Cephalexin capsules for treating bacterial infections

Cephalexin is an oral cephalosporin antibiotic used to treat infections caused by susceptible bacteria. It is commonly prescribed for infections of the respiratory tract, middle ear, skin, bones, and genitourinary tract. The capsules are available in multiple strengths and are given in divided doses based on infection type, severity, and patient age.

Cephalexin is prescribed for the treatment of infections caused by susceptible bacteria, including:

• Respiratory tract infections caused by Streptococcus pneumoniae and Streptococcus pyogenes.
• Otitis media (middle ear infection) due to Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, Streptococcus pyogenes, and Moraxella catarrhalis.
• Skin and skin structure infections caused by Staphylococcus aureus and Streptococcus pyogenes.
• Bone infections caused by Staphylococcus aureus and Proteus mirabilis.
• Genitourinary tract infections, including acute prostatitis, caused by Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae.

Cephalexin is intended only for bacterial infections confirmed or strongly suspected to be sensitive to this antibiotic to help prevent drug resistance.

Cephalexin

Cephalexin belongs to the cephalosporin class of antibiotics. It works by interfering with the formation of the bacterial cell wall, which is essential for bacterial survival. By disrupting this process, cephalexin kills susceptible bacteria and helps clear infections.

Adults and patients aged 15 years and older

• Usual dose: 250 mg every 6 hours or 500 mg every 12 hours.
• For severe infections, doses up to 4 grams daily divided into 2 to 4 doses may be needed.
• Duration: 7 to 14 days depending on infection type and severity.

Pediatric patients (over 1 year of age)

• Otitis media: 75 to 100 mg/kg/day divided every 6 hours.
• Other infections: 25 to 50 mg/kg/day in divided doses for 7 to 14 days; for β-hemolytic streptococcal infections, at least 10 days of treatment is recommended.
• Severe infections: 50 to 100 mg/kg/day divided doses.

Dosage adjustment for renal impairment (adults and pediatrics ≥15 years)

There is insufficient information for dosing in patients on hemodialysis.

Cephalexin is contraindicated in patients with known hypersensitivity to cephalexin or other cephalosporin antibiotics.

Serious hypersensitivity reactions

Patients with a history of hypersensitivity to cephalexin, other cephalosporins, or penicillins may be at risk. Cross-reactivity occurs in up to 10% of penicillin-allergic patients. Discontinue cephalexin and provide appropriate treatment if allergic symptoms develop, including rash, urticaria, angioedema, anaphylaxis, or severe skin reactions such as Stevens-Johnson syndrome.

Clostridium difficile-associated diarrhea (CDAD)

Can range from mild diarrhea to fatal colitis. Consider CDAD in any patient with diarrhea following antibiotic use, which may occur up to two months after treatment. Discontinue non-directed antibiotics if CDAD is suspected and provide appropriate therapy.

Risk of drug-induced hemolytic anemia

Positive Direct Coombs’ test and hemolytic anemia have been reported. Evaluate patients developing anemia during or after cephalexin therapy and discontinue as needed.

Seizure potential

Rarely, cephalexin may trigger seizures, particularly in patients with renal impairment if dose adjustments are not made. Discontinue if seizures occur and consider anticonvulsant therapy.

Prolonged prothrombin time

Monitor prothrombin time in patients with renal or hepatic impairment, poor nutrition, prolonged therapy, or those on anticoagulants.

Development of drug-resistant bacteria

Use only for proven or strongly suspected bacterial infections to reduce risk of resistance. Prolonged use may lead to superinfection with nonsusceptible organisms.

Common adverse reactions include diarrhea, nausea, vomiting, dyspepsia, and abdominal pain.

Other reported side effects: transient hepatitis, cholestatic jaundice, hypersensitivity reactions, genital and anal itching, candidiasis, dizziness, fatigue, headache, agitation, confusion, hallucinations, joint pain and disorders, reversible interstitial nephritis, eosinophilia, neutropenia, thrombocytopenia, hemolytic anemia, and slight increases in liver enzymes (AST, ALT).

Less common serious reactions reported with cephalosporins include fever, colitis, aplastic anemia, hemorrhage, renal dysfunction, toxic nephropathy, and altered laboratory tests such as prolonged prothrombin time and blood cell count abnormalities.

• Metformin: Cephalexin increases metformin plasma concentrations and decreases its renal clearance. Careful monitoring and metformin dose adjustment may be needed.
• Probenecid: Probenecid inhibits renal excretion of cephalexin; co-administration is not recommended.
• Laboratory tests: Cephalexin may cause false-positive urine glucose tests using Benedict’s or Fehling’s solutions.

Pregnancy

Available data, including epidemiologic studies and animal reproduction studies, have not identified a risk of major birth defects or adverse outcomes with cephalexin use during pregnancy. However, the background risks of birth defects and miscarriage are approximately 2-4% and 15-20%, respectively, in the general population.

Lactation

Cephalexin is present in human breast milk at low levels (