KEFLEX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for KEFLEX (KEFLEX).
Cephalexin is a first-generation cephalosporin antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis and death.
| Metabolism | Cephalexin is not extensively metabolized; it is primarily excreted unchanged in the urine via renal tubular secretion and glomerular filtration. Minor metabolism may occur via hydrolysis. |
| Excretion | Primarily renal (90% or more unchanged via glomerular filtration and tubular secretion); small amounts biliary/fecal (<5%). |
| Half-life | 0.5–1.2 hours in patients with normal renal function (CrCl >50 mL/min); prolonged to >20 hours in ESRD. |
| Protein binding | 6–10% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | 0.2–0.4 L/kg; indicates distribution primarily into extracellular fluid. |
| Bioavailability | Oral: ~90–95% (well absorbed); IM: ~100%. |
| Onset of Action | Oral: ~30–60 minutes; IV: immediate. |
| Duration of Action | 6–8 hours for susceptible organisms; dose adjustment needed for renal impairment. |
| Action Class | Cephalosporins: 1st generation |
| Brand Substitutes | Seafal 500mg Capsule, Q Cef 500mg Capsule, Equitrol Forte 500mg Capsule, Yescef 500mg Capsule, Nexporin 500 Capsule, Cephalkem 250mg Capsule, Equitrol 250mg Capsule, Nexporin 250 Capsule, Apkef 250mg Capsule, Cefrik 250mg Capsule |
250-500 mg orally every 6 hours; maximum 4 g/day.
| Dosage form | FOR SUSPENSION |
| Renal impairment | CrCl 30-49 mL/min: 500 mg every 8-12 hours; CrCl 10-29 mL/min: 250-500 mg every 12-24 hours; CrCl <10 mL/min: 250 mg every 24 hours. |
| Liver impairment | No dosage adjustment required for hepatic impairment; no Child-Pugh based modifications established. |
| Pediatric use | 25-50 mg/kg/day orally divided every 6-8 hours; for otitis media: 75 mg/kg/day divided every 12 hours. |
| Geriatric use | Start at lower end of dosing range; monitor renal function; adjust based on creatinine clearance. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for KEFLEX (KEFLEX).
| Breastfeeding | Excreted into breast milk in low amounts. M/P ratio not established. Considered compatible with breastfeeding due to low infant exposure; monitor infant for diarrhea, rash, or candidiasis. |
| Teratogenic Risk | FDA Pregnancy Category B. Animal studies show no fetal harm. No adequate human studies in first trimester; cephalosporins generally considered low risk. No known teratogenicity in any trimester. |
| Fetal Monitoring |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["Known hypersensitivity to cephalexin or other cephalosporins","Previous immediate hypersensitivity reaction to penicillins (relative contraindication)"]
| Precautions | ["Hypersensitivity reactions, including anaphylaxis","Clostridioides difficile-associated diarrhea","Renal impairment: dose adjustment required","Seizure potential with high doses or renal insufficiency","Prolonged use may result in superinfection","False-positive urine glucose tests with non-enzymatic methods","Use with caution in patients with history of penicillin allergy (cross-sensitivity)"] |
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| Monitor maternal renal function and for signs of hypersensitivity or Clostridioides difficile-associated diarrhea. No fetal-specific monitoring required unless maternal infection warrants. |
| Fertility Effects | No adverse effects on fertility reported in animal or human studies. |