Specialty Spotlight: “Urine for a Wild Ride!” A Review of Diuretic Therapy in Canine Congestive Heart Failure

June 23rd, 2026 | Posted in General, Medical Articles

Specialty Spotlight: “Urine for a Wild Ride!”  A Review of Diuretic Therapy in Canine Congestive Heart Failure

Aaron C. Wey, DVM, DACVIM (Cardiology)

Heart disease is common in canine patients, with estimates as high as 10% of all dogs seen in your hospital developing some form of heart disease during their lifetime.  While all dogs with heart disease do not progress to develop overt signs of congestive heart failure, those that do require frequent communication, consistent monitoring, and therapeutic adjustments over time.  The days of “triple threat” therapy (digoxin, furosemide, and an ACE-inhibitor) from the last generation have been replaced by a more nuanced approach to the individual patient, with a variety of therapeutic strategies to keep dogs comfortable and happy in the last years of their life.  Diuretics are no exception, and this article will focus on several diuretic classes, both new and old, to help manage congestion in your heart failure patients.  In recent years, these drugs have expanded to include agents that not only alleviate fluid retention in the setting of heart failure, they may also offer other indirect cardiovascular benefits.

Dosing information for all bolded medications in this article can be found here: CEG Canine Formulary

• Loop diuretics – Still the mainstay of diuretic therapy, loop diuretics work at the level of the ascending loop of Henle by blocking the Na+/K+/2Cl- cotransporter, which allows more water to be retained in the renal tubule and excreted in the urine. Furosemide is the most common of these agents, but patients often develop resistance (tachyphylaxis) with chronic use, requiring dose escalation over time.  Roughly 10x more potent than furosemide, torsemide has gained favor in this setting as a rescue agent used when patients are approaching a maximal dose of furosemide (12mg/kg/day) or have refractory congestion in spite of furosemide.  Although the drug acts by blocking the same cotransporter, many patients will respond favorably to switching from one loop diuretic to another.  A large scale, randomized study in 2020 demonstrated that torsemide was non-inferior to furosemide, but with additional benefits including less frequent dosing (q24 or BID administration), a mild vasodilatory effect, and theoretically, inhibition of the renin-angiotensin-aldosterone system (RAAS)¹.

• Neprilysin inhibitors (Ni’s) – this class of drugs blocks the naturally occurring enzyme neprilysin from breaking down natriuretic peptides. The latter peptides are more widely known for their diagnostic utility (Ex: NT-proBNP, the N-terminal portion of the prohormone of brain natriuretic peptide).  There are many of these peptides produced by mammals, and as their name suggests, they promote the loss of sodium in the urine (natriuresis).  However, they are relatively short-lived in circulation.  By inhibiting the breakdown of natriuretic peptides, Ni’s allow these neurohormones to have a more potent and lasting diuretic effect.  Consequently, they can have a beneficial influence on fluid balance and further promote diuresis in patients receiving other diuretics.  Because of their tendency to result in compensatory vasoconstriction, all commercially available Ni’s are dosed in combination with a vasodilator, such as an angiotensin receptor blocker (ARB’s such as valsartan, telmisartan).  These are commonly referred to as ARNI’s, and the most common combination used to date in veterinary medicine is the human product combination Entresto® (sacubitril/valsartan).  Due to the combination with ARB’s, therapy with ACE-inhibitors should be avoided or discontinued when using drug combinations like Entresto®.  A small placebo controlled clinical trial using Entresto for managing canine CHF secondary to myxomatous valvular degeneration has been positive², and a larger retrospective study suggests that this drug may be more widely applicable to canine CHF³.  However, it’s use is currently off-label since there are no veterinary approved products on the market, and dosing suggestions can vary significantly.

