Detection and Longitudinal Monitoring of Cyclosporine in Horse Plasma and Urine After Ocular Implant Administration.
Abstract: This paper describes the detection and longitudinal monitoring of cyclosporine in plasma and urine after subconjunctival implant administration in a horse. Sensitive liquid chromatography tandem mass spectroscopy (LC-MS/MS) methods for detecting cyclosporine in horse plasma and urine have been developed and validated, with estimated limits of detection down to 1 pg/mL in both matrices. The developed methods enabled longitudinal monitoring of cyclosporine levels in blood and urine samples collected over 6 months from a horse that had received an ocular cyclosporine implant.
© 2026 John Wiley & Sons Ltd.
Publication Date: 2026-01-18 PubMed ID: 41549061DOI: 10.1002/dta.70026Google Scholar: Lookup
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- Journal Article
- Validation Study
Summary
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Overview
- This study developed sensitive methods to detect and measure the drug cyclosporine in horse plasma and urine.
- The research tracked the presence of cyclosporine over six months in a horse given an ocular implant that releases the drug subconjunctivally.
Introduction to Cyclosporine and Its Ocular Use in Horses
- Cyclosporine is an immunosuppressive drug often used to treat inflammatory eye diseases.
- In horses, delivering cyclosporine via ocular implants directly under the conjunctiva offers localized, sustained release.
- This administration route may reduce systemic side effects compared to oral or injectable forms.
Aims of the Study
- Develop sensitive and specific analytical methods using liquid chromatography tandem mass spectrometry (LC-MS/MS) to detect cyclosporine in horse plasma and urine.
- Validate these methods to ensure accuracy and precision across extremely low concentrations, with detection limits down to 1 pg/mL (picogram per milliliter).
- Use the methods to longitudinally monitor cyclosporine levels in a horse’s blood and urine over 6 months after ocular implant administration.
Methodology
- Sample Collection:
- Blood and urine samples were periodically collected from the horse receiving the cyclosporine ocular implant.
- Sampling extended for a duration of 6 months to track long-term drug release and clearance.
- LC-MS/MS Development and Validation:
- Liquid chromatography tandem mass spectrometry was selected for its high sensitivity and specificity in detecting small-molecule drugs.
- Method validation included determining the limit of detection (LOD), limit of quantification (LOQ), accuracy, precision, and reproducibility in both plasma and urine matrices.
- LOD reached as low as 1 pg/mL, making it possible to detect minute cyclosporine quantities.
Results
- The developed LC-MS/MS methods successfully detected cyclosporine at very low levels in both plasma and urine samples.
- Longitudinal monitoring indicated sustained release and systemic absorption of cyclosporine from the ocular implant.
- Cyclosporine persisted in measurable concentrations in plasma and urine throughout the 6-month study period.
- This demonstrated the implant’s capability for long-term drug delivery and systemic exposure assessment over time.
Implications and Significance
- Validated sensitive detection methods enable veterinarians and researchers to monitor systemic drug levels following localized ocular implant administration.
- The persistence of cyclosporine in plasma and urine suggests systemic absorption despite local administration, important for assessing therapeutic levels and potential side effects.
- Such monitoring can help optimize dosing strategies and improve treatment plans for equine ocular diseases.
- The approach can be extended to study other drugs delivered via ocular implants or localized administration in veterinary and possibly human medicine.
Summary
- This study provided a robust analytical framework for sensitive detection and long-term monitoring of cyclosporine in horses receiving ocular implants.
- The findings support the feasibility of using LC-MS/MS methods for pharmacokinetic studies and therapeutic monitoring in equine ophthalmology.
- Overall, this contributes to advancing safer and more effective ocular drug delivery systems in veterinary practice.
Cite This Article
APA
So YM, Kwok WH, Yap C, Wong COL, Smalley SGR, Forbes BS, Chow DWY, Ho ENM.
(2026).
Detection and Longitudinal Monitoring of Cyclosporine in Horse Plasma and Urine After Ocular Implant Administration.
Drug Test Anal, 18(3), 376-382.
https://doi.org/10.1002/dta.70026 Publication
Researcher Affiliations
- Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, Hong Kong, China.
- Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, Hong Kong, China.
- Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, Hong Kong, China.
- Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, Hong Kong, China.
- Veterinary Clinical Services, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, Hong Kong, China.
- Veterinary Regulation, Welfare and Biosecurity Policy, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, Hong Kong, China.
- Veterinary Specialty Hospital, Wan Chai, Hong Kong, China.
- Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, Hong Kong, China.
MeSH Terms
- Horses / urine
- Horses / blood
- Cyclosporine / blood
- Cyclosporine / urine
- Cyclosporine / administration & dosage
- Cyclosporine / pharmacokinetics
- Animals
- Tandem Mass Spectrometry / methods
- Tandem Mass Spectrometry / veterinary
- Immunosuppressive Agents / urine
- Immunosuppressive Agents / blood
- Immunosuppressive Agents / administration & dosage
- Immunosuppressive Agents / pharmacokinetics
- Drug Implants
- Chromatography, Liquid / methods
- Limit of Detection
- Drug Monitoring / methods
- Doping in Sports
- Administration, Ophthalmic
References
This article includes 20 references
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