Robert Randall was the first U.S. citizen to legally access cannabis based on medical necessity since the start of prohibition. He and his wife, Alice O’Leary Randall, sued the government because THC-rich cannabis was the only effective medicine for his glaucoma. More recently, the American Academy of Ophthamology has taken a stance against cannabis for glaucoma, citing the high dose of THC needed and the efficacy of new medications. But whether or not cannabis is used for glaucoma, doctors should be taking note of the endocannabinoid system in many parts of the eye. Scientists led by Alex Straiker at the University of Indiana — a powerhouse of cannabinoid research — have recently described the role of cannabinoids in healing wounds on the cornea, the protective film on the eye’s surface. They looked at one of the less established cannabinoid receptors, called GPR18, which mediates some of cannabinoids’ effect on blood pressure and cardiovascular health. GPR18 is an orphan receptor, meaning its natural activator is not known. The lead candidate is a compound called NAGly (N-arachidonoylglycine). NAGly is thought to be synthesized from the breakdown products of anandamide. Using a mouse model, the researchers show that activating GPR18 with NAGly speeds up the rate at which cells proliferate to close a wound like a scratch on the cornea. Blocking this receptor has the opposite effect; it slows eye’s ability to repair.
Preventing Pain with Orphan Receptors
Phytocannabinoids consistently confuse scientists because of the multiplicity of their actions. CBD, for example, binds to a handful of neurotransmitter receptors, as well as hormone receptors, ion channels, and a variety of enzymes. Receptors without a known endogenous ligand are called “orphan” receptors. GPR18 is involved in ocular-pressure (and hence glaucoma treatment) as well as cardiovascular function. The receptor named GPR55 is relevant in cancer pathology, and works with the CB2 receptor to regulate immune migration. In a review published in Frontiers in Pharmacology, Mexican and Texan scientists describe the modern approach to pain treatment and propose a future role of cannabinoids, GPR18, and GPR55 in preventing pain.
Natural High: CBD Augments Anandamide
It has been known for some time that CBD acutely increases anandamide levels. The enhancement of cannabinoid tone is presumably responsible for some of CBD’s medical properties, from anti-psychotic actions to anti-inflammatory effects. Initial reports suggested that CBD inhibits FAAH, the enzyme tasked with breaking down anandamide. But subsequent studies didn’t back this up. In 2009, scientists at Stony Brook identified fatty-acid binding proteins (FABPs) that shuttle endocannabinoids around the cell. The Stony Brook group subsequently discovered that CBD and THC can act as endocannabinoid reuptake inhibitors by displacing anandamide from FABP transport molecules, which prolongs the activity of endocannabinoids at the surface of neurons and other cells. Now, a paper from Emma Leishman, Heather Bradwshaw, and other researchers at Indiana University has proposed yet another mechanism by which CBD elevates anandamide: promoting anandamide synthesis. At the risk of sounding overly technical, here’s how it works: Enzymes going by the name phospholipase cut fats out of the cell membrane. Then phospholipase C (PLC) teams up with DAG lipase to produce 2-AG, while a similar enzyme called NAPE-PLD synthesizes anandamide. In cell cultures or the brains of mice, applying CBD increased anandamide levels (along with many closely related fatty acids). But in mice genetically engineered to lack the anandamide synthesizing enzyme NAPE-PLD, CBD had nearly no effect. (Very strangely, anandamide levels were the same in mice without NAPE-PLD, indicating that anandamide can be synthesized in other ways.) THC, meanwhile, tended to decrease the levels of anandamide and related lipids, although there were differences across the various experimental methods used. The authors also found that a mixture of THC and CBD changed the lipid profile of cells differently than either molecule alone. The 1:1 combination created “a mosaic of the individual drug results,” that was different from THC, CBD, or what would be expected from simply adding the two. This indicates a more complex interaction between the cannabinoids, which should not be surprising for anyone familiar with the entourage effect. The effects of CBD are clearly manifold — the modulation of lipids was not quite the same across the researchers’ different models, perhaps because of the other molecular targets of CBD. The mechanism by which CBD would affect NAPE-PLD is still unclear. Yet these results affirm a number of consistent trends. CBD alters the balance between inflammatory and anti-inflammatory lipids, as does THC, and the two phytocannabinoids combine in non-obvious ways. There is a tendency for phytocannabinoids to reduce inflammation and elevate endocannabinoid levels, but this depends on the specific cell, animal, or experiment in question.
