Hydrocortisone acetate (HCA) is a synthetic glucocorticoid corticosteroid and a corticosteroid ester. HCA cream (1% w/w) is used topically in humans and animals to treat a variety of skin conditions to reduce inflammation and itching caused by eczema, dermatitis, allergy and insect bites amongst other conditions. There is no licensed equine product in the UK but it is widely available over the counter and is a product of interest due to the potential risk of secondary drug transfer from human user to horse.
The UK has had several screening findings for HCA in urine. It was unknown whether these were caused by direct topical cream administration. Furthermore, there were concerns over drug stability in urine as it was successfully identified in the A, but not the B sample, on counter analysis, meaning the adverse analytical finding could not be confirmed.
The aims of this study were to establish whether HCA could be detected in urine and plasma following a topical skin administration (5 g HC45 cream 1% w/w, containing 55 mg of HCA) in 2 horses and the assessment of drug stability under different storage conditions and time periods.
HCA was detected in spiked (0.1 ng/ml) plasma and urine samples. However, it was not detected in any post administration samples analysed. It was therefore not possible to perform a stability assessment using these samples. Considerations as to the lack of detection included the low dose administered and the drug’s ability to be absorbed through equine skin. Although it cannot be categorically proven, this study suggests that the transfer of small amounts of cream from human skin should not result in an equine screening finding and it is unlikely that a low dose, single administration to skin via the topical route would cause screening findings. Future studies could be considered.