Calculate exact veterinary cephalexin dosages in mg, oral liquid suspension mL, and tablet split fractions for cats by weight and infection type.
Cephalexin is a prescription-only veterinary antibiotic. This calculator is an educational dosing reference and does not replace a professional clinical diagnosis. Never administer leftover, human-prescribed, or unconfirmed antibiotics to your cat without direct veterinary oversight. Improper antibiotic administration can mask underlying diseases, cause acute gastrointestinal injury, or foster lethal resistant bacterial infections. Always consult your veterinarian before starting or altering any antibiotic regimen.
Oral Suspension 125 mg/5 mL (25 mg/mL). Shake vigorously before drawing.
Standard protocol for feline bacterial folliculitis, superficial pyoderma, and bite abscesses.
Reconstituted suspensions are ideal for precise feline dosing. Always store in the refrigerator and discard after 14 days.
| Cat Weight | Target Dose (mg) | 125 mg/5 mL (25 mg/mL) | 250 mg/5 mL (50 mg/mL) | 100 mg/mL Drops |
|---|---|---|---|---|
| 5 lbs (2.3 kg) | 50.0 mg | 2.00 mL | 1.00 mL | 0.50 mL |
| 8 lbs (3.6 kg) | 80.0 mg | 3.20 mL | 1.60 mL | 0.80 mL |
| 10 lbs (4.5 kg) [Average] | 100.0 mg | 4.00 mL | 2.00 mL | 1.00 mL |
| 12 lbs (5.4 kg) | 120.0 mg | 4.80 mL | 2.40 mL | 1.20 mL |
| 15 lbs (6.8 kg) | 150.0 mg | 6.00 mL | 3.00 mL | 1.50 mL |
Never give adult 500 mg capsules to cats. For tablet formulations, use scored veterinary chewables (75 mg or 150 mg) or divide 250 mg tablets with a pill splitter.
Easy to administer whole or split in half for smaller felines. Flavour-enhanced for easy oral acceptance.
Half a tablet provides 75 mg (suits 7–8 lb cat); one whole tablet provides 150 mg (suits 15 lb cat).
1/2 tablet = 125 mg (suits 12–14 lb cat); 1/4 tablet = 62.5 mg (suits 6–7 lb cat). Use a razor-sharp pill cutter.
Cephalexin commonly causes mild nausea or vomiting on an empty stomach. Administering immediately with a small meal or moist food treat eliminates stomach irritation.
Probiotics (e.g. FortiFlora): If giving feline probiotics to protect gut microflora, space them at least 2 hours apart from the cephalexin dose so the antibiotic does not kill the beneficial probiotic bacteria.
Cephalexin is a semi-synthetic first-generation cephalosporin beta-lactam bactericidal antibiotic. In feline veterinary medicine, it is primarily indicated for aerobic Gram-positive infections caused by Staphylococcus pseudintermedius, Staphylococcus aureus, and Streptococcus species, as well as select susceptible Gram-negative bacilli including Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae.
Cephalexin works by binding to specific penicillin-binding proteins (PBPs) situated within the bacterial cytoplasmic membrane. This binding blocks transpeptidase enzymes, preventing the cross-linking of peptidoglycan chains essential for bacterial cell wall rigidity. The osmotic pressure gradient causes cell wall rupture, resulting in rapid bacterial lysis and death.
Veterinarians select specific beta-lactams and cephalosporins based on infection location, tissue penetration, and bacterial culture sensitivity:
| Antibiotic Name | Drug Class & Generation | Key Bacterial Targets | Typical Clinical Application in Cats |
|---|---|---|---|
| Cephalexin (Keflex) | 1st-Gen Cephalosporin | Staphylococcus, Streptococcus, select E. coli | Feline pyoderma, bite abscesses, uncomplicated UTIs. |
| Cefadroxil (Cefa-Drops) | 1st-Gen Cephalosporin | Similar to cephalexin; longer half-life | Oral liquid suspension formulated specifically for felines. |
| Cefovecin (Convenia) | 3rd-Gen Cephalosporin | Extended Gram-positive & select Gram-negative | Single long-acting 14-day subcutaneous injection for fractious cats. |
| Amoxicillin-Clavulanate (Clavamox) | Potentiated Penicillin | Broad spectrum + Anaerobic activity (Pasteurella) | Contaminated fight wounds, cat bite cellulitis, respiratory infections. |
Cephalexin exhibits rapid gastrointestinal absorption, achieving peak serum concentrations within 1 to 2 hours of oral administration. Its elimination half-life ($t_{1/2}$) in healthy felines is approximately 1.5 to 2.0 hours. Because cephalexin is a time-dependent bactericidal antibiotic, drug concentrations at the site of infection must remain above the Minimum Inhibitory Concentration (MIC) for at least 50% to 70% of the dosing interval.
This rapid elimination explains why cephalexin must be administered strictly every 8 to 12 hours. Skipping doses or extending intervals allows surviving bacteria to multiply and develop plasmid-mediated beta-lactamase resistance.
Feline esophageal anatomy is uniquely predisposed to medication retention: the distal third of the cat's esophagus transitions from skeletal muscle to smooth muscle with weaker peristalsis. When solid capsules or dry tablets are given without liquid ("dry pilling"), studies show that over 80% of pills remain trapped in the feline esophagus for up to 5 minutes.
Trapped cephalexin tablets dissolve locally against delicate esophageal mucosa, releasing acidic caustic chemical residues that cause severe erosive esophagitis and life-threatening esophageal strictures (scarring and narrowing of the throat).
While cephalexin has a wide therapeutic safety margin, adverse reactions can occur. Monitor your cat for:
Authoritative, veterinary-backed answers regarding feline cephalexin dosages, liquid suspensions, side effects, and antibiotic course adherence.