CB1 and learning
If THC makes people forgetful while they’re high, one might reasonably expect that blocking the CB1 receptor that mediates the high will promote focus and the ability to learn. But is this true? There are several issues to consider when systemically blocking the CB1 receptor, such as the increased rates of suicidal thoughts. This is, without a doubt, an unacceptable side effect. However, it’s still useful for scientists to tease apart the roles of cannabinoids in learning. Researchers at Wake Forest University, working with Allyn Howlett (the head of the team who discovered the CB1 receptor in 1988) recently published one such study. They used a rat model of learning and compared the effect of a CB1 inhibitor (Rimonabant) given acutely to chronic administration or no drug at all. The blockade of CB1 increased the expression of genes that modulate synaptic plasticity. It would appear that this makes the brain more adaptable and able to learn. But not only did the drug-treated rats not learn better, tests showed they were worse after a week. This is not surprising when considering how “learning” was measured. The researchers’ test of learning required the rats to forget, and it is well established that blocking CB1 prevents animals from letting go of irrelevant memories. In particular, the trained rats that got Rimonabant tended to worsen over time (relative to controls). This could mean that they were simply learning at a slower rate, or that chronic inhibition of CB1 led to other changes in the brain. These maladaptive changes may have been the genetic markers of brain plasticity that the scientists had found; An adaptive brain doesn’t grow indefinitely, rather it finely tunes neural connections, sometimes cutting back what is not needed and forming more useful synapses with the newly freed bandwidth. Totally preventing CB1 activation with Rimonabant may have promoted the growth side of plasticity, but other studies shows that it also shuts down the brain’s ability to prune unhelpful connections. Cannabinoids tie significantly into human learning and memory, but harnessing this with blunt chemical tools seems unlikely.
Exercise for Depression
It’s increasingly recognized that the runner’s high, which used to be attributed to endorphins, is conferred partly by endocannabinoids in the brain. In response to the stress of exercise, the brain produces anandamide, “the bliss chemical” which provides that feeling of elation along with pain reduction and health benefits. A collaboration between researchers in Wisconsin and at Iowa State University has sought to understand this phenomenon in women suffering from depression. Exercise is known to have antidepressant properties and depression is associated with changes in our endocannabinoid system; could a blissful runner’s high help pull someone up from a depressive low? Women diagnosed with major depressive disorder were assigned to a moderate exercise routine involving only 30 minutes of cycling. This routine increased anandamide levels and decreased depressive feelings. Endocannabinoid levels are often diminished in people with depression, and restoring cannabinoid tone with exercise seems promising. Of course, exercise is an important contribution to health independent of its interaction with the endocannabinoid system. Oddly, the same elevation in endocannabinoid levels was not seen when the participants exercised for 30 minutes at whatever intensity they desired. OEA (an anandamide-like molecule involved in feeling satiated with food or alcohol) levels in the blood also increased with moderate exercise, but not with the preferred-intensity group. The blood-concentration of 2-AG actually decreased with exercise, but this may have been a spurious result, as previous studies have shown an increase of 2-AG levels after working out, and the statistical methodology in this article is prone to false results.
CBD and Organ Transplant
With CBD becoming more mainstream, doctors are on the lookout for how this powerful chemical affects human health. But a typical adult in the U.S. takes at least one pharmaceutical, and CBD’s interaction with other medications can be significant, especially given how easily one can overdose on common drugs. A new potential interaction has been highlighted by scientists at the University of Cincinnati, in Ohio. They report a woman using an extremely high dose of pure CBD for epilepsy — between 2-3 grams per day. She was also taking tacrolimus, a common immunosuppresive drug, to treat a kidney disorder. When combining these two treatments, tacrolimus levels in the blood rose by three-fold — dangerous result. Because the addition of CBD helped control the seizures, her doctors helped her adjust the dose of these two drugs. This is commonly what happens with drug-drug interactions — there is an important need to monitor drug levels, but the interaction can be managed without ill effect for many patients.
