I am here to study the various claims regarding Cannabis use in dogs and cats.

When Cannabis first started to become legal for medicinal use in various countries, there was a flood of articles proclaiming it as the new wonder drug. My eye-rolly muscles automatically activate when this happens. (I am a natural sceptic.)

Imagine my surprise when I did start to properly look into the research.

But firstly, what I want to do here is:

1. look into all of the claims that are commonly made and check the research behind them
2. look into the feasibility of using the mostly human research for dogs and cats
3. define precisely exactly which cannabis you should use

Starting with number 2.

Humans to Pets?

Cannabis for dogs and cats? Research for a potential new cure for a disease is often done in vitro at first – this means in the test tube.  This is a good place to start, but often, a substance that kills a virus or cancer cells in a test tube will never be a cure. There are other factors – is it toxic? Can it reach the point where it is needed? Does it do harm on the way there? Does it work in the cell environment, etc.

If however, the initial in vitro research looks promising, animal trials are usually the next step. Usually mice or rats are used. Sometimes dogs and cats.

Thereafter, proper human clinical trials are done. The best kind of clinical trial is called a Randomised Double Blind Placebo Controlled Study (RDBPC). This means that you are randomly divided into two groups – the control group and the test group. No-one knows who is in which group – neither the patients nor the doctors nor anyone else. The control group are given an inactive drug that is identical in every respect to the active drug, which is given to the test group. Effects are recorded for each patient.

The Cannabis research is a mixture of all three of these. I tend to ignore the in vitro research – it is too early and too dangerous to take this seriously. For our purposes, dog/cat trials are obviously very informative as to how the substance works in our favourite species. But the RDBPC trial is the most useful and the most conclusive.

Human and dog/cat bodies are similar in most important aspects, so you can tentatively use a natural substance that has been thoroughly tested in humans for dogs and cats. But it is important to:

1. inform your vet
2. thoroughly research any possible interactions with other medications

   

3. thoroughly check the toxic lists for dogs and cats
4. start slowly and carefully and accurately – be very careful not to overdose
5. work out a dose according to body weight: dose for dog or cat = human dose x (bodyweight of your dog or cat /bodyweight average human)
6. Inform your vet (yes, it is important enough to write twice!)

Cannabis falls into the category of a very new substance – not because it is actually anything new, but because we are using it for new species, for new illnesses and we are purifying it in new ways (more about this later). So, what I am trying to say here is, proceed with care.

Which Cannabis?

The Cannabis species we are talking about is Cannabis sativa – aka dagga, marijuana or grass. But there are now three varieties – Hemp, CBD oil and the good old Cannabis that has been illegally consumed for decades.

All three of these contain molecules called cannabinoids. The two main cannabinoids are:

1. Cannabidiol (CBD)
2. Tetrahydrocannabinol (THC)

THC is the psychoactive cannabinoid that makes you high. Obviously we want to minimise this effect when we are feeding our animals.

CBD is the medicinal cannabinoid, so a higher percentage of this is desirable when treating animals. It has no psychoactive effect.

Hemp, CBD oil and the Cannabis commonly smoked all come from different strains of Cannabis sativa. Also, different parts of the plant are used.

But the main differences between the effects of these three varieties is the relative amounts of the two main cannabinoids. I’ve made a little table for you:

Cannabis Variety → Cannabinoids ↓	Hemp oil	Psychoactive Cannabis	CBD oil
THC	< 0.3%	5 – 29%	1 – 5%
CBD	Low	Low	18 – 20%

So hemp, which is used for all sorts of things including biofuel, clothing and health foods, has low medicinal value and low psychoactivity. It is completely legal.

CBD oil has the best medicinal properties.

Bear in mind, I know nothing about the legalities of these products in your area. Nor do I know where to find them or the method of manufacturing them.

 

Claims and Research

According to a LOT of people on the internet ;-), Cannabis can cure:

• Inflammation
• Cancer
• Low appetite/ nausea
• Anxiety
• Diabetes
• Parkinsons
• Alzheimers
• Cerebral ischemia (stroke)
• Epilepsy

Let’s take these one by one and look at the actual research.

