Placebo effect in antiepileptic drug trials

Pregabalin: the next new thing

Safety and Efficacy of Two Pregabalin Regimens for Add-on Treatment of Partial Epilepsy

Beydoun A, Uthman BM, Kugler AR, Greiner MJ, Knapp LE, Garofalo EA; Pregabalin 1008-009 Study Group

Neurology 2005;64:475–480

Objective

To evaluate the efficacy, tolerability, and safety of two pregabalin regimens administered as adjunctive therapy to that of placebo in patients with medically refractory partial epilepsy.

Methods

A multicenter, double-blind, randomized, parallel-group, placebo-controlled trial was performed. After a prospective 8-week baseline phase, patients were randomized to 12 weeks of double-blind treatment with placebo or pregabalin, 600 mg/day, administered twice daily (BID) or 3 times daily (TID). Primary efficacy was measured as change in seizure frequency from baseline of either pregabalin regimen compared with placebo. Secondary efficacy comparisons included the proportion of patients experiencing ≥50% reduction in seizure frequency (responder rate) and median percentage change from baseline in seizure frequency. Safety/tolerability assessments included adverse events (AEs), physical and neurologic examinations, and clinical laboratory evaluation. Efficacy and safety analyses were performed on the intent-to-treat (ITT) population.

Results

Pregabalin treatment resulted in seizure frequency reductions: 53% for pregabalin TID ( P ≤ 0.0001) and 44% for pregabalin BID ( P ≤ 0.0001) compared with a 1% increase for placebo. Responder rates were 49% for pregabalin TID and 43% for pregabalin BID compared with 9% for placebo ( P ≤ 0.001). Both pregabalin regimens were similar in efficacy and tolerability. The most common AEs were dizziness, somnolence, and ataxia.

Conclusions

Pregabalin administered at 600 mg/day is safe, generally well tolerated, and efficacious as adjunctive therapy for the treatment of patients with partial seizures, with or without secondary generalizations. This dose can be administered on a twice-daily or 3-times-daily schedule with similar efficacy and tolerability results.

Clinical development of antiepileptic drugs in adults

Over the last two decades, ten so-called newer antiepileptic drugs (AEDs) have been approved around the world, the majority of which have found and maintained a place in the seizure-fighting armamentarium for the whole spectrum of epilepsies and epileptic syndromes; some of these drugs have features that are improved compared with the older drugs. Within that same time period, the process of clinical development of AEDs has also undergone changes and has become much more complex and costly. Efforts are underway to shift decision-making about the clinical viability of AED candidates to earlier development stages, using the concept of translational medicine. However, thus far all of the newer AEDs have undergone a standard development as an adjunct in the control of adult partial seizures; in some cases, development has been expanded to other seizure types and pediatric syndromes. Currently, the path to global approval for use in monotherapy is under review and is often debated with regulatory authorities. Clinical treatment guidelines consider randomized, blinded, well controlled studies as the premier level of evidence-based medicine; these studies originate mostly in confirmatory phases of the development program. However, with the rigid designs and criteria in regulatory driven trials, effectiveness in the clinical practice setting may not be sufficiently predicted by these studies, leading to frustrations from individual practitioners. Finally, additional safety issues regularly occur only after the postlaunch exposure to a broader population making necessary a continuing, and thorough, pharmacovigilance after the AED has come to market.