Diphenhydramine For Cats: Dosage Chart By Weight 

Diphenhydramine is an antihistamine medicine used for cats, dogs and other small pets to treat allergic reactions such as hives, vaccine reactions, sneezing, itching, insect or flea bites and pollen allergens etc.

Diphenhydramine also works as a sedative agent and can be used to treat motion sickness and help with agitation associated with allergic symptoms.

 Knowing about the safe dosage of Diphenhydramine for a feline is essential to avoid the risk of toxic reactions.

This article is a comprehensive researched guide about Diphenhydramine for cats, its safe dosage, benefits, side effects, safe serving ideas and more.

Diphenhydramine For Cats

Is Diphenhydramine safe for cats?

For cats, Diphenhydramine oral use is not FDA approved. Still, it is among the most prescribed medication by veterinarians. For cats, Diphenhydramine is safe when following the dosing instructions.

However, this doesn’t mean that the treatment will be safe and effective for all felines. Different pets can react differently to the medication.

Diphenhydramine is not recommended for felines allergic to the medication and having health issues such as glaucoma, kidney or liver illnesses, heart problems, seizures or epilepsy.

You must take your veterinarian’s advice before giving the medication to your kitty.

Diphenhydramine Dosage for Cats

The general dose of Diphenhydramine tablets for cats is 2mg/kg or 1mg/lbs and liquid form is 0.8ml/kg or 0.4ml/lbs 3 times a day. Do not administrate more than three times a day and must keep a gap of at least 8 hours. Overdosing can lead your pet to severe health complications and can be fatal.

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Remember that the dose can be increased and decreased depending on the health issues being treated and individual pet conditions. Your veterinarian can ideally decide the safe amount according to the situation.

For felines, the liquid form of the medicine is usually considered more effective than the tablets form because kitties can have difficulty swallowing the pills and also, the liquid dose can be easily identified and administrated.

Diphenhydramine Dosage chart by weight for cats

Cat Weight in KgCat weight in lbsLiquid Diphenhydramine dosageDiphenhydramine Tablet form dosage
2 kg4 lbs1.6 ml4 mg
3 kg6 lbs2.4 ml6 mg
4 kg9 lbs3.2 ml8 mg
5 kg11 lbs4 ml10 mg
6 kg13 lbs4.8 ml12 mg
7 kg15 lbs5.6 ml14 mg
8 kg18 lbs6.4ml16 mg

Common Brand names of Diphenhydramine HCI

  • Benadryl®
  • Vetadryl®
  • Banophen®
  • Genahist®
  • Diphenhist®
  • Unisom®
  • Sominex ®

Diphenhydramine Side effects

The most common side effects of Diphenhydramine in cats are:

Minor Side Effects:

  • Vomiting & Diarrhea
  • Sedation
  • Increase in Thirst
  • Agitation
  • Drooling
  • Restlessness

Severe Side Effects:

Severe side effects occur as a result of overdosing.

  • Increase or decrease in heart rate
  • Difficulty breathing
  • Rapid or slow breathing
  • Unconsciousness
  • Pale gums
  • Seizures

Which cats should not take Diphenhydramine?

Diphenhydramine is not considered safe for all cats. The Feline who falls in the below conditions should Never take Diphenhydramine without a professional veterinarian’s advice.

Diphenhydramine is not safe for cats having health issues such as intestinal obstruction, heart problems, seizure disorders, prostatic hypertrophy, kidney and liver illness, bladder neck obstruction, and allergic lung disease.

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Cats with Hyperthyroidism and hypertension, Working dogs, and hunting dogs should not take during or prior to going to the field due to the sedative side effects.

Pediatric or neonatal queen cats should not take Diphenhydramine without a vet prescription.

Diphenhydramine Precautions For use in cats

Never ever increase the dose without your vet’s advice. Always offer a safe dosage.

Never give more than 2mg/kg or 1mg/lb, and make sure to keep at least 8 hours gap between the two doses.

Never give two doses at once or give extra doses without your veterinarian’s advice.

For felines, Prefer liquid form over tablet form. Avoid the liquid Diphenhydramine that contains xylitol or any other toxic ingredients for cats.

If you are giving the tablet form, make sure to divide it into pieces to the safe amount.

For easy swallowing, you can hide the pill in your kitty’s food.

Chose the product having only one Diphenhydramine HCl active ingredient. Avoid products that contain any extra ingredients.

Keep a close eye on your pet. If you observe any adverse effects, do not give the next dose and contact your veterinarian immediately at the animal posing control helpline.

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How much time does Diphenhydramine take to start work in cats?

Diphenhydramine usually takes 30 mins to 1 hour to absorb in the body and to start its effect. For sedation and motion sickness, it is better to give a 1-hour prior to driving trip.

For the treatment of other allergic reactions, you can see the improvement of the medication gradually till the completion of the dosage.

Which medicine should not be taken parallel with Diphenhydramine?

Diphenhydramine can interact with certain medications and can cause health complications. Diphenhydramine can react with the below-mentioned drugs.

  • Anticholinergic drugs
  • Home remedies (May be)

Ensure to inform your vet if your kitty is already taking any of the above-listed medications.

Why does a cat foam at the mouth after taking Diphenhydramine?

Many feline owners often report to us that after taking Diphenhydramine, their pet starts foaming at the mouth. Why?

Foaming in a cat’s mouth is one of the side effects associated with Diphenhydramine. Due to the bitter taste of the medicine, a feline can start to drool, which cause hypersalivation and form foam in the mouth.

Severe foaming can also indicate a poisoning reaction, so if you observe excessive foaming, make sure to contact your veterinarian or call animal poisoning control help line at  (888) 426-4435.

What is the lethal dose of diphenhydramine for felines?

Cats are usually considered more sensitive to medicine than dogs and other large pets. Therefore special consideration is needed regarding the dose of any medication.

Offering diphenhydramine more than 3mg/kg can be lethal for cats. Do not exceed 2mg/ kg per dose. 

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