硝酸甘油
**硝酸甘油 (NTG)** 是一種強效、速效的**有機硝酸鹽**，在獸醫學中主要作為**靜脈擴張劑**使用。 * **主要用途**：作為**充血性心衰竭 (CHF)** 和心因性肺水腫的急性輔助治療。 * **臨床要點**：由於連續使用 48-72 小時內會迅速產生**硝酸鹽耐受性 (tachyphylaxis)**，因此通常僅限於急診住院期間的短期穩定治療，而不作為慢性的門診藥物。常採用間歇性給藥（例如：使用 12 小時，停用 12 小時）來減輕耐受性。 * **給藥方式**：最常以局部塗抹（藥膏或透皮貼片）的方式，應用於無毛區域，如耳廓內側、腋下或腹股溝。 > **注意**：雖然在人類心絞痛和急性高血壓中非常有效，但由於小動物的透皮吸收差異大且容易產生耐受性，其療效有時存在爭議，但它仍是急重症照護中處理急性體液過載的重要藥物。
作用機制: 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.
各物種劑量
- 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.
給藥途徑
禁忌症
- Severe anemia
- Hypersensitivity to nitrates
不良反應
- Rashes or erythema at the application site
- Orthostatic hypotension
- Transient headaches (common in humans, suspected in animals)
- Lethargy or weakness secondary to hypotension
藥物相互作用
- 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.
監測
- 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
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 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。