The nephrologist’s guide to cannabis and cannabinoids
Correspondence to Joshua L. Rein, DO, Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, 1 Gustave L. Levy Place, Box 1243, New York, NY 10029, USA. E-mail: [email protected]
This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. http://creativecommons.org/licenses/by-nc-nd/4.0
Purpose of review
Cannabis (marijuana, weed, pot, ganja, Mary Jane) is the most commonly used federally illicit drug in the United States. The present review provides an overview of cannabis and cannabinoids with relevance to the practice of nephrology so that clinicians can best take care of patients.
Cannabis may have medicinal benefits for treating symptoms of advanced chronic kidney disease (CKD) and end-stage renal disease including as a pain adjuvant potentially reducing the need for opioids. Cannabis does not seem to affect kidney function in healthy individuals. However, renal function should be closely monitored in those with CKD, the lowest effective dose should be used, and smoking should be avoided. Cannabis use may delay transplant candidate listing or contribute to ineligibility. Cannabidiol (CBD) has recently exploded in popularity. Although generally well tolerated, safe without significant side effects, and effective for a variety of neurological and psychiatric conditions, consumers have easy access to a wide range of unregulated CBD products, some with inaccurate labeling and false health claims. Importantly, CBD may raise tacrolimus levels.
Patients and healthcare professionals have little guidance or evidence regarding the impact of cannabis use on people with kidney disease. This knowledge gap will remain as long as federal regulations remain prohibitively restrictive towards prospective research.
Cannabis (marijuana, weed, pot, ganja, Mary Jane; Fig. Fig.1) 1 ) is the most commonly used federally illicit drug in the United States. As of December 2019, 33 states and the District of Columbia have medical cannabis programs. Eleven states and the District of Columbia have legalized recreational use. Several countries worldwide have legalized recreational use whereas many others have medical cannabis and decriminalization laws. The prevalence of cannabis use more than doubled between 2001 and 2013 in the United States  particularly among people over the age of 50 and even more so among those over 65 years [2▪,3,4▪,5▪]. These age groups are enriched with chronic illness including chronic kidney disease (CKD) that is associated with excess morbidity and mortality .
Cannabis sativa W.O.Müll. (A) flowering male and (B) seed-bearing female plant, actual size; (1) male flower, enlarged detail; (2) and (3) pollen sac of same from various angles; (4) pollen grain of same; (5) female flower with cover petal; (6) female flower, cover petal removed; (7) female fruit cluster, longitudinal section; (8) fruit with cover petal; (9) same without cover petal; (10) same; (11) same in cross-section; (12) same in longitudinal section; (13) seed without hull. From Franz Eugen Köhler’s Medizinal-Pflantzen. Published and copyrighted by Gera-Untermhaus, FE Köhler in 1887 (1883–1914). Original figure is now in the public domain. https://commons.wikimedia.org/wiki/File:Cannabis_sativa_Koehler_drawing.jpg.
Cannabis is the dried flower bud of the Cannabis sativa and Cannabis indica plants, and naturally contains numerous phytocannabinoids. Δ 9 -tetrahydrocannabinol (THC) and cannabidiol (CBD) are the most abundant and well described phytocannabinoids, with differing activities and affinities for the ubiquitously expressed Gi/o-protein-coupled cannabinoid receptors CB1 and CB2. THC is the primary psychoactive component of cannabis and is a partial agonist to CB1 and CB2 receptors. In contrast, CBD is nonintoxicating and has little affinity for these receptors but acts as a negative allosteric modulator of CB1 with pharmacological effects on other receptor systems including GPR55, TRPV1, 5-HT1A, adenosine A2A, and nonreceptor mechanisms . Plant breeding has created numerous genetically unique Cannabis chemovars, enhancing certain desired effects. For example, chemovars with a higher concentration of THC are selectively produced for recreational use, because THC activation of CB1 mediates the psychotropic effects of cannabis, whereas medical cannabis generally has higher CBD levels than recreational chemovars, often even exceeding the THC content. In fact, symptom relief may be obtained with THC doses lower than what is needed to induce psychotropic effects. Endogenous cannabinoids are eicosanoids derived from cell membrane phospholipids. The two primary endocannabinoids are anandamide/N-arachidonoylethanolamine and 2-arachidonoylglycerol, which are the natural ligands for the cannabinoid receptors. The endocannabinoid system is present in many tissues including the kidney where it has been shown to influence renal blood flow [8,9], glomerular filtration rate , fibrosis [11–13], proteinuria [14–21], and tubular function [22–27]. The endocannabinoid system has been comprehensively reviewed elsewhere [28,29▪,30] including specific interactions with the kidney [31,32,33▪,34▪,35–38]. Whole cannabis contains numerous cannabinoid compounds with different affinities, making the predicted cumulative effect on cannabis receptors, and potential renal effects difficult to predict.
