The response to anthelmintic treatment in clinical cases of meningeal worm (Parelaphostrongylus tenuis) infestation remains unpredictable. In a previous study, ivermectin (IVM) was not detected in cerebrospinal fluid (C.S.F.) following subcutaneous administration to healthy llamas of IVM at 500μg/kg. In the present study, the same IVM dose was added to 1 L 0.9% NaCl and administered intravenously over 30 minutes to 6 healthy llamas. C.S.F and blood were collected, at baseline and 2, 4, 6, 12, 24, 48 and 60 hr after IVM administration. Serum and C.S.F. were stored at -400C and IVM concentration was determined using high performance liquid chromatography (H.P.L.C.). No IVM was detected in the serum or C.S.F. in baseline samples. Concentrations of IVM ranging from 2291- 7742 ng/ml were present in serum at 2 hr post dosing but values decreased to between 103-615 ng/ml at the 4 hr sampling, and ranged from 11- 48 ng/ml at 60hr. Low concentrations of IVM were found in the C.S.F. of all llamas on at least one of the sampling times. Immediately after administration of IVM three of the llamas showed transient lethargy and decreased appetite for 12-24 hours. One llama developed acute neurological signs 7 days after IVM administration and was euthanased three days later. Histopathologic examination revealed diffuse myelinic oedema in the brain and spinal cord. Two other llamas developed C.S.F. changes consistent with septic inflammation. C.S.F. concentrations of IVM can be achieved following I.V. administration at 500μg/kg, however, because of the possibility of neurological damage, I.V. administration of IVM at this dose is not recommended.
- cerebrospinal fluid,
- ivermectin concentrations,
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