Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking Sildenafil or Tadalafil. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

 

Serious signs of an allergic reaction include:

Call 911 or your doctor right away if you have any of the following.

• Wheezing, trouble breathing or chest pressure
• Chest pain or heartbeat that does not feel normal
• Swelling of the mouth, face, lips, tongue, or throat
• Weakness on one side of the body or face
• Trouble speaking or thinking
• Loss of eyesight or hearing
• Very bad headache.
• Rash/hives/itchiness
• Red, swollen, blistered, or peeling skin (with or without fever)
• Dizziness or passing out
• Change in eyesight/blurry vision
• Change in hearing or ringing in ears
• Changes in balance
• Very bad muscle pain, back pain, soreness, or weakness
• If you have a painful erection (hard penis) or an erection that lasts for longer than 4 hours. If this is not treated right away, it may lead to lasting sex problems and you may not be able to have sex. 

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