Chlorpheniramine is an antihistamine drug used for the treatment of acute inflammatory and allergic conditions. Read this DogAppy article to find its uses, side effects, and more.
Chlorpheniramine is not approved by the Food and Drug Administration for use in animals, but is recommended legally by veterinarians as an off-label drug for treating dogs with allergy symptoms.
Chlorpheniramine is an antihistamine drug that helps treat allergic reactions in dogs. When allergens get attached to the dog’s body, histamines are produced. Histamine is an inflammatory biochemical that is produced due to allergens or inflammation. This chemical moves inside of the body to find specific histamine receptors and links to them. It causes redness, skin irritation, and swelling. Histamine receptors are of two types; H1 and H2. When histamine links to H1 receptors, small blood vessels enlarge. The activation of H1 receptors increases the permeability of blood vessels and causes itching and swelling. It also results in the contraction of the smooth muscles of the bronchi, which may lead to trouble in breathing.
Drugs that suppress the action of histamines are called antihistamines. Chlorpheniramine is an antihistamine that blocks the action of histamine on H1 receptors. It works by linking with the H1 receptor. It is most commonly sold under the brand name Chlor-Trimeton. It is available in liquid, tablet, and capsule forms, and is bitter to taste.
▸ Chlorpheniramine is a mild antihistamine. It can be used to alleviate allergy symptoms, if the allergens are drug-induced, or brought in due to inhalation or contact.
▸ It is used to treat acute inflammatory and allergic conditions like vaccination reactions, snakebites, blood transfusion reactions, and stings and insect bites.
▸ It is also used to treat itching of the eyes, ears, or skin and for treating urticaria in dogs and cats.
▸ It can be used as an antianxiety medication or as an anti-depressant and to keep away from motion sickness.
The common side effects of the drug include:
- Dry mouth
- Loss of appetite
- Urinate retention
In rare cases, it may lead to constipation and vision problems.
Dosage and Administration
▸ Chlorpheniramine is available in 2, 4, 8, or 12 milligram portions.
▸ In the form of syrup, it is available as 2 mg/5 ml oral syrup.
▸ It is also available as 10 mg/ml and 100 mg/ml in the form of injections.
▸ It is taken two to three times a day in tablet, injection, or syrup form. The usual dosage for dogs is 2 to 8 mg every 8 to 12 hours (twice a day).
Dosage Based on Dog Weight
|Dog weight (in pounds)
|Dose (based on 4mg tablet )
|1/4-1/2 tablet 2-3 times daily
|1/2 to 1 tablet 2-3 times daily
|1 to 2 tablets 2-3 times daily
|2 to 4 tablets 2-3 times daily
|4 to 6 tablets 2-3 times daily
Source: The Cheyenne West Animal Hospital website
▸ After taking chlorpheniramine orally, its action begins within 15 to 30 minutes. Its effect is seen in one to two hours and the duration of effect is about four to six hours.
▸ Always follow the advice of your veterinarian for the dosage directions.
▸ Contents of the capsule may be mixed with food. But do not let the contents dissolve before the dog eats the food.
▸ If you forget to give a dose, give it as soon as you remember. If it is time for the next dose, skip the one you missed. Do not give two doses at the same time.
▸ Overdose of chlorpheniramine may have serious side effects like ataxia (inability to coordinate voluntary muscle movements), shivers, abnormally slow heartbeat, coma and even death.
▸ Consult your vet before giving chlorpheniramine to your dog.
▸ It should be used carefully in pets with hyperthyroidism, high blood pressure, heart disease, glaucoma (eye disease), enlarged prostate, lung disease, asthma, problems in urinating or stomach or intestinal obstruction.
▸ Avoid using this drug on animals with hypersensitivity to this drug or to other related antihistamines.
▸ Chlorpheniramine should not be used with MAOIs (monoamine oxidase inhibitors).
▸ If your dog is taking metoclopramide or phenothiazines, exercise caution.
▸ After using the drug, if the dog experiences hyperactivity, breathing problems, facial swelling, hives, scratching, sudden attack of diarrhea, shock, pale gums, cold limbs, or coma, stop giving the drug immediately and consult your veterinarian.
▸ Avoid using this drug if the dog is pregnant.
▸ The drug is not recommended for use in military dogs and police dogs as it may lead to excessive sedation.
▸ Avoid using chlorpheniramine with other medications such as acetaminophen, antidepressants, or with caffeine.
▸ Close the drug container tightly.
▸ Keep the container at room temperature and away from moisture.
▸ Avoid storing the drug in the bathroom.
▸ Keep out of the reach of children and pets.
To prevent allergies in dogs, it is necessary to know what’s causing them. If the cause of the allergy is shampoos, dust, or flea bites, avoiding exposure to these is advisable. Prevention is always better than cure.
Disclaimer: This article is for informational purposes and should not be taken as a substitute for veterinary advice.