For metronidazole and tinidazole: Infections caused by certain protozoa such as Trichomonas vaginalis Trichomonal Vaginitis Trichomonal vaginitis is a vaginal infection caused by the protozoa Trichomonas vaginalis. Trichomonal vaginitis is usually sexually transmitted. It can cause a green or yellow discharge... read more , Entamoeba histolytica Amebiasis Amebiasis is an infection of the large intestine and sometimes the liver and other organs that is caused by the single-celled protozoan parasite Entamoeba histolytica, an ameba. The amebas... read more , and Giardia lamblia Giardiasis Giardiasis is an infection of the small intestine caused by the single-celled protozoan parasite Giardia. The main symptoms are abdominal cramping and diarrhea. People may have abdominal... read more , and for bacterial vaginosis Bacterial Vaginosis (BV) Bacterial vaginosis is a common condition that occurs when the balance of bacteria in the vagina (vaginal microbiome) is altered. Bacterial vaginosis causes a thin, yellow-green or gray discharge... read more

For metronidazole: Pelvic and abdominal bacterial infections

Nausea, vomiting*

Headache*

Flushing*, rash

Metallic taste

Numbness and tingling in the hands and feet (peripheral neuropathy)

Dark urine