Physicians remain poorly educated with respect to cannabis and the endocannabinoid system [39,40▪]. The federal stigma against cannabis in the United States, leading up to the Marihuana Tax Act of 1937 and the Controlled Substances Act of 1970, have strongly limited research and prevented teaching about the drug in medical education. State legalized consumption of cannabis is in conflict with federal law where it remains a Schedule I controlled substance without accepted medical use and a high potential for abuse. Despite this, the World Health Organization classifies CBD as having no potential for abuse  and several oral cannabinoid-based pharmaceuticals are U.S. Food and Drug Administration (FDA) approved, having demonstrated efficacy in treating certain medical conditions. Cannabis derived CBD (Epidiolex) is an FDA approved medication for pediatric epilepsy whereas synthetic THC is FDA approved as dronabinol (Marinol, Syndros), and a synthetic THC analogue as nabilone (Cesamet). The cannabis extract nabiximols (Sativex, THC/CBD 1:1) is approved for medical use outside of the United States.
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CANNABIS AND CANNABINOIDS
Cannabis can be home grown or purchased from retail and medical dispensaries, dependent on the jurisdiction. Cannabis contains over 200 phytocannabinoids, terpenoids, and flavonoids that may act in concert, described as the ‘entourage effect’, so that the combination of plant components act synergistically to be more efficacious than the individual isolated compounds [42,43]. Cannabis can be consumed as dried flower bud through smoking burned plant material or heated in a vaporizer to the vaporizing points for the various cannabinoids (311°F–428°F) without burning the plant and generating smoke. Recently, electronic cigarettes and vape pens have become a popular means to inhale heated aerosol from a concentrated oil containing cannabinoids and/or nicotine. Unfortunately, some THC oil concentrates from illicit manufacturers/underground vape-makers have been associated with fatal lung injury attributed to inhalation of chemical irritants [44▪,45], including vitamin E acetate, used as an oil diluent .
Cannabis and isolated cannabinoids can also be processed into foods or ‘edibles’. Over 90% of current users consume cannabis through inhalation whereas oral consumption accounts for less than 10% of cannabis use . Inhalation provides an onset of action within minutes and allows for real-time dose titration. Peak effects are seen within 15–30 min with a half-life of 1–2 h. After oral consumption, the onset of action may be delayed up to 1–2 h, with peak effects at 2–3 h and half-life of 3–6 h. Inexperienced users who do not feel an effect right away may be tempted to overconsume innocuous appearing edible preparations that can lead to drug accumulation and prolonged adverse side effects. For this reason, edibles have been associated with higher rates of emergency room visits, primarily for acute psychiatric symptoms, intoxication, and cardiovascular symptoms [48▪]. Cannabinoids are highly lipophilic and bioavailability is increased with high fat intake compared to consumption on an empty stomach . THC and CBD may interact with the metabolism of prescription medications . CBD is metabolized by CYP3A4 and CYP2C19 with a growing body of evidence suggesting it is also a potent inhibitor of these pathways [51,52] including CYP2C9  and CYP2D6 . The clinical relevance of these interactions is largely unknown. THC has a large volume of distribution (Vd) with slow elimination from the body. Cannabinoids are primarily cleared by the liver and the minority of inactive metabolites are excreted in the urine, accounting for 20% of metabolite elimination. Terminal half-life varies based on frequency of use: several days in infrequent users to over 1 month in heavy chronic users. Cannabinoid pharmacokinetics have been comprehensively reviewed [55,56▪,57]. Evidence regarding the pharmacokinetics of cannabinoids in people with impaired kidney function is scarce. The only published study evaluated 200mg of oral CBD and found no statistically significant differences in maximum measured plasma concentration (Cmax), time to Cmax, area under the plasma concentration–time curve (AUC) from time zero to last measurable concentration, or AUC from time zero to infinity values between participants with severe renal impairment (mean eGFR ∼22 ml/min/1.73 m2) and normal renal function [58▪]. Given the primary hepatic metabolism, dose adjustments are unlikely to be needed. The large Vd for THC and high protein binding  suggest limited clearance with hemodialysis.
