Cephalexin (Keflex) is a first-generation cephalosporin that inhibits bacterial cell wall synthesis. It is used to treat the following conditions:

• Treatment of infections of the bone caused by Staphylococcus aureus or Proteus mirabilis.
• Treatment of infections of the genitourinary tract (including acute prostatitis), caused by Escherichia coli, P. mirabilis, and Klebsiella pneumoniae.
• Treatment of otitis media caused by Streptococcus pneumoniae, H. influenzae, Staphylococcus aureus, Streptococcus pyogenes, and Moraxella catarrhalis.
• Treatment of infections of the respiratory tract caused by Strep. pneumoniae and Strep. pyogenes.
• Treatment of skin and soft tissue infections caused by Staph. aureus or S. pyogenes

Off-Label Use of Cephalexin (Keflex) in Adults include:

• For the prophylaxis of endocarditis
• Prosthetic joint infection

Cephalexin Dose in Adults

• The usual dose is 250 to 1,000 mg 4 times a day or 500 mg twice daily to a maximum dose of 4 gms/day.

Dose in specific situations:

• As an alternative agent in the treatment of mild erysipelas and nonpurulent Cellulitis:
  • 500 mg 6 hourly for at least 5 days. The duration may be prolonged if the response to treatment is slow

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• As n alternative agent in the treatment of uncomplicated Cystitis:
  • 500 mg twice daily for 5 to 7 days.

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• As an alternative agent for the prophylaxis of endocarditis prior to a dental or invasive respiratory tract procedure:
  • 2 gms 30 - 60 minutes before the procedure.

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• Treatment of Impetigo or ecthyma:
  • 250 to 500 mg 6 hourly for 7 days.

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• Treatment of Prosthetic joint infection:
  • • It should be used following intravenous therapy and joint debridement. The duration of therapy may vary from a minimum of 3 months to indefinitely
  • Methicillin-susceptible Staphylococci:
    • • 500 mg every three or four times a day (in combination with rifampin for the first 3 to 6 months of therapy)
    • As an alternative agent for beta-hemolytic Streptococci:
      • 500 mg every three or four times a day
    • As an alternative agent for Cutibacterium spp:
      • 500 mg every three or four times a day

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• As an alternative agent for group A Streptococcal pharyngitis in patients with mild penicillin allergy:
  • 500 mg twice daily for 10 days

Cephalexin Dose in Childrens

Usual dosing for the treatment of susceptible infections:

• Infants, Children, and Adolescents:
  • Mild to moderate infection:
    • 25 to 50 mg/kg/day in two to four divided doses to a maximum daily dose of 2,000 mg/day
  • Severe infections:
    • 75 to 100 mg/kg/day in three or four divided doses to a maximum daily dose of 4,000 mg/day

Peritoneal Catheter infections:

• Infants, Children, and Adolescents:
  • 10 to 20 mg/kg/day orally once a day in two divided doses to a maximum dose of 1,000 mg/dose

Dose in group A streptococcal Pharyngitis & tonsillitis:

• Children and Adolescents less than 15 years of age:
  • 25 to 50 mg/kg/day orally in two divided doses to a maximum dose of 500 mg/dose
• Adolescents older than 15 years:
  • 500 mg orally in two divided doses
• IDSA recommendation (alternate dosing):
  • Infants, Children, and Adolescents:
    • 20 mg/kg/dose in two divided doses for 10 days to a maximum dose of 500 mg/dose.

Impetigo (caused by Staphylococcus or streptococcus):

• Infants, Children, and Adolescents:
  • 25 to 50 mg/kg/day in three or four divided doses to a maximum dose of 250 mg/dose for 7 days.

Acute Otitis media:

• Infants and Children:
  • 75 to 100 mg/kg/day  in four divided doses to the usual maximum dose of 500 mg/dose in mild to moderate infections and 1000 mg/dose in severe infections.

Skin and soft tissue infections like cellulitis and erysipelas:

• Infants, Children, and Adolescents less than 15 years:
  • 25 to 50 mg/kg/day in two divided doses to a maximum dose of 500 mg/dose (for a total of 10 days in patients with infections caused by β-hemolytic streptococcal infections)
• Adolescents older than 15 years:
  • 500 mg twice daily.
• IDSA recommendations:
  • Infants, Children, and Adolescents:
    • 25 to 50 mg/kg/day in four divided doses to a maximum dose of 500 mg/dose for a minimum of 5 days

For prophylaxis of Endocarditis prior to a dental or respiratory tract procedure:

• Infants, Children, and Adolescents:
  • 50 mg/kg administered 30 to 60 minutes before the procedure to a maximum dose of 2,000 mg/dose.

