Nitroglycerin
Glyceryl trinitrate
Also known as: Nitro-bid · Minitran · Nitro-Dur · Nitrek · glyceryl trinitrate · glonoine · GTN · nitroglycerol · NTG · trinitrin · trinitroglycerin
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Adjunctive treatment of heart failure | 2% NTG at ¼ to 1 inch | Topical | q6-12h | — | 🌎 NA |
| Adjunctive treatment of heart failure | 2.5-10 mg/24hr transdermal patch | Topical | 12 hours on, 12 hours off | — | 🌎 NA |
| Adjunctive treatment of pulmonary edema | ¼-2 inches | Topical/Mucous membranes | q8h | during the first 48 hours | 🌎 NA |
| Cardiogenic pulmonary edema (headed for oxygen) | ¼ inch for small dogs up to 1 inch for large dogs | Topical | q8h | for the first 24 hours | 🌎 NA |
| Venodilator for adjunctive treatment of systolic heart failure | ¼ inch per 5 kg of body weight of the 2% ointment | Topical | three times daily | for the first 24 hours | 🌎 NA |
- Adjunctive treatment of heart failure: If nitroprusside not used; apply to hairless area in the axilla or groin.
- Adjunctive treatment of pulmonary edema: Applied cutaneously or directly to mucous membranes (all animals tolerate the paste given orally).
- Cardiogenic pulmonary edema (headed for oxygen): Apply on the inner ear pinnae, groin or axilla as needed. Wear gloves to apply.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| 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 | 🌎 NA |
| To enhance resolution of pulmonary edema | ¼ to ½ inch | Topical | q6h | — | 🌎 NA |
| Adjunctive treatment of heart failure | 2.5-5 mg/24hr transdermal patch | Topical | 12 hours on, 12 hours off | — | 🌎 NA |
| Adjunctive treatment of pulmonary edema | ¼ inch | Topical/Mucous membranes | every 8 hours | during the first 48 hours | 🌎 NA |
| Cardiogenic pulmonary edema (headed for oxygen) | ¼ inch | Topical | q8h | for the first 24 hours | 🌎 NA |
| Adjunctive treatment of hypertension | ¼ inch | Topical | q6-8h | — | 🌎 NA |
- Adjunctive treatment of heart failure (severe pulmonary edema secondary to HCM): 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: To reduce nitrate tolerance, alternate 12 hrs with and 12 hrs without nitroglycerin therapy.
- Adjunctive treatment of pulmonary edema: Applied cutaneously or directly to mucous membranes.
- Cardiogenic pulmonary edema (headed for oxygen): Apply on the inner ear pinnae, groin or axilla as needed. Wear gloves to apply.
- Adjunctive treatment of hypertension: Applied to pinna.
Ferrets
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Adjunctive therapy for heart failure | ⅛th inch strip | Topical | q12h | for the first 24 hours of therapy | 🌎 NA |
| Dilative cardiomyopathy | ⅛th of an inch | Topical | once to twice daily | — | 🌎 NA |
- Adjunctive therapy for heart failure: Applied to inside of pinna.
- Dilative cardiomyopathy: Applied to shaved skin. Apply to ear pinna or skin of thigh. May cause hypotension.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Nitroglycerin (NTG) is a potent, rapid-acting organic nitrate primarily utilized as a venodilator in veterinary medicine.
- Primary Use: Acute adjunctive management of congestive heart failure (CHF) and cardiogenic pulmonary edema.
- Clinical Pearl: Due to the rapid development of nitrate tolerance (tachyphylaxis) within 48-72 hours of continuous use, it is typically reserved for acute, short-term hospital stabilization rather than chronic outpatient therapy. Intermittent dosing (e.g., 12 hours on, 12 hours off) is often employed to mitigate this tolerance.
- Administration: Most commonly applied topically (as an ointment or transdermal patch) to hairless areas such as the inner pinna (ear flap), axilla, or groin.
