Question 1

What is Diphenhydramine used for?

Accepted Answer

Diphenhydramine is indicated for: Acute allergic reaction, Allergic reactions, mild sedation, motion sickness, pre-chemotherapy, sedation.

Question 2

What routes can Diphenhydramine be administered by?

Accepted Answer

Available routes: PO, IM, IV.

Question 3

Which species have cited Diphenhydramine dosing data?

Accepted Answer

Diphenhydramine dosing in the ExoticRx formulary covers 2 species: Cat (Domestic), Dog (Domestic).

Question 4

Is Diphenhydramine a controlled substance?

Accepted Answer

Diphenhydramine is not federally scheduled as a controlled substance, but is veterinary prescription only in most jurisdictions.

Question 5

What are the warnings or contraindications for Diphenhydramine?

Accepted Answer

Sedation common (first-generation). Anticholinergic effects (dry mouth, urinary retention). Ensure product does not contain xylitol or pseudoephedrine. Dogs and cats. Less effective than second-gen antihistamines for pruritus.

Question 6

What are the side effects of Diphenhydramine?

Accepted Answer

Sedation common (first-generation). Anticholinergic effects (dry mouth, urinary retention). Ensure product does not contain xylitol or pseudoephedrine. Dogs and cats. Less effective than second-gen antihistamines for pruritus.

Question 7

How does Diphenhydramine work?

Accepted Answer

Competitive antagonist at histamine H1 receptors. Also has anticholinergic, anti-motion sickness, and mild sedative properties.

Species	Route	Dose	Frequency	Evidence	Source
Dog (Domestic)	IM	2–4 mg/kg	Single dose or q8h	Moderate	Plumb's Veterinary Drug Handbook, 9th Ed
Dog (Domestic)	PO	2–4 mg/kg	q8-12h	Moderate	Plumb's Veterinary Drug Handbook, 9th Ed

Diphenhydramine

Drug Class

Routes

Indications

Mechanism of Action

Side effects & warnings

Species with Diphenhydramine dosing data (3 dose rules)

Evidence levels across 3 dose rules

Backed by a published primary source

Sample dosing (2 of 3 cited rules)

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