Ivermectin Concentrations in Blood and Cerebrospinal Fluid Following Intravenous Administration to Healthy Llamas
ACVIM 2008
Sarel van Amstel; Ashley Portmann; Sherry Cox; Thomas Doherty; Shelley Newman
University of Tennessee, College of Veterinary Medicine
Knoxville, TN, USA

The response to anthelmintic treatment in cases of meningeal worm (Parelaphostrongylus tenuis) remains unpredictable. In a previous study, ivermectin (IVM) was not detected in cerebrospinal fluid (CSF) following subcutaneous administration to healthy llamas. The aim of this study was to determine if a single IV administration of the same dose (2.5 ml/100 pounds bodyweight) of IVM [Ivomec® Injection Sterile 1% Solution (Merial)] results in measurable IVM concentrations in CSF. The IVM dose was added to 1 L 0.9% NaCl and given over 30 minutes to 5 healthy llamas. CSF and blood were collected from indwelling spinal (lumbo-sacral) and jugular catheters respectively, at baseline and 2, 4, 6, 12, 24, 48 and 60hr after IVM administration. Serum and CSF were stored at -40°C and IVM concentrations were determined using HPLC.

Immediately after administration of IVM 3 of the llamas showed transient lethargy and decreased appetite. One llama developed acute neurological signs (paralysis and seizures) 7 days after IVM administration and was euthanized 3 days later having failed to respond to supportive treatment. Histopathologic examination revealed diffuse myelinic edema in the brain and spinal cord. Although it is possible that these histological changes resulted from IVM administration, IVM was only detected in the CSF at the 4hr sampling (0.11ng/ml). Two other llamas developed laboratory changes consistent with septic inflammation in the CSF (increase in nucleated cells predominantly neutrophils) and in one of these cases free and phagocytosed bacteria were present. The CSF returned to normal in both llamas after antibiotic treatment and neither llama had clinical signs at any stage. Results are reported as mean and range.

The results indicate that CSF concentrations of IVM can be achieved following IV administration at the dose used in this study; however, it is not known whether these concentrations are therapeutic in cases of meningeal worm infestation. In addition, because of the possibility of IVM-induced neurological changes it is recommended that IVM not be administered at this dose IV.

 

Serum IVM (ng/ml)

CSF IVM (ng/ml)

2hr

4751

(2291-7742)

[n = 5]

0.258

(0-0.57)

[n = 5]

4hr

491

(102-615)

[ n = 5]

0.282

(0.1-0.68)

[n = 5]

6hr

298

(86-555)

[ n = 5]

0.78

(0-2.49)

[n = 5]

12hr

124

(58-222)

[n = 5]

0.145

(0-0.44)

[n = 4]

24hr

67

(23-208)

[n = 5]

0.115

(0-0.22)

[n = 4]

48hr

38

(10-118)

[n = 5]

0.09

(0-0.15)

[n = 5]

60hr

22

(11-48)

[n = 5]

0

0

[n = 4]

Speaker Information
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Sarel van Amstel


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