馬尿酸烏洛托品
Methenamine Hippurate
Hexamethylenetetramine hippurate
別名: Hiprex · Urex · Hexamine amygdalate · Hexamine mandelate · Mandelato de metenamina · Aci-steril · Reflux · Urocedulamin
由 VetSheet 獸醫團隊審訂更新於 2026年4月5日本內容以實證獸醫文獻為本
劑量為合格獸醫專業人員的臨床參考。請務必對照最新仿單及個別病患確認。
各物種劑量
🌎 NA — North America🌍 EU — Europe
狗
| 適應症 | 劑量 | 途徑 | 頻次 | 療程 | 地區 |
|---|---|---|---|---|---|
| Urinary tract infection prophylaxis | 10 mg/kg | PO | q6h | — | 🌎 NA |
| Urinary tract infection prophylaxis | 10 mg/kg | PO | q6h | — | 🌎 NA |
| Urinary tract infection prophylaxis | 10-20 mg/kg | PO | q8-12h | — | 🌎 NA |
- Urinary tract infection prophylaxis: Methenamine mandelate; use with ammonium chloride to acidify urine and increase effectiveness
- Urinary tract infection prophylaxis: Methenamine mandelate
- Urinary tract infection prophylaxis: Methenamine mandelate; urine pH may need to be lowered by use of an acidifying diet and/or urinary acidifiers
貓
| 適應症 | 劑量 | 途徑 | 頻次 | 療程 | 地區 |
|---|---|---|---|---|---|
| Urinary tract infection prophylaxis | 250 mg | PO | q12h | — | 🌎 NA |
- Urinary tract infection prophylaxis: Methenamine hippurate
劑量為合格獸醫專業人員的臨床參考。請務必對照最新仿單及個別病患確認。
概覽
馬尿酸烏洛托品是一種泌尿道防腐劑，主要用於預防反覆發作的泌尿道感染 (UTIs)。
- 臨床應用： 在獸醫學中不常作為第一線藥物，且在犬貓的療效證據有限。通常保留用於傳統抗生素治療無效或有禁忌症的具抗藥性、反覆性下泌尿道感染。
- 機制依賴性： 其療效嚴格依賴於酸性尿液環境（pH 值 < 6.5，理想情況下 < 5.5）。在鹼性尿液中，該藥物不具活性。
- 抗菌譜： 活化後，它對革蘭氏陽性菌（葡萄球菌、腸球菌）和革蘭氏陰性菌（大腸桿菌、假單胞菌、變形桿菌）提供廣效、非特異性的殺菌活性，據報導對某些真菌病原體也有效。
- 臨床要點： 由於它會轉化為甲醛，細菌不會對其產生質體介導或染色體抗藥性，這使其在慢性預防中具有獨特的價值。
作用機轉
Methenamine is a prodrug that requires an acidic environment for activation.
- Hydrolysis Pathway: In an acidic urinary environment (pH < 6.5) → methenamine is hydrolyzed → formaldehyde + ammonia.
- Bactericidal Action: Formaldehyde acts as a non-specific bactericidal agent by denaturing bacterial proteins and nucleic acids.
- Role of Hippurate: The hippuric acid salt component serves a dual purpose: it acts as a weak acid to help lower the urinary pH (facilitating the conversion to formaldehyde) and possesses mild, non-specific antibacterial activity of its own.
- Systemic Inactivity: At physiological blood pH (7.4), methenamine remains stable and inactive, ensuring that formaldehyde is only generated locally within the urinary bladder.
安全性與警告
禁忌症
- Hypersensitivity to methenamine or its salts
- Renal insufficiency
- Metabolic acidosis
- Severe hepatic impairment (due to ammonia production during hydrolysis)
- Severe dehydration
不良反應
- Gastrointestinal irritation (nausea, vomiting, anorexia)
- Dysuria (secondary to formaldehyde irritation with long-term use)
- Systemic acidosis (potential)
- Lipoid pneumonitis (reported in humans using oral suspension)
注意事項
Crucial Efficacy Requirement: Urine pH MUST be kept below 6.5 (ideally ≤ 5.5) for the drug to be effective.
- Urea-Splitting Bacteria: Infections with urea-splitting organisms (e.g., Proteus, some Staphylococcus, Pseudomonas) naturally alkalinize the urine, potentially rendering methenamine ineffective.
- Acidification Therapy: Concurrent use of urinary acidifiers (e.g., methionine, ammonium chloride, ascorbic acid) or prescription acidifying diets is often required.
- Species Sensitivity: Cats reportedly do not tolerate methenamine as well as dogs.
- Pregnancy: FDA Category C. Crosses the placenta; use with caution during pregnancy. Enters milk, but no adverse effects reported in nursing offspring.
藥物交互作用
Not recommended; an insoluble precipitate may form in the urine.
May reduce the efficacy of methenamine by preventing its conversion to formaldehyde in the urine.
監測
- Urine pH (must remain < 6.5)
- Clinical efficacy (resolution or prevention of UTI symptoms)
- Urinalysis and urine cultures
藥物動力學
吸收
Well absorbed from the GI tract. Up to 30% of a dose may be hydrolyzed by gastric acid to ammonia and formaldehyde (reduced with enteric-coated tablets).
分佈
Crosses the placenta and is distributed into milk. Plasma concentrations of formaldehyde and methenamine are very low and have negligible systemic antibacterial activity.
代謝
Hydrolyzed in acidic urine (pH < 6.5, maximal at ≤ 5.5) to ammonia and formaldehyde.
排除
70-90% of a dose is excreted unchanged into the urine within 24 hours. Peak formaldehyde concentrations occur in the urine at about 2 hours post-dose (3-8 hours with enteric-coated tablets).
過量
Dogs have tolerated single IV dosages of up to 600 mg/kg of methenamine hippurate without overt toxic effects.
Management of Large Oral Overdoses:
- Implement established gut emptying protocols (emesis/gastric lavage) if ingestion is recent.
- Maintain hydration status with intravenous fluids.
- Provide symptomatic and supportive care as required, monitoring for systemic acidosis and gastrointestinal distress.
可用產品
劑型
- Oral tablets
人用標示
- Methenamine Hippurate Oral Tablets: 1 gram (Hiprex, Urex)
各地核准狀態
暫無法規資料: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
儲存與穩定性
Store commercially available methenamine products at room temperature. Because acids hydrolyze methenamine to formaldehyde and ammonia, do not mix with acidic vehicles before administering. Physically incompatible when mixed with most alkaloids and metallic salts.
飼主須知
- 給藥方式： 請嚴格按照處方給藥。如果您的寵物出現腸胃不適（嘔吐或食慾不振），請嘗試在飯後給藥。
- 飲食的重要性： 此藥物僅在寵物的尿液呈酸性時才有效。嚴格按照獸醫師的指示餵食任何特殊的處方飲食或給予尿液酸化劑是至關重要的。
- 依從性： 請勿漏服。必須持續給藥以防止感染復發。
- 監測： 您的獸醫師可能需要定期檢查您寵物的尿液 pH 值，以確保藥物正常發揮作用。
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