Pharmacokinetics of ivermectin in llamas (Lama glama)

Abstract

The pharmacokinetic behaviour of ivermectin was investigated in adult llamas (Lama glama) by using high performance liquid chromatography with a lower limit of quantification of 2 ng/ml to measure its concentration in serum. Llamas were treated with one of three commercial formulations (injectable, pour-on or oral paste) at dosages recommended by the manufacturer, or with an experimental injectable sustained-release formulation. In five llamas given 1 per cent ivermectin subcutaneously at 200 microg/kg, the median peak serum concentration (Cmax) was 3 ng/ml and the area under the serum concentration-time curve (AUC) was 13.5 ng x day/ml. In six llamas treated topically with 0.5 per cent ivermedin pour-on at 500 microg/kg, Cmax was 2.5 ng/ml or less and the AUC was 7.75 ng x day/ml or less. In seven llamas with measurable concentrations of ivermedin, the median times to peak serum concentration (tmax) were six days after subcutaneous injection and seven days after treatment with the pour-on formulation. In six llamas, the serum concentration of ivermectin remained less than 2 ng/ml for 124 hours after treatment with a 1.87 per cent oral paste at 200 microg/kg. In five llamas treated subcutaneously with 25 per cent ivermectin sustained-release microspheres at 1500 microg/kg, the median Cmax was 5 ng/ml and the median AUC was 224 ng x day/ml.

Llamas and alpacas in Europe: Endoparasites of the digestive tract and their pharmacotherapeutic control

“…Oral administration (0.2 mg/kg BW) did not lead to detectable plasma levels (Jarvinen et al, 2002). This finding is in agreement with the data obtained in cattle, sheep and horses showing a lower bioavailability of ivermectin after oral dosing than after SC administration (Pope et al, 1985;Marriner et al, 1987;Bogan and McKellar, 1988;Chiu et al, 1990).…”

“…Several studies on the pharmacokinetics of ivermectin for the treatment of GINs following subcutaneous (SC) (0.2 mg/kg bodyweight [BW]) or topical (0.5 mg/kg BW) administration to llamas and camels have shown low maximum blood concentrations (<2-4 ng/mL) (Oukessou et al, 1996;Jarvinen et al, 2002;Burkholder et al, 2004). Oral administration (0.2 mg/kg BW) did not lead to detectable plasma levels (Jarvinen et al, 2002).…”

First report of anthelmintic resistance in Haemonchus contortus in alpacas in Australia

“…No anthelmintics are registered for use in alpacas in Australia, and the animals on this farm received oral doses at sheep dose rates, although some authors suggest that alpacas should receive 1.5 times the dose rate of MLs for sheep [8,21]. Off-label anthelmintic use is further complicated by the observation that different formulations of orally administered compounds affect absorption in SACs [22] and those other anthelmintic classes require even greater dose rates than those used in sheep [23]. Scales were not available on the farm, and under-dosing of anthelmintics might also have contributed to the development of anthelmintic resistance on this farm.…”

Anthelmintic Resistance in Camelid Parasites

“…3 Since loss of anthelmintic efficacy progresses gradu ally, an anthelmintic with lowlevel resistance may still have clinical benefit, particularly if two anthelmintics from differ ent classes are used simultaneously. 23 The subcutaneous and pouron ivermectin treat ments resulted in similar plasma concentrations, but the counterparts. 20 Most dosing recommendations for camelids have been extrapolated from ruminants such as cattle and sheep rather than from scientific investigations that test alpacas and llamas specifically.…”