Drug Classification & Information

Sildenafil is a pulmonary arterial vasodilator meaning it relaxes the arteries within the lungs.  Sildenafil’s vasodilation is due to phosphodiesterase V inhibitor effects.  The brand name of this medication is Viagra.  There is now a generic formulation available which has made this treatment more cost effective in veterinary medicine.

Indications for Use

Sildenafil is indicated for the treatment of pulmonary hypertension.

Potential Drug Interactions

When combined with other vasodilators (amlodipine, ACE inhibitors) there is a risk for systemic hypotension.  Phenobarbital may decrease sildenafil concentrations.  Some anti-fungal therapies may reduce sildenafil metabolism thereby increasing blood levels.

Drug Side Effects

Side effects are uncommon – gastrointestinal side effects such as reduced appetite have been noted.  Nasal congestion with nasal discharge has also been noted.

Therapeutic Monitoring

When used for the treatment of pulmonary hypertension, echocardiography is used to assess response to treatment.  If used in combination with other vasodilators, periodic systemic blood pressure measurement is recommended.

Dosage Forms

Human:  20, 25, 50 & 100 mg tablets (generic)