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Benadryl for Pets Dosage & General Information

Benadryl®

Updated on September 10, 2024

Antihistamine used primarily in veterinary medicine for treating the symptoms associated with allergic disease and allergic reactions; variably effective. Use in veterinary medicine is extra label. 

Benadryl®

Summary

Used For: Allergies, acute allergic reactions, motion sickness, mild sedation, some anti-nausea effects

Brands: Benadryl®

Species: Dogs, cats, ferrets, guinea pigs, rabbits, birds (Psitticines), horses, cattle

Other names: iphenhydramine, Allermax, Banophen, Compoz Nighttime sleep aid and many others

Drug type: Antihistamine

Prescription required: No

Pregnancy and lactation: Safe if not administered when the animal is near term

Side effects: Lethargy, sleepiness, dry mouth, urine retention, mild GI signs possible

General description

Diphenhydramine is the generic name for an antihistamine that has many uses in veterinary medicine. This drug is typically given as an injection to animals that are experiencing a reaction to vaccinations or blood transfusion, or other causes of anaphylaxis. The human drug Benadryl® is available over-the-counter in most pharmacies, and does have some efficacy for treating mild allergic disease in veterinary patients, however efficacy is often highly variable from patient to patient, and the liquid form of the medication is very difficult to administer to veterinary patients due to the taste. It is strongly recommended that any medication be used in consultation with your veterinarian.

Uses

Reducing itchiness associated with allergic skin disease, treating severe allergic reactions associated with blood product transfusions or vaccine reactions, pretreatment before vaccination in known reactors

How it works

Diphenhydramine prevents the binding of compounds called histamines to the body’s histamine receptors. Histamines are produced in the body and are released during periods of acute and chronic inflammation.

Dosage

Benadryl use in pets is extra-label. Please consult your veterinarian before you give Benadryl to your pet. **Dogs:** For allergies: 2 – 4 milligrams per kilogram of body weight by mouth every 8 – 12 hours; for allergic reactions or anaphylaxis: 0.5 – 2 milligrams per kilogram of body weight subcutaneously, intramuscularly, or intravenously (extra-label); for prevention of motion-sickness or for reduction of nausea: 2- 4 milligrams per kilogram of body weight by mouth or intramuscularly every 8 hours **Cats:** For allergies: 2 – 4 milligrams per kilogram of body weight by mouth every 8 – 12 hours; for allergic reactions or anaphylaxis: 0.5 – 2 milligrams per kilogram of body weight subcutaneously, intramuscularly, or intravenously (extra-label) **Ferrets:** To prevent vaccine reactions: 2 milligrams per kilogram of body weight by mouth, intravenously, or intramuscularly 10 minutes prior to vaccination; to prevent reactions to the chemotherapeutic drug doxorubicin: 5 milligrams intramuscularly **Guinea pigs:** 2 to 5 milligrams per kilogram of body weight by mouth **Rabbits:** 1 – 2 milligrams per kilogram of body weight by mouth every 12 hours **Birds:** To help treat itchiness caused by feather picking in parrots: 2 milligrams per kilogram of body weight by mouth every 12 hours **Cattle:** To help treat anaphylaxis: 0.5 – 1 milligram per kilogram of body weight intramuscularly or intravenously; to help treat aseptic laminitis: 55 – 110 milligrams per 100 kilograms of body weight intravenously or intramuscularly

Forms

Diphenhydramine HCl capsules and tablets in 12.5 milligram, 25 milligram, and 50 milligram sizes; Diphenhydramine oral liquid in 12.5 milligrams per 5 milliliters and 25 milligrams per 5 milliliters strengths; Diphenhydramine solution for injection, 50 milligrams per milliliter

Storage information & handling

Store at room temperature, do not freeze.

What results can I expect?

Reducing in itchiness and redness of skin in the case of allergic disease. For severe allergic reactions and anaphylaxis, produces reduction of swelling and resolution of other signs, especially when used in conjunction with corticosteroids. Typically produces drowsiness, although animals become refractory to this effect over time.

Missed Dosage

If a dose is missed, continue with the next dosage at the scheduled time.

Overdose / acute toxicity

Overdose is uncommon but can produce excitement, seizures, depression (lethargy to coma), dryness of the mouth, respiratory depression and death.

Side effects

* Lethargy * Sleepiness * Dryness of the mouth * Retention of urine * GI effects (vomiting, diarrhea, decreased to absent appetite)

Contraindications

* Previous sensitivity * Angle closure glaucoma * Enlarged prostate * Obstruction of the pylorus or bladder neck * COPD * Hyperthyroidism * Cardiac Disease * High blood pressure

Drug interactions

The actions of some drugs in the anticholinergic class (i.e. atropine) may be potentiated when given with Benadryl®. Increased sedation may occur with drugs that depress the central nervous system.

Precaution

In most healthy animals Benadryl® is a safe drug to use, however discuss any potential contraindications your pet may have with your veterinarian before using.

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Disclaimer

The information contained on this page is for educational purposes only. This medication should only be given under the advice of a veterinarian who has examined your pet under the laws applicable to your state of residence.