For Cats, Consider Prednisolone

Cats are considered resistant to many of the adverse effects of glucocorticoids. Subsequently, higher (relative to dogs) doses have been recommended. In this study, 11 healthy cats (5 in normal body condition, 6 overconditioned) had lean body mass objectively determined by bioelectric impedance analysis. A 2-drug crossover trial was performed with a 3-week washout between treatments. Eight cats first received prednisone; the remaining 3 initially received prednisolone. All received a total dose of 2 mg/kg. Blood samples were drawn pre-and posttreatment at 1, 2, 4, 6, 8, 12, and 24 hours after administration. Both prednisone and prednisolone were assayed using high-performance liquid chromatography. The study confirmed the conversion of prednisone to prednisolone in cats; however, 2 mg/kg PO prednisolone produced a significantly higher plasma concentration (4-fold) compared with PO prednisone. There was also a significantly higher plasma drug concentration (2-fold) in overconditioned cats compared with normal conditioned cats. The study suggested low bioavailability of prednisone compared with prednisolone in cats and that lean body mass or ideal body weight should be considered when dosing.

CommentaryThis study offers 2 clinically relevant applications: First, prednisolone should be used in cats and prednisone (a prodrug requiring conversion) should be avoided. Should prednisone be prescribed, the cat will be significantly underdosed from the intended treatment approach. Second, lean body weight should be prudently considered when prescribing prednisolone to overweight and obese cats. When dosed on a body weight basis, obese cats may have increased targeted plasma levels. This could increase an overconditioned patient’s risk for complications (eg, diabetes from insulin resistance, heart failure from fluid retention). In rabbits and humans, prednisolone is known to have limited distribution into adipose tissue, and cats are likely similar in this regard.—Jonathan Bach, DVM, DACVIM, DACVECC

SourceInfluence of body condition on plasma prednisolone and prednisone concentrations in clinically healthy cats after single oral dose administration. Center SA, Randolph JF, Warner KL, et al. Res Vet Sci 95:225-230, 2013.