フロセミド
フロセミドは強力で即効性のある**ループ利尿薬**であり、獣医療において体液過剰状態の管理に広く使用されています。多くの動物種において、**うっ血性心不全 (CHF)** および**肺水腫**治療の要となります。強力な利尿作用を促すことで、心臓の前負荷を急速に軽減し、静脈うっ血を改善します。 主な心疾患への応用に加え、フロセミドは以下の目的でも使用されます： * **乏尿性腎不全：** 乏尿を多尿に転換し、尿量を確保するため。 * **高カルシウム血症：** 腎臓からのカルシウム排泄を促進するため（事前の輸液による細胞外液補充が必要）。 * **運動誘発性肺出血 (EIPH)：** 競走馬において鼻出血を軽減するための予防的使用。 * **乳房浮腫：** 牛の分娩後における使用（FDA承認）。 その強力な作用のため、フロセミドは著しい体液および電解質の変動を引き起こす可能性があり、水分状態や血清電解質（特にカリウム）の慎重なモニタリングが必要です。
作用機序: Furosemide acts primarily on the **thick ascending limb of the loop of Henle** in the nephron. * **Inhibition of NKCC2:** It reversibly binds to and inhibits the **Na⁺/K⁺/2Cl⁻ cotransporter** on the luminal membrane → prevents the reabsorption of sodium, potassium, and chloride. * **Loss of Medullary Hypertonicity:** This disruption abolishes the hypertonic medullary interstitium → impairs the kidney's ability to concentrate urine → results in profound, dose-dependent diuresis. * **Electrolyte Excretion:** It significantly increases the renal excretion of water, Na⁺, K⁺, Cl⁻, Ca²⁺, Mg²⁺, H⁺, NH₄⁺, and bicarbonate. * **Hemodynamic Effects:** Furosemide induces mild **renal venodilation** and transiently increases glomerular filtration rate (GFR) via prostaglandin release. This venodilation provides rapid relief in acute cardiogenic pulmonary edema, often before the onset of significant diuresis.
動物種別の用量
- As a general diuretic · 2.5-5 mg/kg (lower dose suggested for cats) · PO, IV or IM · once or twice daily at 6-8 hour intervals
- For severe acute pulmonary edema (parenteral dosing) · Initially 2- 4 mg/kg IV or IM. The dose may be repeated within 1-2 hours. · IV, IM · Repeat within 1-2h · Cats that can tolerate an IV injection may benefit from a faster onset of action. Reduce dosing sharply once respiratory rate starts to decrease.
- For heart failure (oral dosing) · Maintenance dose usually ranges from 6.25 mg once a day to 12.5 mg PO q8h (higher doses, up to 37.5 mg PO q12h have been used) · PO · SID to q8h · Doses must be titrated carefully. Instruct owner to count sleeping respiration rates.
- For chronic therapy (CHF) · initially, try 6.25 mg/cat/day. Some can be maintained on 6.25 mg every other day. · PO · SID or EOD · Goal is to give the 'lowest possible dose'.
- In combination with rest, vasodilators and rate-control · 1-4 mg/kg · IV, IM or PO · q1-12 hours
- For adjunctive treatment of moderate to severe hypercalcemia · 2-4 mg/kg · IV, SC or PO · two to three times daily · Volume expansion is necessary prior to use.
- For acute oliguric renal failure · Initially 2 mg/kg IV; if no substantial diuresis develops in one hour, double to 4 mg/kg. If successful, repeat at 8 hour intervals · IV · q8h
- For acute oliguric renal failure (fluid replete patients) · bolus at 1-6 mg/kg IV. If diuresis ensues, can repeat dose every 6-8 hours or a CRI at 0.1-1 mg/kg/hr · IV · q6-8h or CRI
投与経路
禁忌
- Anuria
- Hypersensitivity to furosemide
- Progressive renal disease if increasing azotemia and oliguria occur during therapy
- Seriously depleted electrolytes
- Severe dehydration
- Severe electrolyte depletion
- Hepatic coma
- Dehydration
- Pericardial effusion where cardiac tamponade is confirmed
有害事象
- Fluid and electrolyte abnormalities (hyponatremia, hypokalemia, hypocalcemia, hypomagnesemia)
- Prerenal azotemia (secondary to dehydration)
- Ototoxicity (especially in cats with high-dose IV therapy)
- Gastrointestinal distress
- Hematologic effects (anemia, leukopenia)
- Weakness and restlessness
- Hypokalaemia
- Hypochloraemia
- Hypocalcaemia
- Hypomagnesaemia
- Hyponatraemia
- Dehydration
- Polyuria/polydipsia (PU/PD)
- Prerenal azotaemia
- Ototoxicity (especially in cats)
- Gastrointestinal disturbances
薬物相互作用
- ACE INHIBITORS (e.g., enalapril, benazepril) · Increased risks for hypotension, particularly in patients who are volume or sodium depleted secondary to diuretics
- AMINOGLYCOSIDES (gentamicin, amikacin, etc.) · Increased risk for ototoxicity
- AMPHOTERICIN B · Loop diuretics may increase the risk for nephrotoxicity development; hypokalemia
- CORTICOSTEROIDS · Increased risk for GI ulceration; hypokalemia · moderate
- DIGOXIN · Furosemide-induced hypokalemia may increase the potential for digoxin toxicity · major
- INSULIN · Furosemide may alter insulin requirements
- MUSCLE RELAXANTS, NON-DEPOLARIZING (e.g., atracurium, tubocurarine) · Furosemide may prolong neuromuscular blockade
- PROBENECID · Furosemide can reduce uricosuric effects
- SALICYLATES · Loop diuretics can reduce the excretion of salicylates
- SUCCINYLCHOLINE · Furosemide may potentiate effects
- THEOPHYLLINE · Pharmacologic effects of theophylline may be enhanced when used with furosemide · moderate
- Aminoglycosides · Potentiates nephrotoxicity and ototoxicity · major
モニタリング
- Serum electrolytes (especially potassium, sodium, calcium, magnesium)
- BUN, creatinine
- Blood glucose
- Hydration status
- Blood pressure, if indicated
- Clinical signs of edema, patient weight, if indicated
- Evaluation of ototoxicity, particularly with prolonged therapy or in cats
- Resting respiratory rate (at home by owner)
- Serum electrolytes (Potassium, Sodium, Chloride, Calcium, Magnesium)
- Renal parameters (BUN, Creatinine)
- Blood pressure
- Clinical signs of ototoxicity (especially in cats)
- Serum electrolytes (especially Potassium, Sodium, Chloride)
- Renal function (BUN, Creatinine)
- Clinical signs of edema/heart failure resolution
過量投与
The LD50 in dogs after oral administration is >1000 mg/kg; after IV injection >300 mg/kg. Chronic overdosing at 10 mg/kg for six months in dogs led to development of calcification and scarring of the renal parenchyma. **Acute overdosage** may cause severe electrolyte and water balance problems, CNS effects (ranging from lethargy to coma and seizures), and cardiovascular collapse. **Treatment:** * Empty the gut after recent oral ingestion using standard protocols. * **Avoid concomitant cathartics** as they may exacerbate fluid and electrolyte imbalances. * Aggressively monitor and treat electrolyte and water balance abnormalities supportively. * Monitor respiratory, CNS, and cardiovascular status.
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