トリアムテレン
トリアムテレンは**カリウム保持性利尿薬**であり、犬の**うっ血性心不全（CHF）**の補助治療においてスピロノラクトンの代替薬として検討されることがあります。 * **臨床的有用性**: 獣医療における使用経験および薬物動態データは限られています。小動物には、通常スピロノラクトンが第一選択となります。 * **主な利点**: ループ利尿薬（フロセミドなど）やチアジド系利尿薬でよく見られる過剰なカリウム喪失を防ぎつつ、浮腫や体液貯留を管理するのに役立ちます。
作用機序: Triamterene exerts a direct effect on the **late distal convoluted tubule** and **collecting duct** of the kidneys. * **Mechanism**: It directly blocks **epithelial sodium channels (ENaC)** on the lumenal side of the kidney tubule → inhibits the reabsorption of sodium (Na+) → decreases the electrical gradient across the tubular membrane → reduces the driving force for the secretion and excretion of potassium (K+) and hydrogen (H+) ions. * **Aldosterone Independence**: Unlike spironolactone, triamterene does **not** competitively inhibit aldosterone. Its action is independent of endogenous aldosterone levels. * **Net Effect**: Increases urinary excretion of sodium, calcium, magnesium, and bicarbonate while retaining potassium and chloride. It has little effect on blood pressure when used alone but can slightly reduce Glomerular Filtration Rate (GFR).
動物種別の用量
- Adjunctive treatment of recurrent heart failure associated with chronic mitral valve insufficiency · 1-2 mg/kg PO q12h · PO · q12h · Documentation of use is limited; spironolactone is drug of choice.
- As a diuretic for adjunctive treatment of CHF · 2-(4) mg/kg/day PO · PO · q24h
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
- Anuria
- Severe or progressive renal disease
- Severe hepatic disease
- Hypersensitivity to triamterene
- Preexisting hyperkalemia or history of triamterene-induced hyperkalemia
- Concurrent therapy with another potassium-sparing agent (e.g., spironolactone, amiloride)
- Concurrent potassium supplementation
有害事象
- Hyperkalemia (most significant risk)
- Gastrointestinal upset
- Hyponatremia
- Headache or dizziness (reported in humans)
- Increased sensitivity to sunlight
- Hypersensitivity reactions (rare)
- Nephrolithiasis (rare)
- Blood dyscrasias such as agranulocytosis, thrombocytopenia, or megaloblastosis (rare)
薬物相互作用
- ACE Inhibitors (e.g., enalapril, benazepril) · Increased risks for hyperkalemia.
- Antidiabetic Agents (insulin, oral hypoglycemics) · Triamterene may increase blood glucose levels.
- Antihypertensive Agents · Possible potentiation of hypotensive effects.
- Diuretics, Potassium-Sparing (spironolactone, amiloride) · Increased risk of hyperkalemia; concurrent use is contraindicated.
- Lithium · Triamterene may reduce lithium clearance, increasing the risk of lithium toxicity.
- NSAIDs (especially indomethacin) · May increase the risks of nephrotoxicity when used concurrently.
- Potassium Supplements or High Potassium Foods · Increased risk for hyperkalemia.
- Quinidine · Laboratory interaction: Triamterene may interfere with the fluorescent assay of quinidine.
モニタリング
- Serum electrolytes (especially potassium)
- BUN and creatinine
- Hydration status
- Blood pressure, if indicated
- Signs of edema
- Patient weight, if indicated
過量投与
The oral LD50 for triamterene in mice is 380 mg/kg. * **Clinical Signs**: Fluid and electrolyte imbalance (especially hyperkalemia) is the most likely risk. Gastrointestinal effects or hypotension are also possible. * **Management**: Consider gut emptying protocols for very large or unknown quantity ingestions. Acute overdoses should generally be managed by observation, with rigorous fluid, electrolyte (especially serum potassium), and acid-base monitoring. Initiate supportive treatment 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。