This was the info given to me a few years ago by a vet at a dog expo. I gave it to my vet to read and he agreed with it. It's a pain to make the original heartworm dosage, but it's also the correct dosage. Some vets are mixing it up and selling it to people who can't afford the heart guard and other such types for their dogs.
They are also finding the ivermectin sensitivity in all herding breeds, including German Shepards and their like, especially white ones. Ivermectin is not for use in pups under 8 weeks old because they have the same issue as the herding dogs.....the brain/blood barrier isn't developed. With certain lines and individuals within the herding breeds, that barrier never develops, which causes the problems. The heart guard and the like are dosed so that even those that are sensitive to invermectin are supposedly able to tolerate it without the side effects.
USING IVERMECTIN TO PROTECT AGAINST HEARTWORM IN DOGS
The correct dosage for dogs is 0.0015 mg to 0.003 mg per pound of body weight. That's 1.5
mcg to 3 mcg per pound of body weight.
If you are using the 1% ivermectin straight out of the bottle and giving your dog 1/10th of
a cc (0.1 cc = 0.1 ml) per pound of body weight, you are dosing your dog at the rate of 1 mg
per pound of body weight. That is FAR FAR over the recommended dose of no more than 0.003 mg
per pound of body weight. Even if you're doing it at 1/10 cc per TEN lbs it's still way too
much. I don’t THINK anyone is doing this with the 1% ivermectin, but some of the posts were
a little unclear on this. Doing it THIS way – straight, uncut – with the 1% ivermectin would
be far riskier than anything I personally would want to be involved with.
If you are cutting it at the rate of 1:9 with propylene glycol, you end up with 1 mg of
ivermectin per ml (it is now a 0.1 % solution).
If you then give 1/10th of a cc per 10 lbs, which I think is what people were recommending,
you are still dosing at 0.01 mg per pound of body weight, or 10 mcg per pound. 1/10 cc has
1/10 mg of ivermectin in it. So a 20 lb dog would get 2/10 cc, with 2/10 mg of ivermectin in
it, which is 200 mcg of ivermectin when the suggested dose for this size dog is between 23
mcg and 60 mcg. This is essentially the same as the ferret dosage, roughly between 3.5 to 10
times higher than it needs to be. Probably not dangerous, but why waste the stuff? If you’re
cutting it anyway, why not just cut it down to something more precisely manageable?
Here’s what I do:
½ ml of 1% Ivomec injectable cattle wormer added to 49.5 ml of propylene glycol. There was 5
mg of ivermectin in the ½ ml of 1% ivomec, now suspended in 50 ml of propylene glycol, for a
concentration of 5 mg/ 50ml. This is 0.1 mg per ml, or 100 mcg per ml.
For those slightly less obsessed with precision than I, you could make this ½ ml of the 1%
Ivomec added to 10 tsp of propylene glycol (3 T plus 1 tsp). Measure this using an accurate
1/4 c measure and take out 2 tsp. It works out roughly the same. If you try to do it with a
tsp or T at a time, you keep adding errors with every spoonful - use the 1/4c measure and
take out 2 tsp, it'll be closer. Plus it's easier.
Multiply the weight of your dog by 2. This gives you, in MICROGRAMS, how much medication to
give your dog. If it’s a little less or a little more you are still within the safe zone of
1.15 to 3 mcg per pound of body weight. You can actually use any number between 1.15 and 3,
I just picked 2 because it’s easy to do in your head. Heartguard uses 2.72 as their upper
limit; notice that smaller dogs are getting more, sometimes significantly more, than 2.72
mcg per pound in the weight ranges that Heartguard uses. So yes there is room for slop.
Then divide that by 100 to determine how many cc’s of the above mixture to squirt into the
lil’ pup’s mouth.
SO if your dog weighs 24 lbs:
24 x 2 = 48; divide by 100 = 0.48 cc
We can’t measure in hundredths of a cc, so just round to the nearest whole 1/10th of a cc.
In this case, a 24 lb dog should get ½ cc of the above mixture. (rounding 0.48 up to 0.5, or
SO, weight of the dog in pounds x 2 / 100 = # of cc’s of this mixture to give the puppy to
protect it from heartworm.
A 100 lb dog using this solution would get 2 cc of solution. (100 x 2 / 100 = 2). Anything
between 1.2 cc to 3 cc would be safe for a dog this size (it’s weight x the amount in mcg
per pound, so where there is a 2, any number from 1.15 to 3 – the dosage range for heartworm
control – could have been used).
