Azathioprine Capsule
Azathioprine is a compounded formulation containing Azathioprine, prepared by Mixlab for veterinary use. Available by prescription.
Use as directed by your veterinarian.
The uses and pharmacology described below reflect the FDA-approved labeling for this active ingredient; your veterinarian determines whether and how they apply to your animal's treatment plan.
Veterinarians most commonly consider azathioprine for the management of autoimmune conditions such as immune-mediated hemolytic anemia (IMHA), immune-mediated thrombocytopenia (ITP) and certain dermatological health challenges like pemphigus complex. It is frequently a point of discussion when a patient requires long-term immune modulation and the veterinarian aims in the context of addressing the dosage of concurrent corticosteroids to minimize secondary effects. By interfering with the production of specific immune cells, your veterinarian can manage the physiological environment in the context of addressing self-targeted tissue damage.
At a pharmacological level, azathioprine is a prodrug that is converted in the body to its active metabolite, 6-mercaptopurine. This metabolite acts as a purine antagonist, stopping the synthesis of DNA and RNA within rapidly dividing cells. Because T-lymphocytes and B-lymphocytes must proliferate rapidly during an immune response, they are particularly sensitive to this interference. By inhibiting the synthesis of nucleic acids, the medication manages the proliferation of these cells, thereby dampening the overall immune response. Your veterinarian will determine the clinical appropriateness of azathioprine based on your pet’s diagnostic testing results and metabolic health profile.
Prescription only. Use only under the direction of a licensed veterinarian. This information is not a substitute for veterinary diagnosis, prescribing or monitoring. Compounded drugs are not approved by the FDA for safety or effectiveness.
Commonly observed effects following the administration of azathioprine include gastrointestinal changes such as vomiting, loose stools or a decrease in appetite. A significant clinical consideration for this medication is its potential to influence the bone marrow, which may manifest as a decrease in white blood cell or platelet counts. Your veterinarian will monitor for these shifts through frequent blood work, including complete blood counts (CBC), to ensure the medication remains suitable for your pet’s health status. Owners should watch for signs of persistent lethargy, unusual bruising or fever and contact their veterinarian promptly if these occur.
This medication is typically used with extra caution or avoided in patients with known severe liver disease or pre-existing bone marrow suppression. It is strictly avoided in feline patients, as cats lack sufficient amounts of the enzyme (thiopurine methyltransferase) required to metabolize this medication safely, which can lead to life-threatening toxicity. Before starting a protocol, ensure your veterinarian has a complete history of all other prescriptions and supplements your pet is receiving, as significant interactions can occur with certain heart medications or other immunosuppressants. Your veterinarian is the right person to provide guidance on the necessary duration of use and the most commonly considered monitoring plan for your pet's individual needs.
Yes. Azathioprine is a potent prescription immunosuppressant and can only be dispensed by a licensed pharmacy upon receipt of a valid authorization from a licensed veterinarian. Mixlab verifies all authorizations before any medication is prepared or shipped to your home.
Yes. While azathioprine is available as a commercial tablet, Mixlab can compound this medication into specialized strengths or alternative flavored dosage forms—such as oral liquids or smaller capsules—if your veterinarian determines a customized preparation better suits your dog's needs. The decision between a commercial and compounded product rests with the prescribing veterinarian.
Veterinarians do not prescribe azathioprine for cats because they lack the specific liver enzyme needed to break down the medication safely. Without this enzyme, the medication can cause severe, often fatal, suppression of the bone marrow, which is why alternative immunosuppressants are discussed for feline patients.
Veterinarians typically recommend very frequent blood work, often every 1–2 weeks during the initial phase of the protocol and then periodically thereafter. This monitoring is essential to ensure that the medication is managing the immune system without causing unintended shifts in the bone marrow or liver function.
