Pharmacokinetics of mycophenolic acid and its effect on CD4+ and CD8+ T cells after oral administration of mycophenolate mofetil to healthy cats

Abstract Background Mycophenolate mofetil (MMF) is an immunosuppressant used in human and veterinary medicine. Little pharmacokinetic and pharmacodynamic information on MMF is available in cats. Objective To evaluate the plasma disposition of mycophenolic acid (MPA) and assess its effect on total peripheral blood mononuclear cells and CD4+/CD8+ ratios after PO administration of MMF. Animals Healthy cats (n = 10). Methods Mycophenolate mofetil was administered at a dosage of 10 mg/kg q12h (n = 3), 15 mg/kg q12h (n = 3), and 15 mg/kg q8h (n = 4) for 7 days. Concentrations of MPA and derivatives were determined using ultra‐high‐performance liquid chromatography. Flow cytometry was used to assess CD4+/CD8+ T‐cell ratios. Results All cats biotransformed MMF into MPA. Half of the cats (5/10) had adverse effects within 1 week of MMF administration. Area under the curve limit of quantification (AUC0‐LOQh) of MPA ranged from 1.27 to 2.03 hours·μg/mL and from 1.77 to 8.54 hours·μg/mL after the first and last PO dose of 10 mg/kg. The AUC0‐loqh of MPA ranged from 2.18 to 31 hours·μg/mL after the first dose of 15 mg/kg of MMF. Before the first dose of MMF, the average total number of PBMC ranged from 1.2 to 9.3 million/mL. At the last dose of MMF, the average total number of PBMC ranged from 3 to 5 million/mL. Conclusion Mycophenolic acid was detected in all cats. The dose 10 mg/kg given q12h for 1 week was tolerated (n = 3). The efficacy of MMF as an immunosuppressant and long‐term safety in cats of this dosage regimen is unknown.