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Sirolimus is a new drug for management of ventricular hypertrophy in cats with subclinical hypertrophic cardiomyopathy (HCM) and is now available for use in veterinary patients.
Pharmacology of Sirolimus
Sirolimus, also known as rapamycin, inhibits mTOR (ie, mechanistic target of rapamycin) signaling, subsequently altering anabolic and catabolic processes and resulting in attenuation of cardiac hypertrophy. Sirolimus is an immunosuppressant drug, but this effect does not appear to be of clinical concern at the conditionally approved dosage.
Contraindications of Sirolimus
Sirolimus is contraindicated in cats hypersensitive to it. This drug should not be used in cats with pre-existing diabetes mellitus. Sirolimus has not been studied in cats that are pregnant, lactating, or intended for breeding.
Adverse Effects of Sirolimus
In cats with subclinical HCM, adverse effects caused by sirolimus occurred at a rate similar to placebo.1 Serious adverse effects possibly related to sirolimus included progression to CHF, (eg, arrhythmia, syncope), diabetes mellitus, ketoacidosis, and sudden death.1,2 Other reported adverse effects included lethargy, GI effects (eg, vomiting, diarrhea, inappetence), and subclinical elevation of liver enzymes.2
Additional Information & Administration Instructions
Echocardiography is required to establish a diagnosis of subclinical HCM. Sirolimus is indicated only for use in otherwise healthy cats; this drug has conditional approval and should therefore not be used in cats with comorbid conditions.
A comprehensive look at managing HCM is provided by the experts at Standards of Care (paid subscription only).