Hyaluronidase is a genetically designed protein. Trastuzumab is a cancer medicine.

Hyaluronidase and trastuzumab is a combination medicine used to treat certain types of breast cancer.

Hyaluronidase and trastuzumab may also be used for purposes not listed in this medication guide.

This medicine can cause heart failure, especially if you have heart disease or if you are also receiving certain other cancer medicines (such as daunorubicin, doxorubicin, epirubicin, or idarubicin)

Tell your doctor if you have ever had:

• heart problems;
• high blood pressure; or
• if you have recently had an infection.

Do not use hyaluronidase and trastuzumab if you are pregnant. This medicine can cause injury or death to the unborn baby. Use effective birth control to prevent pregnancy while you are using this medicine and for at least 7 months after your last dose.

If you become pregnant while using this medicine or within 7 months after you stop, your name may be listed on a pregnancy registry to track the effects of hyaluronidase and trastuzumab on the baby.

It may not be safe to breast-feed while using this medicine and for up to 7 months after your last dose. Ask your doctor about any risk.

Use Herceptin Hylecta (Hyaluronidase And Trastuzumab) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Some side effects may occur during the injection. Tell your caregiver right away if you feel dizzy, nauseated, feverish, chilled, short of breath, or if you have diarrhea, a rash, chest pain, swelling in your face, or trouble breathing.

Call your doctor at once if you have:

• new or worsening cough, wheezing, shortness of breath or rapid breathing;
• swelling in your face or lower legs, rapid weight gain;
• fast or pounding heartbeats, fluttering in your chest;
• a light-headed feeling, like you might pass out;
• blisters or ulcers in your mouth, red or swollen gums, trouble swallowing;
• fluid build-up in the lungs--pain when you breathe, feeling short of breath while lying down, gasping for breath, cough with foamy mucus; or
• low blood cell counts--fever, sore throat, tiredness, skin sores, pale skin, cold hands and feet, feeling light-headed.

Common side effects may include:

• nausea, vomiting, diarrhea;
• fever, chills, tiredness;
• cough, breathing problems;
• swelling;
• hair loss;
• flushing (sudden warmth, redness, or tingly feeling);
• headache, muscle or joint pain;
• cold symptoms such as stuffy nose, sneezing, sore throat;
• sleep problems (insomnia);
• rash; or
• pain, burning, itching, swelling, warmth redness, bruising, bleeding, skin changes, or a hard lump where the medicine was injected.

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.

Follow your doctor's instructions about any restrictions on food, beverages, or activity.