Efficacy of trilostane for the treatment of equine Cushing's syndrome.

Authors: McGowan C M, Neiger R

Journal: Equine veterinary journal

DOI: 10.2746/042516403776014271 PubMed: 12880011Log in to save

Summary

# Editorial Summary: Trilostane for Equine Cushing's Syndrome McGowan and Neiger investigated trilostane—a 3-beta hydroxysteroid dehydrogenase inhibitor previously established in canine practice—as a treatment for equine Cushing's syndrome (ECS), evaluating both clinical efficacy and safety over a 1–2 year period in 20 horses (mean age 21 years) receiving 0.4–1 mg/kg daily (mean 0.5 mg/kg). All treated horses showed resolution of lethargy, whilst polyuria and polydipsia resolved in all 11 cases where present; notably, 13 of 16 horses (81%) with recurrent or chronic laminitis demonstrated improvement, with no adverse effects documented. Biochemical confirmation of therapeutic efficacy emerged through combined dexamethasone suppression and thyrotropin-releasing hormone stimulation testing, showing significant cortisol reduction 30 days post-treatment (160 ± 53.0 to 130 ± 46.1 nmol/l; P = 0.01). For practitioners managing older horses with PPID—particularly those presenting with laminitis, altered water intake, or lethargy—trilostane offers a well-tolerated alternative addressing both clinical signs and underlying endocrine dysfunction, though direct comparative studies with pergolide warrant attention to guide evidence-based therapeutic selection.

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Practical Takeaways

•Trilostane is a safe, effective medical option for managing equine Cushing's syndrome without reported adverse effects, offering improvement in common clinical signs including laminitis
•Expect clinical improvements within the treatment period with meaningful reduction in cortisol dysregulation confirmed by endocrine testing
•Consider trilostane as a first-line therapy for Cushing's cases, though direct comparison with pergolide (the standard at the time) requires further research

Key Findings

•Trilostane at 0.4–1 mg/kg daily reduced lethargy in all 20 treated horses over 1–2 years
•Polyuria/polydipsia improved in all 11 horses presenting with these signs
•Laminitis improved in 13 of 16 horses (81%) with recurrent or chronic disease
•Cortisol response to TRH stimulation decreased significantly (P=0.01) from 160±53.0 to 130±46.1 nmol/l after trilostane treatment, with no reported side effects

Conditions Studied

equine cushing's syndromelethargypolyuriapolydipsialaminitis

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