> Western Medicines > Letrozole

What is Letrozole for?

Letrozole belongs to a class of medications called aromatase inhibitors. It works by blocking the synthesis of estrogen hormone in the body and inhibits the growth of malignant tumours. Therefore, it is used to treat hormone-related breast cancer in postmenopausal women.

How to use it?

Letrozole is available as a tablet which may be taken by mouth. It may be taken with or without food. Take 2.5 mg once daily to treat breast cancer. The duration of treatment is usually 5 years. This medication is intended for postmenopausal women (who no longer have menstrual periods) only.

What are the side effects of Letrozole?

Common side effects of Letrozole include drowsiness, hot flushes, fatigue, increased sweating, headache, nausea, vomiting, constipation, diarrhoea, indigestion, appetite change, hair loss, rashes, and swelling of limbs and ankles.

Who should not take Letrozole?

  • People who are allergic to Letrozole or any component of the formulation
  • Women with breast cancer who are still having periods
  • Patients with a history of bone fractures or osteoporosis

Pharmacist Tips:

  • This medication can make you drowsy. Avoid driving or operating machinery until you know how you respond to Letrozole.
  • Continue taking Letrozole even when you feel well.

Common dosing schedule:
Letrozole is taken once daily. Try to take it at the same time each day.


This schedule is for reference only, adjustments may be made according to individual needs.


Some common medications Letrozole may interact with:

  • Oestrogen-containing medicines, e.g. Estradiol
  • Other medicines for cancer treatment, e.g. Tamoxifen

Letrozole may interact with many other medications. Please notify your doctor or pharmacist if you are taking the above medication, dosage adjustments might be needed.

Where to buy Letrozole in Hong Kong?

In Hong Kong, Letrozole is a prescription only medicine, and requires a prescription from a doctor to be purchased in a pharmacy. It can also be obtained from doctors. To find a pharmacy near you, refer to the list of pharmacies (“Authorized Sellers of Poisons”) from the Hong Kong Department of Health.


For more information about drug names and ingredients, you can visit Hong Kong’s Drug Office at https://www.drugoffice.gov.hk

Need more information?

For detailed information about the use of Letrozole in children, pregnancy and breastfeeding, and for questions about drug interactions, please check with your pharmacist or doctor.

Disclaimer: our goal is to provide you with the most relevant drug information and common dosage for Hong Kong. This information does not constitute medical advice. For specific treatment recommendations and advice, always discuss with your doctor or pharmacist, and follow the instructions included with your specific medicine.

Brands in Hong Kong
Available dosage
  • 2.5mg (Tablets)
Drug class
Sub class
Aromatase Inhibitors