cephalexin
(sef a lex' in)
cephalexin
Apo-Cephalex (CAN), Biocef, Keflex, Novo-Lexin (CAN), Nu-Cephalex
(CAN), PMS-Cephalexin (CAN)
cephalexin hydrochloride monohydrate
Biocef, Keftab
Pregnancy Category B
Drug classes
Antibiotic
Cephalosporin (first generation)
Therapeutic actions
Bactericidal: Inhibits synthesis of bacterial cell wall, causing cell death.
Indications
• Respiratory tract infections caused by S. pneumoniae, group A beta-hemolytic
streptococci
• Dermatologic infections caused by staphylococci, streptococci
• Otitis media caused by S. pneumoniae, H. influenzae, streptococci, staphylococci,
M. catarrhalis
• Bone infections caused by staphylococci, P. mirabilis
• GU infections caused by E. coli, P. mirabilis, Klebsiella
Contraindications and cautions
• Contraindicated with allergy to cephalosporins or penicillins.
• Use cautiously with renal failure, lactation, pregnancy.
Available forms
Capsules—250, 500 mg; tablets—250, 500 mg, 1 g; oral suspension—125, 250 mg/5 mL
Dosages
ADULTS
1–4 g/day in divided dose; 250 mg PO q 6 hr usual dose.
• Skin and skin-structure infections: 500 mg PO q 12 hr. Larger doses may be
needed in severe cases; do not exceed 4 g/day.
PEDIATRIC PATIENTS
25–50 mg/kg/day PO in divided doses.
• Skin and skin-structure infections: Divide total daily dose, and give q 12 hr.
Dosage may be doubled in severe cases.
• Otitis media: 75–100 mg/kg/day PO in four divided doses.
Pharmacokinetics
Route Peak Duration
PO 60 min 8–10 hr
Metabolism: T1/2: 50–80 min
Distribution: Crosses the placenta, enters breast milk
Excretion: Renal
Adverse effects
• CNS: Headache, dizziness, lethargy, paresthesias
• GI: Nausea, vomiting, diarrhea, anorexia, abdominal pain, flatulence,
pseudomembranous colitis, liver toxicity
• GU: Nephrotoxicity
• Hematologic: Bone marrow depression
• Hypersensitivity: Ranging from rash to fever to anaphylaxis; serum sickness
reaction
• Other: Superinfections
Interactions
Drug-drug
• Increased nephrotoxicity with aminoglycosides
• Increased bleeding effects with oral anticoagulants
• Disulfiram-like reaction may occur if alcohol is taken within 72 hr after
cephalexin administration.
Drug-lab test
• Possibility of false results on tests of urine glucose using Benedict's solution,
Fehling's solution, Clinitest tablets; urinary 17-ketosteroids; direct Coombs' test.
Nursing considerations
Assessment
• History: Penicillin or cephalosporin allergy, pregnancy, or lactation
• Physical: Kidney function, respiratory status, skin status; culture and sensitivity
tests of infected area
Interventions
• Arrange for culture and sensitivity tests of infection before and during therapy if
infection does not resolve.
• Give drug with meals; arrange for small, frequent meals if GI complications
occur.
• Refrigerate suspension, discard after 14 days.
Teaching points
• Take this drug with food. Refrigerate suspension; discard any drug after 14 days.
• Complete the full course of this drug even if you feel better.
• This drug is prescribed for this particular infection; do not self-treat any other
infection.
• These side effects may occur: Stomach upset, loss of appetite, nausea (take drug
with food); diarrhea; headache, dizziness.
• Report severe diarrhea with blood, pus, or mucus; rash or hives; difficulty
breathing; unusual tiredness, fatigue; unusual bleeding or bruising.
Adverse effects in Italic are most common; those in Bold are life-threatening.
