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Top 5 Vasodilator Options for Dogs in Canada — 2025 Veterinary-Backed Guide to Hydralazine, Nitrates and Sildenafil (Which One Fits Your Pet?)

Published on Thursday, August 21, 2025

Vasodilator agents relax blood vessels to lower systemic and pulmonary blood pressure in dogs with heart disease or hypertension. Common prescription examples include hydralazine formulations and nitrates, and selective pulmonary vasodilators such as sildenafil. These medicines are frequently used alongside ACE inhibitors, diuretics, or positive inotropes to optimize hemodynamics and symptom control. Canadian pet owners and veterinarians prefer specific vasodilators based on the type of hypertension (systemic versus pulmonary), route and flexibility of dosing (tablet, ointment, or compounded suspension), safety profile, monitoring requirements, and local availability. For many owners, appeal comes from proven clinical benefit, straightforward dosing for outpatient use, and access to veterinary guidance and compounding services in Canada to suit small or difficult-to-dose patients.

Quick Menu

1. Best Arterial Vasodilator

2. Best Venodilator Nitrate Option

3. Best Topical Emergency Vasodilator

4. Best Compounded Dosing Flexibility

5. Best Pulmonary Hypertension Specialist Choice

1
BEST ARTERIAL VASODILATOR

Apresoline (Hydralazine) 10mg Tablets

Apresoline (Hydralazine) 10mg Tablets

Apresoline is positioned as a best-in-class arteriolar vasodilator for dogs because it reliably reduces systemic afterload, is widely available in generic form, and is one of the most cost-effective prescription options for chronic management. Compared with nitrates like Isordil or Nitro-Bid that primarily unload the venous side, hydralazine targets arterial resistance and pairs well with venodilators for balanced blood pressure control; versus compounded suspensions it lacks dosing flexibility for very small patients but offers stable, low-cost tablet dosing.

3.8
★★★☆☆
  • Fast artery relaxer

  • Low-dose friendly

  • Fast artery relaxer

  • Low-dose friendly

Review Summary

75%

"Owners report hydralazine lowers blood pressure reliably in dogs when used as prescribed but some see side effects like increased heart rate and occasional GI upset; tablets can be awkward to dose for very small dogs. Overall users find it effective as part of combination therapy for hypertension. "

  • Vintage heart-helper

  • 10 mg oral tablets used off-label to reduce systemic vascular resistance and afterload in hypertensive or heart-failure dogs

  • Vintage heart-helper

  • 10 mg oral tablets used off-label to reduce systemic vascular resistance and afterload in hypertensive or heart-failure dogs

Increased Safety & Security

Time-Saving Convenience

Apresoline is positioned as a best-in-class arteriolar vasodilator for dogs because it reliably reduces systemic afterload, is widely available in generic form, and is one of the most cost-effective prescription options for chronic management. Compared with nitrates like Isordil or Nitro-Bid that primarily unload the venous side, hydralazine targets arterial resistance and pairs well with venodilators for balanced blood pressure control; versus compounded suspensions it lacks dosing flexibility for very small patients but offers stable, low-cost tablet dosing.

  • Fast artery relaxer

  • Low-dose friendly

  • Vintage heart-helper

  • 10 mg oral tablets used off-label to reduce systemic vascular resistance and afterload in hypertensive or heart-failure dogs

  • Direct smooth muscle relaxant with relatively rapid onset for systemic vasodilation

  • Fast artery relaxer

  • Low-dose friendly

  • Vintage heart-helper

  • 10 mg oral tablets used off-label to reduce systemic vascular resistance and afterload in hypertensive or heart-failure dogs

  • Direct smooth muscle relaxant with relatively rapid onset for systemic vasodilation

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$20-60 CAD

2
BEST VENODILATOR NITRATE OPTION

Isordil (Isosorbide Dinitrate) 10mg Tablets

Isordil (Isosorbide Dinitrate) 10mg Tablets

Isordil is highlighted as a market leader among oral nitrates for dogs because it produces sustained venodilation that helps reduce preload and is easy to dose as a tablet formulation for outpatient care. Compared with Nitro-Bid ointment, Isordil provides longer systemic coverage without the topical handling or storage considerations, and when combined with hydralazine it offers a complementary hemodynamic effect; it is generally mid-range in cost and avoids the flavor and compounding premiums of liquid preparations.