Inflammation

Scientists have found that CBD blocks the progression of arthritis in mice. It seems to use two methods – anti-inflammatory and immune suppression. The optimal oral dose in this study was 25 mg per kg bodyweight (BW) per day. (Bear in mind though, immune suppression might be an unwanted side effect…)^3,4

Cancer

When CDB was first investigated, no cancer fighting ability was found for this molecule. But, looking backward, this was probably due to the very high dose used – 200 mg per kg BW.⁴ Then, in vitro studies started to show activity against human Gliomas (brain tumours)⁵, breast cancer^7,8 and Leukaemia⁶. It seemed that CBD was inducing apoptosis in the cancer cells. (Apoptosis is when normal cells die because they are programmed to do so. Cancer cells usually lack this ability.) But then, just to complicate matters, THC was found to either increase or decrease the growth of some lung and breast cancer cells, depending on their pathology (its complicated…).^9,10

Low appetite and nausea

Most of the cancer research I found was around decreasing nausea  and subsequently increasing appetite in chemotherapy patients. If cancer patients are eating well, this can make an enormous difference. Studies in mice and rats have confirmed that both THC and CBD decrease nausea and vomiting.^{11, 12, 13}

Anxiety

A study in 1974 compared the effects on humans of THC only vs THC and CBD. It found that when CBD was present, anxiety was less.¹⁴ Another study (double blind) compared humans doing that most stressful task, public speaking. Placebo, two conventional anti-anxiety drugs and CBD were trialed. CBD, as well as the two drugs, had definite anti-anxiety effects.¹⁵ This was confirmed in two other trials using blood flow and MRI.^{16, 17} Dosages in these studies ranged from 1 to 300 mg/kg BW.

Diabetes

CBD’s potent anti-inflammatory action lead researchers to test it in other auto-immune diseases. Mechoulam tested non obese diabetic prone (NOD) mice before they got diabetes. 86% of the mice not receiving CBD got diabetes, compared to only 30% of those receiving CBD.¹⁸ (This is Type 1 diabetes.)

Parkinsons, Alzheimers

There is also good research to support CBD’s role in these two diseases, but I’m not going to go into detail because these diseases aren’t common in pets.

Cerebral ischemia/ stroke

Cerebral ischemia is where a blood clot blocks blood flow to the brain, resulting in tissue death and/or a stroke. Scientists artificially induced this situation in gerbils (I know, it’s horrible…) They then treated half of the gerbils with CBD. All neurons survived in the gerbils treated with CBD oil, unlike the placebo group.¹⁹ The optimal dose was 5 mg/kg BW.

Epilepsy

I love this story. A little girl, Charlotte, from Colorado, suffered from Epilepsy. Charlotte’s mom, when medical cannabis became legal, started to do research. She decided to give her daughter a strain of cannabis which was high in CBD and low in THC. This strain is now known as Charlotte’s Web. Charlotte’s seizures decreased from 50 per day to 2 to 3 per month.^{20, 22} This has since been confirmed in other studies.²¹

So, although it is early days, each of those claims I was so sceptical of, has been confirmed.

 