Tacrolimus is a mainstay medication for organ transplant, so this possible interaction could be important for patients who need an organ transplant. Moreover, there has been some research on the potential to use CBD in transplant patients. Both THC and CBD tend to tone down immune activity and they have recently been suggested for treating graft-versus host disease, a potentially deadly reaction to organ transplants. How relevant is a cannabinoid-drug interaction like this to the average person? It depends greatly on the dose of CBD. In this case, there are probably two proteins that CBD interferes with to increase drug exposure — it inhibits CYP3A4, an enzyme that breaks down more than half of all pharmaceuticals, and it can inhibit P-gp, a protein which pumps chemicals out of certain cells. But this woman was using multiple grams of CBD per day. If she got this from good quality cannabis flower (say, a flower that’s 20% CBD by weight), she would have to eat half an ounce each day.That’s not the normal dose that people take, even those using cannabis for epilepsy. When unpurified cannabis extracts are used, the common doses are 10-100 times lower. THC and other plant compounds appear responsible for this greater potency, and the consequent lesser risk of drug-drug interactions. In other words, THC seems to make CBD a safer more effective medicine.
Dosing Pure CBD
CBD is clearly a useful medicine in the treatment of some types of epilepsy, yet patients are faced with dilemmas when they must decide which product to use, how to incorporate it with other medications, and how to begin dosing. Isolate CBD products have the advantage of being standardized, although they suffer from numerous limitations. There is plentiful evidence that orally ingesting high doses of pure CBD reduces pediatric seizures. Kids are first given a single dose of 5 mg CBD per kg of body weight (written 5 mg/kg CBD) per day. Then the dose is cautiously raised by around 5-10 mg/kg each week and the administration is spread out across two or three doses a day. All the while, the patient’s doctor will be looking out for new side effects and changes in the metabolism of other drugs. Some patients find sufficient relief at 20 mg/kg CBD, whereas other take up to 50 mg/kg per day.
A recent article published in CNS Drugs reaffirms this general protocol. Patients in this study were given between 10-40 mg/kg CBD, split into two doses a day, for six days. A bidirectional drug-drug interaction was reported between CBD and clobazam (a benzodiazepine anti-epileptic drug), which has been seen previously. Patients using clobazam had about 2.5-3 fold higher exposure to the highest dose of CBD, and this 40 mg/kg dose of CBD also elevated clobazam levels. Consistent with other reports, CBD and clobazam can be used safely together, but the dose of both drugs should be lower than normal. One 16-year-old on the 40 mg/kg dose had temporarily abnormal liver function (measured by alanine aminotransferase levels), which resolved on its own. This dangerous side effect occurred in one other study of CBD, likely due to an interaction between cannabidiol and valproate. The authors here do not report whether this patient was using valproate as well. Unfortunately, there is a severe conflict of interest among the study’s authors. A single company provided the CBD solution, funded the study, and wrote the results: Insys.
Insys is best known for bribing doctors and illegally marketing fentanyl; it is one of the groups most responsible for the modern opioid epidemic. In early May, top Insys executives were criminally convicted for their role in tens of thousands of overdose deaths. But this lethal criminality somehow not a disqualifying factor in the pharmaceutical world: the DEA gave a green light to Insys for marketing a THC isolate at the start of 2018. They now have clinical trials investigating CBD for epilepsy and numerous drugs for treating opioid addiction, a sick irony.
THC Makes Oxycodone Safer
Many prohibitionist arguments are being flipped on their heads. CBD’s anti-anxiety effects have replaced much of the reefer madness mentality. Rather than causing lung cancer, marijuana appears to have anti-cancer activity, if anything. And in spite of the gateway theory, whereby casual cannabis use supposedly escalates to heroin, we find that cannabis helps to treat pain and reduce opiate use. An animal study out of the Scripps Research Institute reaffirms that THC generally reduces the addictiveness of opioids. In simple words, when animals (including humans) are given THC, they have less interest in seeking opioids, alcohol, and other drugs. They respond less intensely to cues or triggers that remind them of past addictions. Although everyone has a unique response to cannabinoids, this is the average effect.
The recent Scripps study looked specifically at self-administration, which is the gold standard animal model in addiction research. Not only were the rats uninterested in oxycodone after getting THC, but THC potentiated the painkilling effect. So while THC made oxycodone less addictive, it also made it a more effective pain treatment. Oxycodone is one of the opiates most responsible for modern opioid addiction.