Using the 1:9 ration, the amount of ivermectin per cc is (from above) 1 mg, or 1000 mcg. So
the calculation for the 1:9 ration (1 cc of 1% ivermectin added to 9 cc of propylene glycol)
For 1:9 solution ONLY: weight in lbs x 3 / 1000 = cc’s to give, or, for example:
100 lb dog => RANGE of appropriate dosage would be
100 x 1.15 / 1000 = 0.115 cc MINIMUM to 100 x 3 / 1000 = 0.3 cc MAX
50 lb dog => RANGE of appropriate dosage would be
50 x 1.15 / 1000 = 0.057 cc MINIMUM to 50 x 3 / 1000 = 0.15 cc MAX
20 lb dog => RANGE of appropriate dosage would be
20 x 1.15 / 1000 = 0.023 cc MINIMUM to 20 x 3 / 1000 = 0.06 cc MAX
We can’t give less than 1/10 of a cc, so you can see how much harder it gets to dose your
dog properly the smaller they get. If you have BIG dogs, it doesn’t matter much, you can get
something that falls within the recommended treatment range; but if you have SMALL dogs, you
end up routinely overdosing them. That’s why I favor the lower concentration solution. I’ve
never had a dog over 40 lbs, and most of them were 25 lbs or less.
Again, as long as you cut it at least 1:9 and use the formula above (more accurate than 1/10
cc per 10 lbs), you’re probably (PROBABLY) not going to do any lasting damage to your
(non-collie) dog, but if you’re cutting it anyway, and you have smaller dogs, why not cut it
to something a bit more manageable?
Of course, you can skip all this mixing and stuff and go right to the .27% ivomec for swine.
Then the calculations would be as follows:
Weight of your dog x 3 / 2700 = # of cc’s of 0.27% Ivomec.
In this case a 24 lb dog would get : 24x3=72, 72/2700 = 0.0267 cc. Since it’s awfully hard
to get less than 1/10 cc, you’d probably go ahead and give the dog 1/10 cc. This is still
"overdosing", but it’s about the same as what folks are doing with the 1:9 solution or the
Ferret Mix. It’s no worse, not dangerously high for non-susceptible dogs, and skips all the
mucking about with having to cut the solution (and find a source for propylene glycol).
So if you wanted to skip any mixing at all, you could give 0.27% (NOT 1%) ivomec as follows:
20 lbs – 100 lbs 1/10 cc (delivers 270 mcg of ivermectin)
100 lbs – 200 lbs 2/10 cc (delivers 540 mcg of ivermectin)
I can’t imagine a dog bigger than 200 lbs, but if there are any out there, you could give
them 3/10 of a cc of the straight 0.27% Ivomec. That’d be a scary big dog indeed.
I wouldn’t do this with puppies – they’re more sensitive to overdose. In fact you should not
be giving ivermectin in any form whatsoever to puppies under 6 weeks of age – it can cross
the blood-brain barrier just like it does in collies until they’re older. 8 weeks would
probably be safer. If you’re going to dose really small dogs (under 20 lbs) and puppies, cut
the stuff and stick to the recommended dosages.
Here’s a reference for dosing information that includes gastrointestinal worming and skin
Here’s a treatment schedule for demodectic mange that includes the use of ivermectin:http://www.petplace.com/dogs/demodicosis-red-mange-in-dogs/page4.aspx
WHERE TO GET PROPYLENE GLYCOL: Beg a cup or so off of a large animal vet, or if you know
someone who raises cattle, they probably have some. I've never been able to find it to buy
in anything less than a gallon size. We're talking TEASPOONS here, for most of us who aren't
breeders anyway. DO NOT SUBSTITUTE ETHYLENE GLYCOL, IT IS POISONOUS AND WILL KILL KILL KILL
Do not attempt to mix with water as Ivermectin is NOT water soluble. It won't distribute
evenly in water, stick with the propylene glycol.
The higher dosage of ivermectin that is used (even by veterinarians) for treating mange and intestinal worms is 50-100 times the dosage needed to prevent heartworms. The higher dosage is often used to treat mange mites and intestinal worms and the typical product used is 'Ivomec', a 1% solution of ivermectin labeled for injectable use to control parasites in cattle. This product is typically administered orally at 1 ml per 100 lbs of dog. That would be 1/10th ml per 10 lbs. There is also a generic ivermectin 1% solution available. 'Ivomec' ivermectin also comes in a less concentrated 0.27% solution labeled for injectable use in grower/feeder pigs.
Ivermectin also comes in a more concentrated paste wormer for horses. The horse paste wormer has been marketed under several brand names including "Zimectrin" and "Eqvalan". The paste is much too difficult to measure accurately in small doses and should never be used for dogs.