There is no evidence to suggest that CBD has any adverse effect on kidney function. In fact, CBD prevented cisplatin induced nephrotoxicity in a mouse model by reducing oxidative stress . However, some products may contain toxic contaminants such as heavy metals, pesticides, and solvents. A study of 84 CBD products sold online found that 42% of products contained more CBD than stated on the label, 26% were overlabeled, whereas only 31% contained the stated amount . Additionally, 20% of these products were contaminated with THC that could potentially be detected on a urine toxicology screen. Some products do not contain a sufficient quantity of CBD to achieve pharmacological activity.
Consumers should scrutinize labels, ensure that the product has been made with good manufacturing practice, ensure cannabinoid extraction using carbon dioxide, ensure organic certification by the U.S. Department of Agriculture, and purchase from a certified medical dispensary or company that has a certificate of analysis. If CBD is regularly consumed, careful monitoring of clinical parameters and drug interactions is warranted.
SYMPTOMS ASSOCIATED WITH CHRONIC KIDNEY DISEASE AND END-STAGE RENAL DISEASE
Over 1.5 million people with advanced CKD and about 750 000 people with end-stage renal disease (ESRD) live in the United States . One-quarter to one-half of patients with CKD experience chronic symptoms such as pain, nausea, anorexia, sleep disturbance, anxiety, and depression , several of which are approved indications for medical cannabis. In addition, anxiety, depression, and insomnia are the most common psychiatric conditions that people self-treat with cannabis . Evidence supports the use of cannabis in patient populations without CKD for treating several of these symptoms including chronic pain, nausea, and loss of appetite. The rationale for its use in patients with CKD and ESRD has been previously reviewed by myself and others [71,72,73▪].
Pain prevalence among patients with CKD and ESRD is as high as 50% . Pain attributed to kidney disease occurs from polycystic kidney disease, renal colic from nephrolithiasis, renal osteodystrophy, or uremic neuropathy. Historically, cannabis has been recommended for a wide range of ailments including as a spasmolytic for cases of renal colic and to facilitate the excretion of small kidney stones .
Over 60% of dialysis patients receive at least one opioid prescription annually and approximately 20% of them take prescription opioids chronically . Both short-term and chronic use of prescription opioids are associated with increased morbidity and mortality [76,77]. Cannabis could have a therapeutic role in pain management that deserves clinical consideration and further clinical trial investigation. Access to medical cannabis has been associated with decreased opioid prescriptions and dose reductions [78–82,83▪]. The National Academies concluded that substantial evidence exists for the use of cannabis and cannabinoids to treat chronic pain  while meta-analyses and systematic reviews of cannabis use, including prescription cannabinoids, have given mixed results for treating chronic pain [85–87].
IMPAIRED KIDNEY FUNCTION
Recreational cannabis is most often smoked (>90%) [47,88] and generally contains higher THC content whereas medical cannabis is vaporized or consumed orally and often has a higher CBD content. Medical cannabis programs in several states only allow for edibles and vaporizers and do not allow smoking. Existing research regarding cannabis is biased towards recreational cannabis consumed by smoking prior to or early into state legalization programs.
