General Description : Diphenhydramine is an affordable antihistamine that has been prescribed to your pet to treat an allergic reaction to drugs or an environmental allergen, to prevent motion sickness or as a tranquilizer. There are several other uses for this medication. It is generally well-tolerated, but you can expect to see drowsiness. Available over-the counter (OTC) in many forms: 25 mg capsules or minitabs, 12.5 mg chewable tablets; 50 mg capsules or tablets, oral elixir and syrup.

What is this drug?

An antihistamine
Given by mouth
Reasons for prescribing:

Used for acute inflammatory and allergic conditions such as: snake bites, vaccination reactions, blood transfusion reactions, bee strings and insect bites, and the management of itchy skin
Used in the treatment of mast cell tumors
Useful in the treatment of motion sickness
Causes drowsiness, so may be used as a mild tranquilizer
Readily available and inexpensive
What dogs/cats should not take this medication?

Safety in pregnant or nursing pets is unknown
Use with caution in pets with heart disease, high blood pressure, hyperthyroidism, glaucoma, asthma, urinary obstruction, prostate disease or those with an obstruction of the pylorus
If your pet has had an allergic reaction to diphenhydramine or like products

Read and follow the label carefully.

Give the exact amount prescribed and only as often as directed. It is usually givenup to three times daily. Ideally, give the medication at the same time(s) daily.

Shake liquids before using and measure the dose carefully.

Slow-release capsules should not be mixed or dissolved in food.

Do not give sinus or cold medications containing diphenhydramine to your pet. They can be lethal to your pet.

What if a dose is missed?

If a dose is missed, give it as soon as you can. If it is time already for the next dose, skip the missed dose and go back to the normal schedule. Do not give two doses at the same time.

What to tell/ask veterinarian before giving medication?

Talk to your veterinarian about:

When will your pet need to be rechecked
What tests may need to be performed prior to and during treatment with this drug
What are the risks and benefits of using this drug
Tell your veterinarian about:

If your pet has experienced side-effects on other drugs/products
If your pet has experienced any other medical problems or allergies now or ever
All medicines and supplements that you are giving your pet or plan to give your pet, including those you can get without a prescription. Your veterinarian may want to check that all of your pet’s medicines can be given together.
If your pet is pregnant or nursing or if you plan to breed your pet
Storage and Warnings:

Some oral liquids contain alcohol. Do not use these formulations in your pet.

Store in a tight, light resistant, childproof container in a cool, dry place at room temperature away from heat and direct sunlight. Do not store in the bathroom as it is sensitive to moisture. Do not allow the liquids to freeze.

Keep this and all medication out of reach of children and pets.

Call your physician immediately if you accidentally take this product.

Potential side effects:

Causes drowsiness. This effect lessens over time. Do not use in working dogs as it may cause too much sedation.
Can cause dry mouth, vomiting, diarrhea, loss of appetite and inability to urinate
Cats may experience hyperexcitability or agitation
Diphenhydramine tastes terrible. Getting cats to accept it can be quite a challenge.
This medication interferes with allergic skin testing. Check with your veterinary dermatologist when to discontinue diphenhydramine in advance of allergy testing.
If you notice anything unusual, contact your veterinarian
Can this drug be given with other drugs?

Yes, but possible interactions may occur with epinephrine, MAOIs, metoclopramide, oral anticoagulants (ex. heparin, warfarin) and tranquillizers
Human products containing antihistamines are often combined with pain relievers. These combination products should not be used in animals.
If your pet experiences any unusual reactions when taking multiple medications, contact your veterinarian

Contact your veterinarian immediately if pet receives more than the prescribed amount.

What else should I know?

Notify your veterinarian if your animal’s condition does not improve or worsens despite this treatment.

As with all prescribed medicines, diphenhydramine should only be given to the pet for which it was prescribed. It should be given only for the condition for which it was prescribed.

This is just a summary of information about diphenhydramine. If you have any questions or concerns about diphenhydramine or the condition it was prescribed for, contact your veterinarian.

Call Us