Abstract
Curtis Dewey responds: Our article was (and is) meant to provide a review of the existing literature on the topic of feline seizure disorders as well as our clinical opinions on the subject. Individual clinicians are certainly entitled to their own opinions regarding therapeutic choices for their patients, and a respectful interchange of ideas is to be encouraged. Although we do not necessarily agree with all of the opinions of this correspondent, the letter does raise some points of discussion that are difficult to manage within the limited realm of a review article.
In our article, the statement regarding oral diazepam being contraindicated in cats was clearly stated as an opinion. It is also a very well supported and defensible opinion. The two independent reports of cats experiencing a fatal side effect associated with oral diazepam use should not be discounted because 13 years have passed since these publications, or because no further publications regarding the subject have appeared. The lack of further reports on this topic is to be expected for two reasons. One reason is that more reports of the same subject in the literature would likely be considered superfluous, both by potential authors and editors. Another potential reason is that clinicians may, in general, be more wary of using oral diazepam for feline seizures because of the fear of fatal hepatic necrosis, a fear that was non-existent prior to the independent reports by Center et al and Hughes et al in 1996. Neither of these reports addressed the incidence of this side effect, so how rare it actually is remains a mystery.
Although the evidence of efficacy of oral diazepam is largely based on clinical experience over many years, we feel that there is no validity to arguing against this drug's efficacy. We agree that it is both frustrating and unfortunate that oral diazepam has a ‘black mark’ upon it, when we know that it is an effective anti-seizure drug for cats that is usually safe to use. We did not place the black mark on diazepam, we just reminded (and justifiably so) the JFMS readers that it remains. Veterinarians are certainly allowed to use oral diazepam in cats for seizures or for any other relevant purpose. However, few would argue that close monitoring of such patients (including regular blood work to check liver enzymes) is paramount should oral diazepam be chosen as a therapy. It is entirely a clinician's prerogative to choose oral diazepam over ‘medications superior in efficacy and lower in side effects’ if he or she so chooses. We completely disagree that it is ‘wrong and unfair’ to reiterate the possibility of a fatal drug side effect in a review article, or to express our opinion that other options should be chosen. We absolutely agree that it is ‘wrong and unfair’ for anti-seizure medication choices in cats to be so limited, but we are working on that.
The letter makes a valid point regarding the use of bromide in cats being contraindicated - we share this opinion. There probably should have been a text box stating our stance on bromide use in cats, as there was in the diazepam section. The adverse effect associated with bromide use in cats is not dose-or time-related and does not abate with dose reduction. These features fit with a description of ‘idiosyncratic’, but an incidence of 30–42% does not (this incidence of an adverse effect is not really ‘rare’ as the letter correctly points out). Perhaps some other terminology, like a type B drug reaction, would be more appropriate. Some of the statements in the letter regarding bromide use in cats need to be corrected for the benefit of JFMS readers. The reported incidence of the pulmonary side effect of bromide in cats is 30–12% based on two reports in the literature. It is not 50%. Of the cats reported in the literature in which respiratory signs developed while on bromide therapy, discontinuation of bromide resulted in resolution of these signs in 69%, and improvement in another 15%, for a total of 84% of cats. Perhaps the letter's author intended the phrase ‘little scientific support’ to mean that the studies that clearly documented recovery from pulmonary side effects following bromide discontinuation in cats had small case numbers. Although the evidence is anecdotal to support fatal consequences of bromide use in cats (information on VIN posts, although very useful, does belong in the anecdotal category), we do agree that this particular side effect can be life-threatening. However, the prognosis for recovery from bromide-related pulmonary dysfunction in cats should be considered to be more favorable than suggested by this letter; these cats should be afforded ample time and nursing care to recover from bromide-related pulmonary damage. In summary, we do feel that bromide use in cats is contraindicated because it is not a very effective drug choice and is potentially dangerous in this species.
We appreciate the input regarding our review article and hope that the article will instigate more discussion and questions among JFMS readers. Treatment of feline seizure disorders in cats is, as evidenced by this correspondence, a controversial subject. If applied appropriately, the energy and passion from controversy can be channeled into positive and collaborative action. At Cornell University, we have, with the help of a number of colleagues in both academia and private practice, targeted our frustrations regarding the limited drug choices for seizuring cats towards finding new therapeutic options. Oral levetiracetam appears to be very effective and safe for cats. We have recently completed a pharmacokinetic study evaluating pregabalin in normal cats. The pharmacokinetic profile for pregabalin in cats looks very favorable, and we are currently working on the manuscript and planning a clinical trial. We have already found this drug to be safe and effective in treating canine epilepsy, and hope that it will show similar promise in cats.