From the Guidelines
Cephalexin can be dosed twice daily (BID) instead of four times daily (QID) for certain infections, such as those caused by Staphylococci, oxacillin-susceptible, or β-hemolytic streptococci, as indicated in Table 3 of the guidelines by the Infectious Diseases Society of America 1.
Key Considerations
- The decision to use BID dosing should be based on the specific microorganism, patient factors, and local resistance patterns.
- For Staphylococci, oxacillin-susceptible, cephalexin 500 mg PO tid or qid is recommended, but alternative treatments include cefadroxil 500 mg PO bid, which suggests that BID dosing may be effective for this type of infection 1.
- For β-hemolytic streptococci, penicillin V 500 mg PO bid to qid is the preferred treatment, but cephalexin 500 mg PO tid or qid is an alternative, indicating that BID dosing may be suitable for this infection as well 1.
Dosing Regimen
- When switching from QID to BID dosing, ensure the daily dose remains appropriate for the infection severity.
- The total daily dose should typically remain the same, so 500 mg BID equals 1000 mg daily, comparable to 250 mg QID.
- BID dosing improves medication adherence since fewer daily doses are easier for patients to remember.
Important Notes
- Always consider the specific infection, patient factors, and local resistance patterns when determining the optimal dosing regimen.
- Clinical and laboratory monitoring for efficacy and safety should occur based on the clinical judgment of the clinician caring for the patient 1.
From the FDA Drug Label
The usual adult dose is 250 mg every 6 hours For the following infections, a dosage of 500 mg may be administered every 12 hours: streptococcal pharyngitis, skin and skin structure infections, and uncomplicated cystitis in patients over 15 years of age. For streptococcal pharyngitis in patients over 1 year of age and for skin and skin structure infections, the total daily dose may be divided and administered every 12 hours.
Cephalexin dosing can be administered every 12 hours for certain infections, such as:
- Streptococcal pharyngitis
- Skin and skin structure infections
- Uncomplicated cystitis in patients over 15 years of age A dosage of 500 mg every 12 hours can be used for these infections, which is equivalent to bid (twice a day) dosing. However, for other infections, the usual adult dose is 250 mg every 6 hours, which is equivalent to qid (four times a day) dosing. 2
From the Research
Cephalexin Dosage Frequency
- The standard dosage frequency of cephalexin is every 6 hours (qid) or every 12 hours (bid) depending on the infection being treated 3.
- A study from 1983 suggests that cephalexin can be effective in twice-daily dosages, which can enhance medication compliance 4.
- However, the provided studies do not directly compare the efficacy of cephalexin bid versus qid.
- A literature review and meta-analysis from 2013 found that reducing the dosing frequency of oral therapies, including antibiotics like cephalexin, can improve adherence and compliance rates 5.
- The study found that twice-daily (bid) dosing schedules were associated with higher adherence rates compared to thrice-daily (tid) or four-times daily (qid) dosing schedules, although the difference was not as significant as once-daily (od) dosing 5.
Antibiotic Treatment of Skin and Soft Tissue Infections
- Cephalexin is commonly used to treat skin and soft tissue infections caused by Staphylococcus aureus and Streptococcus pyogenes 3, 4, 6, 7.
- The choice of antibiotic and dosage frequency may depend on the severity of the infection, the presence of toxinic symptoms, and the patient's ability to adhere to the treatment regimen 6, 7.
- Other antibiotics, such as amoxicillin-clavulanate, may be recommended as first-line treatment for skin and soft tissue infections in certain cases 6, 7.