メタゾラミド
Methazolamide
N-(4-methyl-2-sulfamoyl-Δ2-1,3,4-thiadiazolin-5-ylidene)acetamide
別名: Neptazane · GlaucTabs · Glaumetax · MZM · Methazolamidum
VetSheet 獣医チームが監修更新日 2026年4月5日エビデンスに基づく獣医学リファレンス
用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。
動物種別用量
🌎 NA — North America🌍 EU — Europe
犬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Medical treatment of glaucoma | 2.5-5 mg/kg PO q8-12h | PO | q8-12h | — | 🌎 NA |
| Medical treatment of glaucoma | 2-4 mg/kg PO two to three times a day | PO | two to three times a day | — | 🌎 NA |
| Medical treatment of glaucoma | 3-5 mg/kg divided q12h PO | PO | q12h | — | 🌎 NA |
| Medical treatment of glaucoma | 2-5 mg/kg PO two to three times a day | PO | two to three times a day | — | 🌎 NA |
| Medical treatment of glaucoma | 2.2-4.4 mg/kg PO two to three times a day. | PO | two to three times a day | — | 🌎 NA |
| Medical treatment of glaucoma | 2-10 mg/kg PO two to three times a day. | PO | two to three times a day | — | 🌎 NA |
猫
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Medical treatment of glaucoma | 3-4 mg/kg PO twice a day. | PO | twice a day | — | 🌎 NA |
| Medical treatment of glaucoma | 1-2 mg/kg PO q8-12h | PO | q8-12h | — | 🌎 NA |
- Medical treatment of glaucoma: Cats may not tolerate oral carbonic anhydrase inhibitors (CAIs) as well as dogs. Reported side effects include lethargy, inappetence, vomiting. Topical CAIs may be better tolerated.
用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。
概要
メタゾラミドは、獣医学において主に開放隅角緑内障の内科的治療に使用される経口炭酸脱水酵素阻害薬（CAI）です。
歴史的に眼圧（IOP）を下げるための主力薬でしたが、現在では全身性CAIは主に局所点眼薬（ドルゾラミド、ブリンゾラミドなど）に取って代わられています。局所薬は同等の眼圧下降効果を持ちながら、全身性の副作用の発生率が大幅に低いためです。
臨床上の重要なポイント：
- 全身への影響： 経口投与されるため、メタゾラミドは全身の炭酸脱水酵素を阻害し、代謝性アシドーシスや電解質異常（特に低カリウム血症）を引き起こす可能性があります。
- 臨床的有用性： 通常、局所治療に抵抗性のある緑内障の症例や、局所投与が困難な場合に限定して使用されます。
- 動物種による感受性： 猫は経口CAIの副作用に特に敏感であり、著しい嗜眠や食欲不振を示すことがあります。
作用機序
Methazolamide acts via noncompetitive, reversible inhibition of the enzyme carbonic anhydrase (CA), specifically the CA-II isoenzyme.
- In the Eye (Ciliary Body): Inhibition of CA → reduces the formation of hydrogen (H+) and bicarbonate (HCO3-) ions from carbon dioxide and water → decreases the availability of these ions for active transport into the posterior chamber → decreased aqueous humor production → reduced intraocular pressure (IOP).
- In the Kidneys (Proximal Tubule): Inhibition of CA → increased renal tubular secretion of sodium (Na+), potassium (K+), and bicarbonate (HCO3-) → increased urine alkalinity and volume, often resulting in a mild hyperchloremic metabolic acidosis.
- In the CNS: Exhibits anticonvulsant activity independent of its diuretic effects, potentially due to localized CA inhibition in the brain or secondary to systemic metabolic acidosis.
安全性・警告
禁忌
- Significant hepatic disease (may precipitate hepatic coma)
- Renal or adrenocortical insufficiency
- Hyponatremia or hypokalemia
- Hyperchloremic acidosis or severe electrolyte imbalance
- Severe pulmonary obstruction (inability to increase alveolar ventilation to compensate for metabolic acidosis)
- Hypersensitivity to carbonic anhydrase inhibitors or sulfonamides
- Chronic, noncongestive, angle-closure glaucoma (long-term use may mask the condition by lowering IOP while angle closure progresses)
有害事象
- GI disturbances (vomiting, diarrhea, inappetence)
- Metabolic acidosis (often manifesting as heavy panting in dogs)
- CNS effects (sedation, depression, disorientation, excitement)
- Hematologic effects (bone marrow depression, thrombocytopenia)
- Renal effects (crystalluria, dysuria, renal colic, polyuria, polydipsia)
- Hypokalemia
- Hyperglycemia
- Hyponatremia
- Hyperuricemia
- Hepatic insufficiency
- Dermatologic effects (rash)
- Hypersensitivity reactions
- Weakness or cardiac arrhythmias (secondary to electrolyte imbalances)
注意事項
Laboratory Interferences: By alkalinizing the urine, carbonic anhydrase inhibitors may cause false-positive results in determining urine protein using bromphenol blue reagent, sulfosalicylic acid, nitric acid ring test, or heat and acetic acid test methods. They may also decrease iodine uptake by the thyroid gland in hyperthyroid or euthyroid patients.
