Diphenhydramine (brand name: Benadryl®, Vetadryl®, Banophen®, Genahist®, Diphenhist®, Unisom®, Sominex ®) is an antihistamine used in cats, dogs, ferrets and other small mammals, birds, horses, and cattle to treat allergic reactions, motion sickness, and vomiting. It is also used as a mild sedative, and is one of the therapies for mast cell tumors.
Its use in small and large animals to treat allergic reactions and other conditions is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their direction may be significantly different from those on the label.
Antagonists that selectively block specific histamine receptors have been developed. H1 antagonists block the actions of histamine responsible for increased capillary permeability and wheal and edema formation. However, because histamine is only one component of an incredibly complex inflammatory cascade, antihistamines have very weak anti-inflammatory activity. H1 antihistamines may be useful to treat immediate hypersensitivity reactions such as anaphylaxis by blocking bronchoconstriction and vasodilation. H1 antagonists may be less effective to treat allergic inflammatory diseases, such as atopy, primarily because mediators other than histamine play important roles in such conditions. H2 (now classified as inverse agonists of the H2 receptor, such as cimetidine and ranitidine) antagonists are routinely used to block the gastric secretory effects of histamine and have limited anti-inflammatory effects.
Features of Antihistamine Drugs For Cattle
Tripelennamine is an antihistamine. It competitively inhibits histamine binding at the H1 receptors on sensitive cells in the respiratory tract, intestines, blood vessels, and skin. When compared to other antihistamines, tripelennamine has minimal anticholinergic properties and is only moderately sedating
Tripelennamine Side Effects
- Sedation, CNS depression, and decreased coordination are the most-common side effects with any antihistamine use. Less-common side effects include excitement, fine tremors, whole body tremors, and seizures. Gastrointestinal side-effects such as colic or loss of appetite are possible.
- Antihistamines may thicken mucous in the respiratory tract. Extra caution should be used in horses with respiratory problems due to excess mucous.
- High doses of antihistamines have been shown to cause birth defects in laboratory animals. It is not known if tripelennamine is excreted in milk. It should be used in pregnant or lactating animals only if the benefits outweigh the risks.
- Tripelennamine should not be administered intravenously in the horse due to potential CNS stimulation.
- Individual animals may react differently to antihistamines. Very young animals and very old animals may be more sensitive to the sedating side-effects of antihistamines. When using antihistamines in these populations, they should be used at the lowest possible dose.
- Tripelennamine has some abuse potential for human drug abusers. One should be aware of unusual requests for this drug.
- Antihistamines should be discontinued prior to skin testing.
For intramuscular and intravenous use.
Cattle, horses, sheep and swine: Administer 1 mL per 45 kg of body weight.
Dogs and cats: Administer 0.5 mL per 10 kg of body weight.
When used intramuscularly, doses may be repeated every 2 hours if necessary.
Prices of Antihistamine Drugs For Cattle
$66.90 – $118.99