Finasteride
Finasteride is a synthetic 4-azasteroid compound that acts as a competitive and specific inhibitor of 5-alpha-reductase. In veterinary medicine, it is primarily utilized for the medical management of **benign prostatic hyperplasia (BPH)** in intact male dogs. It offers a highly effective alternative to surgical castration, particularly for valuable breeding studs, as it reduces prostate size without significantly impacting fertility or circulating testosterone levels. Additionally, finasteride is used off-label as an adjunctive therapy for **adrenal disease** in ferrets, helping to manage androgen-driven clinical signs such as prostatic enlargement and urinary blockages in affected males.
Mecanismo: Finasteride specifically and totally inhibits the intracellular enzyme **5-alpha-reductase** (predominantly Type II). * **Pathway**: Testosterone → (via **5-alpha-reductase**) → **Dihydrotestosterone (DHT)** DHT is a highly potent androgen and is the primary hormone responsible for the development and enlargement of the prostate gland. By blocking this conversion, finasteride significantly reduces DHT concentrations in the prostate, liver, and skin. This leads to prostatic involution and a reduction in clinical signs of BPH. Because it does not directly block testosterone or its receptors, normal testosterone-dependent functions (such as spermatogenesis and libido) are largely preserved.
Dosificación por especie
- Adjunctive treatment of adrenal disease · 5 mg (total dose) · PO · once daily · tablet
- Benign prostatic hyperplasia · 0.1-0.5 mg/kg · PO · once daily · for a 10-50 kg dog, one 5 mg tablet daily
- Benign prostatic hyperplasia · <15 kg: 1.5 mg (approx. 1/3 of a 5 mg tablet); 15-30 kg: 2.5 mg (1/2 tablet); >30 kg: 5 mg (one tablet) · PO · daily
- Benign prostatic hypertrophy · 5 mg per dog · PO · q24h · Extended treatment course (<8 weeks) may be required for full efficacy · Alternative to castration. Use when delmadinone or osaterone are not appropriate.
Las dosis son una referencia clínica para veterinarios colegiados. Confirme siempre con la ficha técnica vigente y el paciente individual.
Vías de administración
Contraindicaciones
- Hypersensitivity to finasteride
- Sexually developing animals
- Females (especially pregnant females)
- Sexually-developing dogs
- Breeding dogs (due to secretion in semen and teratogenic potential)
Efectos adversos
- Decreased libido
- Decreased ejaculate volume
- Impotence (rare/mild)
- Secreted into semen
- Causes fetal anomalies (teratogenic)
Interacciones farmacológicas
- Anticholinergic drugs · May precipitate or aggravate urinary retention thereby negating the effects of the drug when used for BPH
Monitorización
- Prostate exam (to evaluate efficacy and reduction in size)
- Prostate size (via palpation or ultrasound)
- Resolution of clinical signs (e.g., tenesmus, dysuria, hematuria)
Sobredosis
Limited information is available regarding acute toxicity. Mild **gastrointestinal effects** (such as vomiting or diarrhea) may be noted in the event of an overdose. Supportive care is recommended.
La referencia de fármacos de VetSheet está destinada a veterinarios colegiados como apoyo a la decisión clínica, no sustituye el juicio profesional ni la ficha técnica vigente del fabricante.