Get emergency medical help if you have signs of an allergic reaction to Herceptin: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Some side effects may occur during the injection, or in the days afterward. Tell your caregiver right away if you feel dizzy, nauseated, itchy, light-headed, weak, short of breath, or if you have a headache, fever, chills, or chest pain.
Call your doctor at once if you have:
new or worsening cough;
a light-headed feeling, like you might pass out;
severe headache, blurred vision, pounding in your neck or ears;
blisters or ulcers in your mouth, red or swollen gums, trouble swallowing;
heart problems - pounding heartbeats, dizziness, swelling in your lower legs, rapid weight gain, feeling short of breath;
low blood cell counts - fever, chills, tiredness, skin sores, easy bruising, unusual bleeding, pale skin, cold hands and feet, feeling light-headed; or
signs of tumor cell breakdown - tiredness, weakness, muscle cramps, nausea, vomiting, diarrhea, fast or slow heart rate, decreased urination, tingling in your hands and feet or around your mouth.
Your cancer treatments may be delayed or permanently discontinued if you have certain side effects.
Common Herceptin side effects may include:
heart problems;
nausea, diarrhea, weight loss;
headache;
trouble sleeping, feeling tired;
low blood cell counts;
rash;
fever, chills, cough, or other signs of infection;
mouth sores;
altered sense of taste; or
cold symptoms such as stuffy nose, sinus pain, sore throat.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Herceptin side effects (more detail)
