All medications may cause side effects, but usually patients have no, or minor, side effects. Common side effects of COZAAR may include: cold or flu symptoms (stuffy nose, sneezing, sore throat, fever), dry cough, muscle cramps, pain in your legs or back, stomach pain, diarrhea, headache, dizziness, tired feeling, sleep problems (insomnia) faintness/ feeling light-headed, pain or burning when you urinate, pale skin, short of breath, rapid heart rate, trouble concentration, wheezing, chest pain, drowsiness, confusion, mood changes, increased thirst, loss of appetite, nausea/vomiting, swelling, weight gain, feeling short of breath, urinating less than usual or not at all, high potassium (slow heart rate, weak pulse, muscle weakness, tingly feeling)