# Deworming - can you OD?



## JustDressageIt (Oct 4, 2007)

I was reading the label of my dewormer (Ivermectin by Bimectin) and (as with all horses) you dose by weight. I have always just guessed at horses' weights (bad bad, I know) and I was just wondering if there are any adverse effects of giving a horse too much ivermectin dewormer? If so, how much more than the recommended amount would be considered an overdose? What will happen? 
Any information would be wonderful!


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## tim (Dec 31, 2007)

Haha, no don't worry. Overdosing on wormer is generally considered to be 5 times the proper dose. It's not easy to do it accidentally with an adult horse. You want to be careful with foals though. 

I'm not sure what would happen though. Colic maybe? Founder?

Ok EDIT: Ivermectin is extra safe. It can be given 60 times the standard dose without causing harm. Or so I read here.


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## BluMagic (Sep 23, 2007)

lol. i use ivermectin as well and I just give the whole tube. I think its like 1500lbs or something.


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## Ryle (Jul 13, 2007)

While it's not likely that you will cause problems by over-dosing ivermectin, pyrantel or fenbendazole a little it can happen. Especially if there is some pre-existing damage to the liver, central nervous system or kidneys or if your horse is eating certain plants in the pasture in the case of ivermectin. Moxidectin requires more careful dosing than the other dewormers, but it still has a fair safety margin. 

Neurological deficits including loss of balance, blindness and depression are symptoms of overdose of ivermectin or moxidectin.

You are always better off calculating your horse's weight or dosing a little higher than you "think" your horse's weight is because under-dosing increases the possibility of the parasites becoming resistant to the drugs we have to use.


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## my2geldings (Feb 18, 2008)

Ryle said:


> While it's not likely that you will cause problems by over-dosing ivermectin, pyrantel or fenbendazole a little it can happen. Especially if there is some pre-existing damage to the liver, central nervous system or kidneys or if your horse is eating certain plants in the pasture in the case of ivermectin. Moxidectin requires more careful dosing than the other dewormers, but it still has a fair safety margin.
> 
> Neurological deficits including loss of balance, blindness and depression are symptoms of overdose of ivermectin or moxidectin.
> 
> You are always better off calculating your horse's weight or dosing a little higher than you "think" your horse's weight is because under-dosing increases the possibility of the parasites becoming resistant to the drugs we have to use.


Good thread.


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## JustDressageIt (Oct 4, 2007)

Awesome! I have dewormed many a horse, but have always used dewormers with the little ring that spins down to the correct weight - the one I used today didn't, and it shot up so fast that I accidentally gave Maia the whole tube. It was an Invermectin, as I already said, and I did a bit of reading and am not too worried now 
Thank you all for your replies... I would hate to have ruined my brand new horse!! Gah wouldn't that be lovely? I sound like such a newbie owner, sad hey?


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## kitten_Val (Apr 25, 2007)

I pop the whole tube in, because I do waste little on way anyway.


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## jazzyrider (Sep 16, 2007)

i always give the whole tube to my guys. the tubes go up to 600kg which at most is only about 100kg more than my lightest horse so i figure there are no issues and i have never noticed any side effects. i use the ivermectin as well.


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