Among participants with an estimated glomerular filtration rate (eGFR) less than 60 ml/min/1.73 m 2 ) in the multicenter Assessment, Serial Evaluation, and Subsequent Sequelae of Acute Kidney Injury (ASSESS-AKI) study self-reported chronic cannabis usage was associated with more rapid eGFR decline compared to those with an eGFR more than 60 ml/min/1.73 m 2 over a median 4.1 years . Cannabis usage was not associated with changes in albuminuria over time. Conversely, sicker patients who may already have progressive CKD may be more inclined to use medical cannabis for symptom management. An analysis of the Chronic Renal Insufficiency Cohort (CRIC) Study from 2003 to 2008 among 3939 adults with baseline eGFR between 20 and 70 ml/min/1.73 m 2 did not demonstrate an association between cannabis use and CKD progression over 5.5 years of follow-up [90▪].
Among healthy individuals, analysis of the Coronary Artery Risk Development in Young Adults (CARDIA) Study did not demonstrate a longitudinal association between cannabis use and eGFR change, rapid eGFR decline, or prevalent albuminuria after 15 years of follow-up in 3765 participants . Past or current cannabis use was reported by 83% of participants. The CARDIA study began in 1988 and at that time, cannabis had lower THC content and a lower THC/CBD ratio than current levels. Similar findings were revealed in a cross-sectional analysis of 13 995 adults aged 18–59 years in the nationally representative National Health and Nutrition Examination Survey (NHANES) from 2007 to 2014 that did not find a clinically significant effect of self-reported past or current cannabis use on serum creatinine, eGFR, microalbuminuria, or stage 2 or higher CKD .
Renal function in cannabis users with CKD should be closely monitored, the lowest effective dose should be used, and smoking should be avoided. It is currently unknown if other routes of administration attenuate kidney risk but they at least avoid potential pulmonary complications.
ACUTE KIDNEY INJURY
Synthetic cannabinoids are potent CB1 agonists originally developed as research compounds but have emerged on the marketplace as popular and potentially dangerous recreational drugs referred to as ‘spice’ or ‘K2’. Numerous cases during 2012 have linked synthetic cannabinoids to acute kidney injury (AKI) [93–95]. Specifically, the synthetic cannabinoid XLR-11 has been identified as a nephrotoxic compound  possibly related to effects on proximal tubule mitochondrial function . Synthetic cannabinoids may be nephrotoxic, but a noncannabinoid contaminant has been proposed as an alternative explanation [97,98]. Nausea, vomiting, and flank pain are common in the majority of cases. Kidney biopsy most often demonstrates acute tubular necrosis with some cases of acute interstitial nephritis . Synthetic cannabinoids are not detected on standard blood and urine toxicology screens. Therefore, nephrologists should have a high index of suspicion when diagnosing unexplained AKI.
Cannabinoid hyperemesis syndrome (CHS)  is a rare complication of heavy and frequent cannabis use over many years characterized by intractable vomiting that is relieved with hot showers. CHS is occasionally associated with prerenal AKI [101–106], treated with intravenous fluids and antiemetics. Interestingly, hypophosphatemia was observed in a case series of 6 men with CHS .
CB2 is widely expressed on immune cells and cannabinoids have immunomodulatory effects in animal models of allogeneic transplantation and autoimmune diseases [108–111]. As such, cannabis and cannabinoids may have immunomodulatory effects among kidney transplant recipients. Interestingly, a study of routine kidney transplant biopsies revealed significant upregulation of glomerular and tubular CB1 expression in those with chronic allograft dysfunction compared to low levels in normal kidney allografts, suggesting a role for CB1 in allograft fibrosis .
Cannabis use in potential transplant recipients may have implications for pretransplant screening, such as delayed candidate listing or contributing to ineligibility [113▪], with implications for posttransplant outcomes. There is concern regarding adherence to immunosuppressive medications, the ability to follow instructions, and attendance of follow-up appointments. An American Society of Transplantation survey revealed that about half of transplant centers vary in their policy according to the organ, whereas slightly more than one-quarter of centers rejected all candidates regardless of organ [114▪]. Drug screening of potential transplant donors and recipients should consider the prolonged excretion of THC metabolites which may range from a few days in casual users to several weeks to over 1 month with chronic heavy use.
