Medically reviewed on March 25, 2018
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- Cephalexin Monohydrate
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Daxbia: 333 mg [contains brilliant blue fcf (fd&c blue #1), fd&c yellow #10 (quinoline yellow), fd&c yellow #6 (sunset yellow)]
Keflex: 250 mg, 500 mg, 750 mg [contains brilliant blue fcf (fd&c blue #1), fd&c yellow #10 (quinoline yellow), fd&c yellow #6 (sunset yellow)]
Generic: 250 mg, 500 mg, 750 mg
Suspension Reconstituted, Oral:
Generic: 125 mg/5 mL (100 mL, 200 mL); 250 mg/5 mL (100 mL, 200 mL)
Generic: 250 mg, 500 mg
Brand Names: U.S.
- Antibiotic, Cephalosporin (First Generation)
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.
Rapid (90%); delayed in young children and may be decreased up to 50% in neonates
Widely into most body tissues and fluids, including gallbladder, liver, kidneys, bone, sputum, bile, and pleural and synovial fluids; CSF penetration is poor
Urine (80% to 100% as unchanged drug) within 8 hours
Time to Peak
Serum: ~1 hour
Neonates: 5 hours; Children 3-12 months: 2.5 hours; Adults: 0.5 to 1.2 hours (prolonged with renal impairment)
6% to 15%
Use: Labeled Indications
Bone infections: Treatment of bone infections caused by Staphylococcus aureus and/or Proteus mirabilis.
Genitourinary tract infections: Treatment of genitourinary tract infections, including acute prostatitis, caused by Escherichia coli, P. mirabilis, and Klebsiella pneumoniae.
Otitis media: Treatment of otitis media caused by Streptococcus pneumoniae, Haemophilus influenzae, S. aureus, Streptococcus pyogenes, and Moraxella catarrhalis.
Respiratory tract infections: Treatment of respiratory tract infections caused by S. pneumoniae and S. pyogenes.
Skin and skin structure infections: Treatment of skin and skin structure infections caused by S. aureus and/or S. pyogenes.
Off Label Uses
Community-acquired pneumonia (children)
Following clinical guideline recommendations on the management of CAP reduces the incidence of morbidity and mortality related to pneumonia. Cephalexin is the preferred oral agent for the treatment of children with CAP due to methicillin-susceptible Staphylococcus aureus (MSSA). IV cefazolin therapy should be initiated in the inpatient setting to potentially reduce morbidity and mortality.
Based on the American Heart Association (AHA) guidelines for the prevention of infective endocarditis, cephalexin is an effective and recommended alternative agent for prophylaxis against infective endocarditis in patients with certain cardiac conditions who are undergoing dental or respiratory tract procedures and are allergic to penicillins or ampicillin. Note: Cephalexin should not be used in patients with a history of anaphylaxis, angioedema, or urticaria with penicillins or ampicillin.
Prosthetic joint infection
Based on the Infectious Diseases Society of America (IDSA) guidelines for the management of prosthetic joint infection, cephalexin is an effective and recommended agent for treatment (following pathogen-specific IV therapy in patients undergoing 1-stage exchange or debridement with retention of prosthesis) and long-term oral antimicrobial suppression of prosthetic joint infection caused by staphylococci (methicillin-susceptible) (for the first 3 to 6 months of therapy, in combination with rifampin), and an effective and recommended alternative agent when this condition is caused by beta-hemolytic streptococci or Cutibacterium species.
Hypersensitivity to cephalexin, other cephalosporins, or any component of the formulation
Usual dosage range: Oral: 250 to 1,000 mg every 6 hours or 500 mg every 12 hours (maximum: 4 g/day)
Cellulitis (nonpurulent)/erysipelas, mild (alternative agent): Oral: 500 mg 4 times daily for at least 5 days (duration should be extended if not resolved/slow response) (IDSA [Stevens 2014])
Cystitis, uncomplicated (alternative agent): Oral: 500 mg every 12 hours for 5 to 7 days (Hooton 2018)
Endocarditis, prophylaxis (dental or invasive respiratory tract procedures) (alternative agent) (off-label use): Oral: 2 g 30 to 60 minutes prior to procedure. Note: AHA guidelines 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 (AHA [Wilson 2007]).
Impetigo or ecthyma: Oral: 250 to 500 mg 4 times daily for 7 days. Note: Not an appropriate agent if MRSA is suspected or confirmed (Baddour 2018; IDSA [Stevens 2014]).
Pharyngitis, streptococcal (alternative agent): Oral: 500 mg every 12 hours for 10 days (IDSA [Shulman 2012])
Prosthetic joint infection (off-label use): Oral: Treatment (following pathogen-specific IV therapy in patients undergoing 1-stage exchange or debridement with retention of prosthesis). Note: Duration ranges from a minimum of 3 months to indefinitely, depending on patient-specific factors (Berbari 2018):
Staphylococci (methicillin-susceptible): 500 mg every 6 to 8 hours. For the first 3 to 6 months of therapy, combine with rifampin (Berbari 2018; IDSA [Osmon 2013]).
