Cephalexin
KEFLEX
What it isFirst-generation cephalosporin that inhibits penicillin-binding proteins; skin, soft-tissue and urinary infections.
Why this oneNarrow, reliable MSSA and streptococcal coverage makes it a go-to oral step-down drug for uncomplicated skin infection.
What limits itNo MRSA coverage. Renal adjustment and frequent dosing complicate use; allergy risk follows side-chain similarity, not a blanket penicillin label.
FDA-approved for
- skin infections (1971)
- urinary tract infection (1971)
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Bacterial infections | Adult/>=15 yr | 250 mg q6h | 250 mg q6h or 500 mg q12h | 4 g/day |
| Otitis media | Peds >1 yr | 75-100 mg/kg/day divided q6h | 75-100 mg/kg/day divided q6h | |
| Other infections | Peds >1 yr | 25-50 mg/kg/day in divided doses | 25-50 mg/kg/day (severe: 50-100 mg/kg/day) |
Renal CrCl 30-59: no adjustment, max 1 g/day; 15-29: 250 mg q8-12h; 5-14 (not on dialysis): 250 mg q24h; 1-4 (not on dialysis): 250 mg q48-60h
Hepatic Undefined
Instructions
- Duration 7-14 days (>=10 days for beta-hemolytic streptococcal infections)
- Use lower dose in renal impairment (seizure risk)
Contraindications
- Known hypersensitivity to cephalexin or other cephalosporins
Cautions
- Serious hypersensitivity/anaphylaxis (cross-reactivity with penicillins up to 10%)
- C. difficile-associated diarrhea
- Direct Coombs' seroconversion/hemolytic anemia
- Seizure potential (renal impairment)
Adverse reactions
- Diarrhea
- Nausea
- Vomiting
- Dyspepsia
- Abdominal pain
Pregnancy No established drug-associated risk of birth defects or miscarriage; no evidence of fetal harm in animals
Lactation Present in human milk (RID <1%); no data on breastfed child or milk production
NO BOXED WARNINGS
Principal riskHypersensitivity; cross-reactivity with penicillin is lower than once taught
Cost, est. cash$4–$80/month
Generic entry1986
Classes and tags
Clinical profile
Legacy pregnancy categoryB
Defining liabilityAllergy, gastrointestinal effects and agent-specific renal, hepatic, hematologic or interaction risks.
Mechanism of action: Cephalexin ballicule
Open Cephalexin in the interactive console ↗
Memory aids: mascots and interaction avatars
Cephalopod with a beta lactam necklace
