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Does food affect activated charcoal absorption? | VETgirl Veterinary CE Podcasts

In this VETgirl online veterinary CE podcast, we review whether mixing dog food with activated charcoal works. After all, it’s usually easier to get a dog to eat the charcoal if you mix it with some palatable food with poisoning cases, right? Well, have you ever wondered about the effect of that food on the adsorptive capacity of the charcoal? Will it decrease its efficacy in terms of helping to eliminate that toxin from your patient’s system?

So, Wilson et al out of Royal Veterinary College wanted to try to answer that question. In a prospective, in vitro laboratory study called “In vitro study of the effect of dog food on the adsorptive capacity of activated charcoal,” the authors mixed fixed amounts of acetaminophen (50 mg) and activated charcoal (1 g) with different amounts of dog food (2-14 g) – specifically canned Hill’s a/d. They then measured the amounts of residual, non-adsorbed acetaminophen in the different mixtures, and they found some good news.

Without any dog food added, the activated charcoal reduced the acetaminophen concentration by 99.6%, showing us that yes, activated charcoal works for certain toxicants! Without any charcoal added, the dog food adsorbed a significant proportion of the acetaminophen by itself (about 25%). No, this doesn’t mean just to feed a dog poisoned with acetaminophen, by the way. As the amount of dog food added to the charcoal increased, there were higher residual amounts of acetaminophen that were not adsorbed (p=0.0018). For every 1 g increase in dog food, a 5.15 mg/L increase in acetaminophen was expected. That said, even with the highest amount of dog food, 98.6% of the acetaminophen was still adsorbed.

So, what can we take away from VETgirl podcast?

This study demonstrates that adding dog food to activated charcoal significantly reduces its adsorptive capacity. That said, the reductions were small and may not be clinically significant.
The dog food itself had some adsorptive capacity, but the authors were unable to determine if this was still true when the charcoal was added as well since the pharmacodynamics aren’t known regarding which substance will better adsorb acetaminophen. They also pointed out that as the dog food is digested, the acetaminophen may be released into the system again.

Overall, this was a nicely done prospective study with a solid objective and conclusions. Since it is in vitro, it remains to be seen if these findings translate to clinical patients, other types of toxins, and other types of dog food, however. Based off this study, VETgirl believes that yes, you can mix dog food with activated charcoal to encourage your intoxicated patient to eat it – just keep in mind that it may reduce the charcoal’s adsorptive capacity, but it’s unlikely that the effect will be clinically significant. When in doubt, give the smallest amount of food possible to minimize this effect!

Remember that certain toxicants don’t bind to charcoal – check out our other podcast on activated charcoal to find out more. If you’re not sure if the toxicant even binds to activated charcoal, call the ASPCA Animal Poison Control Center for life-saving advice.

References:
1. Wilson HE, Humm KR. In vitro study of the effect of dog food on the adsorptive capacity of activated charcoal. J Vet Emerg Crit Care 2013;23(3):263-267.

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