クロロチアジド
クロロチアジドは**チアジド系利尿薬**であり、獣医学においては主に犬の**腎性尿崩症**、全身性高血圧の管理、およびシュウ酸カルシウム尿石症の予防に使用されます。 一般的な浮腫の治療においてはループ利尿薬（フロセミドなど）にほぼ取って代わられていますが、依然として重要な標的治療薬です。 > **臨床のポイント：** チアジド系薬剤は、尿崩症患者において逆説的に尿量を減少させます。軽度の体液減少状態を引き起こすことで、近位尿細管でのナトリウムと水分の再吸収が代償的に増加し、最終的に遠位ネフロンに到達する濾液量が減少するためです。
作用機序: Chlorothiazide acts primarily on the **distal convoluted tubule (DCT)** of the nephron. * **Primary Mechanism:** Inhibits the **Na⁺/Cl⁻ symporter** in the luminal membrane of the DCT → prevents reabsorption of sodium and chloride → promotes osmotic diuresis. * **Electrolyte Effects:** Enhances excretion of sodium, chloride, potassium, magnesium, phosphate, iodide, and bromide. * **Calcium Sparing:** Unlike loop diuretics, thiazides *decrease* urinary calcium excretion with chronic use, making them useful for preventing calcium oxalate uroliths. * **Hemodynamic Effects:** Decreases glomerular filtration rate (GFR). The resulting volume depletion activates the renin-angiotensin-aldosterone system (RAAS), which contributes to downstream potassium wasting (hypokalemia).
動物種別の用量
- Treatment of diabetes insipidus · 20-40 mg/kg · PO · q12h · May be tried
- As a diuretic · 20-40 mg/kg · PO · q12h · Twice daily
- General dosing for adult cattle · 4-8 mg/kg · PO · once or twice daily
- General dosing · 2 g · PO · once to twice daily
- Treatment of nephrogenic diabetes insipidus · 20-40 mg/kg · PO · q12h
- Treatment of systemic hypertension · 20-40 mg/kg · PO · q12-24h · Use with dietary salt restriction
- As a diuretic · 20-40 mg/kg · PO · q12h · Twice daily
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
- Hypersensitivity to thiazides or sulfonamides
- Anuria
- Pregnancy in otherwise healthy females with only mild edema (relative contraindication)
有害事象
- Hypokalemia
- Hypochloremic alkalosis
- Dilutional hyponatremia
- Hypomagnesemia
- Hypercalcemia
- Hypophosphatemia
- Hyperuricemia
- Gastrointestinal distress (vomiting, diarrhea)
- Pancreatitis
- Hypersensitivity / dermatologic reactions
- Polyuria
- Hematologic toxicity
- Hyperglycemia
- Hyperlipidemias
- Orthostatic hypotension
薬物相互作用
- Amphotericin B · Increased risk for severe hypokalemia
- Corticosteroids / Corticotropin · Increased risk for severe hypokalemia
- Diazoxide · Increased risk for hyperglycemia, hyperuricemia, and hypotension
- Digitalis / Digoxin · Thiazide-induced hypokalemia, hypomagnesemia, and/or hypercalcemia may increase the likelihood of digitalis toxicity
- Insulin · Thiazides may increase insulin requirements
- Lithium · Thiazides can increase serum lithium concentrations
- Methenamine · Thiazides can alkalinize urine and reduce methenamine effectiveness
- NSAIDs · May increase risk for renal toxicity; NSAIDs may reduce diuretic actions of thiazides
- Neuromuscular blocking agents · Response or duration of nondepolarizing agents (e.g., tubocurarine) may be increased
- Probenecid · Blocks thiazide-induced uric acid retention
- Quinidine · Half-life may be prolonged by thiazides due to urine alkalinization
- Vitamin D or Calcium Salts · Hypercalcemia may be exacerbated
モニタリング
- Serum electrolytes (especially potassium)
- BUN and Creatinine
- Blood glucose
- Hydration status
- Blood pressure (if indicated)
- Hemograms (if indicated)
過量投与
Acute overdosage may cause **electrolyte and water balance problems**, CNS effects (ranging from lethargy to coma and seizures), and GI effects (hypermotility, GI distress). Transient increases in BUN have also been reported. **Treatment:** * Empty the gut after recent oral ingestion using standard protocols. * **Avoid concomitant cathartics** as they may exacerbate fluid and electrolyte imbalances. * Monitor and treat electrolyte and water balance abnormalities supportively. * Monitor respiratory, CNS, and cardiovascular status; provide symptomatic and supportive care as required.
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。