Streptococci, beta-hemolytic (alternative agent): 500 mg every 6 to 8 hours (Berbari 2018; IDSA [Osmon 2013])
Cutibacterium spp (alternative agent): 500 mg every 6 to 8 hours (IDSA [Osmon 2013]; Kanafani 2018)
Refer to adult dosing.
Usual dosage range:
Children >1 year and Adolescents <15 years: Oral: 25 to 100 mg/kg/day in divided doses every 6 to 8 hours (maximum: 4 g/day)
Adolescents ≥ 15 years: Oral: 250 to 1,000 mg every 6 hours; maximum daily dose: 4 g/day
Community-acquired pneumonia (CAP) (PIDS/IDSA [Bradley 2011]), Staphylococcus aureus (methicillin-susceptible), mild infection or step-down therapy (preferred) (off-label use): Infants >3 months and Children: Oral: 75 to 100 mg/kg/day in 3 to 4 divided doses
Cystitis, uncomplicated: Adolescents ≥15 years: Refer to adult dosing.
Endocarditis, prophylaxis (dental, oral, or invasive respiratory tract procedures) (off-label use): Infants, Children, and Adolescents: Oral: 50 mg/kg 30 to 60 minutes prior to procedure (maximum dose: 2 g). Note: 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 (AHA [Wilson 2007]).
Impetigo: Children: Oral: 25 to 50 mg/kg/day in 3 to 4 divided doses; continue for 7 days, depending upon clinical response (IDSA [Stevens 2014])
Otitis media: Children: 75 to 100 mg/kg/day in 4 divided doses
Pharyngitis, streptococcal: Children >1 year: Oral: 25 to 50 mg/kg/day divided every 12 hours. Note: Recommended by the IDSA as an alternative agent for group A streptococcal pharyngitis in penicillin-allergic patients (avoid in patients with immediate-type hypersensitivity to penicillin) at a dose of 40 mg/kg/day divided twice daily (maximum: 1,000 mg daily) for 10 days (IDSA [Shulman 2012]).
Severe infections: Children: Oral: 50 to 100 mg/kg/day in divided doses every 6 to 8 hours
Skin and skin structure infections:
Children >1 year and Adolescents <15 years: Oral: 25 to 50 mg/kg/day in divided doses every 6 to 12 hours
Adolescents ≥15 years: Refer to adult dosing.
Alternative recommendations: Children: 25 to 50 mg/kg/day divided every 6 hours (IDSA [Stevens 2014])
Dosing: Renal Impairment
Adolescents >15 years and Adults:
CrCl ≥60 mL/minute: No dosage adjustment necessary.
CrCl 30 to 59 mL/minute: There are no specific dosage adjustments provided in the manufacturer’s labeling; maximum recommended daily dose: 1,000 mg/day.
CrCl 15 to 29 mL/minute: 250 mg every 8 to 12 hours
CrCl 5 to 14 mL/minute (not yet on dialysis): 250 every 24 hours
CrCl 1 to 4 mL/minute (not yet on dialysis): 250 mg every 48 to 60 hours
End stage renal disease (ESRD) on intermittent hemodialysis: There are no dosage adjustments provided in the manufacturer’s labeling; however the following guidelines have been used by some clinicians (Aronoff 2007): Oral: 250 to 500 mg every 12 to 24 hours; moderately dialyzable (20% to 50%); give dose after dialysis session.
Peritoneal dialysis: There are no dosage adjustments provided in the manufacturer’s labeling; however, the following guidelines have been used by some clinicians (Aronoff 2007): Oral: 250 to 500 mg every 12 to 24 hours.
Dosing: Hepatic Impairment
There are no dosage adjustments provided in the manufacturer’s labeling.
Administer without regard to food. If GI distress, take with food. Give around-the-clock to promote less variation in peak and trough serum levels.
Capsule: Store at 25°C (77°F); excursions permitted to 15ºC to 30ºC (59ºF to 86ºF).
Powder for oral suspension: Store at 20°C to 25°C (68°F to 77°F). Refrigerate after reconstitution; discard after 14 days.
Tablet: Store at 20°C to 25°C (68°F to 77°F).
