ニトログリセリン
**ニトログリセリン (NTG)** は、獣医療において主に**静脈拡張薬**として使用される、強力かつ即効性のある**有機硝酸エステル**です。 * **主な用途**: **うっ血性心不全 (CHF)** および心原性肺水腫の急性期の補助療法。 * **臨床上のポイント**: 連続使用後48〜72時間以内に**硝酸薬耐性 (タキフィラキシー)** が急速に発現するため、通常は慢性的な外来治療ではなく、急性期の短期的な入院安定化のために限定して使用されます。耐性を軽減するために、間欠的投与（例：12時間貼付、12時間休薬）がしばしば用いられます。 * **投与方法**: 最も一般的には、耳介内側、腋窩、鼠径部などの無毛部に局所的（軟膏または経皮パッチ）に適用されます。 > **注意**: ヒトの狭心症や急性高血圧には非常に有効ですが、小動物では経皮吸収のばらつきや急速な耐性発現のため、その有効性には議論の余地がある場合があります。しかし、急性の容量負荷に対する救急集中治療においては依然として重要な薬剤です。
作用機序: Nitroglycerin acts as a prodrug that donates **nitric oxide (NO)** to vascular smooth muscle, initiating a cascade that leads to vasodilation. * **Nitroglycerin** → converted to **Nitric Oxide (NO)** in smooth muscle cells. * **NO** → activates the enzyme **soluble guanylyl cyclase (sGC)**. * **sGC** → increases intracellular levels of **cyclic GMP (cGMP)**. * **cGMP** → activates **protein kinase G (PKG)** → leads to dephosphorylation of myosin light chains. * **Result**: **Vascular smooth muscle relaxation**. > **Pharmacological Pearl**: At standard doses, NTG primarily dilates venous capacitance vessels. This significantly reduces **preload** (left ventricular end-diastolic pressure) and venous return to the heart, effectively relieving pulmonary congestion and decreasing myocardial oxygen demand. At higher doses, it may also provide some arteriolar dilation, thereby reducing afterload.
動物種別の用量
- Adjunctive treatment of heart failure (severe pulmonary edema secondary to HCM) · ⅛th to ¼ inch of a 2% cream · Topical · every 4-6 hours · for the first 24 hours · Apply to a hairless area (e.g., inside the earflap) as long as furosemide is being administered concomitantly. Efficacy is suspect but safe. Wear gloves.
- To enhance resolution of pulmonary edema · ¼ to ½ inch · Topical · q6h · To reduce nitrate tolerance, alternate 12 hrs with and 12 hrs without nitroglycerin therapy.
- Adjunctive treatment of heart failure · 2.5-5 mg/24hr transdermal patch · Topical · 12 hours on, 12 hours off
- Adjunctive treatment of pulmonary edema · ¼ inch · Topical/Mucous membranes · every 8 hours · during the first 48 hours · Applied cutaneously or directly to mucous membranes.
- Cardiogenic pulmonary edema (headed for oxygen) · ¼ inch · Topical · q8h · for the first 24 hours · Apply on the inner ear pinnae, groin or axilla as needed. Wear gloves to apply.
- Adjunctive treatment of hypertension · ¼ inch · Topical · q6-8h · Applied to pinna.
- Adjunctive therapy for heart failure · ⅛th inch strip · Topical · q12h · for the first 24 hours of therapy · Applied to inside of pinna.
- Dilative cardiomyopathy · ⅛th of an inch · Topical · once to twice daily · Applied to shaved skin. Apply to ear pinna or skin of thigh. May cause hypotension.
投与経路
禁忌
- Severe anemia
- Hypersensitivity to nitrates
有害事象
- Rashes or erythema at the application site
- Orthostatic hypotension
- Transient headaches (common in humans, suspected in animals)
- Lethargy or weakness secondary to hypotension
薬物相互作用
- Antihypertensive drugs · Use of nitroglycerin with other antihypertensive drugs may cause additive hypotensive effects.
- Phenothiazines · May increase hypotensive effects.
- Sildenafil (and other PDE inhibitors) · May profoundly increase risk for severe, potentially fatal hypotension.
モニタリング
- Clinical efficacy (resolution of pulmonary edema, improved breathing)
- Sites of application for signs of rash or erythema
- Blood pressure, particularly if hypotensive effects (lethargy, weakness) are seen
過量投与
If severe hypotension results after topical administration: * **Decontamination**: Immediately wash the site of application with soap and water to prevent any further absorption of the ointment. * **Supportive Care**: Intravenous fluids may be administered if necessary to support blood pressure. * **Contraindications**: **Epinephrine is contraindicated** as it is ineffective in this scenario and may further complicate the animal's cardiovascular condition.
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。