It is very important that your doctor check your progress closely while you are receiving this medicine to make sure it is working properly.
Do not take sildenafil (Viagra®), tadalafil (Cialis®), or vardenafil (Levitra®) while you are using this medicine. Using these medicines together may cause blurred vision, dizziness, lightheadedness, or fainting. If you are taking these medicines and you experience an angina attack, you must go to the hospital right away.
Dizziness, lightheadedness, or faintness may occur, especially when you get up quickly from a lying or sitting position. Getting up slowly may help.
This medicine may cause headaches. These headaches are a sign that the medicine is working. If you have severe pain, talk with your doctor.