Can Worming Tablets Make A Dog Feel Unwell

icon May 18, 2024

Worming tablets, or dewormers, are an essential aspect of canine healthcare. These medications help to eliminate parasitic worms that can infest a dog's gastrointestinal tract, leading to a host of health issues if left untreated. While worming tablets are generally effective and safe, there are instances where they can make a dog feel unwell. This article explores the reasons behind this, the types of reactions that may occur, and how to manage and prevent adverse effects.

The Importance of Deworming

Parasitic worms like roundworms, hookworms, tapeworms, and whipworms can cause serious health issues in dogs, ranging from mild discomfort to severe illness and even death. Deworming is essential for the dog's health and to prevent spreading parasites to other pets and humans.

Dogs should generally be dewormed every three months. Puppies may need more frequent treatment, typically every two weeks until 12 weeks old, then monthly until six months old. Consult your veterinarian for a schedule tailored to your dog's specific needs and risk factors.

Veterinarians recommend regular deworming based on the dog's age, lifestyle, and risk of exposure. However, like any medication, dewormers can sometimes cause side effects.

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How Deworming Tablets Work

Worming tablets work by targeting specific types of parasitic worms within the dog's body. The active ingredients in these medications vary, but they generally function by either paralyzing the worms, disrupting their metabolism, or otherwise incapacitating them, allowing the dog's body to expel the parasites naturally.

Common active ingredients in worming tablets include:

a. Pyrantel Pamoate:
Effective against roundworms and hookworms, it works by paralyzing the worms, which are then expelled through the feces.

b. Praziquantel:
Targets tapeworms by causing severe muscle spasms in the worms, leading to their disintegration and removal.

c. Fenbendazole:
A broad-spectrum dewormer that treats roundworms, hookworms, whipworms, and some tapeworms by disrupting their energy metabolism.

d. Milbemycin Oxime:
Used in heartworm prevention and also effective against intestinal worms, it works by interfering with the parasites' nerve transmission.

These medications are generally safe, but they can sometimes cause adverse reactions, which can make a dog feel unwell.

Common Side Effects of Worming Tablets

While most dogs tolerate deworming tablets well, some may experience side effects. These side effects can vary depending on the type of worming tablet used, the dog's overall health, age, and individual sensitivity to the medication. Common side effects include:

Gastrointestinal Upset

The most frequently reported side effects are gastrointestinal in nature. These can include:

♣ Vomiting:
A dog might vomit shortly after taking the medication. This is often a transient reaction, but if it persists, veterinary advice should be sought.

♣ Diarrhea:
Loose stools or diarrhea can occur as the body expels the parasites and adjusts to the medication.

♣ Loss of Appetite:
Some dogs may temporarily lose their appetite following deworming.

♣ Abdominal Discomfort:
The process of expelling the worms can cause mild abdominal pain or discomfort.

Lethargy and Fatigue

Dogs may feel unusually tired or lethargic after taking worming tablets. This can be a result of the body’s immune response to the dying parasites and the effort required to expel them.

Allergic Reactions

Though rare, some dogs can have an allergic reaction to the active ingredients in worming tablets. Signs of an allergic reaction may include:

♣ Swelling:
Particularly around the face, lips, or eyes.

♣ Hives:
Raised, itchy bumps on the skin.

♣ Difficulty Breathing:
In severe cases, an allergic reaction can cause respiratory distress.

Neurological Symptoms

Certain dewormers, particularly those used for severe infestations or specific parasites, can sometimes cause neurological symptoms such as:

♣ Tremors:
Shaking or trembling, which can be mild or severe.

♣ Ataxia:
Loss of coordination, resulting in unsteady movements.

In very rare cases, dogs may experience seizures.

Factors Influencing Side Effects

Several factors can influence the likelihood and severity of side effects from worming tablets:

1. Dog’s Age and Health

Puppies and senior dogs are more susceptible to side effects due to their developing or aging bodies. Dogs with underlying health conditions, such as liver or kidney disease, may also have a higher risk of adverse reactions.

2. Dosage and Administration

Incorrect dosage, whether too high or too low, can lead to side effects. It’s crucial to follow the veterinarian’s dosage instructions carefully. Overdosing can increase the risk of toxicity, while underdosing may not effectively clear the infestation, leading to ongoing symptoms.

Note(symptoms of overdose of dewormer in dogs):

Symptoms of a dewormer overdose in dogs can include vomiting, diarrhea, excessive drooling, loss of appetite, lethargy, and tremors. In severe cases, dogs may experience seizures, difficulty breathing, or collapse. Immediate veterinary attention is crucial if an overdose is suspected to provide appropriate treatment and prevent serious health complications.

3. Type of Parasite

The type and severity of the parasitic infestation can impact how a dog reacts to the medication. A heavy parasite load can cause a significant die-off reaction, leading to more pronounced symptoms as the body expels the worms.

4. Sensitivity to Ingredients

Some dogs may have a sensitivity or allergy to specific ingredients in worming tablets. This can lead to side effects even at the correct dosage.

Managing and Mitigating Side Effects

If a dog experiences side effects after taking worming tablets, there are several steps that can be taken to manage and mitigate these reactions:

Monitoring and Supportive Care

Closely monitor the dog for any signs of adverse reactions, particularly in the first few hours after administration. Provide plenty of water and a comfortable resting place. In case of gastrointestinal upset, offering small, bland meals can help soothe the digestive system.

Contacting the Veterinarian

If side effects are severe or persistent, contact a veterinarian for advice. They may recommend supportive treatments such as anti-nausea medication or fluids to help manage the symptoms. In cases of allergic reactions, immediate veterinary attention is essential to manage potentially life-threatening symptoms.

Alternative Deworming Options

For dogs that react poorly to standard worming tablets, veterinarians may suggest alternative treatments. These can include:

Topical Dewormers:
Applied to the skin, these can be an option for dogs sensitive to oral medications.

Injectable Dewormers:
Administered by a veterinarian, these can bypass the gastrointestinal tract, reducing the risk of digestive upset.

Natural Remedies:
While not as effective as conventional medications, some natural deworming agents may be used under veterinary guidance for mild infestations.

Preventing Side Effects

While it's impossible to eliminate the risk of side effects entirely, certain measures can reduce the likelihood:

Proper Dosage

Ensure the correct dosage based on the dog’s weight and the type of parasite being treated. Regularly update the dog's weight and health status with the veterinarian to adjust the dosage if necessary.

Pre-Treatment Evaluation

Before administering a dewormer, have the dog evaluated by a veterinarian to ensure they are healthy enough for the treatment. This is particularly important for puppies, senior dogs, and those with pre-existing health conditions.

Gradual Introduction

For dogs with a history of sensitivity, a gradual introduction of the medication under veterinary supervision can help monitor for adverse reactions. This can involve starting with a lower dose and gradually increasing it.

Hydration and Nutrition

Maintain the dog’s hydration and provide a balanced diet to support their overall health and immune system. A well-nourished dog is better equipped to handle the effects of deworming medication.


While worming tablets are an essential tool in maintaining canine health, they can sometimes make a dog feel unwell. The side effects can range from mild gastrointestinal upset to more severe allergic and neurological reactions. Understanding the factors that contribute to these side effects and taking steps to manage and prevent them can help ensure that deworming is a safe and effective process for all dogs.

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