List of products in the National Drug Code with proprietary name . Sildenafil is used to treat high blood pressure in the lungs (pulmonary hypertension). It works by relaxing and widening the blood vessels in your lungs which allows the blood to flow more easily. Decreasing high blood pressure in the lungs allows your heart and lungs to work better and improves your ability to exercise. This medication is not recommended for use in children. Discuss the risks and benefits of this medication with the doctor.