3.3
★★★☆☆
  • Nitrate quick-release

  • Tablet dosing simple

  • Nitrate quick-release

  • Tablet dosing simple

Review Summary

65%

"Isosorbide dinitrate gets mixed feedback: some owners note improved congestion and breathing while others see limited benefit or rapid tolerance and episodes of low blood pressure. Administration and variable response are common complaints. "

  • Classic chest-calmer

  • Oral isosorbide dinitrate that primarily reduces preload through venodilation and is used adjunctively in canine cardiac care

  • Classic chest-calmer

  • Oral isosorbide dinitrate that primarily reduces preload through venodilation and is used adjunctively in canine cardiac care

Increased Safety & Security

Time-Saving Convenience

Isordil is highlighted as a market leader among oral nitrates for dogs because it produces sustained venodilation that helps reduce preload and is easy to dose as a tablet formulation for outpatient care. Compared with Nitro-Bid ointment, Isordil provides longer systemic coverage without the topical handling or storage considerations, and when combined with hydralazine it offers a complementary hemodynamic effect; it is generally mid-range in cost and avoids the flavor and compounding premiums of liquid preparations.

  • Nitrate quick-release

  • Tablet dosing simple

  • Classic chest-calmer

  • Oral isosorbide dinitrate that primarily reduces preload through venodilation and is used adjunctively in canine cardiac care

  • Slower onset and longer duration than sublingual nitrates, often dosed several times daily

  • Nitrate quick-release

  • Tablet dosing simple

  • Classic chest-calmer

  • Oral isosorbide dinitrate that primarily reduces preload through venodilation and is used adjunctively in canine cardiac care

  • Slower onset and longer duration than sublingual nitrates, often dosed several times daily

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$25-80 CAD

3
BEST TOPICAL EMERGENCY VASODILATOR

Nitro-Bid (Nitroglycerin) 2% Ointment

Nitro-Bid (Nitroglycerin) 2% Ointment

Nitro-Bid stands out for acute and topical use because nitroglycerin ointment delivers rapid vasodilation transdermally, making it valuable when oral administration is impractical or when a fast onset is required. Compared with oral nitrates like Isordil, Nitro-Bid has a quicker effect but typically higher per-dose cost and added handling/storage considerations; it occupies a distinct niche versus systemic agents such as hydralazine and sildenafil by providing localized, short-acting venodilation.

3.6
★★★☆☆
  • Topical vasodilator

  • Local application control

  • Topical vasodilator

  • Local application control

Review Summary

70%

"Topical nitroglycerin ointment is praised for fast, localized vasodilation and rapid clinical effect but many users find it messy, difficult to apply, and worry about owner exposure and systemic hypotension. It’s often considered useful for short-term or focal problems but inconvenient for long-term use. "

  • Sticky but trusty

  • 2% topical nitroglycerin ointment provides fast-acting vasodilation useful for acute afterload reduction

  • Sticky but trusty

  • 2% topical nitroglycerin ointment provides fast-acting vasodilation useful for acute afterload reduction

Increased Safety & Security

Time-Saving Convenience

Nitro-Bid stands out for acute and topical use because nitroglycerin ointment delivers rapid vasodilation transdermally, making it valuable when oral administration is impractical or when a fast onset is required. Compared with oral nitrates like Isordil, Nitro-Bid has a quicker effect but typically higher per-dose cost and added handling/storage considerations; it occupies a distinct niche versus systemic agents such as hydralazine and sildenafil by providing localized, short-acting venodilation.

