The Letrozole that caused difficulties for me was manufactured by Amneal and purchase from Chemist King.I have managed ok on Letrozole manufactured by Apotex and now Sandoz from Chemist Warehouse.I switched brands as Sandoz and Amneal were $12-15 cheaper per script than Apotex.
Please be aware that each of us may react differently to the same drug as our physiology is different.Also I am not side effect free - vaginal atrophy is a major issue for me.Also joint pain and swelling in my lower limbs has been helped a lot by a daily one hour walk.