Optimal Timing for Cephalexin Four Times Daily Dosing
Take cephalexin every 6 hours around the clock (e.g., 6 AM, 12 PM, 6 PM, 12 AM) to maintain consistent antibiotic levels throughout the day. 1
Standard Four Times Daily Dosing Schedule
The FDA-approved dosing interval for cephalexin is every 6 hours when prescribed four times daily 1. This translates to:
- 6:00 AM
- 12:00 PM (noon)
- 6:00 PM
- 12:00 AM (midnight)
Alternatively, you can adjust these times by 1-2 hours to fit your schedule (e.g., 7 AM, 1 PM, 7 PM, 1 AM), but maintain the 6-hour intervals as closely as possible 1.
Dosing Considerations by Indication
For Most Infections
- Adults: 250 mg every 6 hours is the usual dose, though 500 mg every 6 hours may be needed for more severe infections or less susceptible organisms 1
- The Infectious Diseases Society of America recommends 500 mg four times daily for skin and soft tissue infections caused by methicillin-susceptible Staphylococcus aureus (MSSA) 2, 3
For Pediatric Patients
- Standard dosing: 25-50 mg/kg/day divided into 4 doses (every 6 hours) 1
- For MSSA infections: Higher doses of 75-100 mg/kg/day divided into 3-4 doses may be required 2
- For otitis media: 75-100 mg/kg/day in 4 divided doses is necessary 1
Duration of Therapy
- Most infections: Continue for 7-10 days depending on clinical response 2
- Streptococcal infections: Must be administered for at least 10 days to prevent rheumatic fever 4, 1
- Cystitis: Continue for 7-14 days 1
Important Clinical Considerations
Absorption and Food
Cephalexin is absorbed in the upper intestine (not the stomach) and can be taken with or without food 5. Taking it with food may reduce gastrointestinal upset if it occurs.
Why Every 6 Hours Matters
Cephalexin is rapidly cleared by the kidneys, with 70-100% of the dose appearing in urine within 6-8 hours 5. The every-6-hour dosing maintains adequate tissue concentrations needed to kill bacteria, as cephalosporins require the free drug concentration to exceed the minimum inhibitory concentration for at least 40% of the dosing interval 6, 7.
Common Pitfall: Skipping the Nighttime Dose
Do not skip the midnight dose when prescribed four times daily. While less frequent dosing regimens (twice or three times daily) can be effective for certain infections 8, 6, 9, if your provider specifically prescribed four times daily dosing, this suggests either:
- A more severe infection requiring higher sustained drug levels
- An organism requiring more aggressive dosing
- A specific infection type (like otitis media) where four times daily dosing is standard 1
When Less Frequent Dosing May Be Appropriate
For uncomplicated streptococcal pharyngitis or skin infections, cephalexin 500 mg every 12 hours (twice daily) may be sufficient 1. However, this is a different prescription than four times daily dosing. Research shows twice-daily dosing of 1 gram can be effective for urinary tract infections 8 and some respiratory/soft tissue infections 9, but do not change your prescribed regimen without consulting your provider 2.
Renal Impairment
If you have kidney disease (creatinine clearance <30 mL/min), dosage reduction is required 5. Consult your provider about appropriate dose adjustments.
Storage of Liquid Suspension
If using oral suspension, refrigerate after mixing and discard after 14 days 1.