EFFICACY OF THE NEW ANTIEPILEPTIC DRUGS IN DOGS
When recommending a novel treatment, it is helpful if you can provide information on the expected effectiveness of the treatment,
especially when the treatment involves a considerable investment of time or money on the pet owner's part. Unfortunately,
extensive data of this nature are not available for the use of the new antiepileptic drugs in canine epilepsy. Rather, the
information on drug use described above was obtained by administering the new antiepileptic drug in an open-label fashion:
Dogs with poorly controlled seizures were given a new antiepileptic drug, and seizure frequency during administration of the
new drug was compared with seizure frequency before the new drug was initiated. Because the studies were not placebo-controlled,
the information obtained regarding drug efficacy may be inaccurate.
A reduction in seizure frequency during placebo administration has been documented in people with epilepsy,17 and, in my opinion, a similar phenomenon may occur in dogs. One likely cause for this placebo effect is regression to the
mean, which is a statistical term used to describe the fluctuations that occur in biological variables over time and take
the form of a sine wave around the mean. Epilepsy is a waxing and waning disorder, and fluctuations in seizure frequency are
common over the course of the disease. Clients are most likely to seek a change in therapy for their pets when seizures are
poorly controlled. Over time, improvement in the seizure frequency is probable, regardless of the treatment administered.
However, this improvement may be erroneously attributed to a recently instituted change in therapy. Open-label studies cannot
account for this bias, and, consequently, the efficacy reported in such studies may be falsely elevated.
Thus, from the information available to date, you can recommend a trial with a new antiepileptic drug, but, in my opinion,
no representation should be made with respect to efficacy. As experience with these drugs grows in veterinary medicine and
more research is performed on their applicability to dogs, additional information will become available to further guide recommendations
on their use.
The management of refractory seizures can pose a considerable challenge to practitioners and pet owners. Ongoing patient follow-up
is critical, and directed, appropriate therapy and monitoring should be used to optimize treatment results. With the approval
of several new antiepileptic drugs for the management of human epilepsy over the last two decades, the treatment options available
for our canine patients have also increased. Although our knowledge is still somewhat limited on these novel antiepileptic
drugs, studies and clinical experience available to date suggest that they have the potential to improve seizure control and
minimize adverse effects in affected dogs. Continued evaluation of these drugs in veterinary patients should provide additional
details on how to use these therapies most effectively in managing canine epilepsy.
Editors' note: UCB Pharma provided levetiracetam for a clinical trial Dr. Muñana participated in.
Karen R. Muñana, DVM, MS, DACVIM (neurology)
Department of Clinical Sciences
College of Veterinary Medicine
North Carolina State University
Raleigh, NC 27606