Diphenhydramine, also known as Benadryl®, is an antihistamine which is commonly used in dogs. Benadryl® can be effective in managing numerous canine diseases and conditions but, like any other other-the-counter medication, it should be administered only with the advice and consultation of a veterinarian to ensure that the proper dosage is administered and that the medication is used appropriately.
Uses of Diphenhydramine (Benadryl®)
The most common usages of diphenhydramine take advantage of its antihistaminic properties. However, it also has additional pharmacological effects which make the drug an appropriate choice under other circumstances as well. The most common usages for diphenhydramine are:
- as a sedative
- to prevent and control motion sickness
- as an anti-emetic medication to control vomiting
- to treat the extrapyramidal side effects (such as tremors and anxiety) when using phenothiazine medications (such as chlorpromazine or acepromazine)
- as an aid in treating organophosphate or carbamate poisoning (to control tremors)
- to prevent secondary allergic reactions when doxyrubicin therapy is indicated
- to treat urticaria (a skin reaction often seen with canine allergic reactions) and angioedema (localized swelling similar to hives). Benadryl® may be used in conjunction with prednisone and/or epinephrine to treat these conditions.
- to treat canine atopy (a canine allergy that frequently causes skin disease)
- to reduce pruritis (itchiness)
- to treat reverse sneeze syndrome
- as a presurgical therapy prior to removing splenic mast cell tumors (to counter the histaminic effects of the mast cells
Potential Side Effects of Benadryl® or Diphenhydramine
As with any medication, there is potential for side effects when diphenhydramine (Benadryl®) is administered. Potential side effects include:
- central nervous system depression resulting in lethargy and/or sleepiness
- anticholinergic effects such as dry mouth and urinary retention
- gastrointestinal effects such as vomiting, diarrhea or lack of appetite
The sedative effects of this antihistamine may diminish with time. Working dogs may be adversely affected by diphenhydramine as a result of its sedative effect, however.
Contraindications to the Use of Diphendramine or Benadryl®
Benadryl® (diphenhydramine) is contraindicated under certain circumstances. Animals which are hypersensitive to diphenhydramine or other drugs in its class should not receive the medication. In addition, diphenhydramine has anticholinergic effects which can adversely affect other conditions, such as:
- angle closure glaucoma
- enlarged prostate (hypertrophy of the prostate gland)
- pyloroduodenal obstruction
- obstruction at the neck of the urinary bladder
- chronic obstructive pulmonary disease (COPD)
Diphenhydramine should be used cautiously in patients with these conditions. In addition, caution is indicated for patients suffering:
- cardiovascular disease (heart disease)
- hypertension (high blood pressure)
- hyperthyroidism
Diphenhydramine (Benadryl®) – A Useful Antihistamine for Dogs
Diphenhydramine, more commonly known as Benadryl®, has a number of uses in dogs and is a commonly prescribed canine medication. Though it is available over-the-counter and is a reasonable safe drug when used appropriately, it does have the potential for side effects and there are patients in which the use of diphenhydramine may be contraindicated. Therefore, this antihistamine should be used only under the supervision of a veterinarian and only at the prescribed dosage.
Source:
Donald C. Plumb; "Diphenhydramine HCl"; Plumb's Veterinary Drug Handbook, 5th ed.; 2005.
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