Assertion: viagra's use | /r/Causes | headache
Facets:
Source sentences:
text: Using Viagra can cause heart attacks; priapism, or a permanent erection, requiring medical attention; muscle aches or pain; bloody nose; diarrhea; difficulty breathing; headache; flushing or dilation of the blood vessels that causes the skin to appear very red; cold symptoms such as a runny or congested nose and sneezing.