Use in treatment of Mild community-acquired Pneumonia and mild infections caused by Methicillin-sensitive S. aureus.

• Infants older than 3 months, Children, and Adolescents:
  • 75 to 100 mg/kg/day orally in three or four divided doses to a maximum daily dose of 4000 mg/day

Use of Cephalexin in the treatment of Urinary tract infection:

• Empiric therapy in febrile patients:
  • Infants older than 2 months and Children less than 2 years of age:
    • 50 to 100 mg/kg/day in four divided doses for 7 - 14 days
• Treatment:
  • Children and Adolescents less than 15 years of age:
    • 25 to 50 mg/kg/day in two or four divided doses to a maximum dose of 500 mg/dose for 7 - 14 days
    • A dose of 50 to 100 mg/kg/day in two or four divided doses to am amximum dose of 4000 mg day may be advised in severe infections
  • Adolescents older than 15 years:
    • 250 mg every 6 hours or 500 mg twice daily for 7 - 14 days. Higher doses upto 4 gms may be required in severe infections.

As a step-down therapy in Osteoarticular infection like septic arthritis and osteomyelitis:

• Infants, Children, and Adolescents:
  • 100 mg/kg/day in three or four divided doses to a maximum daily dose of 4000 mg.

Pregnancy Risk Factor B

• Cephalexin crosses the placental barrier however, adverse fetal outcomes have not been observed when used during pregnancy.
• It may be used for the prevention of endocarditis in high-risk patients before a vaginal delivery.

Cephalexin (Keflex) use during breastfeeding:  

• Cephalexin enters breastmilk. It may modify the infant's bowel flora and may cause GI disturbances in the infant.
• The manufacturer recommends weighing the benefits of breastfeeding and risks to the infant and the benefits of maternal treatment.
• It may also be used to treat mastitis if other first-line agents cannot be used.

Cephalexin Dose in Renal Disease:

• CrCl  of more than 30 mL/minute.
  • No dose adjustment is required

• CrCl 15 - 29 mL/minute:
  • 250 mg twice or thrice daily.
• CrCl 5 - 14 mL/minute:
  • 250 mg once a day
• CrCl 1 - 4 mL/minute:
  • 250 mg every second or third day.

• End-stage renal disease (ESRD) on intermittent hemodialysis:
  • 250 - 500 mg once or twice daily. 20 - 50% of the dose may be given after dialysis.

• Peritoneal dialysis:
  • 250 to 500 mg once or twice daily.

Cephalexin Dose in Liver Disease:

The manufacturer has not recommended any dose adjustment in patients with liver disease.

Common Side Of Cephalexin Include:

• Central nervous system:
  • Agitation
  • Confusion
  • Dizziness
  • Fatigue
  • Hallucination
  • Headache
• Dermatologic:
  • Erythema multiforme
  • Genital pruritus
  • Skin rash
  • Stevens-Johnson syndrome 
  • Toxic epidermal necrolysis
  • Urticaria
• Gastrointestinal:
  • Abdominal pain
  • Diarrhea
  • Dyspepsia
  • Gastritis
  • Nausea
  • Pseudomembranous colitis
  • Vomiting
• Genitourinary:
  • Genital candidiasis
  • Vaginal discharge
  • Vaginitis
• Hematologic & oncologic:
  • Eosinophilia
  • Hemolytic anemia
  • Neutropenia
  • Thrombocytopenia
• Hepatic:
  • Cholestatic jaundice
  • Hepatitis
  • Increased serum ALT
  • Increased serum AST
• Hypersensitivity:
  • Anaphylaxis
  • Angioedema
  • Hypersensitivity reaction
• Neuromuscular & skeletal:
  • Arthralgia
  • Arthritis
  • Arthropathy
• Renal:
  • Interstitial nephritis (rare)

Contraindication to Cephalexin (Keflex) include:

• Allergic reactions to cephalexin, penicillins, other cephalosporins, or any component of the formulation

Warnings & Precautions

• Hypersensitivity reactions:
  • Allergic reactions including a rash, urticaria, anaphylaxis, angioedema, erythema multiforme, SJS (Stevens-Johnson syndrome), toxic epidermal necrolysis [TEN]) have been reported.
  • Treatment should be discontinued if allergic reactions are noted.

