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PetDosageChart

First-generation antihistamine · For Dogs

How much Chlor-Trimeton (Chlorpheniramine) can I give my dog?

Standard Chlor-Trimeton dose for dogs is 0.35 mg per kg (0.16 mg per lb), given Every 8-12 hours. Use the calculator below for your dog's exact weight, or jump to the weight-by-weight chart.

Onset
30-60 minutes
Duration
8-12 hours
Class
First-generation antihistamine

Calculator estimate from Plumb’s Veterinary Drug Handbook. Not yet vet-reviewed — see our methodology .

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. Sourced from Plumb's Veterinary Drug Handbook and the Merck Veterinary Manual.

Dosage Calculator · 01

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By Weight

Chlor-Trimeton dose by dog weight

Pick your dog's weight to jump to a dedicated page with the dose, frequency, safety notes, and FAQ for that size.

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Dosage Chart · 02

Chlor-Trimeton dosage for dogs by weight

Scroll sideways to see full table

Weight Low Dose Standard Max Safe Frequency
5 lbs (2.3 kg) 0.5mg 1mg 1mg Every 8-12 hours
10 lbs (4.5 kg) 1mg 1.5mg 2.5mg Every 8-12 hours
15 lbs (6.8 kg) 1.5mg 2.5mg 3.5mg (4mg tablet) Every 8-12 hours
20 lbs (9.1 kg) 2mg 3mg (4mg tablet) 4.5mg (4mg tablet) Every 8-12 hours
25 lbs (11.3 kg) 2.5mg 4mg (4mg tablet) 5.5mg Every 8-12 hours
30 lbs (13.6 kg) 2.5mg 5mg 7mg (2 × 4mg) Every 8-12 hours
40 lbs (18.1 kg) 3.5mg (4mg tablet) 6.5mg 9mg Every 8-12 hours
50 lbs (22.7 kg) 4.5mg (4mg tablet) 8mg (2 × 4mg) 11.5mg (3 × 4mg) Every 8-12 hours
60 lbs (27.2 kg) 5.5mg 9.5mg 13.5mg Every 8-12 hours
70 lbs (31.7 kg) 6.5mg 11mg (3 × 4mg) 16mg (4 × 4mg) Every 8-12 hours
80 lbs (36.3 kg) 7.5mg (2 × 4mg) 12.5mg (3 × 4mg) 18mg Every 8-12 hours
90 lbs (40.8 kg) 8mg (2 × 4mg) 14.5mg 20.5mg (5 × 4mg) Every 8-12 hours
100 lbs (45.4 kg) 9mg 16mg (4 × 4mg) 22.5mg Every 8-12 hours
120 lbs (54.4 kg) 11mg (3 × 4mg) 19mg (5 × 4mg) 27mg (7 × 4mg) Every 8-12 hours
150 lbs (68 kg) 13.5mg 24mg (6 × 4mg) 34mg Every 8-12 hours

Common Uses · 03

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

Allergies Itching Allergic reactions Hives Insect bite reactions

Administration · 04

How to give Chlor-Trimeton to your dog

Give chlorpheniramine tablets by mouth with food to reduce stomach upset. The small 4 mg tablets can be given whole or hidden in a soft treat or pill pocket. If using syrup, measure the dose carefully with a syringe. Avoid any product containing decongestants (pseudoephedrine or phenylephrine). Maintain a consistent dosing schedule every 8-12 hours for best allergy control.

Available Forms

Tablet, Syrup

Give with Food?

Yes — give with food

Side Effects · 05

Side effects of Chlor-Trimeton in dogs

Common side effects

Drowsiness
Dry mouth
Sedation
Decreased appetite

Serious side effects — call your vet

  • Urinary retention
  • Severe sedation
  • Rapid heart rate
  • Seizures at high doses

Emergency · 06

When to call the vet

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

  • Excessive sedation or inability to wake your dog
  • Difficulty urinating or no urine output
  • Rapid or irregular heartbeat
  • Tremors or seizure activity
  • Allergic reaction to the medication (facial swelling, hives, difficulty breathing)

For Cats

Looking for Chlor-Trimeton dosage for cats?

View the Chlor-Trimeton dosage chart and calculator for cats.

Related · 08

Related medications for dogs

Sources · 09

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.

Read more about our methodology and how we calculate dosages.

Transparency · 11

How this page was made

Sourced from Plumb's Veterinary Drug Handbook, the reference used in US vet schools. Every dose, frequency, and tablet count on this page is generated from that data, then checked against the published references below.

Sources cited
  • Plumb's Veterinary Drug Handbook
  • Merck Veterinary Manual
Calculator formula
Doses scale linearly from a standard basis of 0.35 mg per kg (0.16 mg per lb) of body weight, given Every 8-12 hours. The calculator multiplies that basis by your dog's weight and rounds to the closest available tablet size.
Last-reviewed status
Automated from Plumb’s, not yet vet-reviewed.

More on our methodology and editorial process — how we source, calculate, and review dogs dosage data.

Frequently Asked · 07

Questions about this medication

How does chlorpheniramine compare to diphenhydramine (Benadryl) for dogs?
Chlorpheniramine is generally less sedating than diphenhydramine while still providing effective antihistamine action. It can be a good alternative for dogs that become too drowsy on Benadryl, though individual responses vary between dogs.
Can I use the human version of chlorpheniramine for my dog?
Plain chlorpheniramine tablets (4 mg) can be used, but you must avoid any formulations containing decongestants like pseudoephedrine or phenylephrine, as these are dangerous for dogs. Always check the ingredient list and consult your vet.
How long can my dog take chlorpheniramine?
Chlorpheniramine can be used long-term for chronic allergies under veterinary supervision. Unlike steroids, antihistamines have fewer long-term side effects. However, some dogs may develop tolerance over time, requiring a switch to a different antihistamine.
Will chlorpheniramine make my dog sleepy?
Drowsiness is the most common side effect, especially during the first few days of use. Most dogs develop some tolerance to the sedation over time. If excessive drowsiness persists, consult your vet about adjusting the dose.
Can chlorpheniramine be combined with other allergy treatments?
Yes, chlorpheniramine is often used alongside other treatments such as omega-3 fatty acids, medicated shampoos, or even other allergy medications under veterinary guidance. Combining therapies can improve allergy control.

Safety · 10

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