How To Sedate A Cat With Benadryl: What You Need To Know

Benadryl or (diphenhydramine hydrochloride) is a antihistamine that blocks the effects of histamine by preventing them from attaching to H1 receptors on small blood vessels and smooth muscles.

Once you give Benadryl to your cat it should kick in relatively quick and will take about 30 minutes to take effect. Sometimes it can take a little bit longer for your cat to feel the effects.

Benadryl Uses

Benadryl has many uses as a medication in both humans and cats. These include:

  • Anxiety
  • Motion sickness
  • Sneezing
  • Coughing
  • Vaccine reactions
  • Allergies
  • Skin Reactions
  • Bug Bites

Forms Of Benadryl

There are three types of Benadryl. You can administer by tablet, liquid and injection.

Benadryl Dosage For Cats: How Much To Give Them

Your cat can take 1 milligram (mg) per pound, or 2 mg per kilo and can be taken up to two times a day safely. Here is a table to help you how much to give them.

6.6 lbs3 kg6 mg
7.7 lbs3.5 kg7 mg
8.8 lbs4 kg8 mg
9.9 lbs4.5 kg9 mg
11 lbs5 kg10 mg
12.1 lbs5.5 kg11 mg
13.2 lbs6 kg12 mg

Can I Give My Cat Children’s Benadryl?

There is no Benadryl specifically made for cats so you can give them childrens Benadryl if that’s the only thing that you have. In fact, it may even be easier to administer it as its easier to measure.

What Is The Lethal Dose Of Benadryl For Cats?

It is tough to overdose on antihistamines but for a cat to overdose on Benadryl it would take 15 times the amount of a regular dose for it to kill your cat. Say your cat was about 10 pounds then the amount to overdose on Benadryl would be 150 mg.
If you suspect that your cat has taken too much Benadryl then contact your vet immediately.

What Happens When A Cat Overdoses On Benadryl?

An overdose can lead to a lot of things you would rather want to avoid. These include:

  • Seizures
  • Coma
  • Difficulties breathing
  • Death

How To Give Your Cat A Benadryl Tablet

One way that you can give your cat Benadryl is through a tablet. There are a couple of ways that you can administer this tablet to them. They include:

Crushing The Tablet: The best way of giving them Benadryl is crushing the tablet into a powder and putting in some type of food that they eat. This would probably be the best way of giving your cat Benadryl if they are aggressive and stubborn. The best food to use would be in wet cat food, treats or some type of meat that they enjoy such as chicken turkey, beef etc.

Raw pill: Cats can be very resistant to taking pills so if you have an aggressive cat this method will not go well for you and do not recommend doing it this way. If you want to give them Benadryl by raw tablet you will need two people to do this. You will want to have one person holding down the cat so they don’t scratch you.

Then what you want to do is lift their head up and gently lift their mouth open. Once their mouth is open drop the pill in and hold their mouth shut until you see them swallow it. If your cat is very docile this can be an easy method to administer the tablet.

Get Flavored tablets: You can actually get tablets that are flavored like chicken, fish or other flavors from a compounding pharmacy. This will make it a lot easier to give your cat the medicine.

How to Give Your Cat Liquid Benadryl

Sometimes its easier to give your cat liquid Benadryl. To do this it is quite easy to do with a little practice. Its also very similar to giving them a tablet or pill.

Have the cat facing away from you. then hold the cats head with your left hand and have the syringe with your right. Lift their head up to the ceiling, Hold their whiskers back and lift up their top lips. Put the syringe in their mouth (back third) then hold their mouth closed for about 3 seconds and you’re done.

If you have an aggressive cat veterinarians in hospitals and shelters will actually do things like administer it through the side of their mouth or they will wait for the cat to hiss at them and squirt it down their throat. It can be messy but it works.

Some Considerations about Liquid Benadryl

The problem with liquid Benadryl is that they will taste it a lot more than a capsule or a tablet which as a result they will be more likely to foam at the mouth (which I explain later in the article). The odor can also put off cats as they really don’t like the way that Benadryl smells.

If you want to avoid this foaming phenomenon then you just administer it at the back third of the tongue. You want to avoid letting the medication hit the front of the tongue which is what causes the foaming.


Some of these methods take a little practice but it gets easier as you do it more often. After you attempt it a couple of times you’ll have it down by then.

Why Is My Cats Mouth Foaming After Giving Them Benadryl?

This can be quite alarming to see and you may think its a sign of overdosing but this is completely normal and not a cause for concern. When cats ingest something that tastes particularly unpleasant (especially in larger volumes) they can display this side effect and Benadryl is known to taste bad to cats.

It tastes very bitter to them and that’s what causes the foaming. Just wipe everything up and they should be fine eventually. Even though this is harmless you want to avoid this happening because it will be harder to give them medication in the future as they know it will taste bad.

How Long Does Benadryl Last?

First off you must understand that every drug has something called a “half life”. A half life is a certain amount of time for the medication to be reduced down to 50 percent.

For Benadryl in particular it really depends on the weight, health and activity level of your cat. Typically your cat will feel the effects of Benadryl for about 8 to 12 hours which would be really good for long car rides.

Side Effects Of Benadryl

This medication can help your cat a lot but there are unfortunately some side effects from taking it. These include:

  • Dialated pupils
  • Foaming Of The Mouth
  • Hyperexcitability
  • Vomiting
  • Diarrhea
  • More or less frequent urination
  • Drowziness
  • Dry Mouth

Drug Interactions

Benadryl may react to the following medications.

  • Amitraz
  • Epinephrine
  • Furazolidone
  • Heparin sodium or calcium
  • Selegiline
  • Warfarin sodium

Things To Consider

Cats cannot take this medication if they have certain medical conditions as it can be dangerous or lethal to them. These include:

  • Glaucoma
  • Kidney Disease
  • Liver Disease
  • Hyperthyroidism
  • Heart Disease
  • High Blood Pressure

If you give your cat generic Benadryl make sure that it has only one active ingredient. It will say diphenhydramine hydrochloride. If there are other active ingredients it can lead to severe poisoning in cats so this is very important to check before administering the medicine beforehand

Benadryl is also safe to use if your cat is pregnant as it is a category B drug by the FDA. You should however always check with you vet just in case.


Benadryl can be a bit scary to give to your cat but it isn’t as bad as you would think it would be. If you do everything carefully you shouldn’t do anything bad to your cat as this is a very common thing people do when traveling with their cats.