クエン酸塩（クエン酸カリウム、クエン酸ナトリウム、クエン酸）
クエン酸塩は獣医学において主に**尿アルカリ化剤**として使用され、慢性腎臓病（CKD）や尿細管性アシドーシスに伴う**慢性代謝性アシドーシス**の管理に役立ちます。 特に**クエン酸カリウム**は、犬や猫の**シュウ酸カルシウム結石**の形成を予防するために推奨されます。嗜好性が高く、CKD患者に多い低カリウム血症のカリウム補給にもなるため、炭酸水素ナトリウムよりも好まれることがよくあります。 *臨床のポイント*: シュウ酸カルシウム結石の予防には非常に効果的ですが、尿のpHが高くなりすぎるとリン酸カルシウム結石の形成を促進する恐れがあるため、過度なアルカリ化は避ける必要があります。
作用機序: Citrate salts are absorbed from the gastrointestinal tract and **oxidized in the liver** to produce **bicarbonate** (HCO3-), which acts as a systemic alkalinizing agent, raising blood pH and subsequently urine pH. In the urinary tract, the mechanism is twofold: 1. **Alkalinization**: The resulting alkaline urine increases the solubility of calcium oxalate. 2. **Chelation**: Excreted citrate directly **complexes with calcium** in the urine → decreases the concentration of free calcium available to bind with oxalate → inhibits the formation and growth of calcium oxalate crystals.
動物種別の用量
- Adjunctive therapy to inhibit calcium oxalate formation · Initially 50-100 mg/kg PO q12h · PO · q12h · Goal is to achieve a urine pH of approximately 7.5.
- Decrease possibility of calcium oxalate stone formation (Nutrived Potassium Citrate Granules) · 1 scoop mixed or sprinkled on food per day · PO · q24h
- Adjunctive therapy to inhibit calcium oxalate formation · 100-150 mg/kg/day PO · PO · q24h · It is unclear whether this dose will actually increase urinary citrate in cats.
- Adjunctive therapy of chronic renal failure as a potassium supplement and alkalinizing agent · Initially, 75 mg/kg PO q12h · PO · q12h
- Significantly acidemic chronic renal failure · 2.5 mEq (total dose) potassium or 15-30 mg/kg as potassium citrate PO q12h · PO · q12h
- Hypokalemic chronic renal failure · 2-4 mEq (total dose) of potassium per day as potassium citrate or potassium gluconate · PO · q24h
- Adjunctive therapy to inhibit calcium oxalate crystal formation (hypocitraturia) · 40-75 mg/kg PO q12h · PO · q12h · Avoid overzealous urinary alkalinization as calcium phosphate uroliths may form.
- Adjunctive therapy to inhibit calcium oxalate crystal formation · Initially 50 mg/kg PO q12h · PO · q12h · Monitor urine pH; goal is to obtain values of 7-7.5.
- Decrease possibility of calcium oxalate stone formation (Nutrived Potassium Citrate Granules) · 1 scoop mixed or sprinkled on food per 10 lb. body weight per day · PO · q24h
投与経路
禁忌
- Heart failure
- Severe renal impairment (with azotemia or oliguria)
- Urinary tract infections (UTI) associated with calcium or struvite stones
- Aluminum toxicity
- Hyperkalemia or conditions predisposing to it (adrenal insufficiency, acute dehydration, uncontrolled diabetes mellitus) - for potassium citrate
- Peptic ulcer disease
- Delayed gastric emptying, esophageal compression, or intestinal obstruction (specifically for tablet formulations)
有害事象
- Gastrointestinal distress (nausea, vomiting, diarrhea)
- Hyperkalemia (specifically with potassium citrate)
- Fluid retention (specifically with sodium citrate)
- Metabolic alkalosis (rare)
薬物相互作用
- Amphetamines · Alkalinized urine can decrease excretion, potentially increasing toxicity.
- Pseudoephedrine / Ephedrine · Alkalinized urine can decrease excretion.
- Antacids · May cause systemic alkalosis. Aluminum-containing antacids may cause aluminum toxicity, especially in renal insufficiency. Sodium bicarbonate combinations may cause hypernatremia.
- Aspirin (Salicylates) · Alkalinized urine can increase the excretion of salicylates, decreasing their efficacy.
- Fluoroquinolones (e.g., ciprofloxacin, enrofloxacin) · Solubility is decreased in an alkaline environment; monitor for signs of crystalluria.
- Lithium · Alkalinized urine can decrease excretion.
- Methenamine · Concurrent use is not recommended as methenamine requires an acidic urine for efficacy.
- Quinidine · Alkalinized urine can decrease excretion.
- Tetracyclines · Alkalinized urine can decrease excretion.
- ACE Inhibitors (e.g., enalapril, lisinopril) · May lead to increases in serum potassium levels (hyperkalemia) when used with potassium citrate.
- Cyclosporine · May increase serum potassium levels when used with potassium citrate.
- Digoxin · May increase serum potassium levels when used with potassium citrate.
モニタリング
- Serum potassium, sodium, bicarbonate, chloride
- Acid/base status
- Urine pH
- Urinalysis (monitor for crystalluria)
- Serum creatinine and CBC (particularly in chronic renal failure)
過量投与
Overdosage and acute toxicity generally fall into 4 categories: 1. **Gastrointestinal distress and ulceration** 2. **Metabolic alkalosis** 3. **Hypernatremia** (with sodium citrate) 4. **Hyperkalemia** (with potassium citrate) **Treatment**: If an overdose occurs and preventing absorption is reasonable (especially with tablets), employ gut-emptying protocols if not contraindicated. Treat GI effects with intravenous fluids or supportive care. Hyperkalemia, hypernatremia, and metabolic alkalosis should be treated symptomatically. Contact an animal poison control center for specific treatment modalities.
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