Potassium Bromide

(for veterinary information only)


Available in                          
250 mg and 500 mg                    
CHEWABLE TABLETS,                
and through                         
compounding pharmacies               
in assorted strength                    
liquids and capsules                   


In older times, bromides were licensed and used routinely for treating seizure disorders in humans; however, when phenobarbital was introduced the human market for bromides was completely eclipsed. It soon became unprofitable to continue the FDA registration for bromides and the manufacture of bromides became relegated to chemical companies only. Until recently, potassium bromide was not even a licensed medication in the United States and special approval from the FDA had to be obtained if it was to be used. Because of the veterinary demand, an approved product is now available.

Potassium bromide is a highly reliable anticonvulsant medication in dogs. When compared to phenobarbital, potassium bromide seems to be similarly effective and have fewer undesirable side effects. For years, no drug manufacturer stepped forward to relicense this material as a medication but, fortunately, compounding pharmacies have been willing to provide custom-made prescriptions. Recently PRN Pharmacal® has begun producing both flavored solution and chewable tablets.

Potassium bromide works by competing with chloride ions for access to brain tissues. As bromide levels in the brain rise and chloride levels drop, electrical activity in the central nervous system is inhibited, making the initiation of a seizure difficult.


This medication was initially reserved for dogs who either cannot tolerate phenobarbital for seizures control due to unacceptable side effects or who need additional seizure control medication beyond what their phenobarbital can provide. In fact, seizure control with potassium bromide is so effective that many practitioners reach for it as a first choice therapy without even using phenobarbital.

Stable blood levels of potassium bromide require 3-4 months to achieve so often phenobarbital is started concurrently to gain faster seizure control with the idea that the phenobarbital will eventually be discontinued. Alternatively, to reduce the time to achieve a stable blood bromide level, loading doses may be used initially. In this situation, very high potassium bromide doses are given at intervals over a couple of days before switching to a maintenance dose. The patient is usually quite sedated during this induction period so it is common for this type of loading to be done in the hospital with the patient discharged when sedation is resolved.

Potassium bromide is effective in cats but can cause a life-threatening inflammatory lung disease so it is regarded as a last choice in this species.


Some nausea is associated with the administration of potassium bromide. Giving the medication with food generally controls this.

Since potassium bromide is a salt, excess thirst and urination can be observed with this medication.

Drowsiness or grogginess, which can be marked, is not abnormal during a loading period when potassium bromide therapy is started. It is important not to give more potassium bromide to a groggy pet even if another dose is due.

Occasionally a dog will develop a cough which resolves when potassium bromide is discontinued.

In human beings, a toxicity syndrome called “bromism” results when blood bromide levels become too high. Symptoms reported include: drowsiness, weakness, muscle tremors and soreness, appetite loss, and constipation as well as skin rashes. For this reason bromide levels are monitored periodically. A similar syndrome can occur in dogs if bromide levels become too high.

Dogs with a history of pancreatitis may experience an exacerbation if potassium bromide is used to treat a seizure disorder. This is particularly true for patients taking both bromide and phenobarbital.


The use of potassium bromide as a sole seizure control agent is no longer uncommon; however, the concurrent use of potassium bromide with phenobarbital allows for a reduction of phenobarbital use by 30% to 50%, which is usually enough to alleviate negative phenobarbital side effects. In many cases phenobarbital can be tapered off completely without seizure recurrence.


The administration of potassium bromide interferes with laboratory measurement of chloride, thus any tests for chloride will be falsely elevated.

Potassium bromide should be given with food.

In cats, over 1/3 of patients develop a severe asthma-like lung condition. Potassium bromide is not a good choice for seizure control in the cat. Phenobarbital or diazepam would be good alternatives.

Abruptly discontinuing potassium bromide can precipitate severe seizures. If it becomes desirable to discontinue therapy, your veterinarian can instruct you regarding weaning slowly off the drug.

Patients with kidney disease will require reductions in potassium bromide dosing as this drug is removed via the kidneys. Consequently, because potassium bromide is not metabolized by the liver, it is a good choice for seizure control for dogs with liver disease.

Page last updated: 5/24/2014