Vetdrugs 2.0Bromide is a long-acting anticonvulsant used mainly for maintenance seizure control in dogs. Potassium bromide is commonly used alone or with another antiseizure drug, particularly when phenobarbital alone does not provide adequate control. Slow elimination means concentrations accumulate over weeks rather than reaching a stable level immediately.
Potassium and sodium bromide contain different proportions of bromide and are not equivalent by salt mass. Bromide undergoes little or no metabolism and is handled by the kidneys. Dietary chloride and renal function can therefore materially change exposure even without a change in the prescribed salt amount.
Group
Anticonvulsant halide
Mechanism of Action
Bromide ions alter neuronal anion handling and are thought to pass through or compete with chloride-associated pathways. Their accumulation favors membrane hyperpolarization and reduced neuronal excitability, raising the threshold for seizure generation and limiting spread of epileptic discharges. The exact anticonvulsant mechanism is not completely resolved.
Because bromide is not substantially metabolized, clearance depends mainly on renal handling. Chloride competes with bromide for tubular reabsorption: increased chloride intake generally increases bromide elimination, while reduced chloride intake can increase retention. This explains why diet or fluid changes can alter seizure control or toxicity.
A long elimination half-life produces gradual accumulation and persistent effects. It is suited to maintenance therapy rather than rapid termination of an ongoing seizure, and serum concentrations may continue changing for some time after a regimen adjustment.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Epilepsy with phenobarbital — Maintenance | 30–40 mg/kg | PO | Every 24 h | Potassium bromide salt dose; adjust to measured serum bromide. |
| Epilepsy monotherapy — Maintenance | 40–50 mg/kg | PO | Every 24 h | Potassium bromide salt dose; higher requirements may occur with high-chloride diets. |
| Oral loading | Reference only | PO | Potassium bromide 600 mg/kg total divided over 3–5 days; an alternative is 200 mg/kg once daily for 5 days. These are distinct cumulative schedules, not interchangeable total doses. | |
| Alternative oral loading — Loading | 60 mg/kg | PO | Every 24 h | Up to 15 days; Potassium bromide; slow loading alternative, with serum monitoring. |
| Intravenous sodium bromide loading | Reference only | IV | Sodium bromide 800–1200 mg/kg total infused intravenously over 8 hours. Never substitute potassium bromide. | |
| Epilepsy with phenobarbital — Initial | 20–30 mg/kg | PO | Every 24 h | Potassium bromide salt; give with food and titrate using serum bromide and seizure control. |
| Epilepsy maintenance — Maintenance | 35 mg/kg | PO | Every 24 h | Potassium bromide salt alternative. |
| Rapid oral loading — Loading | 50 mg/kg | PO | Every 6 h | Up to 2 days; Eight doses total over 48 hours, giving 400 mg/kg total potassium bromide. Do not give the entire load at once. |
| Five-day divided loading — Loading | 62.5 mg/kg | PO | Every 12 h | Up to 5 days; Two equal doses from a total of 125 mg/kg/day potassium bromide; follow with 35 mg/kg once daily. |
| Rectal loading — Loading | 100 mg/kg | RECTAL | Every 4 h | Up to 1 days; Potassium bromide when oral dosing is impossible; six total doses, not an open-ended repeated regimen. |
| Alternative rapid loading | Reference only | PO | Potassium bromide 400–600 mg/kg total loading is described with wording that also says per day and spans 24 hours to five days. The cumulative amount and distribution are ambiguous; do not calculate a daily repeat from this passage. | |
| Alternative intravenous sodium bromide loading | Reference only | IV | Sodium bromide 600–1200 mg/kg IV over 8 hours; use sterile filtered sodium bromide, not potassium bromide, and measure serum concentration before additional loading. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Epilepsy | 30 mg/kg | PO | Every 24 h | Potassium bromide. Feline use is discouraged because bronchitis and poor control are common. |
| Epilepsy | 10–20 mg/kg | PO | Every 24 h | Potassium bromide; feline use is strongly discouraged because potentially serious pulmonary disease occurs. |
Horses
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Epilepsy — Loading | 100 mg/kg | PO | Once | Potassium bromide salt. |
| Epilepsy — Maintenance | 25 mg/kg | PO | Every 24 h | Potassium bromide salt. |
Indications
- Maintenance treatment of canine epilepsy as a primary antiseizure drug in selected patients.
- Adjunctive maintenance treatment of canine seizures inadequately controlled by phenobarbital or another suitable antiseizure drug.
- Selected maintenance seizure-control plans where reducing reliance on a hepatically metabolized anticonvulsant is desirable.
Contraindications
- Feline use is discouraged because of bronchial adverse effects and unreliable seizure control.
- Potassium bromide requires caution with impaired potassium regulation; sodium bromide requires caution with sodium-sensitive disease.
- Renal dysfunction and advanced age can reduce tolerance and require lower dosing.
Interactions
- Dietary chloride accelerates elimination; dietary changes can alter concentrations.
- Combined phenobarbital treatment increases sedation and has been associated with pancreatitis.
- Bromide may falsely increase measured chloride.
Adverse effects
- Sedation and ataxia
- Polyphagia, polydipsia and polyuria
- Gastrointestinal upset
- Paradoxical excitement
- Bronchitis and cough in cats
Toxicity
Bromism causes weakness, abnormal gait, depression, delirium or hyperexcitability. Stop treatment and consider saline diuresis for substantial toxicity.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Compounded potassium bromide 250 mg/mL | Oral Liquid | 250 mg / mL | PO |
| Compounded sodium bromide 216 mg/mL | Oral Liquid | 216 mg / mL | PO |
Monitoring and Administration
Monitor serum bromide, aiming approximately 1–2 mg/mL with phenobarbital; monotherapy may require 2–2.5 mg/mL and sometimes higher concentrations. Interpret results with clinical response.
Keep dietary chloride consistent. When substituting salts, sodium bromide doses are approximately 15% lower: 30 mg/kg potassium bromide corresponds to about 25 mg/kg sodium bromide.
A compounded potassium bromide liquid can contain 25 g salt in a final 100 mL; sodium bromide liquid can contain 21.6 g salt in a final 100 mL. These are salt strengths, distinct from bromide-ion strengths. Aqueous preparations have reported stability of 180 days.
Intravenous loading requires sodium bromide, never potassium bromide. A sterile filtered 3% sodium bromide solution is described; refrigerate to limit microbial growth. Avoid chloride-containing flavorants.
Without loading, one monitoring approach samples at 3–4 weeks and again at 2.5–3 months. After a five-day load, measure soon after loading, then at one and three months. Sample timing within the day is less important than consistent interpretation.
Reducing phenobarbital is individualized. One approach waits three months, adequate seizure control and bromide at least 1.5 mg/mL, then reduces phenobarbital by 25% every 2–4 weeks. Faster withdrawal requires a different monitored plan. Do not combine different taper schedules automatically.