Cephalexin
Cephalexin is a beta-lactam antibacterial. Formulation, species and infection site determine its clinical use.
Group
First-generation cephalosporin
Mechanism of Action
Binds penicillin-binding proteins and disrupts bacterial cell-wall synthesis.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Pyoderma, skin and soft-tissue infections | 22–25 mg/kg | PO | Every 12 h | |
| Urinary tract infection | 22–25 mg/kg | PO | Every 12 h | |
| Deep or superficial pyoderma | 22–33 mg/kg | PO | Every 8–12 h | |
| Recurrent pyoderma | 22 mg/kg | PO | Every 12 h | For deep pyoderma a separate eight-hour alternative is described. |
| Deep pyoderma | 22 mg/kg | PO | Every 8 h | |
| Superficial pyoderma | 30–40 mg/kg | PO | Every 24 h | Up to 28 days |
| Pyoderma | 22–35 mg/kg | PO | Every 12 h | |
| Respiratory infection | 20–40 mg/kg | PO | Every 8 h | |
| Soft-tissue infection | 30–50 mg/kg | PO | Every 12 h | |
| Systemic infection | 25–60 mg/kg | PO | Every 8 h | |
| Orthopedic infection | 22–30 mg/kg | PO | Every 6–8 h | Up to 28 days |
| Pyometra or metritis adjunct | 10–30 mg/kg | PO | Every 8–12 h | Antibiotic dosing is only one part of pyometra management; assess source control and systemic illness. |
| Urinary tract infection | 30–40 mg/kg | PO | Every 8 h | Historical alternatives specify acute cystitis 7–10 days, chronic disease up to four weeks and pyelonephritis 4–8 weeks; use an infection-specific current treatment plan. |
| Neonatal bacterial infection | 10–30 mg/kg | PO | Every 8–12 h | Neonates only; weak patients require safe assisted feeding/administration rather than forced oral dosing. |
| Secondary bacterial infection with juvenile cellulitis | 20 mg/kg | PO | Every 8 h | Puppies 3–16 weeks. Juvenile cellulitis itself is not established as a primary bacterial disease; use only for a separate bacterial indication. |
| Infectious otitis | 22 mg/kg | PO | Every 12 h |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Bacterial infections | 22–25 mg/kg | PO | Every 12 h | |
| Soft-tissue infection | 30–50 mg/kg | PO | Every 12 h | |
| Systemic infection | 35 mg/kg | PO | Every 6–8 h | |
| Bacterial infections | 22 mg/kg | PO | Every 8 h | Give with food if gastrointestinal upset occurs. |
| Gram-positive infection | 22 mg/kg | PO | Every 12 h | |
| Gram-negative infection | 30 mg/kg | PO | Every 8 h | |
| Bacterial infections | 20–40 mg/kg | PO | Every 8 h |
Horses
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Susceptible gram-positive infection | 30 mg/kg | PO | Every 8 h | Only highly susceptible bacteria with MIC ≤0.5 mcg/mL; equine oral absorption is very low. |
| Bacterial infections | 22–33 mg/kg | PO | Every 6 h | Oral absorption is poor; use only for a sufficiently susceptible organism. |
Rabbits
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Historical oral cephalexin treatment | Reference only | PO | 11–22 mg/kg orally every eight hours appears in the older source. Oral cephalosporins can cause serious dysbiosis in rabbits; do not treat this as a routine first-line rabbit regimen. |
Guinea pigs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Historical injectable cephalexin treatment | Reference only | IM | 50 mg/kg IM daily is described; no compatible veterinary injectable preparation is established here and serious dysbiosis is a concern. |
Ferrets
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Bacterial infections | 15–25 mg/kg | PO | Every 8–12 h |
Birds
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Bacterial infections | 35–50 mg/kg | PO | Every 6 h | Oral suspension. |
| Alternative bacterial infection treatment | 40–100 mg/kg | PO | Every 6 h |
Ratites
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Bacterial infections | 15–22 mg/kg | PO | Every 8 h | |
| Historical megabacteriosis treatment | Reference only | PO | The older passage lists 50 mg/kg orally four times daily for five days, but megabacteriosis is associated with Macrorhabdus, a yeast. This is not promoted as an antibacterial treatment for that organism. |
Indications
- Pyoderma, skin, soft-tissue and urinary infections
Contraindications
- Cephalosporin hypersensitivity; assess prior severe beta-lactam allergy.
Interactions
- Avoid mixing with other drugs in the same vial or syringe unless compatibility is established.
Adverse effects
- Hypersensitivity
- Gastrointestinal upset
- Injection-site reactions with parenteral products
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Cephalexin 75 mg tablet | Tablet | 75 mg / tablet | PO |
| Cephalexin 150 mg tablet | Tablet | 150 mg / tablet | PO |
| Cephalexin 300 mg tablet | Tablet | 300 mg / tablet | PO |
| Cephalexin 600 mg tablet | Tablet | 600 mg / tablet | PO |
| Cephalexin 100 mg/mL oral liquid | Oral Liquid | 100 mg / mL | PO |
| Cephalexin suspension 125 mg/5 mL | Oral Liquid | 125 mg / 5 mL | PO |
| Cephalexin suspension 250 mg/5 mL | Oral Liquid | 250 mg / 5 mL | PO |
| Cephalexin 250 mg capsule | Capsule | 250 mg / capsule | PO |
| Cephalexin 500 mg capsule | Capsule | 500 mg / capsule | PO |
Monitoring and Administration
Choose treatment using organism identity, infection site and susceptibility testing. Reassess clinical response and renal function where impaired clearance may increase exposure.
Food-animal authorization and withdrawal periods depend on the exact formulation, species, regimen and jurisdiction; do not transfer foreign approvals or residue intervals to another product.
Refrigerate suspension and discard after 14 days. Enteral admixtures are for immediate use.
Cephalexin may interfere with urine glucose tests. Methicillin-resistant staphylococci are clinically resistant; cephalothin is not a preferred susceptibility marker.
Septic shock and severe systemic illness can reduce oral absorption; use a suitable parenteral antibacterial instead of relying on a high oral dose.
Historical long treatment durations are not automatic minimums. Reassess site, culture, source control and response rather than carrying an old duration into every infection.