BCG (Intravesical): Antibiotics may diminish the therapeutic effect of BCG (Intravesical). Avoid combination
BCG Vaccine (Immunization): Antibiotics may diminish the therapeutic effect of BCG Vaccine (Immunization). Monitor therapy
Cholera Vaccine: Antibiotics may diminish the therapeutic effect of Cholera Vaccine. Avoid combination
Lactobacillus and Estriol: Antibiotics may diminish the therapeutic effect of Lactobacillus and Estriol. Monitor therapy
MetFORMIN: Cephalexin may increase the serum concentration of MetFORMIN. Monitor therapy
Multivitamins/Minerals (with ADEK, Folate, Iron): May decrease the serum concentration of Cephalexin. Specifically, the zinc contained in many multivitamins may decrease cephalexin absorption. Management: Consider administering multivitamins at least 3 hours after cephalexin. Consider therapy modification
Multivitamins/Minerals (with AE, No Iron): May decrease the serum concentration of Cephalexin. Specifically, the zinc contained in many multivitamins may decrease cephalexin absorption. Management: Consider administering multivitamins at least 3 hours after cephalexin. Consider therapy modification
Probenecid: May increase the serum concentration of Cephalosporins. Monitor therapy
Sodium Picosulfate: Antibiotics may diminish the therapeutic effect of Sodium Picosulfate. Management: Consider using an alternative product for bowel cleansing prior to a colonoscopy in patients who have recently used or are concurrently using an antibiotic. Consider therapy modification
Sucroferric Oxyhydroxide: May decrease the serum concentration of Cephalexin. Management: Administer cephalexin at least 1 hour before administration of sucroferric oxyhydroxide. Consider therapy modification
Typhoid Vaccine: Antibiotics may diminish the therapeutic effect of Typhoid Vaccine. Only the live attenuated Ty21a strain is affected. Management: Vaccination with live attenuated typhoid vaccine (Ty21a) should be avoided in patients being treated with systemic antibacterial agents. Use of this vaccine should be postponed until at least 3 days after cessation of antibacterial agents. Consider therapy modification
Vitamin K Antagonists (eg, warfarin): Cephalosporins may enhance the anticoagulant effect of Vitamin K Antagonists. Monitor therapy
Zinc Salts: May decrease the absorption of Cephalexin. Management: Consider administering oral zinc salts at least 3 hours after cephalexin. Exceptions: Zinc Chloride. Consider therapy modification
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
Frequency not defined.
Central nervous system: Agitation, confusion, dizziness, fatigue, hallucination, headache
Dermatologic: Erythema multiforme (rare), genital pruritus, skin rash, Stevens-Johnson syndrome (rare), toxic epidermal necrolysis (rare), urticaria
Gastrointestinal: Abdominal pain, diarrhea, dyspepsia, gastritis, nausea (rare), pseudomembranous colitis, vomiting (rare)
Genitourinary: Genital candidiasis, vaginal discharge, vaginitis
Hematologic & oncologic: Eosinophilia, hemolytic anemia, neutropenia, thrombocytopenia
Hepatic: Cholestatic jaundice (rare), hepatitis (transient, rare), increased serum ALT, increased serum AST
Hypersensitivity: Anaphylaxis, angioedema, hypersensitivity reaction
Neuromuscular & skeletal: Arthralgia, arthritis, arthropathy
Renal: Interstitial nephritis (rare)
Concerns related to adverse effects:
• Hypersensitivity: Allergic reactions (eg, rash, urticaria, angioedema, anaphylaxis, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis [TEN]) have been reported. If an allergic reaction occurs, discontinue immediately and institute appropriate treatment.
• 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).
• Seizure disorder: Use with caution in patients with a history of seizure disorder; high levels, particularly in the presence of renal impairment, may increase risk of seizures.
• 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.
• Renal impairment: Use with caution in patients with renal impairment; modify dosage in severe impairment.
Concurrent drug therapy issues:
• Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.
• Direct Coombs tests: Positive direct Coombs tests and acute intravascular hemolysis has been reported. If anemia develops during or after therapy, discontinue use and work up for drug-induced hemolytic anemia.
With prolonged therapy monitor renal, hepatic, and hematologic function periodically; monitor for signs of anaphylaxis during first dose
Pregnancy Risk Factor
Adverse events were not observed in animal reproduction studies. Cephalexin crosses the placenta and produces therapeutic concentrations in the fetal circulation and amniotic fluid (Creatsas 1980). Peak concentrations in pregnant patients are similar to those in nonpregnant patients. Prolonged labor may decrease oral absorption (Griffith 1983; Paterson 1972).
• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)
• Patient may experience nausea, vomiting, or diarrhea. Have patient report immediately to prescriber signs of liver problems (dark urine, fatigue, lack of appetite, nausea, abdominal pain, light-colored stools, vomiting, or jaundice), bruising, bleeding, chills, pharyngitis, severe loss of strength and energy, confusion, hallucinations, urinary retention, change in amount of urine passed, seizures, vaginitis, signs of Stevens-Johnson syndrome/toxic epidermal necrolysis (red, swollen, blistered, or peeling skin [with or without fever]; red or irritated eyes; or sores in mouth, throat, nose, or eyes), or signs of Clostridium difficile (C. diff)-associated diarrhea (abdominal pain or cramps, severe diarrhea or watery stools, or bloody stools) (HCAHPS).
• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.
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- Drug class: first generation cephalosporins