2 Answers

Stop taking naproxen and seek medical attention or call your doctor at once if you have any of these serious side effects:

chest pain, weakness, shortness of breath, slurred speech, problems with vision or balance;
black, bloody, or tarry stools;
coughing up blood or vomit that looks like coffee grounds;
swelling or rapid weight gain;
** >> urinating less than usual or not at all; << ** 
nausea, upper stomach pain, itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);
bruising, severe tingling, numbness, pain, muscle weakness;
fever, headache, neck stiffness, chills, increased sensitivity to light, purple spots on the skin, and/or seizure (convulsions) or
severe skin reaction -- fever, sore throat, swelling in your face or tongue, burning in your eyes, skin pain, followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling. http://www.drugs.com/sfx/naproxen-side-effects.html