Sildenafil (Viagra®) for Canine Pulmonary Hypertension

Uses/Indications:  Treatment of Pulmonary Arterial Hypertension in canines (PAH) (pulmonary arterial systolic pressure > 30mm Hg, pulmonary arterial diastolic pressure > 15mm Hg, or mean pulmonary arterial pressure > 20mm Hg), is often associated with heartworm infection, respiratory conditions and acidosis. This is a life-threatening condition if untreated, ultimately causing right sided heart failure and death.

Studies:  1. A randomized, placebo controlled, double-blind, crossover study in dogs with PAH were allocated to receive sildenafil or placebo for 4 weeks, followed by the alternate treatment for 4 weeks. Dogs receiving sildenafil had a significantly lower estimated pulmonary arterial pressure (median: 56mm Hg; range: 34-84mm Hg) than at baseline (median: 72mm Hg, range: 61-86mm Hg, p=0.018), but not significantly lower than dogs receiving placebo. Exercise capacity was significantly greater in dogs receiving sildenafil than those receiving placebo (mean activity count per minute: 101 ± 47 versus 74 ±

32, p=0.05). QOL scores were also significantly higher than dogs receiving placebo.

Adverse Effects:  Gastrointestinal upset, flushing and/or reddening of the skin

Dosing:  1mg to 3mg/kg PO every 8 to 12 hours

Monitoring Parameters:  Systemic arterial blood pressure, Heart rate, Arterial blood gas, Exercise tolerance

**Due to Viagra^® being the only reputable source of Sildenafil, therapy can often be expensive**