Hashish Poisoning in Dogs

If you suspect your dog has consumed hashish, it is vital that you contact your veterinarian immediately. Although it is rare for a pet to consume a fatal dose, supportive care is needed as well as close monitoring by your veterinarian. Clinical signs that may indicate hashish poisoning include depression, hypersalivation and vomiting, or in severe cases, elevated heart and respiratory rates and seizures.

Hashish is the resin extracted from the plant Cannabis sativa. Hundreds of cannabinoids are present in the plant with tetrahydrocannabinol (THC) being considered the main psychoactive agent. THC has many effects and is known to enhance and stimulate the release of norepinephrine, dopamine, and serotonin. The accidental ingestion of hashish in dogs is becoming more common, linked to the increased availability of medical grade THC.

The onset of symptoms from ingestion is often 30-60 minutes. The clinical signs can vary but your dog may display the following signs:

• Depression
• Hypersalivation 
• Dilated pupils
• Hypermetria
• Stupor
• Increased appetite
• Vomiting
• Urinary incontinence
• Tremors
• Hypothermia
• Excitement 

Higher dosages may additionally cause agitation, increased heart and respiration rate, hyperexcitability, and seizures.

Types 

There are two main forms of cannabis sourced from the plant Cannabis sativa:

• Marijuana, which refers to the dried, tobacco like form of the plant; exposure from this source can be from secondhand smoke inhalation or consumption of the dried form
• Hashish, the resin extracted from the flowering plant which is often a much more concentrated source of THC; medical grade THC butter can be found in baked items which have been known to be consumed by pets

Following the consumption of hashish your dog will begin to show clinical symptoms within 30-60 minutes. Highly lipid soluble THC is distributed in fat, liver, brain, and renal tissue after absorption. Although not all the neuro-pharmacologic effects are understood, it is believed that THC acts on two specific cannabinoid receptors CB1 (which is responsible for the central nervous system) and CB2 (peripheral tissues). 

Fifteen percent of THC is excreted through the urine, the rest is passed through the gastrointestinal system and excreted through stools. During the excretion process, enzymes of the intestines can cause the drug to be reabsorbed into the intestinal mucosa several times, allowing it to re-enter the bloodstream. This process, named the enterohepatic cycle, causes the body to be reexposed to the drug and is responsible for its long half-life.

There are tests utilized for THC detection, however, these can often take several days to provide results and as such are not useful from a treatment standpoint. These tests include gas chromatography and mass spectrometry. 

Human drug screening tests can also be used to test your dog’s urine but are considered unreliable. False positives often occur when testing too soon after consumption, and false negatives can occur due to the large number of metabolites in canine urine. 

The diagnosis of hashish poisoning will often be made by your veterinarian from the clinical history and presenting symptoms of your pet. To make a differential diagnosis your veterinarian will need to rule out the following similarly presenting conditions:

• Infections such as meningitis 
• Heat stroke
• Hypoglycemia
• Trauma
• Narcolepsy
• Hydrocephalus
• Lysosomal storage disease
• Other poisonings such as ethylene glycol, heavy metals, other human pharmaceuticals with central nervous system stimulatory effects, and drugs with central nervous system depressant effects

Supportive care

As no antidote currently exists to reverse the effects of THC the treatment is mainly supportive. Your veterinarian will closely monitor vital signs including temperature, heart rate and rhythm and respiration. If your pet is unconscious, he will be monitored for aspiration pneumonia. In the case of hypothermia or prolonged vomiting, fluid therapy may be given as treatment. Your dog will also be provided with warm bedding and heating as needed.

Medication

If your dog is displaying no symptoms and has consumed the hashish within the last hour, your dog may be induced to vomit. This may not be effective as THC can often work as an antiemetic. Your veterinarian may give activated charcoal as an absorbent. There is evidence to suggest that the activated charcoal can reduce the half life of the THC by interrupting the enterohepatic recirculation, resulting in a faster recovery. If your pet is severely agitated the veterinarian may give a benzodiazepine sedative.

The prognosis following hashish poisoning is very good. Hashish has a high safety margin with toxic doses being over 3mg/kg so it is very rare for a fatal dose to be ingested. Due to the mode of metabolism, recovery may take 24-72 hours. Your dog will be watched closely during this time and will be expected to make a full recovery.