臭化カリウム / 臭化ナトリウム
臭化物は最も古い抗てんかん薬の一つであり、19世紀から人間および獣医療で使用されています。これらはハロゲン化物塩であり、主に犬の難治性てんかんの第一選択薬または補助療法として使用されます。特にフェノバルビタール単独では不十分な場合や、肝毒性のために禁忌となる場合に有用です。 **主な臨床的特徴：** * **肝臓への負担がない：** フェノバルビタールとは異なり、臭化物は肝臓で代謝されず完全に腎臓から排泄されるため、肝機能障害を併発しているてんかん犬の第一選択薬となります。 * **非常に長い半減期：** 犬における半減期は約16〜25日です。そのため、定常状態の血清濃度に達するまでに3〜4ヶ月かかります。迅速な発作コントロールを達成するために、しばしば**負荷用量（ローディングドーズ）**が必要となります。 * **食事への感受性：** 臭化物は腎臓での再吸収において塩化物（クロール）と競合します。食事中の塩分（塩化物）摂取量の変化は、血清臭化物濃度に直接的かつ反比例の影響を与えます。 * **猫における禁忌：** 猫では、重篤で喘息に似た下気道疾患（猫の肺炎）を発症するリスクが高く、致命的になる可能性があるため、臭化物の使用は一般的に避けられます。
作用機序: 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.
動物種別の用量
- 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.
用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。
投与経路
禁忌
- 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)
有害事象
- 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)
薬物相互作用
- 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.
モニタリング
- 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)
過量投与
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 の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。