Researchers created a new blood test that can accurately measure the hormone deslorelin, then used it to track how the drug is released from a single implant in three goats over a year. The drug peaked quickly in the blood and then stayed at a steady level for months, while fecal hormone tests showed the goats stopped ovulating.

Management of zoo animals relies on effective and reliable contraception. Deslorelin acetate implants (Suprelorin^&#xae;) are routinely used as a contraceptive tool, therapy for reproductive disease, and to mitigate hormonally-based undesirable behaviors. Because this product was developed for use in dogs, the minimal effective dose and duration of action must be extrapolated to other species. Current dose recommendations from the Association of Zoo and Aquariums Reproductive Management Center are based on accumulated data from use in various taxa. The authors developed a novel liquid chromatography-tandem mass spectrometry assay to measure deslorelin in serum; the method was validated for linearity, limits of detection and quantitation, precision, and specificity. This pilot study then evaluated the pharmacokinetics of deslorelin implants in vivo, using female domestic goats (<i>Capra hircus</i>; n = 3) each with a single 9.4-mg subcutaneous implant. Serum samples were analyzed at baseline and 31 designated time points (15 min-360 d) following placement. The average maximum serum concentration (<i>C</i>_max) for deslorelin was 83 ng/ml, time to <i>C</i>_max (<i>T</i>_max) was 1.3 h, and a plateau phase extended from 30 to 360 d. Fecal estrogen and progestagen reflected anovulatory status following deslorelin placement in all three goats. This study demonstrates that the novel assay is able to successfully measure deslorelin acetate in serum, even to a sensitivity of 0.03 ng/ml. This study lays the foundation for future research regarding dosage recommendations for deslorelin implants in other species.