The Side Effects of Deworming a Puppy

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The reason intestinal worms are a concern in puppies is because these parasites rob puppies of important nutrients. Because a puppy's body is so small, a lack of nutrients can cause them to become quite ill in a short time if untreated. To diagnose worms, your veterinarian will likely take a stool sample and then advise you to administer either an over-the-counter or prescription deworming medication. Deworming side effects in puppies are usually minor and temporary.


You are naturally concerned when your puppy has worms, but it's common and easy to treat.

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What is deworming in puppies?

There are different types of worms that can live in the colon or intestines of puppies and adult dogs. The most common puppy parasites are roundworms, which are usually transmitted from the mother's milk. Other types include whipworms, hookworms, and tapeworms. There are also different types of treatments, but all treatments work by killing the parasites.


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Deworming medication is frequently in the form of a tablet for adult dogs and is also available in liquid form, which is easier for puppies to swallow. Common medications, sometimes referred to as "wormers," include fenbendazole, with the brand name Panacur. Another that is more commonly used in puppies than adults is pyrantel pamoate. Praziquantel is another used specifically for flatworms.


When to deworm puppies

Mother dogs can pass worms to their new puppies before they are even born, so young puppies are often treated for worms. Most of the time, puppies are dewormed at 2, 4, 6, 8, 10, and 12 weeks of age. Depending on the environment, your puppy may not need deworming medication until closer to six weeks of age. It's best to ask your veterinarian about the ideal deworming schedule for your puppy.


Once your puppy reaches 12 weeks, you can begin to treat them monthly with a heartworm preventative that also contains dewormer for other parasites, like roundworms and hookworms. Mother dogs with puppies on the way can be treated with dewormer during mating and before the birth of the puppies.


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Worms in dog feces after deworming

While it may be alarming or just a little gross, it's normal to see dead worms in your puppy or dog's poop after deworming treatment. When the medication kills the parasites, the bodies have to go somewhere! Because the medication begins to work so quickly, the worms in the feces may sometimes still be moving. Most of the worms will be expelled within two to three days, but it is not unusual to find dead worms in your dog's poop up to a week after treatment depending on the seriousness of worm infestation.‌



On the bright side, you'll also notice your pup starting to feel much better as the treatment takes effect. During the deworming process, do not allow your dog to visit dog parks and other areas where dogs socialize. It is also helpful to avoid other dogs' poop to prevent recontamination.


Additional deworming side effects in puppies

In addition to worms in your puppy's poop, there are some other possible minor side effects of deworming treatment. These include diarrhea, vomiting, drooling, and appetite loss. At normal doses, you may not notice many side effects, but if you do see signs of an allergic reaction, such as facial swelling, itchiness, hives, diarrhea, seizures, or shock, seek veterinary care immediately.


Diarrhea in puppies after taking a wormer

After deworming, your puppy may experience minor intestinal issues, such as diarrhea, but this should pass within a few days. If you see blood in their stool or if your puppy's diarrhea lasts longer than three days, contact your veterinarian.

Puppy vomiting after deworming

With puppy deworming, side effects can include vomiting. This is more likely if the worm infestation was severe. Vomiting should not last more than a day after treatment.

Puppy drooling after deworming

A possible side effect of the drug fenbendazole (Panacur) is excessive salivation or drooling in your puppy. Panacur is more often used in adult dogs, and other brands of wormers with a different ingredient can be used in puppies.

Lack of appetite in puppy after deworming

Your puppy may experience a decrease in appetite and/or a lack of energy. Appetite and energy levels should return to normal after about 24 hours. However, if your puppy is a small-breed dog, not eating for even part of a day can potentially result in hypoglycemia, which is serious if not addressed in a timely manner. So, keep a close eye on your dog and consult your veterinarian if you're concerned.


Deworming side effects in adult dogs

Deworming side effects are similar in full-grown dogs. The main difference is that a mature body is better able to handle the deworming medicine, so side effects may not be as noticeable or as serious in a mature dog.

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How long do side effects of deworming treatment last?

Whether it's gastrointestinal upset, drooling, or a lack of appetite, if any of these symptoms last for more than 24 hours, it's a good idea to contact your veterinarian. Most puppies and dogs won't exhibit side effects at all, as the medication is considered very safe. So, any abnormal behavior or lasting effects could be signs of a rare allergic reaction or other problem.

Preventing deworming side effects

The most important step you can take to prevent side effects of deworming in your puppy or dog is to be careful and precise with the dosing. You need to know your dog's weight in order to calculate the right dosage, preferably with the help of your veterinarian. Consulting with your veterinarian before administering treatment is the best way to avoid unnecessary side effects.

To prevent worms or parasites in the first place, make sure your dog receives the proper preventative medications regularly and that their environment is clean and without access to the feces of other dogs or animals.

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Cost of puppy or adult dog deworming

Deworming medication is under $50 on average. Name brands will cost more than off brands. Talk to your veterinarian about the most affordable, effective medication for your puppy or adult dog.

The bottom line

Intestinal parasites are a common health issues in puppies and dogs. Talk to your veterinarian about the best prevention and treatment strategies. Deworming meds are very safe and effective, and potential side effects shouldn't last long.


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