References

1. https://honestmarijuana.com/hemp-oil-vs-cbd-oil/
2. Zuardi, Antonio Waldo. (2008). Cannabidiol: from an inactive cannabinoid to a drug with wide spectrum of action. Revista Brasileira de Psiquiatria, 30(3), 271-280. https://dx.doi.org/10.1590/S1516-44462008000300015
3. Mechoulam RE, Parker LA, Gallily R. Cannabidiol: an overview of some pharmacological aspects. J Clin Pharmacol. 2002;42(11 Suppl):11S-19S.
4. Mechoulam R, Peters M, Murillo-Rodriguez E, Hanus LO. Cannabidiol–recent advances. Chem Biodivers. 2007;4(8):1678-92.
5. Massi P, Vaccani A, Ceruti S, Colombo A, Abbracchio MP, Parolaro D. Antitumor effects of cannabidiol, a nonpsychoactive cannabinoid, on human glioma cell lines. J Pharmacol Exp Ther. 2004;308(3): 838-45.
6. McKallip RJ, Jia W, Schlomer J, Warren JW, Nagarkatti PS, Nagarkatti M. Cannabidiol-induced apoptosis in human leukemia cells: a novel role of cannabidiol in the regulation of p22phox and Nox4 expression. Mol Pharmacol. 2006;70(3):897-908.
7. Ligresti A, Moriello AS, Starowicz K, Matias I, Pisanti S, De Petrocellis L, Laezza C, Portella G, Bifulco M, Di Marzo V. Antitumor activity of plant cannabinoids with emphasis on the effect of cannabidiol on human breast carcinoma. J Pharmacol Exp Ther. 2006;318(3):1375-87.
8. McAllister SD, Christian RT, Horowitz MP, Garcia A, Desprez PY. Cannabidiol as a novel inhibitor of Id-1 gene expression in aggressive breast cancer cells. Mol Cancer Ther. 2007;6(11):2921-7.
9. Preet A, Ganju RK, Groopman JE. D(9)-Tetrahydrocannabinol inhibits epithelial growth factorinduced lung cancer cell migration in vitro as well as its growth and metastasis in vivo. Oncogene. Epub
10. Preet A, Ganju RK, Groopman JE. D(9)-Tetrahydrocannabinol inhibits epithelial growth factorinduced lung cancer cell migration in vitro as well as its growth and metastasis in vivo. Oncogene. Epub
11. Grinspoon L, Bakalar JB. Marihuana, the forbidden medicine. New Haven, CT: Yale University Press; 1997.
12. Parker LA, Mechoulam R, Schlievert C. Cannabidiol, a non-psychoactive component of cannabis and its synthetic dimethylheptyl homolog suppress nausea in an experimental model with rats. Neuroreport. 2002;13(5):567-70.
13. Parker LA, Kwiatkowska M, Burton P, Mechoulam R. Effect of cannabinoids on lithium-induced vomiting in the Suncus murinus (house musk shrew). Psychopharmacology (Berl). 2004;171(2): 156-61.
14. Zuardi AW, Shirakawa I, Finkelfarb E, Karniol IG. Action of cannabidiol on the anxiety and other effects produced by delta 9-THC in normal subjects. Psychopharmacology (Berl). 1982;76(3):245-50.
15. Zuardi AW, Cosme RA, Graeff FG et al. Effects of ipsapirone and cannabidiol on human experimental anxiety. J Psychopharmacol. 1993;7:82-8.
16. Crippa JA, Zuardi AW, Garrido GE, Wichert-Ana L, Guarnieri R, Ferrari L, Azevedo-Marques PM, Hallak JE,McGuire PK, Filho Busatto G. Effects of cannabidiol (CBD) on regional cerebral blood flow. Neuropsychopharmacology. 2004;29(2):417-26.
17. Fusar-Poli P, Crippa JA, Bhattacharyya S, Borgwardt S, Allen P, Martin-Santos R, Seal M, Surguladze SA, O’Carrol C, Atakan Z, Zuardi AW, McGuire P. Distinct efeects of ∆9-tetrahydrocannabinol and cannabidiol on neural activation during emotional processing. Arch Gen Psychiatry. 2008. (In press).
18. Weiss L, Zeira M, Reich S, Har-Noy M, Mechoulam R, Slavin S, Gallily R. Cannabidiol lowers incidence of diabetes in non-obese diabetic mice. Autoimmunity. 2006;39(2):143-51
19. Braida D, Pegorini S, Arcidiacono MV, Consalez GG, Croci L, Sala M. Post-ischemic treatment with cannabidiol prevents electroencephalographic flattening, hyperlocomotion and neuronal injury in gerbils. Neurosci Lett. 2003;346(1-2):61-4.
20. https://www.scientificamerican.com/article/marijuana-treatment-reduces-severe-epileptic-seizures/
21. Devinsky, Orrin, et al. “Cannabidiol in patients with treatment-resistant epilepsy: an open-label interventional trial.” The Lancet Neurology 15.3 (2016): 270-278.
22. https://onlinelibrary.wiley.com/doi/abs/10.1111/epi.12610 cannabis for dogs and cats