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Background: Reserpine is a popular drug in the equine industry for long-term tranquilisation. Clinical observations revealed that blood from horses receiving oral reserpine was hypercoagulable. No studies have documented the pharmacokinetics of orally administered reserpine nor the effects of reserpine on platelets in horses., Objectives: To evaluate the pharmacokinetics of oral reserpine in horses and the effects of clinically relevant concentrations of reserpine on platelet functionality in vitro., Study Design: Experimental controlled study., Methods: The pharmacokinetics of oral reserpine (2.5 mg/horse, once) were determined in six healthy adult horses. Plasma samples were collected and concentrations of reserpine were determined by UPLC-MS/MS. Using this data, the in vitro effects of reserpine on platelets were examined. Aggregation, adhesion and releasate assays for serotonin and thromboxane B 2 were performed on platelets exposed to varying concentrations of reserpine (0.01-10 ng/mL), aspirin (negative control) and saline (unexposed control)., Results: Oral reserpine administration demonstrated low plasma concentrations with a C max of 0.2 ± 0.06 ng/mL and a prolonged half-life of 23.6 ± 6.24 h. Simulations over a dose range of 2-8 μg/kg predicted C max at steady state between 0.06-0.9 ng/mL. Platelets exposed to these reserpine concentrations in vitro displayed increased aggregation and adhesion compared to unexposed or aspirin-exposed platelets as well as compared to higher concentrations of reserpine. These functional changes correlated with lower concentrations of serotonin and higher concentrations of thromboxane B 2 in the platelet suspension supernatant., Main Limitations: This study used a small number of horses and only in vitro platelet experiments., Conclusions: Oral reserpine demonstrates low plasma concentrations and a prolonged half-life in horses. At these concentrations, reserpine causes significant changes in platelet function, most likely due to serotonin release and re-uptake which primes platelets for activation and thromboxane B 2 release. These findings suggest that clinicians should harvest blood for biological processing prior to the onset of reserpine administration., (© 2018 EVJ Ltd.)

Meningeal tumors occurring in a pediatric hospital over a period of 18 years were studied. The incidence of meningeal sarcomas was much lower than has been previously reported. A histologic subtype of meningiomas was found which has not previously been described. In these "sclerosing" tumors only a small portion of the lesion contained viable cells, most of which bore little resemblance to conventional meningothelial cells. The bulk of the lesions consisted of whorling collagen bundles produced by the tumor. All cases in which there was tumor invasion of the brain fell into this category. The prognosis for the sclerosing meningiomas was similar to conventional meningiomas, casting doubt on the value of brain invasion as a marker of malignancy in childhood meningiomas. The recognition of this histologic type may aid diagnosis, guide surgical management, and possibly make postoperative radiotherapy unnecessary.