• Elevated INR:
  • It may result in coagulopathy manifested by an increase in INR, especially in patients with liver and renal impairment, patients with nutritional deficiency, and those on prolonged therapy

• Seizure disorder:
  • High levels of cephalexin especially in patients with renal impairment are at risk of developing seizures.

• Superinfection:
  • Patients on prolonged cephalexin therapy (more than 2 months) may develop superinfections including fungal and bacterial superinfections (e.g. C. difficile-associated diarrhea (CDAD) and pseudomembranous colitis)

• Renal impairment:
  • It should be used with caution in patients with renal impairment. The dose may need to be modified in such cases.

Cephalexin: Drug Interaction

Note: Drug Interaction Categories:

• Risk Factor C: Monitor When Using Combination
• Risk Factor D: Consider Treatment Modification
• Risk Factor X: Avoid Concomitant Use

Monitoring Parameters:

• Monitor renal function, hepatic function, and hematologic parameters periodically in patients on prolonged therapy.
• Monitor for allergic reactions and signs of anaphylaxis during first dose.

How to take Cephalexin?

• Administer without regard to meals.
• It may be administered with meals if the patient develops GI distress.
• It should be administered round the clock to minimize variation in the peak and trough levels.

Mechanism of action of Cephalexin:

Cephalexin (Keflex) is a first-generation cephalosporin that binds to the penicillin-binding proteins (PBPs) and inhibits bacterial cell wall synthesis. Bacteria are then lysed by the action of autolytic enzymes 90% of it is rapidly absorbed and is 6 - 15 % protein bound. It is widely distributed into most tissues and body fluids including the gallbladder, bile, liver, kidneys, bone, sputum, pleural and synovial fluids. It has poor CSF penetration. The half-life elimination in neonates is 5 hours, in children is 2.5 hours and in adults is 0.5 to 1.2 hours. The time to peak serum concentration is about one hour. It is primarily excreted via urine within 8 hours (80 - 100% as unchanged drug)

International Brands of Cephalexin:

• APO-Cephalex
• AURO-Cephalexin
• DOM-Cephalexin
• Keflex
• LUPIN-Cephalexin
• PMS-Cephalexin
• TEVA-Cephalexin
• TEVA-Cephalexin 125
• TEVA-Cephalexin 250
• Acelex
• Airex
• Alexin
• Arlexin
• Asef
• Avloxin
• Axcel
• Bloflex
• Capxin
• Cecan
• Cefabiotic
• Cefacet
• Cefadal
• Cefadin
• Cefadyl
• Cefalin
• Cefalver
• Cefamor
• Cefastad
• Ceff
• Cefovit
• Cefrax
• Celexin
• Cephadar Forte
• Cephalen
• Cephalex
• Cephalexyl
• Cephanmycin
• Cephast
• Cephoxin
• Ceporex Forte
• Ceporexin
• Ceprax
• Ceproex
• Cerexin
• Erocetin
• Falexin
• Farmalex
• Felexin
• Glexil
• Glopixin
• Ibilex
• Inphalex
• Italcefal
• Kefacin
• Kefalex
• Kefalospes
• Kefaxin
• Keflex
• Kefloridina
• Keforal
• Kidolex
• Larixin
• LCLexin
• Lecef
• Lenocef
• Lexin
• Lexipron
• Madlexin
• Meceta
• Medolexin
• Midaflex
• Monocef
• Nafacil-S
• Neokef
• Nufex
• Oracef
• Oriphex
• Ospeksyn
• Ospexin
• Paferxin
• Palitrex
• Pectril
• Pharmexin
• Plecef
• Proxicef
• Ramoxin
• Rancef
• Relaxin
• Sanaxin
• Sef
• Sepexin
• Septilisin
• Servicef
• Servispor
• Sialexin
• Sofilex
• Solulexin
• Sorlex
• Sporicef
• Sporidex
• Sporidin
• Sporidin AF
• Torlasporin
• Uphalexin
• Winlex
• Zecef
• Zelexin

Cephalexin Brands in Pakistan: