De-worming Your Dog

De-worming Dogs

By isak, September 18, 2015

Ever wonder which wormer kills what worm? If you know what specific parasite is affecting your dogs, you don’t need to spend the money on a broad spectrum dewormer when a specific anthelmintic will suffice. Why attack something that isn’t there?

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Interceptor, unlike any of the Droncit, Drontal, Drontal Plus anthelmintics does NOT kill tapeworms of any kind. For that, you need praziquantel (or fenbendazole for the Taeniid-type tapeworms).

Aside from tapeworms, there are other differences (think lawyerly weasle words) if you read the label carefully. I recall that Interceptor (milbemycin oxime) “prevents” heartworm, “kills” hookworms, and “controls” round worms and whipworms. And, that verbage can change over time with added research.

The different wordings relate to whether or not a specific dewormer kills only adults in the intestine, and/or migrating larvae in the tissues, as well as how infective and resistant the environmental forms are.

I believe milbemycin oxime does kill migrating hookworm larvae in the tissues. In addition to which, hookworm larvae in the environment are very fragile and easily removed, believe it or not. Hence, Interceptor can claim to kill hooks.

On the other hand, ascarid and whip worm eggs are tough as nails and almost can’t be killed in the environment. In addition to which, whip worms take two to three months to develop, unlike the hooks and ascarids, which take three weeks. Thus, most people stop treating for whips way too soon. Whips don’t have a tissue-migration stage, so if you treat only once with Interceptor, you won’t kill all the whips because of the juveniles developing in the intestine over two months. If you give it every month, though, it should be good enough.

I’m not sure milbemycin oxime is very effective against the migrating ascarid larvae in the tissues, coupled with the fact the the juveniles become adults in three weeks, not a month. So, if you treat only once, or once every month, you will be missing a few ascarids which will be adults in the intestines at three weeks, making more eggs for a week before the next monthly treatment. Hence the term “control,” which is not the same as kill.

Studies also have shown that milbemycin oxime is not quite as effective in killing either ascarids or hookworms as ivermectin, (at the higher dose lethal to p-glyprotein deficient collie types) or to pyrantel or fenbendazole.

However, pyrantel only kills adult ascarids, so you have to retreat in three weeks. Fenbendazole is only effective in killing migrating larvae if you give it day after day and then only in pregnant bitches. Ivermectin, at the low, Heartguard dose, is not effective against ascarids at all. But, at the high, potentially lethal dose, it’s the best choice. Milbemycin falls in the middle because it is safer than high dose ivermectin but not as effective. Not as effective killing adult ascarids as pyrantel, but does kill at least some of the juveniles. It only has to be given once, instead of three days in a row like fendendazole, but, by giving it once a month, instead of every two to three weeks, leaves a window open.

If this stuff was simple you wouldn’t need to go to vet school!! You could find in inside a matchbook cover.

Therefore, as I said before, “What parasite are you trying to kill?”

The cost of the drug is the least important parameter.

If you’re after tapeworms, you have to use a Droncit-type drug (or Panacur or SafeGuard for “Taeniid” tapeworms only). But, you only have to give it once (AND treat for fleas or lice; or stop feeding mice and bunnies or moose and lemmings to the dogs.)

If you’re after whipworms, use a fenbendazole-type. BUT, you have to treat again two and three MONTHS later and scoop, scoop, scoop.

Droncit (praziquantel) kills tapeworms.

Drontal (praziquantel and pyrantel) kills tapeworms, ascarids (“round” worms), and hook worms.

Drontal Plus (praziquantel, pyrantel, and fenbendazole) kills tapeworms, ascarids (“round” worms), hook worms, and whip worms.

It’s all marketing strategies.

More basics:

If you give only a benzimidazole (fenbendazole, febantel, etc.), like Panacur, it will kill whip worms in one day, but hook worms and ascarids take three days of treatments. So, if you treat with Panacur, you have to give it three days in a row, unless you are absolutely, positively positive that you’re only treating whip worms.

Pyrantel, like Strongid and Nemex, kills only hooks and ascarids in one day, so you only have to give it once. It does not kill whips.

So, by combining pyrantel (in Drontal) with fenbendazole (in Drontal Plus) you only have to treat once, not three days in a row, because the pyrantel kills the hooks and rounds in one day and the fenbendazole kills the whips in one day. (The praziquantel kills the tapes in one day in all three products, regardless.)

Now things get confusing, but fascinating:

Drontal Plus is a great marketing tool designed to keep the dewormer competitive by being “broad spectrum.”

Drontal (praziquantal and pyrantel) was the upgrade of simple Droncit (praziquantel only) years ago to compete with Vercom Paste, which was the first major “broad-spoectrum” anthelmintic. Vercom contained praziquantal (tapes) and febantel (ascarids, hooks, and whips). Febantel gets turned into fenbendazole and oxfendazole by the liver.

