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Medication Safety Issues
Sound-alike/look-alike issues:
Cephalexin may be confused with cefaclor, cefazolin, cephalothin, ciprofloxacin
Pronunciation
(sef a LEKS in)
U.S. Brand Names
Index Terms
Generic Available
Yes
Canadian Brand Names
Pharmacologic Category
Pharmacologic Category Synonyms
Use
Treatment of susceptible bacterial infections including respiratory tract infections, otitis media, skin and skin structure infections, bone infections, and genitourinary tract infections, including acute prostatitis; alternative therapy for acute infective endocarditis prophylaxis
Use: Dental
Prophylaxis in total joint replacement patients undergoing dental procedures which produce bacteremia; alternative oral antibiotic for prevention of infective endocarditis in individuals allergic to penicillins or ampicillin
Note: Individuals allergic to amoxicillin (penicillins) may receive cephalexin provided they have not had an immediate, local, or systemic IgE-mediated anaphylactic allergic reaction to penicillin.
Pregnancy Risk Factor
B
Pregnancy Implications
Adverse events were not observed in animal reproduction studies; therefore, cephalexin is classified as pregnancy category B. Cephalexin crosses the placenta and produces therapeutic concentrations in the fetal circulation and amniotic fluid. An increased risk of teratogenic effects has not been observed following maternal use of cephalexin; however, adequate and well-controlled studies have not been completed in pregnant women. Peak concentrations in pregnant patients are similar to those in nonpregnant patients. Prolonged labor may decrease oral absorption.
Lactation
Enters breast milk (small amounts)/use caution
Breast-Feeding Considerations
Small amounts of cephalexin are excreted in breast milk. The manufacturer recommends that caution be exercised when administering cephalexin to nursing women. Maximum milk concentration occurs ~4 hours after a single oral dose and gradually disappears by 8 hours after administration. Nondose-related effects could include modification of bowel flora.
Contraindications
Hypersensitivity to cephalexin, any component of the formulation, or other cephalosporins
Warnings/Precautions
Concerns related to adverse effects:
• Elevated INR: May be associated with increased INR, especially in nutritionally-deficient patients, prolonged treatment, hepatic or renal disease.
• Penicillin allergy: Use with caution in patients with a history of penicillin allergy, especially IgE-mediated reactions (eg, anaphylaxis, angioedema, urticaria).
• Superinfection: Prolonged use may result in fungal or bacterial superinfection, including C. difficile-associated diarrhea (CDAD) and pseudomembranous colitis; CDAD has been observed >2 months postantibiotic treatment.
Disease-related concerns:
• Renal impairment: Use with caution in patients with renal impairment; modify dosage in severe impairment.
Adverse Reactions
Frequency not defined.
Central nervous system: Agitation, confusion, dizziness, fatigue, hallucinations, headache
Dermatologic: Angioedema, erythema multiforme (rare), rash, Stevens-Johnson syndrome (rare), toxic epidermal necrolysis (rare), urticaria
Gastrointestinal: Abdominal pain, diarrhea, dyspepsia, gastritis, nausea (rare), pseudomembranous colitis, vomiting (rare)
Genitourinary: Genital pruritus, genital moniliasis, vaginitis, vaginal discharge
Hematologic: Eosinophilia, hemolytic anemia, neutropenia, thrombocytopenia
Hepatic: AST/ALT increased, cholestatic jaundice (rare), transient hepatitis (rare)
Neuromuscular & skeletal: Arthralgia, arthritis, joint disorder
Renal: Interstitial nephritis (rare)
Miscellaneous: Allergic reactions, anaphylaxis
Drug Interactions
Aminoglycosides: Increase nephrotoxic potential.
Probenecid: High-dose probenecid decreases clearance of cephalexin.
Typhoid vaccine: Antibiotics may diminish the efficacy of the live, attenuated Ty21a strain vaccine.
Ethanol/Nutrition/Herb Interactions
Food: Peak antibiotic serum concentration is lowered and delayed, but total drug absorbed is not affected. Cephalexin serum levels may be decreased if taken with food.
Storage
Capsule: Store at 15°C to 30°C (59°F to 86°F).
Powder for oral suspension: Refrigerate suspension after reconstitution; discard after 14 days.
Reconstitution
Tablets for oral suspension (Panixine DisperDose™): Tablet must be dissolved in ?10 mL water prior to administration.
Mechanism of Action
Inhibits bacterial cell wall synthesis by binding to one or more of the penicillin-binding proteins (PBPs) which in turn inhibits the final transpeptidation step of peptidoglycan synthesis in bacterial cell walls, thus inhibiting cell wall biosynthesis. Bacteria eventually lyse due to ongoing activity of cell wall autolytic enzymes (autolysins and murein hydrolases) while cell wall assembly is arrested.
