Prescription pillsWhat is Sildenafil?

Sildenafil belongs to a group of medications that delay the breakdown of the enzyme phosphodiesterase 5. It increases substances in the body that induce vasodilation (relaxation of arteries/ veins) within certain regions of blood vessels, like those found in the lungs.


  • Pulmonary Hypertension secondary to primary respiratory disease (chronic bronchitis, COPD, pulmonary fibrosis), chronic mitral valve disease or thromboembolic disease (blood clots).

Adverse Effects

[please contact CVCA should any of these symptoms be noted]

  • Low risk for decreased appetite, vomiting or diarrhea
  • Low blood pressure resulting in lethargy and weakness
  • Skin flushing

Client Information

  • Can be given with or without food
  • Comes in tablet form, but can be reformulated into capsules and liquid suspensions
  • Commonly used with other cardiac and respiratory medications
  • Does not require any specific monitoring

Interactions with Other Drugs

  • Increased risk for low systemic blood pressure when used with other vasodilators (amlodipine, acepromazine, phenoxybenzamine, nitrates)
  • Ketoconazole, itraconazole, cimetidine, erythromycin, and clarithromycin may increase blood levels
  • Phenobarbital may decrease blood levels lowering efficacy
  • The doctors at CVCA have taken this into account, however, please feel free to contact CVCA regarding any concurrent medications your pet may be prescribed

Standard Dosage Forms

Sildenafil tablets 20mg, 25mg, 50mg, 100mg


Viagra, Revatio

Drug Handouts