There are many medicines that start with the letter F, such as Furadantin, Flagyl, and Famvir. Each of these medications has a different purpose and can be used to treat a variety of conditions. Furadantin, for example, is an antibiotic that is used to treat urinary tract infections. Flagyl is an antifungal medication that is used to treat yeast infections. Famvir is an antiviral medication that is used to treat viral infections, such as cold sores. These are just a few of the many medicines that start with the letter F. With so many options available, it is important to talk to a doctor or pharmacist to determine which medication is right for you.