Antihistamines for Dogs and Cats
Information from the following link:
The following is a list of options for antihistamines that are known to be effective in dogs & cats. The name of the active ingredient is listed, with the name of a well known brand in parentheses. Also listed are approximate doses for different weights, and any precautions.
CAUTION: Do not purchase antihistamines that are combination products (multi-symptom, cold/flu medicines, decongestants, etc.), especially products that contain decongestants (often labeled with a D, as in “Zyrtec-D”). These products often contain a high level of stimulants that are toxic, even life-threatening, to animals. In addition, products containing acetaminophen (active ingredient in Tylenol) are deadly for cats.
ANTIHISTAMINES AVAILABLE “OVER-THE-COUNTER”
1) Clemastine (formerly “Tavist”) – One of the more effective choices. Unfortunately, the over the counter form of Tavist containing the antihistamine “clemastine” has become unavailable. Available in: 1.34mg tablets, 2.68mg tablets, and 0.67mg/5ml liquid
Dosage:
DOG WEIGHT (in pounds)
5-15
15-25
25-50
50-70
Over 70
CATS:
Dose (tablet = 1.34mg tablet)
(liquid) 1-2cc or ¼ tablet twice daily
½ tablet twice daily
1 tablet twice daily
1 or 2 tablets twice daily
2 tablets twice daily
¼ to ½ tablet once daily (1.34mg tablets). Very effective in cats.
May cause: sedation, hyperactivity, or diarrhea (in cats only). Discuss with your veterinarian if your pet has: Prostatic hypertrophy (intact male dogs), urinary or GI obstruction, or severe heart disease. NOTE: Do not confuse this product with a similar product called “Tavist N.D,”which is a different type of antihistamine, and is less effective.
2) Diphenhydramine (“Benadryl”) - Available in: 12.5mg children’s tablets, 25mg capsules, and 12.5mg/5ml liquid (liquid not recommended if it contains alcohol)
Dosage:
DOG WEIGHT (in pounds)
5-10
10-15
15-35
35-50
50-80
Over 80
Dose (tablet = 12.5mg, capsule = 25mg)
½ children’s tablet twice daily
1 children’s tablet 2-3 times daily
1 capsule 2-3 times daily
1 or 2 capsules 2-3 times daily
2 or 3 capsules 2-3 times daily
3 or 4 capsules 2-3 times daily
CATS: Generally not recommended. Clemastine, Chlorpheniramine and Cyproheptadine are more effective.
May cause: sedation, hyperactivity, diarrhea (rare), vomiting (rare), or loss of appetite (rare). Discuss with your veterinarian if your pet has: glaucoma, GI or urinary obstruction, COPD (chronic lung disease), hyperthyroidism, seizure disorders, heart disease or high blood pressure. NOTE: Do not use Diphenhydramine products that contain any other active ingredients (like acetaminophen). These other products are potentially toxic to your pet (especially cats!).
3) Chlorpheniramine (“Chlor Trimeton”) - Available in: 2mg , 4mg , 8mg tablets, and 2mg/5ml liquid
Dosage:
DOG WEIGHT (in pounds)
5-10
10-20
20-40
40-60
Over 60
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
CATS: 1-4 mg per cat once or twice daily. Very effective in cats.
May cause: sedation or hyperactivity. Discuss with your veterinarian if your pet has: glaucoma, high blood pressure, GI or urinary obstruction, hyperthyroidism, heart disease. NOTE: Do not use chlorpheniramine products that contain any other active ingredients (like acetaminophen). These other products are potentially toxic to your pet (especially cats!).
4) Cetirazine (Zyrtec) - This may be the best antihistamine for eosinophillic inflammation (one of the primary cell types associated with allergies). It is a formerly prescription-only medication that is now available over the counter. Available in: 5mg and 10mg tablets
Dosage:
DOG WEIGHT (in pounds)
Less than 15
15-39
Over 40
CATS:
Dose:
One 5mg tablet once daily
5mg twice daily, or 10mg once daily
10mg twice daily
5mg ½ to 1 tablet 1 or 2 times daily.
May cause: Hyperexcitability in dogs. NOTE: Twice daily dosing is often needed.