Nitazoxanide 200 mg typically starts to show noticeable effects within 48 to 72 hours of the first dose, particularly for treating parasitic infections like giardiasis and cryptosporidiosis. For most patients, symptoms like diarrhea or stomach discomfort begin to improve after a few days. However, it’s important to complete the full prescribed course, usually 3 days, for optimal effectiveness. In some cases, if symptoms persist or worsen, a follow-up consultation may be required. For viral infections like rotavirus, improvements may vary, and the medication may need to be part of a broader treatment plan.