Buy Lasix is a diuretic which is an anthranilic acid derivative, allowing the salt to instead be passed in your urine. Edema associated with congestive heart failure (CHF), Furosemide may also be used for purposes not listed in this medication guide. What are the precautions when taking Lasix tablets? Stop using Lasix and call your doctor, especially with high dosages with immunosuppressant drugs Prednisone.