• Thiazides (Ex: hydrochlorothiazide) – while not new, this class of diuretics warrants mention because they offer a potent, if not overlooked, option in the management of more chronic or severe CHF. By inhibiting the Na+/Cl- cotransporter in the distal convoluted tubule of the nephron, thiazides promote sodium and water excretion further “downstream” so that fewer compensatory mechanisms exist in the kidney to counteract these effects.  This results in a potent diuresis in patients that may be resistant to loop diuretics.  A recent retrospective study evaluating the addition of thiazides to loop diuretics in refractory (Stage D) CHF patients demonstrated significant positive effects and prolongation of life.⁴

• Aldosterone antagonists (Ex: Spironolactone) – Aldosterone is one of the end products of the RAAS system, and it has a variety of effects on the circulatory system that are detrimental to a patient with a failing heart. Specifically, this hormone promotes the retention of sodium and water while simultaneously facilitating potassium excretion.  In patients with a chronically active RAAS (all heart failure patients), repetitive stimulation of mineralocorticoid receptors by aldosterone will also promote inflammation, oxidative stress, and ultimately collagen deposition within the myocardium and vasculature.  Spironolactone competitively binds to mineralocorticoid receptors, thereby blocking these actions.  The effect of this competitive inhibition is diuresis, the retention of potassium (a boon in patients with hypokalemia from loop diuretics), and an anti-fibrotic effect with chronic use.  While the diuretic effect is generally considered “mild” in other settings, it may be significant in heart failure patients with activation of the RAAS.  Numerous trials have documented the benefits of spironolactone in dogs with CHF caused by myxomatous valvular degeneration, so this drug is currently considered standard therapy for congestive heart failure management in these patients along with pimobendan, furosemide, and ACE-inhibitors⁵.

• General considerations: All diuretic therapy should be carefully monitored to ensure that common side effects (dehydration, electrolyte depletion, and secondary renal dysfunction) do not become problematic. Clients should be informed that all diuretics will cause polyuria/polydipsia, and in general, water restriction should never be encouraged at home due to the potential to cause significant azotemia.  The effect of concurrent therapy with other drug classes that can affect renal function (i.e. NSAIDs) should be carefully considered.  Routine lab work is also essential to ensure that patients are tolerating therapy and do not require potassium or chloride supplementation (potassium gluconate, potassium chloride).  A chemistry profile (or more focused “renal panel”, with BUN, creatinine, and electrolytes) should be checked prior to therapy and 1-2 weeks after initiation of treatment with diuretics or any dose escalation.  For chronic therapy, re-evaluation of body weight, congestive symptoms, and lab work is also appropriate every 3-6 months.  With these guidelines and concurrent use of other standard heart failure therapy (pimobendan, ACE-inhibitors), diuretics can provide more time for clients to spend with their pets suffering from CHF.

References:

1. Besche B, Blondel T, Guillot E, Garelli-Paar C, Oyama MA. Efficacy of oral torasemide in dogs with degenerative mitral valve disease and new onset congestive heart failure: The CARPODIEM study. J Vet Intern Med. 2020 Sep;34(5):1746-1758.
2. Newhard DK, Jung S, Winter RL, Duran SH. A prospective, randomized, double-blind, placebo-controlled pilot study of sacubitril/valsartan (Entresto) in dogs with cardiomegaly secondary to myxomatous mitral valve disease. J Vet Intern Med. 2018 Sep;32(5):1555-1563.
3. Carlson, J. A., & Stern, J. A. (2026). Long-term sacubitril/valsartan is well tolerated in dogs with heart failure and myxomatous mitral valve disease and suggests excellent survival benefits. Am J Vet Res. 2026 Apr 15:1-7.
4. Romito, C. Mazzoldi, L. Calebotta, P. Castagna, N.G. Pelle, C. Valente, H. Poser, C. Guglielmini; Short- and long-term effects of hydrochlorothiazide in dogs with relapsing congestive heart failure due to myxomatous mitral valve disease: a retrospective analysis of 38 cases, Journal of Veterinary Cardiology, Volume 60, 2025, Pages 57-69.
5. ACVIM Consensus on MMVD