What is the recommended dosage of cephalexin for adults?

Recommended Dosage of Cephalexin for Adults

The standard adult dosage of cephalexin ranges from 1 to 4 grams daily in divided doses, with the usual adult dose being 250 mg every 6 hours. 1

Standard Dosing Regimens

• Usual adult dose: 250 mg every 6 hours (1 gram daily) 1
• Alternative dosing for specific infections: 500 mg every 12 hours (1 gram daily) for:
  • Streptococcal pharyngitis
  • Skin and skin structure infections
  • Uncomplicated cystitis in patients over 15 years of age 1

Dosing Based on Infection Type and Severity

• Uncomplicated skin infections: 5-7 days of therapy 2

• Respiratory tract infections: 7-10 days of therapy 2

• Urinary tract infections:

  • Treatment should be continued for 7-14 days for cystitis 1
  • Recent evidence suggests that twice-daily dosing (500 mg BID) is as effective as four-times-daily dosing for urinary tract infections 3, 4

• More severe infections:

  • Larger doses may be needed 1
  • If daily doses greater than 4 grams are required, parenteral cephalosporins should be considered 1

Special Considerations

Renal Impairment

• Patients with creatinine clearances less than 30 ml/min require a reduction in cephalexin dosage 5
• The reduction should be proportional to the reduced renal function 5
• In anephric patients, single doses of 250 or 500 mg result in high, prolonged serum concentrations 6

Administration Timing

• Cephalexin is not absorbed from the stomach but is totally and rapidly absorbed in the upper intestine 5
• Food may delay absorption 7

Practical Advantages of Cephalexin

• Can be administered in relatively high oral doses without gastrointestinal irritation 5
• Because it's absorbed high in the intestinal tract, it doesn't disturb lower bowel flora 5
• Has a very low incidence of allergy due to its stability and chemical configuration 5

Common Pitfalls to Avoid

• Dosing frequency: While traditionally prescribed four times daily, recent evidence supports twice-daily dosing for certain infections like UTIs, which may improve patient adherence 3, 4
• Renal function: Failing to adjust dosage in patients with renal impairment can lead to drug accumulation 5
• Duration of therapy: For streptococcal infections, a therapeutic dosage should be administered for at least 10 days to prevent complications 1
• Maximum oral dosing: Remember that if daily doses greater than 4 grams are required, switching to parenteral cephalosporins should be considered 1

By following these dosing guidelines, cephalexin can effectively treat a variety of common infections while minimizing adverse effects and promoting patient adherence.