Tiredness, nausea, loss of appetite, vomiting, diarrhea, headache, constipation, back pain, hot flashes, unusual sweating, dizziness, or trouble sleeping may occur. Nausea and vomiting can be severe. In some cases, your doctor may prescribe medication to prevent or relieve nausea and vomiting. Eating several small meals, not eating before treatment, or limiting activity may help lessen some of these effects. If any of these effects last or get worse, tell your doctor or pharmacist promptly.
Temporary hair loss may occur. Normal hair growth should return after treatment has ended.
Pain or sores in the mouth and throat may occur. Brush your teeth carefully/gently, avoid using mouthwash that contains alcohol, and rinse your mouth often with cool water mixed with baking soda or salt. It may also be best to eat soft, moist foods.
People using these medications may have serious side effects. However, your doctor has prescribed these drugs because he or she has judged that the benefit to you is greater than the risk of side effects. Careful monitoring by your doctor may decrease your risk.
Tell your doctor right away if you have any serious side effects, including: bone fractures, mental/mood changes (such as depression, anxiety), swelling of arms/legs, signs of liver disease (such as nausea/vomiting that doesn't stop, loss of appetite, stomach/abdominal pain, yellowing eyes/skin, dark urine).
Get medical help right away if you have any very serious side effects, including: fast/irregular heartbeat, severe dizziness, fainting.
Letrozole may rarely cause serious (sometimes fatal) problems from blood clots (such as deep vein thrombosis, heart attack, pulmonary embolism, stroke). Get medical help right away if you have: shortness of breath/rapid breathing, chest/jaw/left arm pain, confusion, pain/swelling/warmth in the groin/calf, sudden/severe headaches, trouble speaking, weakness on one side of the body, sudden vision changes.
This product may lower your ability to fight infections. This may make you more likely to get a serious (rarely fatal) infection or make any infection you have worse. Get medical help right away if you have any signs of infection (such as sore throat that doesn't go away, fever, swollen lymph nodes, chills, cough).
A very serious allergic reaction to these drugs is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US -
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.