Flagyl starts working once it reaches a high enough plasma concentration, which occurs about one to two hours after it is taken orally, explains Drugs.com. It may still take a few days to feel better after taking the first dose, according to Mayo Clinic.
The generic form of Flagyl is metronidazole, explains Drugs.com. It is prescribed to fight microbial infections, and it is typically taken for five to 10 days, depending on the organism and the location of the infection, explains MedlinePlus. Typical infections treated with this medication include amoebic dysentery, amoebic liver abscess, anaerobic infections, bacterial vaginosis, Clostridium difficile, giardiasis, Helicobacter pylori and pelvic inflammatory disease, explains MedicineNet.com.
Therapy with Flagyl is associated with a variety of drug interactions and contraindications. Patients taking this drug should avoid consuming alcohol because of a disulfiram-like reaction that occurs when the two are taken together, according to Drugs.com.
Because Flagyl can potentiate the effects of certain drugs, patients taking warfarin and other anticoagulants should monitor their prothrombin time and INR regularly for any changes. Because Flagyl is metabolized in the liver, it should be prescribed in lower doses to patients with liver disease to avoid its accumulation in the bloodstream, explains Drugs.com.