The problem with Vercom Paste was that you still had to give it three days in a row, like Panacur, to kill the ascarids and rounds. But, it got ALL the tapes, not just the mammallian tapes (Taenia) that Panacur got. (Panacur doesn’t kill flea tapeworms).

Vercom was broader spectrum than either Droncit or Panacur, but it still had to be given three days in a row (and it tasted just awful — cats would get mad as hell when treated, especially by day three!!)

So Droncit, by adding pyrantel, could be marketed as a one-day dewormer that killed all types of tapes, plus ascarids and rounds. Unfortunately, it didn’t kill whips. Panacur and Vercom did (but had to be given over three days). The world was not yet perfect.

So Drontal added in fenbendazole initially (instead of febantel, I suppose because of patent laws held by Vercom?). It was called Drontal Plus. Ingenious marketing. Now you could give one pill just one day for tapes, ascarids, rounds, and whips! They nailed the broad spectrum market and blasted the three-day-in-a-row Vercom Paste and Panacur.

Things get even murkier (God bless American free enterprise):

Febantel must not be protected any longer because now Drontal Plus uses it instead of fenbendazole. In addition, pyrantel tartrate is absorbed by the intestines faster than pyrantel pamoate, so many products that used to include the p-pamoate now use p-tartrate.

It gets better:

Even newer is pyrantel emboate, which apparently requires half the dose of the pamoate. AND, Oxantel pamoate got invented, to kill human whip worms, even though its close cousins pyrantel pamoate and p-tartrate don’t. Now oxantel is used for canine whips, as well.

These advances have allowed other companies to capitalize on the “broad spectrum” market. Now you can find an “allwormer” with praziquantel, pyrantel emboate, febantel, and/or oxantel, all mixed up in some combination and licensed for tapes, ascarids, hooks, and whips, and all in a one-day treatment.

I suspect Drontal Plus still uses the pyrantel emboate AND good old febantel because it works as well or better than oxantel, OR because they can’t get the license because of patent infringment. That may change when the patent expires.

Therefore, I would use either the Drontal Plus, with febantel, or the Allwormer, with the oxantel at this time because I can’t find the actual published studies reporting the laboratory effectiveness of febantel against oxantel for whips. Otherwise, the products are the same, in that praziquantel is praziquantel and pyrantel is pyrantel, even though the latter can be absorbed at different rates depending on which analog is used (pamoate, tartrate, emboate). So, read the label.

Oh yes, it gets even better!! Now there’s Drontal for Puppies! This product doesn’t include praziquantel because of the life cycle of tapeworms — young puppies can’t develop them to adulthood that fast. Drontal for puppies is actually Drontal Plus without the praziquantel (Drontal Minus?? – naw, bad marketing). It contains only febantel and pyrantel embonate for ascarids, hooks, and whips.

With Drontal for Puppies, then, you can treat the same way as if you were using Strongid, except you also are killing whips. However, whips are not a problem in very young puppies. Strongid is good enough.

Broad-spectrum marketing doesn’t end here. Heartguard Plus, Interceptor, Sentinel, and Revolution, all employ some facet of the “kill ’em all” anthelmintic strategy now.

Ah, commerce and industry! One spends the first half of one’s veterinary career trying to figure out how a product works and the last half trying to figure out why products get invented in the first place.

Oh yes, money.

Print this out, study it, memorize it, then impress the hell out of your local veterinarian!!

And remember, we don’t give worms to dogs, we de-worm them, which alone is reason enough why I never prescribe “Allwormer.” Drives me absolutely nuts!!

Finally, if you know what specific parasite is affecting your dogs, you don’t need to spend the money on a broad spectrum dewormer when a specific anthelmintic will suffice. Why attack something that isn’t there? After all, worms aren’t weapons of mass destruction.

Good luck and wait a couple of years. This will all change again.

Source: Dr. Jerry Vanek


  1. Josh says:

    My puppy (8weeks old) a Lab/mountain cur mix. Doesn’t seem to be gaining weight. They day after we got him we took him in and had his distemper done and Strongide. We watched him like a hawk but never saw any worms the next day. This was a week ago. He has occasional diarrhea and when he doesn’t it’s somewhat wet looking but solid. You can see his ribs but he plays (non stop). Is never lathargic and seems very happy and destructive. He chews everything. Anyway, should I be concerned? Does he need to be retreated? 8 week old lab weight chart says 12-16 lbs. I’m guessing he’s maybe 8. He just seems to get taller without getting heavier.

    • isak says:

      Congrats on your new baby!

