Medications and Drugs
Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD
GENERIC NAME: cephalexin
BRAND NAME: Keflex
DRUG CLASS AND MECHANISM:
Cephalexin belongs to a class of antibiotics called cephalosporins. They are
similar to penicillin in action and side effects. They stop or slow the growth
of bacterial cells by preventing bacteria from forming the cell wall that
surrounds each cell. The cell wall protects bacteria from the external
environment and keeps the contents of the cell together. Without a cell wall,
bacteria are not able to survive. Bacteria that are susceptible to cephalexin
include Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae,
E. coli and several others. Cephalexin was approved by the FDA in January 1971.
PRESCRIPTION: Yes
GENERIC AVAILABLE: Yes
PREPARATIONS: Tablets: 250 and 500 mg, and 1 g. Capsules: 250, 333, 500 and
750 mg. Powder for Suspension: 125 and 250 mg/5 ml.
STORAGE: Tablets and capsules should be stored at room temperature, 15-30°C
(59-86°F). Suspensions should be refrigerated and discarded after 14 days.
PRESCRIBED FOR: Cephalexin is used to treat infections caused by bacteria
that are susceptible to the effects of cephalexin. Common infections that are
treated with cephalexin include infections of the
middle ear,
tonsils,
throat,
larynx (laryngitis), bronchi (bronchitis) and pneumonia. It also is used for
treating urinary tract, skin, and bone infections.
DOSING: The dose of cephalexin for adults is 1 to 4 grams in divided doses.
Children are treated with 25-100 mg/kg/day in divided doses. The dosing interval
may be every 6 or 12 hours depending on the infection.
DRUG INTERACTIONS: Serious interactions of cephalexin with other drugs are
uncommon.
PREGNANCY: There are no good studies of cephalexin in pregnant women.
Cephalexin should only be used during
pregnancy if there are no other safe
alternatives.
NURSING MOTHERS: Most cephalosporins are excreted in breast milk. Nursing
mothers should avoid using cephalosporins or stop
breastfeeding while taking a
cephalosporin.
SIDE EFFECTS: The most common side effects of cephalexin are diarrhea,
nausea, abdominal pain,
vomiting,
headaches, dizziness, skin rash, fever,
abnormal liver tests and vaginitis. Individuals who are allergic to penicillin
may also be allergic to cephalexin.
Cephalexin, like almost all antibiotics, may cause mild or severe cases of
pseudomembranous colitis, a mild to severe inflammation of the colon.
Antibiotics, including cephalexin alter the normal flora of the colon and permit
overgrowth of a bacterium called
Clostridium difficile. Studies indicate that a
toxin produced by Clostridium difficile is a primary cause of
pseudomembranous
colitis.
Reference: FDA Prescribing Information
Last Editorial Review: 1/10/2008
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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