However, the effective half-life of norfloxacin in these elderly subjects is hours. These events may be severe and generally occur following the administration of multiple doses. This information does not contain any assurances that this product is safe, effective, or appropriate for you. In rats, crystals were reported following doses of 200 mg kg day. Other brands listed are the trademarks of their respective owners and are not trademarks las farmacias en linea noroxin of MERCK CO. The use of Noroxin brand name and generic drugs should be done so only after receiving consultation, and written prescription by licensed physician. Uncomplicated Urinary Tract Infections The suggested dose is 800 milligrams per 400 milligrams should be taken twice day for to 10 days, depending upon the kind of bacteria causing the infection.