Cephalexin
Cephalexin monohydrate
Brand names:Keflex, Daxbia, Panixine
A first-generation oral cephalosporin antibiotic listed in the 2026 TCCC guidelines as the alternative oral wound infection prophylaxis when cefadroxil is unavailable. Cephalexin shares the same antibacterial spectrum as cefadroxil but has a shorter half-life requiring more frequent dosing.
Pharmacology and Actions
Cephalexin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins, disrupting peptidoglycan cross-linking. The result is bacterial cell lysis. The drug provides activity against gram-positive cocci including Staphylococcus aureus (non-MRSA) and Streptococcus species, along with limited gram-negative coverage. This spectrum aligns with the most common wound-contaminating organisms encountered in combat and tactical environments.
Indications
- Open combat wound infection prophylaxis when cefadroxil is unavailable (TCCC 2026)
- Casualty able to take oral medications
- Penetrating trauma with anticipated delayed evacuation
- Mild to moderate skin and soft tissue infections
Absolute Contraindications
- Known cephalosporin or severe penicillin allergy
- Casualty unable to tolerate oral medications
- Active anaphylaxis from any cause
Precautions and Side Effects
Common side effects include gastrointestinal upset, diarrhea, and rash. Cross-reactivity with penicillin allergy occurs in approximately 1 to 10 percent of penicillin-allergic patients; the risk is highest in those with documented severe penicillin reactions. Cephalexin may cause Clostridioides difficile colitis with prolonged use. Renal dose adjustment is required in patients with impaired kidney function. Monitor for signs of allergic reaction in the first hour after administration.
Adult Dosing
Pediatric Dosing
Pediatric dosing is not addressed in primary TCCC doctrine. Standard civilian pediatric dosing is 25 to 50 mg/kg/day divided every 6 to 12 hours, not to exceed adult dose. Consult medical control and local standing orders before administration.
Pharmacokinetics
Peak Effect: PO: 1 hour after administration
Duration: 6 to 8 hours (requires q6h dosing for sustained levels)
Storage and Handling
Store capsules and tablets at controlled room temperature (15 to 30 degrees Celsius). Protect from moisture. Oral suspension requires refrigeration after reconstitution and is generally not carried in TCCC kits due to logistics.
Reconstitution:
Tablet and capsule forms require no reconstitution. Suspension formulations are not typical for TCCC use due to refrigeration requirements after reconstitution.
TCCC and TECC Role
Cephalexin is the alternative oral antibiotic in the 2026 TCCC wound infection prophylaxis algorithm. The primary choice is cefadroxil at 1 gram once daily because of its longer half-life and simpler dosing in tactical environments. Cephalexin is selected when cefadroxil is unavailable, but its q6h dosing schedule is operationally less practical for casualties in prolonged field care. Both agents share the same spectrum and indication: prevention of wound infection in penetrating trauma when oral medications are tolerated and evacuation is delayed.
Cephalexin matters in the tactical environment when cefadroxil is not in the kit. Operationally, the q6h dosing creates real challenges in extended care scenarios because someone has to track and administer doses every 6 hours through the night. Cefadroxil's once-daily dosing is the reason it is preferred. Cephalexin remains the right choice when cefadroxil is out of stock or the casualty has a documented intolerance, but build a dosing schedule the team can actually maintain.
Administering cephalexin to a casualty with a documented severe penicillin allergy without considering cross-reactivity risk. While the cross-reaction rate is low, severe penicillin reactions warrant skipping cephalosporins entirely in favor of a non-beta-lactam alternative when one is available. The wound is not the immediate threat; anaphylaxis at the point of injury is.
This drug profile is provided as educational reference material for trained medical providers. It is not medical advice, not a substitute for formal training, and not a substitute for current published guidelines or medical direction.
Drug administration is governed by your scope of practice, agency standing orders, medical director protocols, and applicable state and federal regulations. Controlled substances are subject to additional handling, accountability, and documentation requirements per DEA and state law. Always verify dosing, indications, contraindications, and route of administration against current published guidelines and your local protocols before administration.
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Penn Tactical Solutions publishes this reference for educational purposes. PTS does not provide medical direction and does not assume responsibility for clinical decisions made in the field. Clinical responsibility rests with the administering provider, their medical director, and their agency.
Educational reference for trained medical providers. Not medical advice. Not a substitute for formal training, current published guidelines, or medical direction. Drug administration is governed by your scope of practice, agency standing orders, medical director protocols, and applicable state and federal regulations. Controlled substances require additional storage, accountability, and documentation per DEA and state law.
In a medical emergency, call 911. This reference is not a substitute for emergency medical services.
Verify dosing, indications, and contraindications against current published guidelines and your local protocols before administration. Confirm content currency against the source citation. Penn Tactical Solutions does not provide medical direction. Clinical responsibility rests with the administering provider, their medical director, and their agency.
Cephalexin
| PO | TCCC 2026: 500 mg PO every 6 hours. Continue until evacuation to higher level of care. Maximum daily dose 4 grams. Standard non-TCCC dosing for skin and soft tissue infection: 500 mg PO every 6 to 12 hours for 7 to 10 days. (Absorption begins within 30 to 60 minutes) |