  • Topical vasodilator

  • Local application control

  • Sticky but trusty

  • 2% topical nitroglycerin ointment provides fast-acting vasodilation useful for acute afterload reduction

  • Topical route is helpful when oral administration is impractical but carries risk of human exposure and sensitization

  • Topical vasodilator

  • Local application control

  • Sticky but trusty

  • 2% topical nitroglycerin ointment provides fast-acting vasodilation useful for acute afterload reduction

  • Topical route is helpful when oral administration is impractical but carries risk of human exposure and sensitization

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$40-120 CAD

4
BEST COMPOUNDED DOSING FLEXIBILITY

Hydralazine Compounded Oral Suspension

Hydralazine Compounded Oral Suspension

The compounded hydralazine oral suspension is a market-leading choice for small or pill-averse dogs because it enables precise, weight‑based dosing and palatable formulations that standard tablets cannot match. Although compounding increases per-unit cost relative to off-the-shelf Apresoline tablets, the technical advantage of customizable concentrations and flavored liquids makes it superior for pediatric, geriatric, or outpatient titration scenarios where dosing flexibility and adherence matter most.

4
★★★★☆
  • Liquid dose accuracy

  • Easy for picky

  • Liquid dose accuracy

  • Easy for picky

Review Summary

78%

"Compounded hydralazine suspension is frequently appreciated for accurate dosing and ease of administration in small dogs and cats, though some owners express concerns about consistency between compounding pharmacies and shelf-life. Most long-term users report good clinical results when potency is confirmed. "

  • Tailored strength magic

  • Compounded hydralazine oral suspension allows precise weight-based dosing for small dogs or patients unable to swallow tablets

  • Tailored strength magic

  • Compounded hydralazine oral suspension allows precise weight-based dosing for small dogs or patients unable to swallow tablets

Increased Safety & Security

Time-Saving Convenience

The compounded hydralazine oral suspension is a market-leading choice for small or pill-averse dogs because it enables precise, weight‑based dosing and palatable formulations that standard tablets cannot match. Although compounding increases per-unit cost relative to off-the-shelf Apresoline tablets, the technical advantage of customizable concentrations and flavored liquids makes it superior for pediatric, geriatric, or outpatient titration scenarios where dosing flexibility and adherence matter most.

  • Liquid dose accuracy

  • Easy for picky

  • Tailored strength magic

  • Compounded hydralazine oral suspension allows precise weight-based dosing for small dogs or patients unable to swallow tablets

  • Provides the same arterial vasodilatory effect as tablets but in a palatable, adjustable concentration

  • Liquid dose accuracy

  • Easy for picky

  • Tailored strength magic

  • Compounded hydralazine oral suspension allows precise weight-based dosing for small dogs or patients unable to swallow tablets

  • Provides the same arterial vasodilatory effect as tablets but in a palatable, adjustable concentration

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$50-150 CAD

5
BEST PULMONARY HYPERTENSION SPECIALIST CHOICE

Sildenafil 20mg Tablets

Sildenafil 20mg Tablets

Sildenafil 20mg is positioned as the lead pulmonary vasodilator option for dogs because it selectively targets pulmonary arterial pressure and is widely used for pulmonary hypertension cases where systemic vasodilators are less effective. Compared with systemic agents like hydralazine or nitrates, sildenafil’s pulmonary specificity reduces the risk of systemic hypotension and is generally available as a cost-effective generic option, making it the preferred choice when pulmonary vasodilation is the clinical priority.

4.5
★★★★☆
  • Pulmonary pressure reducer

  • Dog-sized dosing

  • Pulmonary pressure reducer

  • Dog-sized dosing

Review Summary

88%

"Sildenafil 20 mg is widely reported to improve exercise tolerance and reduce signs of pulmonary hypertension in dogs, with relatively few and usually mild side effects; many owners note clear quality-of-life benefits. It is one of the more consistently well-reviewed vasodilators in veterinary use. "

  • Happy lungs, wagging

  • Sildenafil 20 mg tablets (PDE-5 inhibitor) are widely used to treat pulmonary hypertension in dogs

  • Happy lungs, wagging

  • Sildenafil 20 mg tablets (PDE-5 inhibitor) are widely used to treat pulmonary hypertension in dogs

Increased Safety & Security

Time-Saving Convenience

Sildenafil 20mg is positioned as the lead pulmonary vasodilator option for dogs because it selectively targets pulmonary arterial pressure and is widely used for pulmonary hypertension cases where systemic vasodilators are less effective. Compared with systemic agents like hydralazine or nitrates, sildenafil’s pulmonary specificity reduces the risk of systemic hypotension and is generally available as a cost-effective generic option, making it the preferred choice when pulmonary vasodilation is the clinical priority.

