The nizonide 500mg is a brand name for the drug nitazoxanide, an antiparasitic and antiviral medication. It is primarily used to treat infections caused by protozoa and helminths, such as giardiasis and cryptosporidiosis, which affect the gastrointestinal tract. Nitazoxanide works by inhibiting the growth of these parasites, helping the body clear the infection. Additionally, it has shown some effectiveness against certain viral infections. Nizonide tablets are generally prescribed for short-term use, and the specific dosage and duration depend on the type of infection being treated. Common side effects include nausea, abdominal pain, and headache.