Chlorpheniramine Maleate

By Rania Gollakner, BS, DVM, MPH

What is chlorpheniramine maleate?

Chlorpheniramine maleate (brand names: Chlor-Trimetron®, Aller-chlor®, Chlor-tripolon®, ChlorTabs ®) is an antihistamine used to treat allergic conditions and occasionally used as a mild sedative.

Its use in cats, dogs, horses, ferrets, and birds to treat allergic conditions is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

How is chlorpheniramine maleate given?

Chlorpheniramine maleate is given by mouth in the form of a tablet, liquid syrup, or liquid drops. It can be given with or without food; however, if vomiting occurs when dosed on an empty stomach, give future doses with food. This medication is most effective if given on a regular basis and given prior to exposure to the allergen. If using an extended release tablet, do not break, crush, or split the tablets. Measure liquid forms carefully. When giving this medication, allow access to water at all times.

If purchased over the counter, read the label carefully before giving this medication to ensure the product contains ONLY chlorpheniramine.

This medication will take effect quickly, in about 1 to 2 hours, and improvement in clinical signs should follow.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

The most common side effect is sleepiness. In cats, this medication can cause excitement rather than sedation. Less common side effects include diarrhea, vomiting, lack of appetite, dry mouth and mild straining to urinate. Serious side effects include seizures, abnormal breathing, incoordination, muscle tremors, and coma.

This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Chlorpheniramine maleate should not be used in pets that are allergic to it or other similar antihistamines. Use cautiously in pets with closed-angle glaucoma, enlarged prostate, hyperthyroidism, heart disease, high blood pressure, gastrointestinal or bladder obstruction, or obstructive lung disease (COPD). Use cautiously in geriatric, pregnant or lactating pets, or dogs that are working dogs.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with chlorpheniramine maleate: anticoagulants, MAOIs, phenytoin, or central nervous system depressants. Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

This medication can also interact with skin allergy testing; discontinue this medication at least 2 weeks before allergy testing.

Is there any monitoring that needs to be done with this medication?

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the medication is working. Monitor your pet for adverse side effects.

How do I store chlorpheniramine maleate?

Store the tablets at room temperature between 59°F and 86°F (15°C and 30°C) in a tight container protected from moisture. Store the liquid solution at the same room temperature, away from light and protected from freezing.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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