Steroids in Cats: Uses, Side Effects, and Best Practices

Oct 10

By Tara Ghormley, DVM, DACVIM

Glucocorticoids are among the most frequently prescribed drugs in feline medicine. They can be life-changing—or life-threatening—depending on how they’re used. Despite their widespread use, the literature on steroids in cats remains surprisingly thin. Much of what we know comes from clinical experience rather than controlled studies. This article reviews the basics of how steroids work, the unique ways cats metabolize them, the systemic effects across organ systems, and practical guidance for choosing and dosing the right drug.

How Do Steroids Work?

Glucocorticoids act at the genetic level. Once inside the cell, they bind to the glucocorticoid response element in the nucleus, turning genes on or off. This cascade alters production of prostaglandins, leukotrienes, histamine, cytokines, nitric oxide synthase, and more.

The result is widespread immune modulation:

Neutrophils lose their ability to adhere to vessel walls.
B cells produce fewer antibodies.
Dendritic cell maturation slows.
Macrophages and T cells undergo apoptosis or suppression.

While these effects make steroids powerful anti-inflammatories, they also reduce defenses against fungal, viral, and bacterial infections.

Types of Glucocorticoids

Glucocorticoids are categorized by duration of action:

Short acting (<12 hrs): Hydrocortisone, cortisone.
Intermediate acting (12–36 hrs): Prednisolone/prednisone, methylprednisolone, triamcinolone.
Long acting (>48 hrs): Dexamethasone.

Duration also depends on formulation. Water-soluble compounds (sodium phosphate, sodium succinate) act quickly and clear faster. Less soluble molecules (like acetate) release slowly and last longer. For example, methylprednisolone acetate (Depo-Medrol) has effects for weeks, while adrenal suppression can persist for months.

Prednisone vs. Prednisolone

Here’s where cats differ from dogs: prednisone is poorly bioavailable in cats. Only about 21% is converted to the active form, prednisolone. For this reason, prednisolone should always be prescribed in feline patients.

Other Steroid Options

Dexamethasone: Six to seven times more potent than prednisone, with no mineralocorticoid effect. Often used IV when oral medications are not possible.
Budesonide: Locally acting in the distal intestines. Because 80–90% is metabolized in first-pass circulation, systemic bioavailability is reduced—though adrenal suppression still occurs. Often compounded.
Fluticasone: An inhaled steroid with minimal systemic absorption. Safe for long-term use in asthma management.

Dosing Strategies

Physiologic doses: 0.1–0.2 mg/kg/day.
Anti-inflammatory doses: 0.5–1.0 mg/kg/day.
Immunosuppressive doses: 1–2 mg/kg/day (up to 4 mg/kg/day in special cases).

Cats tolerate higher doses better than dogs, likely due to fewer systemic glucocorticoid receptors. Still, the risk of complications rises with both dose and duration.

Systemic Effects Across Body Systems:

Metabolic Effects

Glucocorticoids increase blood sugar: they increase glucose production in the liver, reduce glucose tissue uptake, and blunt insulin release. In a study of 143 cats on prednisolone for more than 3 weeks, 9.7% developed diabetes mellitus, usually within the first 3 months. Dexamethasone carries an even greater diabetogenic effect.

Steroids also promote lipolysis, raising triglycerides and cholesterol, and contribute to weight gain.

Hepatic Effects

Cats accumulate glycogen in hepatocytes under steroid influence (“steroid hepatopathy”). Unlike dogs, they do not develop hepatomegaly or steroid-induced alkaline phosphatase elevations.

Dermatologic Effects

Steroids suppress keratinocyte and fibroblast activity, thinning the skin, delaying wound healing, and occasionally curling the pinnae. Alopecia and dystrophic calcification (calcinosis cutis) are less common than in dogs.

Musculoskeletal Effects

Steroids reduce bone resorption but promote muscle catabolism, leading to muscle wasting. Cats are less severely affected than dogs.

Gastrointestinal Effects

The risk of ulceration remains uncertain, but combining steroids with NSAIDs is discouraged. Cats are less likely than dogs to develop GI side effects.

Cardiovascular Effects

By expanding plasma volume, glucocorticoids can stress the heart. In one study of 732 cats receiving methylprednisolone acetate, six developed congestive heart failure. Prednisolone may also enlarge cardiac chambers, especially at high doses or in patients with pre-existing heart disease.

Ocular Effects

Topical or systemic steroids worsen corneal ulcers and should be avoided when ulceration is present.

Other Concerns

Mild leukocytosis and neutrophilia are possible.
PU/PD is rare unless secondary to diabetes or glucosuria.
Behavioral changes (lethargy, aggression) are anecdotal but reported.

Choosing the Right Steroid

Steroid selection depends heavily on the disease and comorbidities:

Gastrointestinal disease: Prednisolone is first choice for confirmed IBD or small cell lymphoma (5–10 mg/cat/day). Budesonide may be better for mild disease, or cats with concurrent diabetes or cardiac compromise. Always taper to the lowest effective dose.
Asthma: Prednisolone is best for acute control, but ideally switched to inhaled fluticasone for long-term therapy.
Immune-mediated disease: High-dose prednisolone (≈10 mg/day) with tapering as disease permits.
Lymphoma: Prednisolone is standard, including small cell GI lymphoma. 10 mg/cat is a standard dose which may not be tapered.
Refractory PLE or IBD: Adjunctive immunosuppressants may be required if high dose steroids are insufficient or lead to complications.

Key Takeaways

Cats metabolize steroids differently—always choose prednisolone over prednisone.
Systemic effects span nearly every organ system, with diabetes and cardiac complications being the most significant risks.
Inhaled or locally acting steroids (fluticasone, budesonide) offer alternatives when systemic side effects are a concern.
Overall quantitative evidence for steroid selection is limited in cats; treatment should be individualized and always tapered to the lowest effective dose.
Steroid choice must be tailored not just to the primary condition, but also to comorbidities like diabetes, heart disease, or age-related risks.

Travis Meyer