A retrospective single center study of kidney transplant candidates revealed that cannabis abuse and dependence were associated with a high prevalence of other substance use disorders, psychiatric comorbidities, and strong family histories of addictions, resembling other substance use populations that generally adversely affect kidney graft outcomes . A study of a national kidney transplant database demonstrated that cannabis dependence or abuse (CDOA) in the year before transplant was not associated with death or graft failure in the year after transplant, but was associated with posttransplant psychosocial problems such as alcohol abuse, other drug abuse, noncompliance, schizophrenia, and depression [116▪]. CDOA after kidney transplantation was associated with cardiovascular, pulmonary, psychosocial complications, accidents, and fractures. Accordingly, CDOA was associated with an approximately two-fold increased risk of death-censored graft failure, all-cause graft loss, and death in the subsequent 2 years. Although associations likely, in part, reflect comorbid conditions or behaviors, CDOA after kidney transplantation appears to have consequences for allograft and patient outcomes. Additionally, patients who carry a formal diagnosis of CDOA likely reflect ‘extreme’ users who were not able to hide their use and raised suspicion. Data from patients with CDOA cannot be generalized to all as cannabis does not have adverse effects on life in everyone [117▪]. A single center study of 56 cannabis users out of 1225 kidney recipients from 2008 to 2013 demonstrated that recreational cannabis use, defined by positive urine toxicology screen and/or self-reported recent use, did not affect mortality, graft loss, or graft function 1-year posttransplant . Finally, a single center study of 919 kidney transplant recipients from 2001 to 2015 revealed that smoking status was not significantly associated with acute rejection, eGFR, or pneumonia within 1-year posttransplant. Patients with isolated cannabis use had similar overall graft survival compared to nonusers [119▪].
With regards to kidney donation, a retrospective single center study of 294 living kidney donors and 230 recipients between 2000 and 2016 showed that donor cannabis use did not demonstrate any deleterious effects on donor or recipient posttransplantation eGFR over a mean follow up of 2.1 years for donors and 5.2 years for recipients [120▪]. Among recipients of a kidney from a cannabis user, the rates of acute rejection, graft, and patient survival of the kidney allografts were similar to those from nonusers.
Although rare, fungal contamination of cannabis and pulmonary complications have been reported among kidney transplant recipients, including pulmonary aspergillosis associated with smoking cannabis [121,122] and exogenous lipid pneumonia secondary to smoking weed oil . These cases have occurred prior to current cannabis legalization where microbial testing has become a regulatory requirement in the medical and recreational cannabis markets. Although sterilization of cannabis buds can eliminate fungi and may eliminate the risk of fatal opportunistic infections among immunosuppressed individuals [121,124], several toxigenic fungi and bacteria have been detected in cannabis samples [125,126]. Based on existing evidence, cannabis usage alone should not be the sole deciding factor for declining a patient for kidney transplant listing.
Several case reports demonstrate increased tacrolimus levels associated with CBD in a patient with interstitial nephritis and in non-kidney transplant recipients [127▪,128,129], whereas one small case series of low dose CBD for chronic pain among kidney transplant recipients did not reveal any change in tacrolimus levels . Inaccurate product labeling and batch to batch variability of CBD products  may lead to unpredictable CNI levels, potential toxicity, or underdosing, especially with intermittent use of different cannabinoid products. Furthermore, CBD inhibits hepatic cyclosporine metabolism in vitro and in mice .
MEDICAL RISKS AND COMPLICATIONS
The public health impact of state legalization of cannabis remains unclear and these policies may have contributed to the increasing perception that cannabis is harmless. In fact, more than one-third of U.S. adults strongly or somewhat strongly agree that edible cannabis prevents health problems and more than a quarter strongly or somewhat strongly agree that smoking or vaping cannabis prevents health problems [132 ▪▪ ]. Medical cannabis as an option for those with CKD or ESRD, will include people who are older, frailer, and have more comorbid conditions and co-medications, potentially increasing susceptibility to adverse effects. The most common side effects are dizziness and dry mouth.
Smoking is associated with increased mortality among people with CKD and ESRD . Although smoked cannabis is a source of oxidative stress to the respiratory tract  and associated with bronchial irritation and chronic bronchitis , regular heavy use is associated with lower risk for pulmonary complications compared to tobacco use [136,137]. A systematic review and meta-analysis demonstrated low-strength evidence that smoking cannabis more than once per week for at least 1 year was associated with cough, sputum production, and wheezing while evidence regarding cannabis use and obstructive lung disease and pulmonary function was insufficient [138 ▪▪ ].
