Some patients may experience an allergic reaction to this drug in the form of hives, facial swelling, or increased difficulty in breathing. This is a serious condition and the patient should seek medical help at once. Other side effects that warrant medical intervention include chest pain, abnormal bleeding or bruising, weakness, altered heart rate, vision impairment, blistering skin rashes, jaundice, loss of appetite, darkened urination, or productive coughing with yellow or green mucus. The following milder side effects should be monitored and reported if they are persistent: headaches, insomnia, impotence, swollen breasts, nausea, vomiting, abdominal pain, diarrhea, drowsiness, constipation, or a lowered sex drive.