS 2.0, NPHS 3.3), migraine (PR, CHS 2.0, NPHS 2.6), Alzheimer's disease (PR, NPHS 4.3), and chronic fatigue (PR, CHS 4.1). There were no gender-specific differences in prevalence of chronic conditions among people with epilepsy.

CONCLUSIONS

People with epilepsy in the general population, not only those actively seeking medical care, have a high prevalence of chronic somatic comorbid conditions. The findings are consistent across two independent surveys, which show that people with epilepsy in the general population have a two- to five-fold risk of somatic comorbid conditions, as compared with people without epilepsy. This patient-centered comorbidity profile reflects health aspects that are important to people with epilepsy, and indicate the need for a more integrated approach to people with epilepsy. The impact of epilepsy relative to other comorbid conditions requires further analysis, as does the contribution of comorbidity to epilepsy intractability and to differential health care needs. Similarly, it remains to be determined whether the observed comorbidity patterns are specific to epilepsy or simply reflect a pattern that is common to chronic illnesses in general.

Pregabalin add-on treatment: a randomized, double-blind, placebo-controlled, dose-response study in adults with partial seizures

PURPOSE

To evaluate pregabalin (PGB), 150 mg/day, and PGB, 600 mg/day, as an add-on treatment for patients with refractory partial seizures concurrently treated with one to three anticonvulsants (AEDs).

METHODS

An international (13 countries), multicenter (45 centers), 12-week, double-blind, randomized study in which patients with partial seizures received placebo (n = 96); PGB, 150 mg/day (n = 99); or PGB, 600 mg/day (n = 92); given 3 times a day (t.i.d.). The primary efficacy criterion was reduction in seizure frequency during treatment as compared with baseline, as measured by RRatio, the symmetrical percentage change in seizure rates determined from daily seizure diaries. The RRatio between the 8-week baseline (pretreatment phase) and the 12-week treatment period were compared between each of the PGB groups and the placebo group by using an analysis of variance analysis of the intent-to-treat population.

RESULTS

PGB, 150 mg/day and 600 mg/day, were both significantly more effective than placebo in reducing the RRatio [-11.5 (p = 0.0007) and -31.4 (p < or = 0.0001), respectively, vs. 0.9]. These RRatio values correspond to seizure-frequency reductions from baseline of -1.8, 20.6, and 47.8% for placebo, 150 mg/day, and 600 mg/day, respectively. PGB efficacy was significantly dose related (p < or = 0.0001). Secondary efficacy variables corroborated the findings of the primary analysis. Significantly more patients were responders (> or =50% reduction in seizure frequency) in the PGB, 600 mg/day (43.5%), group than in the placebo group (6.2%) (p < or = 0.001). PGB was well tolerated. Dose-related, treatment-emergent adverse events (> or =10%), mostly mild or moderate in intensity, were somnolence, dizziness, ataxia, diplopia, and weight gain. The withdrawal rate due to adverse events was 10% of patients at 150 mg/day and 18.5% of patients at 600 mg/day, compared with 6.2% of patients receiving placebo.

CONCLUSIONS

PGB, 150 mg/day and 600 mg/day, is highly effective and well-tolerated add-on therapy in patients with partial seizures.

Evidence-based medicine and antiepileptic drugs

Evidence based health care uses systematic literature reviews with statistical strategies like meta-analysis to aid decision-making. This information can help clinicians by organizing data and providing up-to-date quantitative summaries of efficacy and adverse effects of treatments. Limitations of meta-analysis include problems inherent in combining data from trials of somewhat different design, choice of appropriate dosages, and summarizing complex questions as a single odds ratios. I summarize the results of a meta-analysis of the following antiepileptic treatments for partial seizures in adults: gabapentin, lamotrigine, topiramate, tiagabine, valproate and the vagal nerve stimulator. Each treatment was significantly more efficacious than placebo, and there were nonsignificant trends toward differences among the treatments in efficacy and tolerability. Quantitative analysis of adverse effects is presented. Absent the availability of a comprehensive randomized controlled trial for comparison, a rigorously conducted meta-analysis provides some useful information.

New antiepileptic drugs: comparison of key clinical trials

PURPOSE

Data accrued from clinical trials of five new antiepileptic drugs (AEDs) are compared for efficacy in reducing seizures and self-reported adverse events as a basis of selection among new AEDs. Drawbacks to use of these data also are demonstrated.

METHODS

A review of double-blind, placebo-controlled clinical trials of a new AED or placebo added to a standard AED provided data on reduction of complex partial seizures (CPSs). Success is > or =50% fewer CPSs with a new AED or placebo; Overall Improvement is the success rate with drug minus the success rate with placebo. Adverse events were tabulated from product-labeling lists of COSTART items (incidence, > or =5%). The Summary Complaint score is the total number of reports of individual events for each AED.

RESULTS

Efficacy data demonstrate differences in Overall Improvement rates among five new AEDs and placebos (p = 0.001). However, rates of response to placebo also differed significantly among trials (p = 0.01). Adverse events predominantly affect central nervous system, psychiatric, and general body systems. However, patients in the placebo control groups did not consistently report adverse effects. Summary Complaint scores differ among the five new AEDs, but variability in use of COSTART terms nullifies comparisons.

CONCLUSIONS

Comparisons of data for five new AEDs provide information for selection among treatments when a second drug is needed to improve control of CPSs. However, significant differences among the control groups and other problems make comparisons between trials problematic. The final choice should be based on the need of the individual patient for superior seizure control versus minimal adverse effects.