- Use with caution in pregnant animals (FDA Category C in humans; animal studies show adverse fetal effects).
- Combining oral methazolamide with topical dorzolamide does not yield additive reductions in IOP and may increase adverse effects.
- Monitor closely for signs of hypokalemia and metabolic acidosis, especially in cats.
医薬品相互作用
Alkaline urine caused by methazolamide may decrease excretion of tricyclic antidepressants.
Increased risk of methazolamide accumulation and toxicity; increased risk for metabolic acidosis; methazolamide increases salicylate excretion.
Methazolamide may cause hypokalemia, leading to an increased risk for digoxin toxicity.
Rarely, carbonic anhydrase inhibitors may interfere with the hypoglycemic effects of insulin.
Methazolamide alkalinizes urine, which may negate the urinary antiseptic effects of methenamine.
Concomitant use may exacerbate potassium depletion and hypokalemia.
Increased urinary excretion due to alkaline urine, which may reduce phenobarbital serum levels.
May result in decreased primidone concentrations.
Alkaline urine caused by methazolamide may decrease quinidine excretion.
監視
- Intraocular pressure (IOP) / tonometry
- Serum electrolytes (especially potassium and sodium)
- Blood pH / acid-base status
- Baseline CBC with differential, and periodic retests if using chronically
- Clinical signs of adverse effects (lethargy, GI upset, heavy panting)
薬物動態
吸収
Absorbed from the GI tract, albeit more slowly than acetazolamide.
分布
Distributed throughout the body, including the cerebrospinal fluid (CSF) and aqueous humor.
代謝
At least partially metabolized in the liver.
消失
Excreted primarily via the kidneys, leading to increased urine alkalinity.
過剰投与
Information regarding acute overdosage of methazolamide in veterinary species is limited.
Clinical Signs: Expected signs of toxicity include severe electrolyte imbalances (hypokalemia, hyponatremia), profound metabolic acidosis, CNS depression or disorientation, and dehydration secondary to diuresis.
Management:
- Monitor serum electrolytes, blood gases (for acidosis), volume status, and CNS status.
- Treat symptomatically and supportively.
- Administer intravenous fluids to correct dehydration and electrolyte deficits (especially potassium supplementation if indicated).
- Correct severe metabolic acidosis with sodium bicarbonate if necessary, based on blood gas analysis.
製品
製剤
- Tablets
ヒト用医薬品
- Methazolamide Tablets: 25 mg & 50 mg (generic, Rx)
規制ステータス
規制データなし: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Methazolamide tablets should be stored at room temperature in well-closed containers. Tablets typically have an expiration date of 5 years after manufacture.
飼主向け情報
薬の理解： メタゾラミドは、緑内障によるペットの眼圧を下げるために使用されます。眼内で作られる液体の量を減らすことで効果を発揮します。
投与方法：
- 食事と一緒に与える： この薬が胃腸の不調（嘔吐や食欲不振）を引き起こす場合、食事と一緒に与えることで軽減できることがあります。
- 獣医師の指示がない限り、砕いたり噛ませたりしないでください。
注意すべき点：
- 激しいパンティング（あえぎ呼吸）： この薬は血液の酸性度に軽度の変化（代謝性アシドーシス）を引き起こす可能性があり、犬はこれを補うために激しくパンティングすることがあります。過度な場合は獣医師にご相談ください。
- 嗜眠と隠れる行動： 猫はこの薬に特に敏感で、非常に疲れやすくなったり、食事をとらなくなったりすることがあります。
- 多飲多尿： ペットが普段より多く水を飲み、尿の量が増えることに気づくかもしれません。
- 直ちに獣医師の診察を受ける場合： 異常な出血やあざ、極度の虚弱、筋肉の震え、または発疹が見られた場合は、すぐに獣医師の診察を受けてください。
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