Traditionally, treatment for idiopathic epilepsy in dogs (and in cats, although the disease is much rarer in this species) involves the use of the medication phenobarbital (PB). If seizure control is not adequate and/or side effects are unacceptable with PB use, the drug potassium bromide (KBr) is added and the PB dose is reduced or eliminated over time. This is such a standard protocol that I had stopped giving much thought to the medications themselves. After all, they’ve been used for decades (over a century in the case of KBr) in both human and veterinary medicine.
So, when I saw the article "A systematic review of the safety of potassium bromide in dogs" in the Journal of the American Veterinary Medical Association (JAVMA. 2012; 240:705-715), I wondered what the point of the research was — we already know the potential side effects of KBr therapy and how to deal with them if they arise.
It turns out that I was only partially right. Yes, most veterinarians are very familiar with KBr, and scientific studies have been published that support its safety and efficacy. However, potassium bromide is not actually approved by the U.S. Food and Drug Administration (FDA) to treat seizures in either animals or people (neither is phenobarbital, for that matter). These drugs are still legal to use, but no drug company has submitted information about their safety and efficacy or whether they can be consistently manufactured in accordance with the FDA’s quality standards.
In an attempt to determine how safe potassium bromide actually is for dogs, researchers reviewed 111 published studies regarding the drug’s use. To paraphrase the FDA report on the JAVMA article:
- Neurologic — Sedation, ataxia, and behavioral changes were the most common adverse events associated with KBr use. These signs are reversible and usually resolve within several days by lowering the phenobarbital dose (if the dog is on both KBr and PB) or within hours by giving intravenous saline.
- Gastrointestinal — Vomiting, transient diarrhea, and bloody feces. These adverse gastrointestinal (GI) signs usually resolve without needing to stop KBr therapy. Giving the drug with food may lessen GI irritation.
- Gastrointestinal — A ravenous appetite (i.e., polyphagia) or loss of appetite. Both signs are commonly reported with KBr and PB. The authors recommend monitoring eating patterns and weight in dogs on potassium bromide, especially "because polyphagia can lead to garbage ingestion and other complications."
- Pancreatitis — The authors found insufficient evidence to link KBr to a higher risk of pancreatitis. Pancreatitis may be a result of polyphagia and garbage ingestion rather than the drug itself.
- Reproductive — A variety of reproductive effects have been reported in other species. The authors did not find any studies in the published literature that evaluated the effects of KBr in reproductively active dogs.
- Endocrine — Although the thyroid gland is a target organ at higher doses of potassium bromide in rats and people, the drug does not seem to affect thyroid function in dogs. However, because of the small number of dog studies that looked at the effect of potassium bromide on thyroid function, the authors recommend monitoring thyroid hormone levels in dogs on KBr therapy.
- Dermatologic — Skin reactions are rare in dogs on potassium bromide. While uncommon, the skin lesions described areas of white discoloration on the skin, pimple-like lesions, and itchiness.
- Respiratory — Respiratory disease in dogs from potassium bromide use is unlikely to occur.
This is great information. Owners and veterinarians need to remember that current formulations of KBr are not FDA approved and should be on the lookout for (and report) unusual cases of adverse reactions and/or lack of efficacy.
Dr. Jennifer Coates