The label says, word for word:
Zenrelia is indicated for control of pruritus associated with allergic dermatitis and control of atopic dermatitis in dogs at least 12 months of age.
WARNING: INADEQUATE IMMUNE RESPONSE TO VACCINES. Based on results of the vaccine response study, dogs receiving Zenrelia are at risk of an inadequate immune response to vaccines. Discontinue Zenrelia for at least 28 days to 3 months prior to vaccination and withhold Zenrelia for at least 28 days after vaccination.
Due to the risk of infections, dogs should be up to date on vaccinations prior to starting Zenrelia.
Due to the risk of an inadequate immune response to vaccines, do not administer vaccines to a dog receiving Zenrelia.
Zenrelia is not for use in dogs less than 12 months of age.
Dogs should be monitored for the development of infections because Zenrelia may increase susceptibility to infections, including adenoviral hepatitis and pancreatitis, demodicosis, interdigital furunculosis, coccidiosis, and pneumonia, and exacerbation of subclinical or uncomplicated infections.
Every approved medicine has a field study behind it, and the label prints what happened:
In a masked field study assessing effectiveness and safety of Zenrelia for the control of atopic dermatitis in dogs, 181 Zenrelia-treated dogs and 87 placebo-treated dogs diagnosed with atopic dermatitis were evaluated for safety up to 112 days.
The DailyMed label (revised July 2025) has no section titled Contraindications and no Client Information Sheet. Boxed warning history: the original September 19, 2024 labeling warned of "fatal vaccine-induced disease from modified live virus vaccines"; a supplemental approval dated September 19, 2025 (FOI Summary: "This supplement provides for revisions to the boxed warning and Animal Safety Warnings.") removed that language, and the current boxed warning is titled "WARNING: INADEQUATE IMMUNE RESPONSE TO VACCINES". Other label warnings: "Zenrelia modulates the immune system."
The emergency page sorts the signs by how long you have, and the symptom checker asks what you are seeing. Reactions to a medicine can also be reported to the FDA yourself: how to report a problem.
These answers come from the approved label on DailyMed, read on 2 October 2026. Where the label does not say, the answer says so, and the vet or the pharmacist is the one to ask.
The approved use is quoted at the top of this page. It is a tablet given to dogs at least 12 months old for the itch of allergic skin disease and to control atopic dermatitis.
The label gives no time in hours. In its field study of dogs with allergic itch, success was judged over the first 7 days of treatment. After Day 1 of that study, the owners' average itch scores were lower in the dogs given Zenrelia than in the dogs given a placebo, which is a tablet without the drug. In its study of atopic dermatitis, success was measured on Day 28. The label also says the level of the drug in the blood peaks about 2 hours after a dose.
It is a tablet given by mouth once a day, with or without food. The tablets are scored, and the vet works out the amount from the dog's weight. The label does not say what to do if the dog vomits after a tablet.
The label does not say what to do about a missed dose. Call the clinic or the pharmacy before you give the next one.
The studies and the warnings are quoted above. The label has no line telling owners when to call the vet. The warning in the box at the top of the label is about vaccines: a dog on Zenrelia is at risk of not responding properly to a vaccine, so the label has the tablets stopped for at least 28 days to 3 months before a vaccination and held back for at least 28 days after it. Tell any clinic that is about to vaccinate your dog that it takes Zenrelia. The label also says dogs should be monitored for infections, because the drug may make them more likely. If your dog seems unwell, call the vet. The label says to wash your hands immediately after handling the tablets, and to get medical attention immediately if a person swallows one by accident.
Store it at room temperature, between 59° and 77°F; the label allows short spells between 41° and 104°F. The label says to keep it in a safe place out of reach of dogs, cats and other animals, to prevent accidental swallowing or an overdose, and out of the reach of children.
The FDA says the best way to get rid of most unused or expired medicines is a take-back option: a drug take-back location, which can be at a pharmacy or a police station, or a prepaid mail-back envelope. If you cannot use one and the medicine is not on the FDA's flush list, the FDA says to mix it, uncrushed, with something unappealing such as dirt, cat litter or used coffee grounds and to seal the mixture in a plastic bag before throwing it away. Flushing is only for medicines on that list, such as opioids. Do not give leftovers to another pet.
Write the dose, the times and the stop date here, then print this page for the fridge.
Dose and times: _____________________________________________
Stop date: _____________________________________________