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 25-28 September, 2018 | Singapore
The second proposed mechanism is creation of a drug-scavenging ‘lipid sink’, into which lipophilic drugs or toxins are absorbed. In theory, absorption of the
drug into an intravascular lipid compartment draws the molecule away from its site of action, giving the body more time to metabolise and excrete the perpetrator. The toxin needs to be lipophilic enough, however, for it to be attracted to the lipid compartment. It is difficult to determine what is lipophilic enough. The lipophilicity of any chemical is described as its ability to partition into octanol, expressed as the partition coefficient or log P. In general, a log P greater than 1.0 means that a chemical is lipophilic, and above ~3.0, it is highly lipophilic. However, there is some variability in the reported log P (depending on how it is measured) and the behaviour
of the chemical in vivo is affected by it lipophilicity at blood pH, its volume of distribution and other aspects
of pharmacokinetics.(4) Therefore, it is difficult to predict if IVLE will be efficacious for drug-scavenging any particular toxin based solely on log P. Generally, the greatest success has been reported for toxins whereby the log P is greater than 5.0.
Previous reports of utility in dogs and cats
There have been many case reports published in dogs and cats reporting the use of IVLE in toxicoses (Table 1). It is difficult to establish the efficacy of IVLE from case reports as often multiple other drugs are administered at the same time, and it is unknown whether or not
the treatment actually altered the time course of the toxicoses for an individual patient. There is also likely a publication bias whereby instances of perceived efficacy are more likely to be published than lack of efficacy.
The types of toxins that IVLE has been used for generally fall into two categories; neurotoxins and cardiotoxins. Most case reports comment on use of IVLE to treat neurological signs due to permethrin or macrocyclic lactone toxicoses. Perceived response to treatment include various types of neurological improvement,
such as reduced tremors, improved mentation or ability to walk, or reduction in sedative drugs needed. There are also some case reports of use of IVLE in toxicoses that have cardiovascular effects, such as lidocaine and diltiazem. However, the information is too limited to comment on perceived benefits.
There is one study worth mentioning in isolation as the only prospective randomised clinical trial on the use of IVLE in toxicoses.(5) Thirty-four cats were randomised to receive either IVLE or saline placebo (non-blinded) and then clinically staged for signs of toxicoses over the remainder of hospitalisation. The study found that cats that received IVLE showed faster resolution of clinical signs.
The dose administered in most reports consists of a small bolus (usually 1.5mL/kg) followed by 8-15mL/kg over
60 minutes. The use of a bolus was originally designed for resuscitation purposes (i.e. local anaesthetic overdose) and is probably only useful for cardiotoxicity. Use of a bolus for drug-scavenging purposes (i.e. ‘lipid sink’) is questionable and probably unnecessary. The timing of ‘response’ to treatment is usually within several hours of the first dose. Many authors comment on repeating the dose or extending the time of CRI; usually in cases where no initial response was seen.
Table 1. Case reports in dogs and cats(6)
*Retrieved from either or www.
Adverse events
The actual rate of adverse events has not been well established as the evidence relies mostly on case reports. There have been two case reports of corneal lipidosis in cats after IVLE treatment, which resolved within a week, and one report of facial pruritis.
(5, 7, 8) Other adverse events reported in human medicine include fat overload syndrome, pancreatitis, cholestasis, acute kidney injury, acute lung injury, venous thromboembolism, hypersensitivity and increased susceptibility to infection.(9)
Should I use IVLE?
The benefits versus risk need to be weighed carefully when deciding on whether or not to administer IVLE.
In cases where the patient is severely affected by a neurotoxin or cardiotoxin AND there is theoretical benefit based on IVLE’s supposed mechanisms of action, then the possible benefit of a single dose of IVLE likely outweighs the risk of adverse effects. There should be some estimation as to whether or not the toxin is likely
to still be in circulation, rather than bound to tissue. A repeated dose may be used if there is no response

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