Potassium Bromide / Sodium Bromide
Bromides are among the oldest anticonvulsant medications, having been used in human and veterinary medicine since the 19th century. They are halide salts utilized primarily as a first-line or adjunctive therapy for the management of refractory seizure disorders in dogs, particularly when phenobarbital alone is insufficient or contraindicated due to hepatotoxicity. **Key Clinical Features:** * **Hepatic Sparing:** Unlike phenobarbital, bromides are not metabolized by the liver and are excreted entirely by the kidneys, making them the drug of choice for epileptic dogs with concurrent hepatic dysfunction. * **Extremely Long Half-Life:** The half-life in dogs is roughly 16-25 days. Consequently, it takes 3 to 4 months to reach steady-state serum concentrations. **Loading doses** are frequently required to achieve rapid seizure control. * **Dietary Sensitivity:** Bromide competes with chloride for renal reabsorption. Changes in dietary salt (chloride) intake will directly and inversely affect serum bromide levels. * **Feline Contraindication:** Bromides are generally avoided in cats due to a high risk of developing severe, asthma-like lower respiratory tract disease (feline pneumonitis), which can be fatal.
Mechanism: Bromide's anti-seizure activity stems from its generalized depressant effect on neuronal excitability. * **Mechanism:** The bromide ion (Br⁻) is a halide that closely mimics the chloride ion (Cl⁻) in the body. It competes with chloride for transport across cell membranes, particularly at the **GABA_A receptor** chloride channels. * **Pathway:** GABA binds to the receptor → channel opens → Bromide traverses the channel more readily than chloride → **membrane hyperpolarization**. * **Result:** This hyperpolarization lowers the resting membrane potential, making it significantly harder for the neuron to depolarize. This effectively raises the seizure threshold and limits the spread of epileptic electrical discharges across the brain.
Dosing by species
- Refractory seizures (3rd choice therapy) · 10-20 mg/kg/day PO · PO · q24h · Follow same guidelines as dogs. Use with extreme caution.
- Epilepsy (2nd line therapy) · 30 mg/kg PO once daily · PO · q24h
- Seizures (Maintenance) · 20-30 mg/kg PO once daily, with food · PO · q24h · Dose is for potassium bromide. If sodium bromide is used, decrease dose by 15% (i.e., 17-26 mg/kg).
- Seizures (Rapid Loading Dose) · 400 mg/kg PO divided into 8 doses given over a 48-hour period (i.e., 50 mg/kg every 6 hours for 2 days) · PO · q6h · 2 days · Giving entire loading dose at once will usually cause vomiting. Start maintenance dose after loading.
- Seizures (Alternative Loading Dose) · 400-600 mg/kg/day divided and given with food · PO · divided · 1 to 5 days · May be given over 24 hours or more gradually over 5 days. Then go to initial maintenance dose.
- Seizures (Alternative Loading Dose 2) · 125 mg/kg/day for 5 days PO divided q12h · PO · q12h · 5 days · Resume at 35 mg/kg PO once daily after loading.
- Status epilepticus / NPO · 100 mg/kg body weight every 4 hours for 6 total doses · Rectal · q4h · 24 hours
- Seizures (IV Loading - Sodium Bromide) · 600-1200 mg/kg, diluted in a solution and administered over eight hours · IV · once · 8 hours · Sodium bromide only. If target serum bromide concentrations are not reached, additional IV NaBr may be administered. Use with caution.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Cats (relative to absolute contraindication due to severe pulmonary effects)
- Patients with severe renal dysfunction (requires extreme caution and dose adjustment)
- Pregnant or lactating animals (crosses placenta and enters milk, causing fetal growth retardation/intoxication)
Adverse effects
- Profound sedation (especially transiently during loading or when combined with phenobarbital)
- Polyphagia (increased appetite) and subsequent weight gain
- Polydipsia and polyuria (increased thirst and urination)
- Ataxia and hind limb paresis (signs of toxicity)
- Gastrointestinal upset (vomiting, anorexia, constipation)
- Pancreatitis (reported in combination with phenobarbital/primidone)
- Pruritic dermatitis (rare)
- Paradoxical hyperactivity (rare)
- Cats: Severe lower respiratory effects (cough, dyspnea, peribronchial infiltrates)
Drug interactions
- CNS Sedating Drugs · Additive sedation and CNS depression.
- Diuretics (furosemide, thiazides) · May enhance the renal excretion of bromides, lowering serum levels and potentially causing seizure breakthrough.
- High Chloride/Salt Diets · Increases renal excretion of bromide, reducing serum bromide levels and affecting seizure control.
- Low Chloride/Salt Diets · Decreases renal excretion of bromide, increasing serum bromide levels and risking bromide toxicity.
- Drugs that lower seizure threshold (e.g., xylazine) · May potentially reduce the efficacy of antiseizure medications.
Monitoring
- Serum bromide concentrations (Therapeutic range in dogs: 1-3 mg/mL)
- Seizure frequency and severity
- Signs of toxicity (sedation, ataxia, weakness)
- Renal function (BUN, Creatinine, USG)
- Body weight (due to polyphagia)
Overdose
Toxicity (bromism) is more likely with chronic overdoses, but acute overdoses can occur. **Clinical Signs of Bromism:** * Profound sedation to stupor * Ataxia, tremors, and hind limb paresis * Muscle pain * Conscious proprioceptive deficits * Anisocoria and hyporeflexia **Treatment:** * **Acute Ingestion:** Standard gut removal techniques (emesis, gastric lavage). Death from acute oral ingestion is rare as spontaneous vomiting usually occurs. * **Enhancing Excretion:** Administration of parenteral 0.9% sodium chloride (NaCl) or oral sodium chloride, parenteral glucose, and loop diuretics (e.g., **furosemide**) are highly effective in promoting renal excretion and reducing bromide loads in intoxicated patients.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.