cephalexin
noun
ceph·a·lex·in ˌse-fə-ˈlek-sən 
: a semisynthetic cephalosporin C16H17N3O4S with a spectrum of antibiotic activity similar to the penicillins
Example Sentences
Recent Examples on the Web The most common organism responsible for perichondritis is a bug called Pseudomonas aeruginosa, a virulent pathogen with the ability to resist many antibiotics, including the cephalexin prescribed by Jessica’s pediatrician. 
Rick Pescatore, Philly.com, 20 Oct. 2017 Jessica’s pediatrician diagnosed a mild case of a bacterial skin infection known as cellulitis, and gave her a prescription for an antibiotic, cephalexin, along with the standard precautions. Rick Pescatore, Philly.com, 20 Oct. 2017
Rick Pescatore, Philly.com, 20 Oct. 2017 Jessica’s pediatrician diagnosed a mild case of a bacterial skin infection known as cellulitis, and gave her a prescription for an antibiotic, cephalexin, along with the standard precautions. Rick Pescatore, Philly.com, 20 Oct. 2017 Word History
Etymology
cephalosporin + -ex- (of unknown origin) + -in entry 1
First Known Use
1967, in the meaning defined above
Medical Definition
cephalexin
noun
ceph·a·lex·in ˌsef-ə-ˈlek-sən
: a semisynthetic cephalosporin C16H17N3O4S with a spectrum of antibiotic activity similar to the penicillins that is often administered in the form of its hydrochloride C16H17N3O4S·HCl or monohydrate C16H17N3O4S·H2O
Note: Cephalexin is marketed under the trademark Keflex.