Tinidazole is used to treat trichomoniasis (a sexually transmitted disease that can affect men and women), giardiasis (an infection of the intestine that can cause diarrhea, gas, and stomach cramps), and amebiasis (an infection of the intestine that can cause diarrhea, gas, and stomach cramps and can spread to other organs such as the liver). Tinidazole is also used to treat bacterial vaginosis (an infection caused by an overgrowth of harmful bacteria in the vagina) in women. Tinidazole is in a class of medications called nitroimidazole antimicrobials. It works by killing the organisms that can cause infection. Antibiotics will not work for colds, flu, or other viral infections. Using antibiotics when they are not needed increases your risk of getting an infection later that resists antibiotic treatment."