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Cephalexin

Pronunciation

Pronunciation

(sef a LEKS in)

Index Terms

  • Cephalexin Monohydrate

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Capsule, Oral:

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)

Tablet, Oral:

Generic: 250 mg, 500 mg

Brand Names: U.S.

  • Daxbia
  • Keflex

Pharmacologic Category

  • Antibiotic, Cephalosporin (First Generation)

Pharmacology

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.

Absorption

Rapid (90%); delayed in young children and may be decreased up to 50% in neonates

Distribution

Widely into most body tissues and fluids, including gallbladder, liver, kidneys, bone, sputum, bile, and pleural and synovial fluids; CSF penetration is poor

Excretion

Urine (80% to 100% as unchanged drug) within 8 hours

Time to Peak

Serum: ~1 hour

Half-Life Elimination

Neonates: 5 hours; Children 3-12 months: 2.5 hours; Adults: 0.5 to 1.2 hours (prolonged with renal impairment)

Protein Binding

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 MSSA. IV cefazolin therapy should be initiated in the inpatient setting to potentially reduce morbidity and mortality.

Infective endocarditis, prophylaxis

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.

Prophylaxis in patients with prosthetic joint implants undergoing dental procedures which produce bacteremia

Although currently not recommended for routine use prior to dental procedures in patients with prosthetic joint implants to prevent prosthetic joint infection as stated within the American Academy of Orthopaedic Surgeons/American Dental Association Prevention of Orthopaedic Implant Infection in Patients Undergoing Dental Procedures guidelines and a subsequent report of the American Dental Association Council on Scientific Affairs, if deemed to be necessary for select patients at risk for prosthetic joint infection (eg, history of complications associated with joint replacement surgery), antibiotic prophylaxis may be considered. Dentists planning invasive oral procedures should therefore consult with the patient's orthopedic surgeon to determine the risk associated with infection and the need for antibiotics. Based on a retired advisory statement from the American Dental Association and American Academy of Orthopaedic Surgeons, the use of cephalexin (among other antibiotics) was suggested for patients not allergic to penicillin [ADA/AAOS 2003].

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 chronic oral antimicrobial suppression of prosthetic joint infection with Staphylococci (oxacillin-susceptible) after completion of parenteral therapy.

Surgical site infection

Based on the Infectious Diseases Society of America (IDSA) guidelines for the diagnosis and management of skin and soft tissue infections (SSTI), cephalexin is an effective and recommended option for treatment of surgical site infections occurring after surgery of the trunk or extremity (away from axilla or perineum). Systemic antibacterials are not routinely indicated for surgical site infections, but may be beneficial (in conjunction with suture removal plus incision and drainage) in patients with significant systemic response (eg, temperature >38.5°C, heart rate >110 beats per minute, erythema/induration extending >5 cm from incision, WBC >12,000/mm3).

Contraindications

Hypersensitivity to cephalexin, other cephalosporins, or any component of the formulation

Dosing: Adult

Dosing range: Oral: 250 to 1,000 mg every 6 hours or 500 mg every 12 hours (maximum: 4 g/day)

Indication-specific dosing:

Impetigo: Oral: 250 mg every 6 hours; continue for 7 days, depending upon clinical response (IDSA [Stevens 2014])

Infective endocarditis, prophylaxis (dental, oral, or respiratory tract procedures) (off-label use): Oral: 2 g 30 to 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 (AHA [Wilson 2007]).

Prophylaxis in patients with prosthetic joint implants undergoing dental procedures which produce bacteremia (off-label use): Oral: 2 g 1 hour prior to procedure (ADA/AAOS 2003). Note: In general, patients with prosthetic joint implants do not require prophylactic antibiotics prior to dental procedures. In planning an invasive oral procedure, dental consultation with the patient's orthopedic surgeon may be advised to review the risks of infection (Sollecito 2015).

Prosthetic joint infection, chronic oral antimicrobial suppression (off-label use): Oral:

Cutibacterium spp (alternative to penicillin or amoxicillin): 500 mg every 6 to 8 hours (Osmon 2013)

Staphylococci, oxacillin-susceptible (preferred): 500 mg every 6 to 8 hours (Osmon 2013)

Streptococci, beta-hemolytic (alternative to penicillin or amoxicillin): 500 mg every 6 to 8 hours (Osmon 2013)

Skin and skin structure infections: Oral:

Manufacturer’s labeling: 250 mg every 6 hours or 500 mg every 12 hours

Alternate recommendations: 500 mg every 6 hours (IDSA [Stevens 2014])

Streptococcal pharyngitis: Oral: 500 mg every 12 hours. Note: Recommended by the Infectious Disease Society of America (IDSA) as an alternative agent for group A streptococcal pharyngitis in penicillin-allergic patients (avoid in patients with immediate-type hypersensitivity to penicillin) with a duration of 10 days (Shulman 2012).

Streptococcal skin infections: 500 mg every 6 hours (IDSA [Stevens 2014])

Surgical site infection (trunk or extremity [away from axilla or perineum]) (off-label use): Oral: 500 mg every 6 hours (IDSA [Stevens 2014])

Uncomplicated cystitis: Oral: 250 mg every 6 hours or 500 mg every 12 hours for 7 to 14 days

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Usual dose:

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

Indication-specific dosing:

Community-acquired pneumonia (CAP) (IDSA/PIDS 2011), S. 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

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])

Infective endocarditis, prophylaxis (dental, oral, or 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: 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 (AHA [Wilson 2007]).

Otitis media: Children: 75 to 100 mg/kg/day in 4 divided doses

Prophylaxis in total joint replacement patients undergoing dental procedures which produce bacteremia (off-label use): Adolescents ≥15 years: Refer to adult dosing.

Severe infections: Children: Oral: 50 to 100 mg/kg/day in divided doses every 6 to 8 hours

Skin and skin structure infections:

Manufacturer’s labeling:

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.

Alternate recommendations: Children: 25 to 50 mg/kg/day divided every 6 hours (IDSA [Stevens 2014])

Streptococcal pharyngitis: Children >1 year: Oral: 25 to 50 mg/kg/day divided every 12 hours. Note: Recommended by the Infectious Disease Society of America (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: 1000 mg daily) for 10 days (Shulman 2012).

Uncomplicated cystitis: Adolescents ≥15 years: Refer to adult dosing.

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.

Administration

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.

Storage

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).

Drug Interactions

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

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

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

Adverse Reactions

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)

Warnings/Precautions

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.

Disease-related concerns:

• 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.

Other warnings/precautions:

• 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.

Monitoring Parameters

With prolonged therapy monitor renal, hepatic, and hematologic function periodically; monitor for signs of anaphylaxis during first dose

Pregnancy Risk Factor

B

Pregnancy Considerations

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).

Patient Education

• 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.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.

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