CKD and ESRD are associated with increased cardiovascular morbidity and mortality . Endocannabinoids are involved in various functions of the cardiovascular system including blood pressure regulation [140–142]. Some observational studies suggest a higher incidence of cardiovascular events with cannabis exposure, [143–145] while other studies do not [146,147]. Low strength evidence suggests that cannabis use is associated with tachycardia [148▪]. Acutely, cannabis may cause orthostatic hypotension whereas long-term cannabis use may be associated with a modest increase in systolic blood pressure . Systematic reviews do not reveal any hemodynamic effects of either CBD  or THC .
Cognitive impairment is common among people with CKD and ESRD [152–154]. Acute cannabis usage may cause sedation and impair spatial-visual distortion while acute and long-term cannabis use can impair verbal learning, memory, and attention . However, a comprehensive review of recreational cannabis and cognitive function revealed inconsistent findings across studies [156▪].
Given the rapidly expanding market for cannabis, large-scale longitudinal studies are needed to explore the long-term effects of chronic and frequent cannabis use. Consistent with recommendations regarding the use of tobacco and other smoked substances among patients with CKD and ESRD, smoked cannabis should be avoided among people with cardiovascular or pulmonary disease. Other routes of administration such as oral consumption may avoid these risks.
With growing acceptance of both medical and recreational cannabis and cannabinoids, further research is required to determine the efficacy, safety, and acceptability of medical and recreational cannabis use among people with CKD and ESRD. As clinicians, we should be informed and able to provide guidance with the most up to date information for our patients.
The author thanks Joseph Vassalotti and David Goldfarb for their review of the manuscript.
CBD drug interactions: Is CBD safe to take with prescription medications?
If you’ve visited a store that sells health and beauty products lately, you may have noticed that products containing CBD, or cannabidiol, seem to be all the rage. Oil, chocolate, supplements, even carbonated beverages, are filling up shelves—enticing shoppers with claims that using one of these products will cure insomnia, alleviate anxiety, reduce inflammation, or treat PTSD.
And shoppers are buying it, so to speak—one recent report indicated that CBD sales are expected to hit $16 billion by 2026, up from just over $1 billion in 2018. But what exactly is CBD, and is it safe for people who are using prescription medications? Before using it, it’s important to learn about the potential CBD drug interactions.
Is CBD marijuana?
While CBD is one of the active ingredients in marijuana, using CBD itself will not get you high (the component that does that is called tetrahydrocannabinol, or THC). CBD is really just a molecule within the hemp variety of the cannabis plant, and there is at least some anecdotal evidence and preliminary research suggesting that the extraction created from this molecule has some health benefits.
CBD is thought to act on certain receptors in your brain and other parts of the body, in ways that could relieve pain, or help certain health conditions, like childhood seizure disorders. However, as with any “natural” product, the fact that it comes from plants doesn’t automatically render it innocuous. For some people, particularly those taking certain prescription medications, using CBD is risky. It has anticoagulant effects that can thin blood; it can also modestly lower blood pressure. These effects could be dangerous for people with certain medical conditions.
“Herbal products are drugs,” says Rita Alloway, Pharm.D. , research professor of nephrology at the University of Cincinnati College of Medicine. “Just because [something] is herbal … doesn’t mean it can’t interact with any of the pharmaceutically manufactured drugs that you may be taking.”
Does CBD interact with medications?
Case in point: tacrolimus , an immunosuppressive medication used to prevent organ rejection in patients who have had heart, liver, or kidney transplants. CBD interferes with the metabolism of tacrolimus, according to research conducted by Dr. Alloway , who specializes in post-transplant immunosuppression. And because tacrolimus is a narrow therapeutic index drug (meaning the window between efficacy and toxicity is very small), this interference can lead to clinically significant negative outcomes (such as kidney problems or organ rejection), she says.
