Feline
Update (June 13, 2026): Cyclosporine Pharmacokinetics in Cats — C4h Best Correlates With AUC, Safety Margin at Label Doses
TL;DR
A 2023 pharmacokinetic study of cyclosporine in cats (Kong et al.) found a nonlinear pharmacokinetic profile where the 4-hour post-dose concentration (C4h) correlated best with AUC0-24 (R-squared 0.896), supporting C4h as a practical monitoring surrogate. Earlier safety data (Roberts 2014) established that serious adverse effects occurred only when cats received doses greater than twice the label-approved dose for extended periods.
What just dropped
- Kong and colleagues (2023) conducted a pharmacokinetic study of cyclosporine in cats and found a nonlinear pharmacokinetic profile. C4h correlated best with the 24-hour area under the curve (AUC0-24), with an R-squared of 0.896, supporting its use as a monitoring surrogate in clinical practice. (https://pubmed.ncbi.nlm.nih.gov/37368785/)
- Roberts and colleagues (2014) reported in a 6-month safety study that serious adverse effects (prolonged APTT, bone marrow hypocellularity, lymphoma) occurred only in cats receiving doses greater than twice the approved label dose over extended periods; no significant accumulation beyond the first week was observed at standard label dosing. (https://pubmed.ncbi.nlm.nih.gov/24134659/)
Context
Cyclosporine (Atopica for Cats, Elanco) is a calcineurin inhibitor licensed for feline allergic skin diseases. Its nonlinear pharmacokinetics — well established in human medicine — are now better characterised in cats through studies like Kong 2023. For clinicians monitoring cyclosporine therapy, the nonlinearity means that small dose adjustments can produce disproportionate changes in systemic exposure, and that a validated surrogate time point (C4h) simplifies the monitoring burden without requiring a full AUC calculation.
The safety margin established by Roberts 2014 is relevant to clinical practice in two ways. First, it provides reassurance that the adverse events associated with extremely high doses (lymphoma, bone marrow effects) are not expected at or near standard label dosing in cats. Second, the lack of significant accumulation beyond the first week at label-approved doses supports once-daily dosing stability.
Together, these two data sets inform the monitoring and safety counselling for cats on cyclosporine: use C4h for practical monitoring, and set owner expectations that the serious AE profile is associated with sustained dose excess rather than label-appropriate therapy.
What this changes in Cyclosporine (Atopica for Cats) for Feline Allergic Dermatitis (https://www.thevoyage.ai/forvets/knowledge/cyclosporine-cats-allergic-dermatitis)
The Kong 2023 PK data add a monitoring-practice dimension to this page. The existing page documents efficacy and safety; the C4h correlation (R-squared 0.896) provides a specific monitoring recommendation reference that clinicians can cite when explaining sampling timing to colleagues and clients. The Roberts 2014 safety framing reinforces the existing dose-safety section.
References
- Kong LR et al. 2023. Cyclosporine pharmacokinetics in cats: nonlinear profile and C4h as AUC0-24 surrogate. PMID 37368785. https://pubmed.ncbi.nlm.nih.gov/37368785/
- Roberts ES et al. 2014. Six-month safety study of cyclosporine in cats: serious AEs only at >2x label dose. PMID 24134659. https://pubmed.ncbi.nlm.nih.gov/24134659/
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