April 2025
By Garret Pachtinger, VMD, DACVECC, Director of Operations/C0-Founder, VETgirl

In this VETgirl online veterinary continuing education blog, Dr. Garret Pachtinger, DACVECC reviews what the difference is between prednisone and prednisolone, and why you should care in dogs versus cats! Read on to find out why you should be using pred-NIS-olone in cats!

What’s the Difference Between Prednisone vs. Prednisolone

A common question we have received from our VETgirl members is…

“What is the difference between Prednisone and Prednisolone?”

Before we get into their differences, let’s talk about their similarities!

  • Prednisone and prednisolone are both corticosteroids used to treat various inflammatory and immune-related conditions.
  • Both of these glucocorticoids will exert different effects on the body based on the dose used.(1)

For example:

  • Physiological doses of prednisone/prednisolone are 0.2 mg/kg PO q 24 hours (higher with stress in patients with endogenous glucocorticoid deficiency)(2)
  • Anti-inflammatory doses of prednisone/prednisolone are 0.5 mg/kg PO every 12 hours (some recommend 0.5 to 1 mg/kg per day for dogs and 1-2 mg/kg per day in cats)(2)
  • Immune suppressive doses of prednisone/prednisolone are 1-2 mg/kg PO every 12-24 hours.
  • NOTE: Now, the recommendation is to dose based on mg/m2 with maximal doses of 30-40 mg TOTAL twice per day, depending on the resource).(2)

Glucocorticoids can also be used in even lower doses if a patient is deficient in natural production of corticosteroids, such as in the disease process hypoadrenocorticism (Addison’s disease). While they have similar general principles, one of the main differences between prednisone and prednisolone is the way they are metabolized in the body to be active and effective.

    • Prednisone is an inactive prodrug. It needs to be converted by the liver into prednisolone, the active form, to exert its effects.(1)
    • Prednisolone is the active form of the medication. It can be used directly without needing conversion by the liver.

In dogs, this process occurs efficiently. Dogs can readily metabolize prednisone in the liver to become active prednisolone, so prescribing either is fine. However, in cats, the conversion of prednisone to prednisolone is less efficient. It has been reported that following prednisone administration in cats, approximately 25% of the drug is found as the active form, prednisolone. In cats, prednisolone has a 4-fold higher area under the curve, which results in higher plasma prednisolone concentrations.

For this reason, prednisone and prednisolone are not be considered bioequivalent in cats (due to its lower bioavailability). As a result, many choose prednisolone preferentially in cats.

References:
Graham-Mize CA, Rosser EJ, Hauptman J. Absorption, bioavailability and activity of prednisone and prednisolone in cats, in Proceedings. 5th World Congress Vet Dermatol 2005;152-158

Trepanier LA. Glucocorticoids. Clinician’s Brief 2015;pp.43-47

  1. Sarah Bristol says:

    Good read. Some of the information i slightly knew and some i did not. Nice to have a understanding. Will continue to learn these differences.

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