Note: While highly effective in humans for angina and acute hypertension, its efficacy in small animals is sometimes debated due to variable transdermal absorption and rapid tolerance, but it remains a staple in emergency critical care for acute volume overload.
Mechanism of action
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.
Safety & warnings
Contraindications
- Severe anemia
- Hypersensitivity to nitrates
Adverse effects
- Rashes or erythema at the application site
- Orthostatic hypotension
- Transient headaches (common in humans, suspected in animals)
- Lethargy or weakness secondary to hypotension
Precautions
Important Warnings
- Hypotension Risk: Use with extreme caution (if at all) in patients with diuretic-induced hypovolemia, cerebral hemorrhage, head trauma, or other hypotensive conditions.
- Tolerance: Continuous use (48-72 hours) results in the rapid development of tolerance to the drug's effects. Intermittent dosing is recommended.
- Human Exposure: Personnel applying the drug must wear non-permeable gloves to prevent self-absorption, which can cause severe headaches and hypotension.
- Pregnancy: FDA Category C. Use cautiously as a last resort when the benefit clearly outweighs the risks. Unknown if excreted in maternal milk; use with caution in nursing animals.
Drug interactions
Use of nitroglycerin with other antihypertensive drugs may cause additive hypotensive effects.
May increase hypotensive effects.
May profoundly increase risk for severe, potentially fatal hypotension.
Monitoring
- 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
Pharmacokinetics
Absorption
Absorbed through the skin. Onset of action usually within 1 hour; duration of action is 2-12 hours. Transdermal patches have wide inter-patient bioavailability.
Distribution
Systemic distribution following transdermal absorption.
Metabolism
Metabolized in the liver. At least two metabolites have some vasodilator activity and have longer half-lives than the parent drug.
Elimination
Not explicitly detailed in the monograph.
Overdose
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.
Available products
Formulations
- Topical ointment (2%)
- Transdermal patches (0.1 mg/hr to 0.8 mg/hr)
- Sublingual tablets (human)
- Buccal tablets (human)
- Lingual spray (human)
- Extended-release oral capsules/tablets (human)
- Parenteral solutions for IV infusion (human)
Human-labeled
- Nitroglycerin Topical Ointment: 2% in a lanolin-white petrolatum base in 30 g & 60 g tubes and UD 1 g (Nitro-bid®, generic)
- Nitroglycerin Transdermal Systems (patches): 0.1 mg/hr, 0.2 mg/hr, 0.3 mg/hr, 0.4 mg/hr, 0.6 mg/hr & 0.8 mg/hr (Minitran®, Nitro-Dur®, Nitrek®, generic)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
The topical ointment should be stored at room temperature with the cap firmly attached.
Client information
Important Safety and Application Guidelines
- Safety First (Wear Gloves): Always wear non-permeable gloves (like latex or nitrile) when applying the ointment or handling patches. Nitroglycerin is easily absorbed through human skin and can cause severe headaches, dizziness, or a dangerous drop in your own blood pressure.
- Measuring the Dose: The dosage is measured in "inches" of ointment. Use the special measuring papers supplied with the product to get the exact dose prescribed by your veterinarian.
- Application: Apply the ointment to a hairless area as directed (commonly the inside of the ear flap, the groin, or the armpit). Rub the ointment into the skin well.
- Rotate Sites: Change the application site with each dose (e.g., switch from the left ear to the right ear). This prevents skin irritation and helps the medication absorb better. If a rash develops, do not use that site again until it has completely cleared.
- Avoid Contact: Do not pet your animal over the area where the ointment was applied. Keep treated pets away from children or other animals who might touch or lick the area.
- When to Call the Vet: Contact your veterinarian if a skin rash persists, or if your pet seems unusually weak, wobbly, or lethargic (which could be signs of low blood pressure).
- Fire Safety: Despite its name and history as an explosive, medical nitroglycerin is heavily diluted and there is no danger of explosion or fire with the use of this product.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.