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 shown in Table 3 of the guidelines by the Infectious Diseases Society of America 1. When considering a BID dosing regimen for cephalexin, it is essential to take into account the type of infection being treated and the patient's individual circumstances.
- For infections caused by Staphylococci, oxacillin-susceptible, cephalexin 500 mg PO tid or qid is recommended, but an alternative option is cefadroxil 500 mg PO bid, suggesting 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 option, indicating that BID dosing may also be suitable for this type of infection 1. However, it is crucial to note that the decision to use BID dosing should be based on the individual patient's needs and the specific infection being treated, and the total daily dose should typically remain the same.
- The pharmacokinetics of cephalexin, with a half-life of approximately 1 hour in patients with normal renal function, support BID dosing, providing adequate coverage between doses 1.
- BID dosing can improve medication adherence due to the simplified regimen, which is particularly beneficial for patients with busy schedules or those who have difficulty remembering multiple daily doses. It is also important to consider the potential risks and benefits of BID dosing, including the possibility of higher peak concentrations and lower trough levels compared to QID dosing, and to monitor patients for efficacy and safety.
- Clinical and laboratory monitoring for efficacy and safety should occur based on the clinical judgment of the clinician caring for the patient, as stated in the guidelines by the Infectious Diseases Society of America 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.