Heroin is a dangerous illicit drug that should not be used in animals. It, along with other opiates and opioids, can cause severe toxicity when administered to pets.

Signs and symptoms of toxicity: depression and fatigue (dogs), excitation and aggressiveness (cats), involuntary muscle movements, seizures, increased production of saliva, vomiting, defecation (dogs), constipation (cats), changes in urination (dramatic increase or decrease), decreased heart rate, increased panting and dramatic changes in pupil size.

Toxic consumption:
An injection of 25 mg/kg is considered lethal in dogs. In cats, 20 mg/kg of an oral dose is considered lethal.

Dogs: Opioids and Opiates Lethal Consumption
X-Small
Yorkie, Chihuahua
Small
Pug, Boston Terrier, Poodle
Medium
Beagle, Scottish Terrier
Large
Boxer, Cocker Spaniel
X-Large
Retriever, German Shepherd
XX-Large
Great Dane, St. Bernard
1 – 10 lbs.
(0.45 – 4.6 kg)
11 – 25 lbs.
(5 – 11.4 kg)
26 – 40 lbs.
(11.8 – 18.2 kg)
41 – 70 lbs.
(18.6 – 31.8 kg)
71 – 90 lbs.
(32.3 – 40.9 kg)
91 – 110 lbs.
(41.4 – 50 kg)
dog1 dog2 dog3 dog4 dog7 dog6
Heroin (SQ) > 11 mg > 124 mg > 294 mg > 464 mg > 807 mg > 1034 mg

 

Cats: Opioids and Opiates Lethal Consumption
Most Cats

Large Cats
1 – 10 lbs.
(0.45 – 4.6 kg)
11 – 25 lbs.
(5 – 11.4 kg)
cat1 fat cat
Heroin (oral) > 8 mg > 99 mg

 
References:
– Malouin A, Boiler M. Sedatives, muscle relaxants, and opiods toxicity. In: Silverstein DC, Hopper K, eds. Small Animal Critical Care Medicine. St. Louis: Elsevier, 2009; pp.350-356.
– Osweiler, G, et al. (2011). Blackwell’s five-minute veterinary consult clinical companion. Small Animal Toxicology. [Kindle version]. Retrieved from Amazon.com
– image: http://www.emcdda.europa.eu/imglib/Drugprofiles/350Heroin.jpg