Top 5 Advantages of Potassium Bromide as an Antiepileptic Drug

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This article was developed with the expertise of Dr. Fred Wininger, VMD, MS, DACVIM (Neurology).

Idiopathic epilepsy is the most common cause of seizures in dogs, with disease onset most common in young to middle-aged dogs.¹ Several anticonvulsant drugs, including potassium bromide, phenobarbital, levetiracetam, and zonisamide, are available for the control of seizures in dogs with idiopathic epilepsy. Although each of these medications can be an appropriate choice for an individual patient, drug choice can vary based on factors such as concurrent conditions, disease severity, and pet owner needs.

Potassium bromide can offer several advantages as a first-line antiepileptic treatment option for many of these patients. This article will explore 5 key aspects of potassium bromide that can make it a good option for the control of idiopathic epilepsy.

1. Dosing

A study investigating the compliance rate of anticonvulsant therapy showed that <25% of pet owners were 100% compliant in treating their pet’s epilepsy, with only 33% of cases having a compliance rate of ≥80%.² Potassium bromide is a medication that should be administered once daily,³ whereas other first-line anticonvulsant drug options such as phenobarbital⁴ and zonisamide⁵ are administered every 12 hours and levetiracetam⁶ every 8 to 12 hours, depending on the formulation.

With compliance being a significant concern in the treatment of idiopathic epilepsy, once-daily dosing could provide a potential benefit through reduced pet owner commitment. In addition, the long elimination half-life of potassium bromide (median, 15.2 days) can help reduce the clinical impact in the event of missed doses,⁷ whereas even 1 missed dose of phenobarbital can trigger a seizure.⁸

2. Efficacy

A study evaluating the efficacy of potassium bromide to control idiopathic epilepsy over a 6-month period showed that 65% of dogs treated with potassium bromide as a monotherapy experienced a reduction in seizures by >50%, and ≈50% were seizure-free.⁹ Potassium bromide can also reduce seizure frequency when used as an add-on anticonvulsant in conjunction with other anticonvulsants.¹⁰

3. Case Selection

Potassium bromide can be a good choice for patients with liver disease, blood dyscrasias, and/or hypothyroidism, whereas phenobarbital can be hepatotoxic to some dogs,¹¹ and its use should be avoided in dogs with decreased liver function or liver disease. In addition, phenobarbital can decrease serum thyroxine levels,¹¹ an issue not seen with potassium bromide.

Potassium bromide should be used with caution in older patients with comorbidities, patients with renal dysfunction, and/or patients with conditions that predispose them to electrolyte imbalances.⁷

4. Low Side Effect Profile

Most patients tolerate potassium bromide therapy well, with few side effects reported.¹² Reversible polyuria, polydipsia, sedation, and ataxia may be seen with potassium bromide administration, with these side effects being dose-dependent and predictable.¹³ Giving potassium bromide with a meal may reduce potential GI tract irritation that can result in vomiting.¹⁴ Potassium bromide may increase the risk for pancreatitis, and signs of pancreatitis should be thoroughly investigated and treated.¹⁵ Respiratory problems are rare in dogs but can cause life-threatening lung disease in cats; therefore, potassium bromide is generally avoided in this species.^14,15

5. Monitoring Protocols

For patients receiving potassium bromide, it is recommended to measure serum bromide concentrations between 6 and 12 weeks after starting therapy and then annually.¹⁶ As compared with phenobarbital, monitoring of potassium bromide requires less frequent testing, which can reduce costs for pet owners. Patients treated with phenobarbital should have their levels measured 2 weeks after starting the medication or changing doses, again at 6 weeks posttreatment initiation, then every 6 months once therapeutic levels are reached.¹⁶ A routine CBC and serum chemistry profile are also recommended at least every 6 months for patients receiving phenobarbital, especially to monitor for hepatoxicity.¹⁷ The impact of this expense should be considering when weighing medication options.

Conclusion

Potassium bromide can be used as a single-agent antiepileptic drug or as an add-on therapy for patients with inadequately controlled seizures receiving other antiepileptic drugs. Potassium bromide should be considered for patients with liver disease, blood dyscrasias, and/or hypothyroidism. For pet owners, reduced monitoring expenses, a high safety profile, and once-daily administration may make potassium bromide a desirable therapeutic option for their dog as compared with other antiepileptic options.