Pharmacodynamics/Kinetics
Absorption: Delayed in young children
Distribution: Widely into most body tissues and fluids, including gallbladder, liver, kidneys, bone, sputum, bile, and pleural and synovial fluids; CSF penetration is poor
Protein binding: 6% to 15%
Half-life elimination: Adults: 0.5-1.2 hours; prolonged with renal impairment
Time to peak, serum: ~1 hour
Excretion: Urine (80% to 100% as unchanged drug) within 8 hours
Dosage
Usual dosage range:
Children >1 year: Oral: 25-100 mg/kg/day every 6-8 hours (maximum: 4 g/day)
Adults: Oral: 250-1000 mg every 6 hours; maximum: 4 g/day
Indication-specific dosing:
Children >1 year: Oral:
Furunculosis: 25-50 mg/kg/day in 4 divided doses
Impetigo: 25 mg/kg/day in 4 divided doses
Otitis media: 75-100 mg/kg/day in 4 divided doses
Prophylaxis against infective endocarditis (dental, oral, or respiratory tract procedures): 50 mg/kg 30-60 minutes prior to procedure (maximum: 2 g). Note: American Heart Association (AHA) guidelines now recommend prophylaxis only in patients undergoing invasive procedures and in whom underlying cardiac conditions may predispose to a higher risk of adverse outcomes should infection occur.
Severe infections: 50-100 mg/kg/day in divided doses every 6-8 hours
Skin abscess: 50 mg/kg/day in 4 divided doses (maximum: 4 g)
Streptococcal pharyngitis, skin and skin structure infections: 25-50 mg/kg/day divided every 12 hours
Children >15 years and Adults: Oral:
Cellulitis and mastitis: 500 mg every 6 hours
Furunculosis/skin abscess: 250 mg 4 times/day
Prophylaxis against infective endocarditis (dental, oral, or respiratory tract procedures): 2 g 30-60 minutes prior to procedure. Note: American Heart Association (AHA) guidelines now recommend prophylaxis only in patients undergoing invasive procedures and in whom underlying cardiac conditions may predispose to a higher risk of adverse outcomes should infection occur.
Prophylaxis in total joint replacement patients undergoing dental procedures which produce bacteremia: 2 g 1 hour prior to procedure
Streptococcal pharyngitis, skin and skin structure infections: 500 mg every 12 hours
Uncomplicated cystitis: 500 mg every 12 hours for 7-14 days
Dosing adjustment in renal impairment: Adults:
Clcr 10-50 mL/minute: 500 mg every 8-12 hours
Clcr <10: 250-500 mg every 12-24 hours
Hemodialysis: 250 mg every 12-24 hours; moderately dialyzable (20% to 50%); give dose after dialysis session
Dental Usual Dosing
Prophylaxis against infective endocarditis (dental, oral, or respiratory tract procedures): Oral:
Children >1 year: 50 mg/kg 30-60 minutes prior to procedure; maximum: 2 g
Children >15 years and Adults: 2 g 30-60 minutes prior to procedure
Note: American Heart Association (AHA) guidelines now recommend prophylaxis only in patients undergoing invasive procedures and in whom underlying cardiac conditions may predispose to a higher risk of adverse outcomes should infection occur.
Prophylaxis in total joint replacement patients undergoing dental procedures which produce bacteremia: Oral: Adults: 2 g 1 hour prior to procedure
Administration: Oral
Take without regard to food. If GI distress, take with food. Give around-the-clock to promote less variation in peak and trough serum levels.
Monitoring Parameters
With prolonged therapy monitor renal, hepatic, and hematologic function periodically; monitor for signs of anaphylaxis during first dose
Test Interactions
Positive direct Coombs', false-positive urinary glucose test using cupric sulfate (Benedict's solution, Clinitest®, Fehling's solution), false-positive serum or urine creatinine with Jaffé reaction, false-positive urinary proteins and steroids
Dietary Considerations
Take without regard to food. If GI distress, take with food. Panixine DisperDose™ contains phenylalanine 2.8 mg/cephalexin 125 mg.
Patient Education
Do not take any new medication during therapy unless approved by prescriber. Take as directed, at regular intervals around-the-clock (with or without food). Take complete prescription even if feeling better. Maintain adequate hydration (2-3 L/day of fluids) unless instructed to restrict fluid intake. May cause false test results with Clinitest®; use of another type of glucose testing is preferable. May cause diarrhea (yogurt, boiled milk, or buttermilk may help). Report rash; breathing or swallowing difficulty; persistent diarrhea, nausea, vomiting, or abdominal pain; changes in urinary pattern or pain on urination; opportunistic infection (eg, vaginal itching or drainage, sores in mouth, blood in stool or urine, unusual fever or chills); CNS changes (eg, irritability, agitation, nervousness, insomnia, hallucinations); or other adverse reactions. Breast-feeding precaution: Consult prescriber if breast-feeding.
