The relative plasma availabilities of ivermectin in reindeer (Rangifer tarandus tarandus) following subcutaneous and two different oral formulation applications

Abstract

BackgroundOverwintering (breeding) reindeer (Rangifer tarandus tarandus) are commonly treated with ivermectin against parasitic infestations once yearly in autumn-winter roundups. The only preparations registered to reindeer are those for subcutaneous injection. However, also oral extra-label ivermectin administration is used. Twenty-six, 8-month-old reindeer calves were randomly allocated into three groups. Group 1 (n = 9) received oral ivermectin mixture (Ivomec® vet mixt. 0.8 mg/ml, oral ovine liquid drench formulation), Group 2 (n = 9) oral ivermectin paste (Ivomec® vet 18.7 mg/g equine paste), and Group 3 (n = 8) subcutaneous injection of ivermectin (Ivomec® 10 mg/ml vet inj.), each group at a dose of 200 μg/kg body weight. Blood samples were collected at treatment and at days 1, 2, 3, 6, 9 and 16 post treatment. Plasma concentrations of ivermectin were determined by high-pressure liquid chromatography (HPLC) with fluorescence detection.ResultsThe peak plasma concentration (Cmax) was reached by 2 days after each treatment. The Cmax and Area Under Curve (AUC) differed significantly between the groups: Cmax was 30.2 ± 3.9, 14.9 ± 5.7 and 63.1 ± 13.1 ng/ml, and AUC∞ was 2881 ± 462, 1299 ± 342 and 6718 ± 1620 ng*h/ml for groups 1, 2 and 3, respectively (mean ± standard deviation).ConclusionsThe differences in plasma concentrations of ivermectin are concomitant with earlier observed differences in antiparasitic efficacy, which discounts the use of the equine paste in reindeer in favour of the oral ovine liquid drench formulation, or preferably, the reindeer-registered subcutaneous injection formulation.

Ivermectin Plasma Concentration in Iberian Ibex (Capra pyrenaica) Following Oral Administration: A Pilot Study

“…The maximum drug concentration and bioavailability found in Iberian ibex (3.40 ± ng/ml) were lower than those described in goats (6.03 ± 0.95; 15.85 ± 5.29 ng/ml, respectively) after the oral administration of an IVM dose of 0.2 mg/kg (30,31). By contrast, the time to maximum concentration (1 day) was consistent with previous reports of oral administration in other medium-sized ruminants, sheep (1.7 day), goat (2.8 days), and reindeer (2 days for oral mixture, 1 day for oral paste) (15,18,28). By comparing two different oral formulations in reindeer, Oksanen et al (28) found a lower relative plasma availability for a paste than for an oral liquid drench formulation, which could also partially explain the lower values observed in this study.…”

“…By contrast, the time to maximum concentration (1 day) was consistent with previous reports of oral administration in other medium-sized ruminants, sheep (1.7 day), goat (2.8 days), and reindeer (2 days for oral mixture, 1 day for oral paste) (15,18,28). By comparing two different oral formulations in reindeer, Oksanen et al (28) found a lower relative plasma availability for a paste than for an oral liquid drench formulation, which could also partially explain the lower values observed in this study. The solid bolus formulation used in this study does not appear in previous similar trials, but we deemed it: i) better representative, than a liquid drench, of the medicated pellet administration that is already empirically used in Iberian ibex (32); ii) better suited to provide an accurate and precise IVM dosing than medicated pellets.…”

“…This study revealed that IVM plasma concentrations in orally-treated Iberian ibexes drop drastically within four dpa. Not surprisingly, the oral route leads to lower IVM plasma concentrations compared to those reached after a subcutaneous administration (28), likely due to the binding to the particulate phase of digesta (14,29). Moreover, the binding of IVM to plasma albumin and lipoproteins should be taken into account especially in animals with chronic stages of sarcoptic mange usually showing emaciation and poor body condition, in which a decrease in plasma proteins (thus a higher free fraction of IVM in the plasma), might be more likely associated to an unsuccessful treatment (14).…”