Fludrocortisone
**Fludrocortisone** is a potent synthetic corticosteroid with high mineralocorticoid activity and moderate glucocorticoid activity. It is primarily used in veterinary medicine for the management of **hypoadrenocorticism (Addison's disease)** in dogs and cats, particularly when the authorized injectable product (desoxycortone pivalate) is unsuitable. > **Clinical Warning:** Fludrocortisone is about 125 times more potent as a mineralocorticoid than hydrocortisone, and 12 times more potent as a glucocorticoid (approximately 3 times more potent than prednisolone). Supplemental doses of prednisolone may still be required during periods of metabolic or physical stress.
Mechanism: Acts as an **aldosterone analogue** at the mineralocorticoid receptors in the distal convoluted tubule and collecting duct of the kidneys. * **Mineralocorticoid effect:** → Increases sodium (Na+) retention and potassium (K+) excretion. * **Glucocorticoid effect:** → Possesses roughly 3 times the glucocorticoid potency of prednisolone, contributing to anti-inflammatory and metabolic effects.
Dosing by species
- Hypoadrenocorticism (Addison's disease) · 0.01 mg/kg (starting dose); most stable patients require <0.05 mg/kg · PO · q12h (some may only require q24h) · Lifelong · Monitor absolute Na and K concentrations 4-6 hours post-pill. If on q24h dosing, check pre-pill concentrations as well.
- Hypoadrenocorticism (Addison's disease) · 0.01 mg/kg (starting dose); most stable patients require <0.05 mg/kg · PO · q12h · Lifelong · Doses as for dogs; very few reports in cats.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- No specific contraindications listed in the monograph, but use with caution in patients with congestive heart failure, severe hypertension, or renal disease.
- No specific contraindications available in the monograph, but generally contraindicated in patients with systemic fungal infections or known hypersensitivity.
Adverse effects
- Hypertension
- Oedema (including cerebral oedema)
- Hypokalaemia
- Hypercortisolism / Iatrogenic Cushing's syndrome (with long-term overdose)
- Polyuria/polydipsia (PU/PD)
- Clinical signs of hypercortisolism (with long-term overdose)
Drug interactions
- Amphotericin B · Increased risk of severe hypokalaemia · major
- Furosemide · Increased risk of hypokalaemia due to additive potassium-depleting effects · moderate
- Thiazide diuretics · Increased risk of hypokalaemia due to additive potassium-depleting effects · moderate
Monitoring
- Absolute serum sodium concentrations
- Absolute serum potassium concentrations
- Blood pressure
- Clinical signs of hypercortisolism or hypoadrenocorticism crisis
- Body weight and hydration status
- Absolute serum sodium concentrations (4-6 hours post-pill, and pre-pill if q24h)
- Absolute serum potassium concentrations (4-6 hours post-pill, and pre-pill if q24h)
- Clinical signs of hyperadrenocorticism or hypoadrenocorticism
Overdose
Overdosage can lead to **hypertension**, **oedema** (including cerebral oedema), and **hypokalaemia**. Long-term overdosage may result in clinical signs of **hypercortisolism** (iatrogenic Cushing's syndrome, e.g., PU/PD, polyphagia, alopecia, pot-bellied appearance). Treatment involves dose reduction and supportive care.
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.