Geriatric Considerations
Adjust dose for renal function.
Cardiovascular Considerations
May be used for prevention of bacterial endocarditis.
Dental Health: Effects on Dental Treatment
No significant effects or complications reported (see Dental Comment)
Dental Health: Vasoconstrictor/Local Anesthetic Precautions
No information available to require special precautions
Dental Comment
Cephalexin is effective against anaerobic bacteria, but the sensitivity of alpha-hemolytic Streptococcus vary; approximately 10% of strains are resistant. Nearly 70% are intermediately sensitive. Patients allergic to penicillins can use a cephalosporin; the incidence of cross-reactivity between penicillins and cephalosporins is 1% when the allergic reaction to penicillin is delayed. If the patient has a history of immediate reaction to penicillin, the incidence of cross-reactivity is 20%; cephalosporins are contraindicated in these patients.
Mental Health: Effects on Mental Status
May cause nervousness; case reports of euphoria, delusion, illusions, and depersonalization with cephalosporins
Mental Health: Effects on Psychiatric Treatment
May rarely cause neutropenia; use caution with clozapine and carbamazepine
Nursing: Physical Assessment/Monitoring
Assess results of culture/sensitivity tests and patient's allergy history prior to therapy. Assess other pharmacological or herbal products patient may be taking for potential interactions (eg, nephrotoxicity). Assess results of laboratory tests, therapeutic response, and adverse reactions (see Adverse Reactions). Advise patients with diabetes about use of Clinitest® (may cause false-positive test). Teach patient possible side effects/appropriate interventions and adverse symptoms to report (eg, opportunistic infection, hypersensitivity reaction).
Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Capsule: 250 mg, 500 mg
Keflex®: 250 mg, 500 mg, 750 mg
Powder for oral suspension: 125 mg/5 mL (100 mL, 200 mL); 250 mg/5 mL (100 mL, 200 mL)
Keflex®: 125 mg/5 mL (100 mL, 200 mL); 250 mg/5 mL (100 mL, 200 mL)
Tablet: 250 mg, 500 mg
Pricing: U.S. (www.drugstore.com)
Capsules (Cephalexin)
250 mg (30): $8.99
500 mg (30): $14.99
Capsules (Keflex)
250 mg (30): $65.99
750 mg (50): $148.11
Suspension (reconstituted) (Cephalexin)
125 mg/5 mL (100): $7.99
125 mg/5 mL (200): $10.98
250 mg/5 mL (100): $9.99
250 mg/5 mL (200): $19.00
Tablets (Cephalexin)
250 mg (30): $19.99
References
“Advisory Statement. Antibiotic Prophylaxis for Dental Patients With Total Joint Replacements. American Dental Association; American Academy of Orthopedic Surgeons,” J Am Dent Assoc, 1997, 128(7):1004-8.
Aronoff GR, Berns JS, Brier ME, et al, Drug Prescribing in Renal Failure: Dosing Guidelines for Adults, 4th ed. Philadelphia, PA: American College of Physicians; 1999, p 73.
Aronoff GR, Brier ME, Berns JS, et al, “The Renal Drug Book® Online Edition,” available at www.kdp-baptist.louisville.edu/renalbook. Last accessed June 23, 2006.
Dajani AS, Taubert KA, Wilson W, et al, “Prevention of Bacterial Endocarditis Recommendations by the American Heart Association,” JAMA 1997, 277(22):1794-801.
Donowitz GR and Mandell GL, “Beta-Lactam Antibiotics,” N Engl J Med, 1988, 318(7):419-26 and 318(8):490-500.
Saxon A, Beall GN, Rohr AS, et al, “Immediate Hypersensitivity Reactions to Beta-Lactam Antibiotics,” Ann Intern Med, 1987, 107(2):204-15.
Smith GH, “Oral Cephalosporins in Perspective,” DICP, 1990, 24(1):45-51.
Wilson W, Taubert KA, Gewitz M, et al, “Prevention of Infective Endocarditis. Guidelines From the American Heart Association. A Guideline From the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group,” Circulation, 2007, 115. Available at http://circ.ahajournals.org/cgi/reprint/CIRCULATIONAHA.106.183095v1; last accessed July 26, 2007.
International Brand Names
Lexi-Comp.com
Last full review/revision May 2008
Content last modified May 2008
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