Cephalexin Dosage Calculator for Dogs
Calculate the correct cephalexin (Keflex) dose for your dog based on body weight, indication, and formulation. Supports capsules and oral suspension dosing for skin infections, UTI, and deep tissue infections.
PRESCRIPTION MEDICATION
Cephalexin requires a valid veterinary prescription. This calculator is for educational reference only. Always confirm the dose, course length, and formulation with your veterinarian before administering. Do not use leftover antibiotics from a previous infection or another dog.
Cephalexin (Keflex) Dosage Guide for Dogs
Cephalexin is one of the most widely prescribed antibiotics in canine veterinary medicine. As a first-generation cephalosporin, it covers the gram-positive bacteria responsible for most skin infections (pyoderma), as well as common urinary tract pathogens. Correct weight-based dosing, an appropriate course length, and completion of the full prescription are the three factors most strongly linked to clinical success and to preventing antibiotic resistance.
What Is Cephalexin and How Does It Work?
Cephalexin is a first-generation cephalosporin antibiotic that disrupts bacterial cell wall synthesis, causing susceptible bacteria to lyse and die. It is bactericidal (kills bacteria rather than just inhibiting growth) and is most effective against gram-positive bacteria such as Staphylococcus pseudintermedius, the most common cause of canine pyoderma.
Cephalexin is sold under the brand name Keflex in human pharmacies and as Rilexine and other generic names in veterinary medicine. The active ingredient is identical, although veterinary formulations may include palatability enhancers. Cephalexin is well absorbed orally, reaches peak plasma concentrations within 1-2 hours, and is eliminated primarily by the kidneys.
Standard Cephalexin Dosing for Dogs
The standard canine dosing regimen for cephalexin is:
- Routine infections (pyoderma, UTI, soft tissue): 22 mg per kg of body weight every 12 hours (BID), equivalent to 10 mg per pound twice daily
- Severe or deep infections: 30 mg per kg every 12 hours (BID), or in some cases 22 mg per kg every 8 hours (TID)
- Maximum practical daily dose: approximately 60 mg per kg per day
Cephalexin Course Length by Indication
| Indication | Typical Course | Dose Rate |
|---|---|---|
| Uncomplicated UTI | 7-14 days | 22 mg/kg BID |
| Superficial pyoderma | 21-28 days | 22 mg/kg BID |
| Deep pyoderma | 4-6 weeks minimum | 30 mg/kg BID |
| Soft tissue (wound, abscess) | 7-14 days | 22 mg/kg BID |
| Osteomyelitis (bone) | 4-12 weeks | 30 mg/kg BID-TID |
| Otitis externa (ear) | 7-21 days | 22 mg/kg BID |
Course lengths are typical guidelines. Your veterinarian may adjust based on clinical response and infection severity.
Cephalexin Side Effects and Drug Interactions
Cephalexin is generally well tolerated in dogs. The most common side effects are mild and self-limiting.
Common Side Effects
- Vomiting, often resolved by giving with food
- Diarrhea or soft stools
- Decreased appetite
- Drooling or panting
- Mild hyperexcitability or restlessness
Serious But Rare Side Effects
- Allergic reaction (facial swelling, hives, difficulty breathing)
- Severe persistent diarrhea (Clostridium difficile overgrowth)
- Cross-reactivity in dogs with confirmed penicillin allergy
Drug Interactions
- Probenecid: reduces cephalexin elimination and increases plasma concentrations
- Aminoglycoside antibiotics: may increase risk of kidney damage when combined
- Anticoagulants: cephalexin may modestly enhance anticoagulant effect
Cephalexin vs Other Common Dog Antibiotics
| Antibiotic | Class | Best Use Case | Key Consideration |
|---|---|---|---|
| Cephalexin | 1st-gen cephalosporin | Skin, UTI, soft tissue | Most prescribed antibiotic for canine pyoderma |
| Amoxicillin-clavulanate (Clavamox) | Beta-lactam + inhibitor | Broad-spectrum, skin, wound, UTI | Good first-line option with broader coverage |
| Cefpodoxime (Simplicef) | 3rd-gen cephalosporin | Pyoderma, soft tissue | Once-daily dosing improves compliance |
| Cefovecin (Convenia) | 3rd-gen cephalosporin | Skin, soft tissue | Single injection lasts 14 days |
| Doxycycline | Tetracycline | Tick-borne disease, respiratory | Not first-line for pyoderma |
Frequently Asked Questions About Cephalexin for Dogs
How much cephalexin can I give my dog?
The standard canine dose is 22 mg per kg of body weight twice daily for routine infections. Severe or deep infections may use 30 mg per kg twice daily. The maximum practical daily dose is approximately 60 mg per kg per day.
Is cephalexin the same as Keflex for dogs?
Yes. Cephalexin is the generic name; Keflex is the human brand name. Veterinary cephalexin (Rilexine and others) contains the same active ingredient. Human Keflex is often used off-label in dogs under veterinary supervision.
How long does cephalexin take to work in dogs?
Most dogs show clinical improvement within 48-72 hours. Superficial skin infections often show visible improvement within a week. Deep pyoderma may take 2-4 weeks to show full response. Complete the full prescribed course even if symptoms resolve early.
What is cephalexin used for in dogs?
Cephalexin is most commonly prescribed for pyoderma (skin infection), urinary tract infection, soft tissue infection, ear infection, and bone or joint infection caused by susceptible bacteria. It is one of the most prescribed antibiotics in veterinary medicine.
What are the side effects of cephalexin in dogs?
Most common side effects are gastrointestinal: vomiting, diarrhea, and decreased appetite. These can often be reduced by giving with food. Allergic reactions are uncommon but possible, especially in dogs with known penicillin or cephalosporin sensitivity.
Can I give my dog cephalexin and Benadryl together?
Yes. Cephalexin and Benadryl are commonly used together, particularly for treating pyoderma in allergic dogs. See our Benadryl dosage calculator for appropriate antihistamine dosing.
How long is a course of cephalexin for dogs?
Course length depends on infection type: 7-14 days for UTI, 21-28 days for superficial pyoderma, 4-6 weeks for deep pyoderma, and 4-12 weeks for osteomyelitis. Always complete the entire prescribed course.
Should I give cephalexin with food?
Giving cephalexin with food is recommended for dogs with sensitive stomachs to reduce vomiting or nausea. Absorption is not significantly affected by food intake.
What if I miss a dose of cephalexin?
Give the missed dose as soon as you remember if within a few hours. If close to the next scheduled dose, skip the missed dose. Do not double up. Missed doses reduce effectiveness and increase resistance risk.
Can dogs with penicillin allergy take cephalexin?
Use with caution. About 5-10% of patients with confirmed penicillin allergy show cross-reactivity to cephalosporins. Tell your veterinarian about any previous antibiotic reactions before starting cephalexin.
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A Note on Responsible Antibiotic Use
Cephalexin is a safe and effective antibiotic when prescribed and used correctly. Completing the full course, dosing on schedule, and not sharing antibiotics between pets are the most important steps you can take to slow antibiotic resistance and protect future treatment options for your dog and other pets in your community. This calculator provides educational reference only; your veterinarian remains the authority on diagnosis and dosing.