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cephalexin (sef-a-lex-in)

Apo-Cephalex, DOM-Cephalexin, Keflex, Nu-Cephalex, PMS Cephalexin


Therapeutic: anti-infectives

Pharmacologic: first-generation cephalosporins


Treatment of the following infections caused by susceptible organisms: Skin and skin structure infections, Respiratory tract infections, Otitis media, Urinary tract infections, Bone infections.


Binds to bacterial cell wall membrane, causing cell death. Therapeutic Effects: Bactericidal action against susceptible bacteria. Spectrum: Active against many gram-positive cocci, including Streptococcus pneumoniae, group A beta-hemolytic streptococci, staphylococci (including penicillinase-producing strains). Active against the following gram-negative organisms: Escherichia coli, Haemophilus influenzae, Klebsiella pneumoniae, Moraxella catarrhalis, Proteus. Not active against methicillin-resistant staphylococci or enterococci: Enterococcus. Not active against anaerobes.

Adverse Reactions/Side Effects

CNS: SEIZURES (HIGH DOSES). GI: PSEUDOMEMBRANOUS COLITIS, diarrhea, abdominal pain, nausea, vomiting. Derm: rashes, urticaria. Hemat: eosinophilia, hemolytic anemia, neutropenia, thrombocytopenia. Misc: allergic reactions, including anaphylaxis, superinfection.


Examination and Evaluation

  • Watch for seizures; notify physician immediately if patient develops or increases seizure activity.

  • Monitor signs of pseudomembranous colitis, including diarrhea, abdominal pain, fever, pus or mucus in stools, and other severe or prolonged GI problems (nausea, vomiting, heartburn). Notify physician or nursing staff immediately of these signs.

  • Monitor signs of allergic reactions and anaphylaxis, including pulmonary symptoms (tightness in the throat and chest, wheezing, cough dyspnea) or skin reactions (rash, pruritus, urticaria). Notify physician or nursing staff immediately if these reactions occur.

  • Monitor signs of eosinophilia (fatigue, weakness, myalgia), neutropenia (fever, sore throat, signs of infection), thrombocytopenia (bruising, nose bleeds, bleeding gums), or hemolytic anemia (malaise, dizziness, jaundice, abdominal pain). Report these signs to the physician.


  • Always wash hands thoroughly and disinfect equipment (whirlpools, electrotherapeutic devices, treatment tables, and so forth) to help prevent the spread of infection. Use universal precautions or isolation procedures as indicated for specific patients.

Patient/Client-Related Instruction

  • Instruct patient to notify physician immediately of signs of superinfection, including black, furry overgrowth on tongue, vaginal itching or discharge, and loose or foul-smelling stools.

  • Instruct patient and family/caregivers to report other troublesome side effects such as severe or prolonged skin problems (rash, hives) or GI problems (nausea, vomiting, diarrhea, abdominal pain).


Absorption: Well absorbed after oral administration.

Distribution: Widely distributed. Crosses the placenta and enters breast milk in low concentrations. Poor CSF penetration.

Metabolism and Excretion: Excreted almost entirely unchanged in the urine.

Half-life: Neonates: 5 hr; Children: 2.5 hr; Adults: 50–80 min (increased in renal impairment).

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TIME/ACTION PROFILE (blood levels)

PO rapid 1 hr 6–12 hr

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