Chlorpheniramine Maleate for Dogs

Chlorpheniramine maleate, better known by its brand name Chlor-Trimeton, is an antihistamine that may be useful in treating some canine allergies. Let’s look at how chlorpheniramine can help your dog, what some of its common side effects are and in what situations it should not be used.

When Chlorpheniramine May Help Your Dog

Antihistamines help alleviate the symptoms of an allergic reaction, such as hives, irritation, itching, redness and swelling, that most commonly occur on your dog’s skin. These symptoms are caused by a chemical called histamine that your dog’s immune system creates in response to an allergen, which is anything that causes an allergic reaction in his body.

As an antihistamine, chlorpheniramine can help control allergic reactions in your dog that may result from:

  • atopic allergies
  • blood transfusion reactions 
  • insect or snake bites
  • vaccination reactions  (if given prior to the vaccination)

Chlorpheniramine is also used to control itching and skin irritation, motion sickness, seizures and mast cell tumors. The medication can also be prescribed as a mild sedative since one of its most common side effects is drowsiness.

Chlorpheniramine is available in tablet, oral syrup and injectable forms. The amount your dog will take daily depends on his weight. Follow all dosing instructions from your veterinarian carefully.

The use of antihistamines in combination with certain fatty acid supplements may increase the effectiveness of the antihistamine treatment. Discuss possible combinations of supplements and antihistamines with your veterinarian to determine which ones are the best solution to your dog’s allergy problems.

Common Side Effects of Chlorpheniramine

As noted above, the most common side effect of chlorpheniramine is drowsiness. Other common side effects include:

  • appetite loss
  • diarrhea
  • dry mouth
  • inability to urinate
  • lethargy
  • vomiting

Another side effect that owners may have to deal with is the medication’s bitter taste. Some dogs will take the medication at first, but will ultimately refuse to take it, which may require switching to a different antihistamine.

Some dogs may be allergic to chlorpheniramine. Signs of an allergic reaction include:

  • coma
  • facial swelling
  • hives
  • pale gums
  • seizures

These symptoms can also indicate an overdose of chlorpheniramine. Contact your veterinarian’s office or an animal emergency clinic immediately if you see signs of an allergic reaction to or an overdose of chlorpheniramine in your dog.

Do not give chlorpheniramine that has other medications, such as pain relievers, to your dog because these combination medications are harmful to your pet’s health.

Situations in Which Chlorpheniramine Is Not Recommended

Despite its relative safety, chlorpheniramine is not recommended for use in all dogs. Dogs with enlarged prostates, glaucoma, heart disease, hypertension, hyperthyroidism, obstructive pulmonary disease or urinary bladder obstruction should not take chlorpheniramine because the medication’s common side effects may exacerbate these conditions.

Using chlorpheniramine in working or therapy dogs is not recommended because of the medication’s sedative effects. Its safety for pregnant or nursing females is unknown.

Dogs that are having allergy skin tests should not take chlorpheniramine prior to the test being given because the medication will interfere with the test results. If your dog requires allergy skin tests, discuss when you should discontinue chlorpheniramine use with your veterinarian, as well as when you can resume giving your dog this medication.