Are the concentrations in commercially available CBD high enough to cause this interaction? The evidence doesn’t really say one way or another. Dr. Alloway’s research involved a high dosage of CBD that wouldn’t be found in a retail product. However, it “highlights that a drug interaction is there,” she says. Plus, tacrolimus is metabolized in the body by a group of enzymes called cytochrome P450 and CBD is a known inhibitor of this process. What does that mean? If CBD inhibits the metabolism of tacrolimus, the patient can end up with too-high levels of tacrolimus in the body. In light of this, she urges anyone taking tacrolimus to speak with their transplant team before using CBD. Don’t get your hopes up, though—using herbal remedies, particularly those with potential interactions, is generally frowned upon by doctors looking after transplant recipients (including Dr. Alloway).
As for other drugs, well, most haven’t been studied yet. There is preliminary evidence that CBD could have a similar effect to grapefruit juice, impairing how your body metabolizes drugs, and raising serum levels of those medications in your body. And, because cytochrome P450 is responsible for the metabolism of numerous medications , proceed with caution before mixing any prescription pharmaceutical with CBD, Dr. Alloway says.
How about CBD’s therapeutic benefits?
Despite the not-so-great news about CBD for patients using tacrolimus, for some people, CBD is actually life-changing in a positive way. In 2018, for example, the CBD-derived medication Epidiolex received FDA approval for the treatment of Lennox-Gastaut syndrome and Dravet syndrome, two very rare and very severe forms of epilepsy.
But claims that CBD aids in the treatment of certain mental health and psychiatric conditions, don’t pass muster, says Roger McIntyre, MD , professor of psychiatry and pharmacology at the University of Toronto.
“There is no role right now for CBD in managing mental disorders that I [treat], such as depression, bipolar disorder … anxiety and ADHD,” he says. “We just don’t have the evidence that supports [it].”
Furthermore, most prescription medications used to manage these conditions are metabolized by cytochrome P450, making it entirely possible that CBD could interfere with—rather than enhance—treatment.
Dr. McIntrye, who co-authored a 2018 study that concluded that healthcare providers need more information about drug-drug interactions with CBD and psychotropic medication, says much of the information out there is confusing and contradictory. Therefore, he echoes Dr. Alloway’s statement that it is absolutely prudent that patients clear the use of CBD with their doctor before giving it a go.
“[The provider] knows the individual and knows what other treatments they may or may not be taking,” Dr. McIntyre explains. “They have a panoramic view of the patient’s medications, and would have [a better idea] of whether the patient is taking another medication that may have an interaction.”
Can a person on tacrolimus smoke cbd oil for pain
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Cannabis Use Is a Growing Concern in Heart Transplant
A new review of evidence is likely to shape guideline updates on an unaddressed but increasingly common issue in the care of heart transplant candidates and patients.
Cannabis Use Is a Growing Concern in Heart Transplant
Literature review summarizes existing data to help inform international guidelines
Legalization of cannabis for medicinal or recreational use in many countries has created controversy in the heart transplant field. Current International Society for Heart and Lung Transplantation (ISHLT) guidelines, last updated in 2016, provide no guidance about cannabis use in transplant candidates. As a result, policies are varied across centers, sometimes to the detriment of transplant recipients.
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“Cannabis use in heart transplantation is a bigger concern than some providers realize,” says Eileen Hsich, MD, Medical Director of the Heart Transplant Program at Cleveland Clinic. “Data on the topic were limited in 2016. Today we have more data, as cannabis use among transplant patients has become more common.”
International heart transplant guidelines are due for an update, she notes. In preparation, Dr. Hsich and colleagues summarized existing data on cannabis and transplantation, including research on graft failure and death, infection, cancer and cardiovascular complications. The review was recently published in The Journal of Heart and Lung Transplantation.
“We hope this paper will help steer discussion and serve as a resource for the ISHLT as it considers updating transplant guidelines,” says Dr. Hsich. “There are very few articles published on cannabis use and the heart, and ours is the only one that focuses on heart transplantation.”
“We also hope this review highlights the need for future research to further understanding of the impact of cannabis use in heart transplantation,” adds co-author Caroline Olt, MD, an internal medicine resident at Cleveland Clinic.
