Cefaclor Dosage
The standard dosage of cefaclor for adults is 250 mg every 8 hours, which can be doubled to 500 mg every 8 hours for more severe infections or less susceptible organisms. 1
Adult Dosing
- Standard dose: 250 mg orally every 8 hours 1
- Severe infections (e.g., pneumonia) or less susceptible organisms: 500 mg orally every 8 hours 1
- Cefaclor may be administered without dose adjustment in patients with impaired renal function 1
Pediatric Dosing
- Standard dose: 20 mg/kg/day divided every 8 hours 1
- More serious infections, otitis media, or less susceptible organisms: 40 mg/kg/day divided every 8 hours (maximum 1 g/day) 1
- Alternative twice-daily regimen for otitis media and pharyngitis: Total daily dose divided every 12 hours 1
Pediatric Weight-Based Dosing Examples:
- 9 kg child (20 mg/kg/day): 2.5 mL (125 mg/5 mL suspension) three times daily 1
- 18 kg child (20 mg/kg/day): 5 mL (125 mg/5 mL suspension) three times daily 1
- 9 kg child (40 mg/kg/day): 5 mL (125 mg/5 mL suspension) three times daily 1
- 18 kg child (40 mg/kg/day): 5 mL (250 mg/5 mL suspension) three times daily 1
Treatment Duration
- β-hemolytic streptococcal infections: Minimum 10 days of therapy 1
- Most other infections: 3-5 days after resolution of signs and symptoms 2
Critical Clinical Considerations
Cefaclor has significant limitations that restrict its use in modern practice. The 2004 Otolaryngology guidelines explicitly state that cefaclor has poor activity against H. influenzae, fair activity against penicillin-susceptible pneumococci, and no activity against drug-resistant S. pneumoniae (DRSP), resulting in poor overall efficacy against bacterial respiratory tract pathogens 3.
The 2005 sinusitis guidelines further note that cefaclor has inadequate activity against all β-lactamase-producing M. catarrhalis and some H. influenzae, plus a high prevalence of serum sickness-like reactions, making it an unattractive treatment option 3.