Cephalexin (Keflex®)

Section 1.1

Midwives may independently prescribe, order and administer this drug.

Cephalexin is a first generation cephalosporin antibiotic. It interferes with the bacteria’s cell wall formation by weakening the cell wall, causing it to rupture and killing bacteria.

Indications and Clinical Use:

For the treatment of mastitis as well as treatment of asymptomatic or symptomatic urinary tract infection. Used to treat the gram positive cocci (staphylococcus aureus) that commonly cause mastitis. It does not cover methicillin-resistant Staph Aureus (MRSA), which may account for about 21% of the staph aureus cultured. It is also used to treat other bacterial infections such as pneumonia and bone, ear and skin that are not included in the Midwives Regulation – Schedule A and B.

Cephalexin provides good coverage for 1) streptococcus & staphylococcus; and modest coverage for 2) Escherichia coli, Klebsiella and Proteus (EKP) gram negative bacteria implicated in urinary tract infections.


Documented anaphylaxis to any penicillin antibiotic.

Warnings and Precautions:

Prolonged use may result in fungal or bacterial superinfection, including C. difficile-associated diarrhea (CDAD) and pseudomembranous colitis; CDAD has been observed >2 months post-antibiotic treatment.

Use with caution in patients with renal impairment; modify dosage in severe impairment.
Breastfed infants may develop slightly looser stools than normal.


Compatible – generally accepted that cephalosporins are safe to use during pregnancy


Category L1 – Compatible – generally considered to be compatible with Breastfeeding

Adverse Reactions:

Upset stomach, diarrhea, vomiting, vaginal infection and mild skin rash.

The following should be reported to a medical practitioner immediately: severe skin rash, itching, hives, difficulty breathing or swallowing, wheezing, unusual bleeding or bruising, sore throat, painful mouth or throat sores, jaundice and diarrhea.

Dosage and Administration:

Cephalexin (Keflex®): 500 mg orally every 6 hours (qid) for 10-14 days

Asymptomatic Bacteriuria:

Cephalexin (Keflex®): 250 mg orally every 6 hours (qid) for 3 days


Cephalexin (Keflex®):
250 mg orally every 6 hours (qid) for 7-14 days or
500 mg orally every 12 hours (bid) for 7-14 days

Note: Dose and duration of therapy can vary depending on infecting organism, severity of infection, and clinical response of patient. Treat severe staphylococcal infections for at least 14 days.

May be taken with or without food. Taking with food may minimize gastrointestinal distress. Taking an active probiotic concurrently may help minimize changes to GI flora.

Onset of Action:

Rapid absorption, peak in about 1 hour.

Half Life:

Adults: 0.5-1.2 hours; prolonged with renal impairment


Urine (80% to 100% as unchanged drug) within 8 hours;
Maximum milk concentration occurs at 4 hours after a single oral dose and gradually disappears by 8 hours after administration.