Prevalence of cannabis use
Asking heart transplant candidates about use of cigarettes, nicotine products, alcohol and illicit drugs is uniform across U.S. transplant centers, says Dr. Hsich. But asking about cannabis use isn’t. In fact, laws in some states prevent centers from declining transplant candidates due to cannabis use. As a result, some providers don’t view cannabis use as a heart transplant concern.
Moreover, urine toxicology screens are not reliable screening tools, Dr. Hsich notes. “When patients abstain from use before screening, cannabis isn’t always detected in urine toxicology,” she says. “Patients may claim they don’t use it, but we sometimes discover after transplant that the use is more frequent than originally admitted.”
Prevalence appears to be growing, at least anecdotally, she adds. Legalization of cannabis in many states has made products readily available online and at retail outlets including pharmacies and hair salons.
Legal but detrimental
According to the review article, chronic cannabis use is problematic in heart transplantation, mostly because it interferes with immunosuppression.
Cannabis compounds like cannabidiol (CBD) and Δ 9 -tetrahydrocannabinol (THC) interact with enzymes that may affect the potency of immunosuppressive medications like tacrolimus. The challenge of maintaining therapeutic immunotherapy levels is further complicated by inaccurate concentrations of CBD and THC in cannabis products due to lack of regulatory standards.
In addition, chronic cannabis use can cause cannabinoid hyperemesis syndrome, which leads to reduced absorption of immunosuppressants.
“Some patients use cannabis for medicinal purposes, such as to decrease anxiety or pain,” says Dr. Hsich. “We tell them anxiety and pain may intensify after transplantation — but there are safer and more effective ways to address them than using cannabis.”
Key takeaways for heart specialists
Other key takeaways from the literature review include:
- Route of administration, frequency of use and dependency need to be addressed in future transplant guidelines. Inhaling cannabis, which generates carcinogens like smoking tobacco, tends to be more harmful than consuming cannabis through edible and topical products. Also, frequency of use and addiction are more important in determining transplant candidacy than is purpose of use (recreational versus medicinal).
- Casual cannabis use should be distinguished from cannabis use disorder. Infrequent, casual use may have minimal effect on transplant outcomes. However, cannabis use disorder —use for at least a year with history of intoxication, withdrawal, cravings, risky behavior, social impairment and addiction — is associated with noncompliance, graft failure and death among transplant recipients. That conclusion is based on a large analysis of outcomes data in kidney transplant patients, who receive immunosuppressive regimens similar to those for heart transplantation.
“Cannabis may be less addictive than substances like heroin and cocaine, but addiction is still possible and should be viewed like any other addiction,” says Dr. Hsich. “Cannabis use disorder shares the same destructive properties.”
According to ISHLT 2016 guidelines, substance abuse is a contraindication to transplantation. Cannabis use disorder should be considered likewise, says Dr. Hsich, noting that not all providers concur. “I am surprised by the controversy surrounding cannabis,” she says. “Our field more readily accepts avoidance of grapefruit juice since it interferes with many transplant drugs.”
Following Canada’s lead
In 2020, the Canadian Cardiovascular Society/Canadian Cardiac Transplant Network addressed cannabis in a position statement of its own. Despite Canada’s nationwide legalization of cannabis, the statement recommended that patients abstain from smoking, inhaling or vaping it for six months before being listed for heart transplantation. The statement also recommended that patients with cannabis use disorder complete a treatment program with a minimum of six months of abstinence before being listed.
“Based on the data available for cannabis and transplantation, we support the Canadian statement and hope that ISHLT adopts similar guidelines,” says Dr. Hsich.
Meanwhile, all transplant programs can offer treatment consistent with the spirit of the Canadian statement, notes her colleague Edward Soltesz, MD, MPH, a heart transplant surgeon and Surgical Director of the Kaufman Center for Heart Failure Treatment and Recovery. “At Cleveland Clinic, we have established a comprehensive team of multidisciplinary providers to help treat substance use disorders in our patients with heart failure undergoing advanced therapies,” says Dr. Soltesz. “Addiction specialists, social workers and psychiatric providers all collaborate during heart transplant eligibility assessment as well as after listing and transplant to enhance the motivation toward abstinence.”