It should be noted that viagra has some possible side effects, including:

• Headache
• Flushing, facial flushing
• Stomach upset
• Diarrhea
• Nasal stuffiness
• Dizziness
• Sensitiveness to light

Some cares must be taken in using of viagra for the treatment of erectile dysfunction (ED). You must remember these warnings when you want to use VIAGRA:

• Viagra is a prescription medication.
  
• The right dosage for you should be determined by your doctor or health care provider. It is recommended that you should restrict your usage to one dose a day.
  
• You must consult with your doctor before use Viagra if you have heart, blood, kidney and/or liver problems.
• DO NOT take viagra if you are using any other medicines containing nitrate such as nitroglycerin, isosorbide dinitrate, isosorbide mononitrate, amyl nitrate and so on.
  
• If you encounter chest pains, dizziness, and nausea during sex after using viagra, consult with your doctor immediately.