Fludrocortisone in Dogs

Fludrocortisone is a prescription steroid medication most often used in dogs with hypoadrenocorticism, also called Addison’s disease. In this condition, the adrenal glands do not make enough hormones to help regulate sodium, potassium, hydration, blood pressure, and the body’s response to stress. Fludrocortisone helps replace the missing mineralocorticoid effect and, because it also has some glucocorticoid activity, it may reduce or sometimes eliminate the need for a separate daily steroid in some dogs. Even so, many dogs still need additional glucocorticoid support during illness, surgery, travel, or other stressful events, so your vet will tailor the plan to your dog’s needs.

Fludrocortisone works mainly by acting like aldosterone, the hormone that tells the kidneys to hold on to sodium and water while excreting potassium. That shift helps restore blood volume, supports blood pressure, and corrects the low sodium and high potassium pattern often seen in typical Addison’s disease. When the medication is working well, dogs usually have steadier energy, better appetite, fewer stomach upset episodes, and more stable hydration.

This drug also has mild glucocorticoid activity. That matters because Addison’s disease usually involves deficiency of both mineralocorticoids and glucocorticoids. In some dogs, the glucocorticoid effect from fludrocortisone is enough for day-to-day management. In others, your vet may still prescribe prednisone or prednisolone, especially during stress or if clinical signs continue. Because response varies, treatment is guided by repeat exams, electrolyte testing, kidney values, and how your dog feels at home.

Side effects are often related to dose and can happen if a dog receives more steroid effect than needed. Common concerns include increased thirst, increased urination, increased appetite, panting, restlessness, weight gain, or mild stomach upset. Because fludrocortisone can cause the body to retain sodium and water, some dogs may develop swelling, fluid retention, or worsening of underlying heart disease. PetMD also notes caution in pets with kidney disease, heart failure, pregnancy, or existing edema.

More serious problems are less common but need quick veterinary attention. Call your vet promptly if your dog seems weak again, vomits, has diarrhea, collapses, develops marked lethargy, or shows swelling of the limbs or belly. Those signs can mean the Addison’s disease is not well controlled, the dose needs adjustment, or another illness is present. Do not stop fludrocortisone suddenly unless your vet specifically tells you to, because abrupt changes can trigger dangerous hormone imbalance.

Fludrocortisone is given by mouth as a tablet, usually once daily or divided every 12 hours depending on your vet’s plan. Merck lists a common starting dose around 0.02 mg/kg by mouth every 24 hours, or split every 12 hours, with later adjustment based on lab results and clinical response. In practice, many dogs need dose changes over time, and some need higher doses than where they started. Your vet may also recommend a separate glucocorticoid such as prednisone, especially during the early stabilization period or during stressful events.

Give the medication exactly as prescribed and try to keep the schedule consistent. If your dog vomits after a dose, misses a dose, or refuses the tablet, contact your vet for instructions rather than doubling the next dose. Monitoring is a key part of treatment. VCA recommends checking electrolytes and kidney values every 1 to 2 weeks at first, then every 3 to 6 months once stable. Dogs with Addison’s disease usually need lifelong treatment and lifelong follow-up.

Fludrocortisone can interact with other medications, so your vet should review everything your dog takes, including supplements and over-the-counter products. VCA specifically lists aspirin, bupropion, insulin, phenobarbital, potassium-depleting diuretics, and vaccines among items that may require extra discussion or monitoring. The biggest practical concern is that other drugs can change fluid balance, potassium levels, blood sugar control, or steroid response.

Extra caution is often needed if a dog also has heart disease, kidney disease, diabetes, or is taking other steroids or diuretics. That does not always mean fludrocortisone cannot be used. It means the treatment plan may need closer lab monitoring, dose adjustments, or a different Addison’s protocol such as injectable DOCP plus a separate glucocorticoid. If another veterinarian prescribes a new medication, let them know your dog is taking fludrocortisone for Addison’s disease.