Product Name: Letrozole Alias: Femara CAS Registry Number: 112809-51-5 Purity: 98%+ MF: C17H11N5 MW: 285.3 Appearance: White crystalline powder. Dosages And Half Life The half life is approximately 2-4 days. Dosages vary quite a bit, 0.25mg up to 1mg every day or every other day is a good starting dose. It’s best to be conservative with the dosage because …