Anaphylaxis in dogs: initial treatment with adrenaline
4-year-old Labrador that, about 10 minutes after being stung by a wasp in the garden, has vomiting, diarrhoea, pale mucous membranes, tachycardia, weak femoral pulses and a systolic pressure of 70 mmHg.
What is the most appropriate initial treatment?
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A. Intravenous dexamethasone and diphenhydramine, then observe the response
This is the most common mistake. Antihistamines and corticosteroids are adjuncts: they act slowly, do not reverse vasodilation or collapse and must not delay adrenaline.
B. Intramuscular adrenaline (0.01 mg/kg), oxygen and crystalloid boluses, with venous access
Correct. Adrenaline is the only drug that simultaneously reverses vasodilation, increased permeability and mediator release. Fluids are given for the relative hypovolaemia; if there is no response, it is repeated or switched to an intravenous infusion.
C. Dopamine constant rate infusion as the first-line vasopressor
A vasopressor may be needed in refractory anaphylaxis, but the first line is adrenaline, which also stabilises mast cells. Dopamine does not replace adrenaline.
D. Famotidine and maropitant to control the gastrointestinal signs
The vomiting and diarrhoea are a consequence of anaphylactic shock (in dogs the liver and gut are the target organs), not a primary gastrointestinal problem. Treating them does not correct the hypotension.
lightbulb Key takeaway
In dogs anaphylaxis mainly affects the liver and gut (portal venous congestion): vomiting, diarrhoea, sometimes haemorrhagic, and raised ALT; ultrasound may show gallbladder wall oedema. In cats respiratory signs predominate. With collapse after a sting or a drug, give adrenaline first and keep the patient hospitalised for a few hours because of possible biphasic reactions.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.