Preclinical work is only a first step in medicine, and before we jump to conclusions let’s not overlook animal studies where THC potentiates opioids’ addictivness or cannabinoids interfere with the painkilling. But the beneficial effects are seen in human research. People using cannabis are much more likely to decrease or stop opioid use (different surveys suggest that between 30-60% of opioid-users are able to entirely switch to cannabis)
Throughout history, cannabis has been described as a treatment for hundreds of different conditions. If scientists find it hard to believe cannabis can do so much, they may chalk up the results as just a placebo. But the placebo effect is powerful. It accounts for roughly half of the efficacy of opioids and antidepressants. And, ironically, the placebo effect actually functions in part through the endocannabinoid system. The belief that an empty capsule will help an ailment causes your brain to release anandamide, which can kill pain, reduce headaches, and much more.
Not everyone gets the same benefit from placebos, and it tends to run in families, suggesting genetic mutations can alter placebo sensitivity. Researchers at the University of Maryland and the NIH recently highlighted the importance of endocannabinoid genes in the placebo effect. A variant of the FAAH enzyme, which breaks down anandamide, was associated with greater placebo response. The alternative version of this gene is associated with greater rates of addiction and a notably higher pain tolerance. Mutations in FAAH may also relate to obesity, thanks to other chemicals that FAAH regulates. The researchers looked at two other mutations – one in the mu opioid receptor and another in COMT, an enzyme that metabolizes serotonin, dopamine, and many illegal drugs. These mutations interacted with each other to modulate how well people would respond to a placebo.
“Into the Weeds”
A major benefit of legalization is regulation (at least in theory). Cannabis in a legal market can be held to safety standards such as the absence of dangerous pesticides. While autonomous community-enforced regulation can exist without government intervention, this does not happen at the global scale which the cannabis industry has reached today. So how well are governments doing with their pesticides regulations? Bay area journalist Nate Seltenrich recently dug into this issue.
Normally pesticide policy is regulated by the EPA. But the EPA is a federal agency and it has refused to offer guidance for pesticides on cannabis, so each state has reinvented the wheel while guessing at safe levels of pesticides. California and Oregon have compiled different lists of pesticides and their acceptable limits, while further north in Washington, no pesticide testing is required at all. Canada, meanwhile, has a zero-tolerance policy.
Uncertainty has arisen because of the tobacco lobby, which managed to avoid researching any implications of smoking pesticides: “EPA does not assess intermediate or long-term risks [of pesticides] to smokers because of the severity of health effects linked to use of tobacco products themselves”, according to the Government accountability office. So while testing for pesticides drives the cost of legal weed up, it’s hard to know it this even ensures safety.
And that is only considering human health — heavy, systematic use of pesticides has an enormous environmental cost. Seltenrich highlights a few pesticides allowed by California that should arguably be banned entirely: the “possible carcinogen” bifenthrin, and two neurotoxic organophosphates called diazenon and acephate. The latter is also considered a possible carcinogen and possible endocrine disruptor. The Golden State, which is currently considering labeling cannabis a developmental toxin, would do well to ensure that true developmental toxins are not sprayed on cannabis. In fact, the California Depatment of Pesticide regulations published an article on the dangers of pregnant mothers being exposed to organophosphates in cannabis. Unfortunately for consumers, smoked cannabis seems to carry pesticides into the body very well. A publication from chemist Jeffrey Raber, indicated that upwards of 60% of pesticides could be inhaled when smoking a pipe.
But the situation is not solved easily. California is an agricultural region and pesticides can drift from other farms onto cannabis; the extraction process concentrates most pesticides along with cannabinoids leading to failed test results on seemingly good products. Federal legalization would likely standardize U.S. regulations — we hope that states, as laboratories of democracy, will have found a reasonable solution by that time.
Project CBD has been engaged with California’s pesticide regulations in the past. The current issue we are most concerned with is the allowance of neonicotinoids on cannabis (there are three, imidacloprid, thiamethoxam, and acetamiprid). All three of these have been banned in France, and two are banned in mainland Europe because of their toxicity to pollinators and their ability to contaminate groundwater. Imidacloprid is one of the most common pesticides used worldwide. It’s been found at high levels in CA water supplies, and the safety data — on which limits have been based — used a species that’s particularly insensitive to imidacloprid toxicity. This is striking to us, since the original draft regulations banned all three (see page 52).