      If your pup is active and healthy, and he’s eating and drinking normally, he should be okay. However as a note, pyrantel pamoate (Strongid) is not effective against tapeworms, whipworms, or many other types of intestinal parasites. The medication you need for tapeworms is called praziquantel, and it is sold without a prescription under several brand names. You can google “praziquantel for dogs” to see some of the options. This drug is available as a one-time single dose pill or as an injection for pets. The tapeworm dies and is digested. It is not usually seen in the stool after the deworming.

      You said his stools are somewhat wet looking. Doe the stools seem to be covered with mucus? Mucus is naturally occurring in the digestive track to protect against digestive acids, so it’s not uncommon to see mucus unless it is excessive. If it’s excessive, it suggests an imbalance in his digestive tract — maybe he ate something that disagrees with him.

  2. Lisa Youngblood says:

    It took time but e will print and memorize. This will generally ensure the life of all our puppy Preza s. Thank you very much!!!

  3. Adele says:

    I was so during if you have ever heard of using cigarettes to de-worm dogs? A friend told me about it, but it sounds a little weird to me. Two of the dogs we have here with us right now came to us extremely emaciated. We were told that they were not bieng fed but that they had been wormed. One of the dogs started putting weight on and is back to normal while the other will not put on weight no matter what we do. You can see the worms when they go potty. With the amount of animals here we can not afford to go to a vet unless it is a life or death issue. Oh, the two dogs in question are also seniors, 12+ years old. Do you know if cigarettes would work or just cause more problems?

    • isak says:

      I have read that some people use a pinch of chewing tobacco to rid their pets of worms, if your pet will eat it. However, tobacco contains nicotine, which can be very poisonous. In small doses, it harms only the worms, but in doses too large, it can make our animals very ill and even cause death. Be very careful when using tobacco, and be sure to consult your veterinarian on the appropriate dose. Especially in senior pets when you do not know their health history.

      A cheap, but effective way is to sprinkle some food grade diatomaceous earth on their food. You can buy it at gardening centers, feed stores, and maybe pet stores. It’s good for intestinal parasites as well as fleas.

  4. Scarlett Rose says:

    13 year old yorkie who developed extreme hair & weight loss. 3 vet’s clueless. 6 meals a day & eats like he’s starving to death. From 9.9 lbs in may to 4.4 now . Many tests & meds to no avail. Vet gave board spectrum dewormer, no changes. Could he have tapeworms without signs.? Desperate, he can’t last much longer !!! .

    • isak says:

      That’s quite a weight loss. It seems to be greater than what tapeworms would do, however if he still has fleas after he has been dewormed, he can re-infest with tapeworms. The dewormer doesn’t really have any significant longterm effects. It’s a one-time deal. It kills the worms in his digestive tract right now, not new ones that develop.

      I can’t tell you anything more than his vets because they have the ability to do various tests. In general, your vet will consider these possible underlying health concerns:

      • Diabetes, for example, can trigger an increased appetite. Although there is an excess of glucose in their bloodstream, a lack of insulin means that the glucose is effectively “locked out” of the body’s cells. The cells respond by telling the animal that they should still be hungry, so this can result in an abnormally large appetite.
      • Hyperadrenocorticism (also known as Cushing’s Disease) can also cause an increased appetite when the dog’s body produces too much glucocorticoid – the hormone that helps furry friends deal with stress.
      • Conditions causing malabsorption – any disease where a dog can’t properly absorb the nutrients in their food – can result in them being extra hungry. Most of the time these conditions are accompanied by other signs like diarrhea and/or vomiting. Some examples include:
      • Exocrine pancreatic insufficiency (EPI) – most common in German Shepherd dogs, this condition results in a decrease in the enzymes required to digest food. As a result, food can pass through the digestive tract without being broken down properly, thus not being able to be absorbed.
      • Bacterial overgrowth – sometimes associated with EPI but also able to occur as a primary condition, small intestinal bacterial overgrowth (SIBO) can cause the walls of the small intestine being damaged by bacteria, resulting in reduced nutrient absorption and an increased appetite.
      • Reaction to medication(s).

      What are his stools like? How often in a day does he poop? What food is he eating? How is his behavior? Does he drink normally?

      Have you tried puppy food for the extra calories? How about boiled chicken and rice? The rice is slower to digest so maybe slowing that down would help him gain some weight.

  5. Allie says:

    My dog had tapeworms about three weeks ago and we used safeguard which seemed to clear them up.. today I noticed another WORM! We live in North Dakota and right now it’s below zero everyday.. could he be getting them from eating other dogs waste?

    Can I re treat with de wormer again ?

    • isak says:

      The tapeworms can lay eggs that will not hatch for about four weeks. So, yes, you can de-worm your dog again. It is generally recommended to de-worm twice four weeks apart just for this reason. You also need to be sure he is flea-free, too.

  6. Kate says:

    So very informative. Thank you for explaning a complicated problem simply.

  7. Holly Sellers says:

    Thank you so much for all the helpful info on DE-worming products!

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