I Accidentally Gave My Dog Too Much Benadryl?

Giving your dog too much Benadryl can be a serious mistake and can lead to a variety of adverse effects. Benadryl, also known as diphenhydramine, is a commonly used antihistamine that can be helpful in treating allergic reactions, motion sickness, and insomnia in dogs. However, it is important to use the medication only under the guidance of a veterinarian, as an overdose can be dangerous.

Symptoms of a Benadryl overdose in dogs can include drowsiness, confusion, dry mouth, dilated pupils, urinary retention, and in severe cases, seizures and coma. Additionally, it may cause your dog to have a low blood pressure, fast heart rate, and respiratory distress.

If you suspect that your dog has been given too much Benadryl, it is important to seek immediate veterinary care. Treatment for an overdose may include inducing vomiting, administering activated charcoal to absorb the medication, and providing supportive care such as oxygen therapy and IV fluids. In severe cases, more aggressive treatment such as intubation, mechanical ventilation, and even intralipid therapy may be required.

To prevent an overdose, it is important to carefully measure the appropriate dosage and to never exceed the recommended dosage. Benadryl should not be given to dogs with certain health conditions such as glaucoma, high blood pressure, and heart disease, without consulting a veterinarian. Benadryl should not be used in combination with other sedatives or tranquilizers, as this can increase the risk of adverse effects.

Benadryl is not recommended for long-term use, and it should be used only under the guidance of a veterinarian. It is important to keep the medication out of reach of children and pets. If an accidental overdose occurs, it is crucial to seek immediate veterinary care to prevent serious complications.

How long does it take Benadryl to get out of a dog’s system?

The elimination half-life of Benadryl in dogs is estimated to be approximately 4-6 hours. This means that half of the medication will be eliminated from the dog’s system within 4-6 hours of administration.

The complete elimination of Benadryl from a dog’s system can vary depending on several factors, such as the dog’s age, weight, overall health, and the dosage administered. It is important to note that the elimination half-life may be longer in dogs with liver or kidney disease, as these organs play a key role in the metabolism and elimination of drugs from the body.

In general, it is recommended to wait at least 24 hours before administering another dose of Benadryl to a dog. This allows enough time for the majority of the medication to be eliminated from the dog’s system, reducing the risk of adverse reactions or overdose.

Benadryl can cause drowsiness and sedation in dogs, and this effect can last for several hours after administration. Therefore, it is recommended to monitor the dog for signs of sedation and to keep them in a safe and secure environment until the sedative effects have worn off.

What are the side effects of Benadryl for dogs?

While Benadryl is considered generally safe for use in dogs, it can cause a range of side effects, including:

  1. Sedation: Benadryl can cause sedation in dogs, making them drowsy and less alert. This can be useful in certain situations, such as when traveling or when calming a dog with anxiety, but it can also make them less responsive to commands or make it difficult for them to perform normal daily activities.
  2. Dry mouth: Benadryl can cause dry mouth and make it difficult for dogs to swallow or drink water. This can lead to dehydration, and it is important to monitor their water intake if they are taking Benadryl.
  3. Loss of appetite: Some dogs may experience loss of appetite while taking Benadryl, which can lead to weight loss or anorexia.
  4. Constipation: Benadryl may cause constipation, making it difficult for dogs to have bowel movements. This can be uncomfortable and may require additional treatment to manage.
  5. Urinary retention: Benadryl can cause urinary retention, making it difficult for dogs to urinate. This can be dangerous and can lead to bladder infections or other complications.
  6. Excitement or agitation: Benadryl may cause excitation or agitation in some dogs, making them hyperactive or anxious. This can be especially problematic if the dog already suffers from anxiety or aggression.

Benadryl killed my dog?

  • Overdose: Giving your dog too much Benadryl can be lethal, as it can lead to an overdose. Make sure to always follow your veterinarian’s dosing instructions and never give your dog more than recommended.
  • Allergic reaction: Some dogs may have an allergic reaction to Benadryl, which can cause severe symptoms such as difficulty breathing, hives, and swelling. If you notice any of these symptoms after giving your dog Benadryl, seek emergency medical attention immediately.
  • Interactions with other medications: Benadryl can interact with other medications your dog may be taking, leading to dangerous side effects. Make sure to always inform your veterinarian of any other medications your dog is taking before starting Benadryl.
  • Age-related sensitivity: Older dogs may be more sensitive to the effects of Benadryl and may be at higher risk for negative reactions. Be extra cautious when giving Benadryl to an older dog and always follow your veterinarian’s dosing instructions.
  • Pre-existing health conditions: If your dog has a pre-existing health condition such as liver or kidney disease, they may be more sensitive to the effects of Benadryl. Again, always follow your veterinarian’s dosing instructions and be aware of any potential interactions with other medications.

Conclusion of Benadryl for dogs

Benadryl, also known as diphenhydramine, is a commonly used antihistamine in dogs. It is used to treat a variety of conditions including allergies, anxiety, and insomnia. While Benadryl can be an effective treatment option, there are also potential drawbacks and side effects to be aware of.


  • Benadryl is an over-the-counter medication and is widely available.
  • It is generally well-tolerated in dogs and has a relatively low risk of side effects.
  • It can provide relief for a variety of symptoms, including itching, sneezing, and anxiety.


  • Benadryl can cause sedation and drowsiness in dogs, which can be problematic for some animals.
  • It can also cause dry mouth and decreased appetite.
  • It may interact with other medications, such as antidepressants and pain medications, and should be used with caution in dogs taking other medications.

Side effects:

  • Drowsiness and sedation
  • Dry mouth
  • Loss of appetite
  • Vomiting
  • Diarrhea
  • Urinary retention


  • Overdose of Benadryl can cause severe toxicity, including seizures and coma.
  • Dogs should be given the appropriate dosage as prescribed by a veterinarian, and pet owners should be aware of the signs of toxicity.

Drug interactions:

  • Benadryl may interact with other medications, such as antidepressants and pain medications, and should be used with caution in dogs taking other medications.


  • Benadryl should not be used in dogs with certain health conditions, such as glaucoma, prostatic hyperplasia, and bladder obstruction.
  • It should be used with caution in dogs with hypertension or cardiovascular disease.

Research and study:

  • While Benadryl is a commonly used medication in dogs, there is limited research available on its long-term effects and safety.
  • More research is needed to fully understand the potential risks and benefits of using Benadryl in dogs.

Natural or OTC veterinary alternatives:

  • Some pet owners may prefer to use natural or over-the-counter veterinary alternatives for treating their dogs’ symptoms.
  • These alternatives include supplements such as omega-3 fatty acids, quercetin, and bromelain, and herbal remedies such as chamomile, passionflower, and valerian root.

Hannah Elizabeth is an English animal behavior author, having written for several online publications. With a degree in Animal Behaviour and over a decade of practical animal husbandry experience, Hannah's articles cover everything from pet care to wildlife conservation. When she isn't creating content for blog posts, Hannah enjoys long walks with her Rottweiler cross Senna, reading fantasy novels and breeding aquarium shrimp.

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