Cephalexin is a broad-spectrum antibiotic used to treat a wide variety of bacterial infections. The usual recommended dosage of Keflex is 250 milligrams taken every six hours. Cephalexin stops or slows the growth of micro-organisms such as bacteria, fungi, or protozoa. Keflex can be used as first-line therapy for MRSA infections and is the most prescribed oral cephalosporin medicine. Antibiotics as this is likely to result in an overdose. Cephalexin is used to treat a wide variety of bacterial infections. Cephalexin may be given on an empty stomach or with food to prevent stomach upset. Serious interactions of Cephalexin with other drugs are uncommon.