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PetDosageChart

Chlor-Trimeton (Chlorpheniramine) Dosage for Cats

First-generation antihistamine ⏱ Onset: 30-60 minutes ⏳ Duration: 8-12 hours

This dosage information is for educational purposes only. Always consult your veterinarian before giving any medication to your pet. Dosages may vary based on your pet's health conditions, other medications, and individual factors.

Content reviewed by licensed veterinarians. This information is sourced from veterinary drug references including Plumb's Veterinary Drug Handbook and the Merck Veterinary Manual.

Dosage Calculator

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Chlor-Trimeton Dosage Chart for Cats by Weight

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Weight Low Dose Standard Dose Max Dose Frequency
3 lbs (1.4 kg) 0.5mg 0.5mg 0.5mg every 8-12 hours
4 lbs (1.8 kg) 0.5mg 1mg 1mg every 8-12 hours
5 lbs (2.3 kg) 0.5mg 1mg 1mg every 8-12 hours
6 lbs (2.7 kg) 0.5mg 1.5mg 1.5mg every 8-12 hours
7 lbs (3.2 kg) 1mg 1.5mg 1.5mg every 8-12 hours
8 lbs (3.6 kg) 1mg 2mg 2mg every 8-12 hours
9 lbs (4.1 kg) 1mg 2mg 2mg every 8-12 hours
10 lbs (4.5 kg) 1mg 2.5mg 2.5mg every 8-12 hours
12 lbs (5.4 kg) 1.5mg 2.5mg 2.5mg every 8-12 hours
14 lbs (6.3 kg) 1.5mg 3mg (4mg tablet) 3mg (4mg tablet) every 8-12 hours
16 lbs (7.3 kg) 2mg 3.5mg (4mg tablet) 3.5mg (4mg tablet) every 8-12 hours
18 lbs (8.2 kg) 2mg 4mg (4mg tablet) 4mg (4mg tablet) every 8-12 hours
20 lbs (9.1 kg) 2.5mg 4.5mg (4mg tablet) 4.5mg (4mg tablet) every 8-12 hours
25 lbs (11.3 kg) 3mg (4mg tablet) 5.5mg 5.5mg every 8-12 hours

What is Chlor-Trimeton (Chlorpheniramine) used for in cats?

allergies itching allergic skin disease feline eosinophilic granuloma complex

How to give Chlor-Trimeton to your cat

Typical cat dose is 1-2 mg per cat (one-quarter to one-half of a 4 mg tablet) given 2-3 times daily. The small tablet pieces can be hidden in a pill pocket, soft treat, or small amount of wet food. Chlorpheniramine is one of the better-tolerated antihistamines for cats compared to diphenhydramine (Benadryl), which is difficult to dose and poorly accepted by most cats. Use plain chlorpheniramine without added decongestants.

Available Forms

tablet

Give with Food?

Yes — give with food

Side effects of Chlor-Trimeton in cats

Common side effects

drowsiness
dry mouth
decreased appetite
mild GI upset

Serious side effects

  • urinary retention
  • severe sedation
  • paradoxical excitation
  • seizures (overdose)

When to call the vet

Call your vet immediately if your cat shows any of these signs:

  • Difficulty urinating or no urine output (urinary retention)
  • Extreme sedation or inability to rouse
  • Agitation or hyperactivity (paradoxical reaction)
  • Seizures or tremors
  • No improvement in allergy symptoms after 2 weeks

Related Medications for Cats

Antihistamine

Benadryl

Diphenhydramine

For allergies

View dosage chart
Antihistamine (H1 Receptor Antagonist)

Atarax

Hydroxyzine

For Allergic dermatitis and itching

View dosage chart
First-Generation Cephalosporin Antibiotic

Keflex

Cephalexin

For Skin and soft tissue infections

View dosage chart
Second-Generation Antihistamine (H1 Receptor Antagonist)

Claritin

Loratadine

For Allergic dermatitis

View dosage chart

Sources & References

The dosage information on this page is compiled from the following veterinary and pharmaceutical references:

  • Plumb's Veterinary Drug Handbook — the standard veterinary pharmacology reference used by veterinarians worldwide.
  • Merck Veterinary Manual — a trusted, peer-reviewed resource for veterinary professionals and pet owners.
  • DailyMed (FDA Drug Labels) — official FDA-approved drug labeling and prescribing information for Chlorpheniramine.

Frequently Asked Questions

Is chlorpheniramine better than Benadryl for cats?
Many veterinarians prefer chlorpheniramine over diphenhydramine (Benadryl) for cats because it is better tolerated, easier to dose (smaller tablet), and has fewer side effects in felines. Benadryl has a very bitter taste that causes drooling and foaming in cats, making administration difficult. Chlorpheniramine is generally considered one of the best antihistamine choices for cats.
How much chlorpheniramine can I give my cat?
The typical dose is 1-2 mg per cat (not per kilogram), which is one-quarter to one-half of a 4 mg tablet, given every 8-12 hours. This is a flat dose rather than weight-based because the therapeutic range is narrow and most cats fall within a similar size range. Always consult your vet before starting.
Do antihistamines really work for cat allergies?
Antihistamines work for approximately 40-70% of cats with mild to moderate allergies. They are most effective when started early in an allergy flare. For cats that do not respond to antihistamines alone, they can be combined with other treatments like omega-3 fatty acids, steroids, or immunotherapy for better results.
Can I use the extended-release form of chlorpheniramine for my cat?
No, do not use extended-release or sustained-release formulations for cats. These are designed for humans and can release the drug too unpredictably in a cat's smaller GI tract. Use only the immediate-release 4 mg tablets, which can be safely split.
How long can a cat take chlorpheniramine?
Chlorpheniramine is safe for long-term use in cats for ongoing allergy management. Many cats take it seasonally or year-round with minimal side effects. Drowsiness usually diminishes after the first few days of use as the cat develops tolerance.

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