Rilexine is a prescription antibiotic for dogs that contains the active ingredient cephalexin, a first-generation cephalosporin. It is FDA-approved specifically for treating bacterial skin infections in dogs and is also used for urinary tract infections. If your vet recently prescribed Rilexine, here’s what you should know about how it works, what to expect during treatment, and how long your dog will need to take it.
What Rilexine Treats
Rilexine’s FDA-approved use in the United States is for secondary superficial bacterial pyoderma, a common skin infection in dogs caused by the bacterium Staphylococcus pseudintermedius. Pyoderma shows up as red, irritated patches of skin, pustules, crusting, or hair loss, and it often develops after a dog has been scratching or licking due to allergies, parasites, or other skin conditions.
Beyond its FDA-labeled use, veterinarians also prescribe Rilexine for deep skin infections (deep pyoderma) and urinary tract infections, including kidney infections and bladder infections. These are considered off-label but well-established uses supported by veterinary guidance in the UK and Europe.
How It Works
Cephalexin, the drug inside Rilexine, belongs to the same broad family as penicillin. Both work by disrupting the construction of bacterial cell walls. When bacteria try to grow and divide, cephalexin blocks a critical step in building those walls, causing the bacteria to weaken and die. Because animal cells don’t have cell walls, the drug targets bacteria without damaging your dog’s own tissue.
Cephalosporins like cephalexin are effective against many common gram-positive bacteria, which makes them a reliable first-line choice for the staph infections that cause most canine pyoderma.
Dosage and How It’s Given
The standard dose is 22 mg per kilogram of body weight (10 mg per pound), given twice daily. For skin infections specifically, the recommended treatment course is at least 15 days for superficial infections and at least 28 days for deep skin infections. Urinary tract infections typically require 14 days of treatment. In severe or acute cases, your vet may safely double the dose.
Rilexine comes as a chewable, scored tablet in three sizes: 150 mg, 300 mg, and 600 mg. The tablets are chicken-liver flavored with no bitter taste or offensive odor, which makes them significantly easier to give than many antibiotics. Most dogs accept them willingly, either as a treat or mixed into food. The scored line down the middle allows for easy splitting when a dog’s weight falls between tablet sizes.
Why the Full Course Matters
One of the most important things to understand about Rilexine is the treatment length. A 28-day course for deep pyoderma can feel long, especially when your dog’s skin starts looking better after a week or two. But stopping early is one of the most common reasons skin infections come back. The bacteria that survive a partial course are the ones most likely to develop resistance, making the next round of treatment harder.
Your vet may schedule a recheck appointment toward the end of the course to confirm the infection has fully cleared before discontinuing the medication.
Side Effects
Cephalexin is generally well tolerated in dogs. The most commonly reported side effects are digestive: vomiting, diarrhea, and decreased appetite. These tend to be mild and often improve if you give the tablet with food. Allergic reactions are possible but uncommon, and may include facial swelling, hives, or difficulty breathing.
Because cephalexin shares structural similarities with penicillin, there is a small risk of cross-reactivity in dogs that have had allergic reactions to penicillin-type antibiotics in the past. If your dog has ever reacted to an antibiotic, make sure your vet knows before starting Rilexine.
What to Watch For During Treatment
For skin infections, you should start seeing gradual improvement within the first week or so: less redness, fewer pustules, and reduced itching. Hair regrowth in affected areas takes longer and may not be noticeable until several weeks into treatment or even after the course is finished. If the skin looks worse after several days on the medication, or if new areas of infection appear, contact your vet. This could mean the bacteria involved aren’t susceptible to cephalexin, and a culture and sensitivity test might be needed to find a more targeted antibiotic.
For urinary tract infections, signs like frequent urination, straining, or accidents in the house should begin improving within the first few days. If symptoms haven’t changed after three to four days, that warrants a call to your vet as well.