  • Pulmonary pressure reducer

  • Dog-sized dosing

  • Happy lungs, wagging

  • Sildenafil 20 mg tablets (PDE-5 inhibitor) are widely used to treat pulmonary hypertension in dogs

  • Oral dosing is predictable and often tailored as once- or twice-daily depending on disease severity

  • Pulmonary pressure reducer

  • Dog-sized dosing

  • Happy lungs, wagging

  • Sildenafil 20 mg tablets (PDE-5 inhibitor) are widely used to treat pulmonary hypertension in dogs

  • Oral dosing is predictable and often tailored as once- or twice-daily depending on disease severity

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$20-80 CAD

How vasodilators work and what the research shows

Vasodilators reduce vascular resistance by relaxing smooth muscle in arterial and/or venous walls or by targeting signaling pathways that control pulmonary blood flow. Clinical and experimental veterinary literature supports their role in managing systemic hypertension and pulmonary hypertension in dogs, often improving signs such as exercise intolerance, respiratory distress from right-sided failure, and afterload-related cardiac workload. Evidence varies by agent and indication: nitrates and hydralazine have a long history for systemic afterload and preload modulation, while sildenafil — a phosphodiesterase type 5 inhibitor — is well supported for pulmonary hypertension. Veterinary cardiology guidelines emphasize individualized dosing, regular blood pressure monitoring, and evaluation of renal function when using vasodilators.

Mechanisms: hydralazine acts as a direct arteriolar smooth muscle relaxant; nitrates (isosorbide dinitrate, nitroglycerin) donate nitric oxide to produce venodilation and some arterial effects; sildenafil selectively targets pulmonary vasculature by inhibiting phosphodiesterase type 5, increasing cyclic GMP and causing vasodilation.

Clinical effects: vasodilators can lower systemic or pulmonary arterial pressure, reduce cardiac afterload, and in some cases improve exercise tolerance and clinical signs associated with heart failure.

Evidence base: multiple peer-reviewed veterinary studies and clinical reports across the 2000s to 2020s document benefit of sildenafil for canine pulmonary hypertension and support hydralazine/nitrate use for systemic hypertension or acute afterload reduction.

Safety and monitoring: all vasodilators can cause hypotension, weakness, or gastrointestinal upset; monitor blood pressure and renal function regularly; adjust dose with concurrent cardiac drugs.

Important interaction: avoid combining nitrates or other nitric oxide donors with sildenafil or other PDE5 inhibitors because of risk of severe additive hypotension.

In the Canadian 2025 context, vasodilators remain an essential part of veterinary cardiovascular care — chosen based on whether the target is systemic or pulmonary pressure, the need for tailored dosing, and safety monitoring. The five highlighted options on this page — Apresoline (Hydralazine) 10mg Tablets, Isordil (Isosorbide Dinitrate) 10mg Tablets, Nitro-Bid (Nitroglycerin) 2% Ointment, Hydralazine Compounded Oral Suspension, and Sildenafil 20mg Tablets — cover oral, topical and compounded choices commonly used by Canadian clinics and compounding pharmacies. For many cases of pulmonary hypertension, Sildenafil 20mg Tablets is often the preferred choice among these five because of targeted pulmonary vasodilation and a strong clinical evidence base; for systemic hypertension or when precise small-dog dosing is required, a hydralazine compounded oral suspension can be especially useful. We hope you found what you were looking for — use the site search to refine by condition (pulmonary versus systemic hypertension), dosing form, or to expand your review of combination therapies and monitoring guidelines.

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