One of the downfalls to the wildly increasing popularity of CBD use is that not a lot of research has been done in regard to its potential interaction with other drugs. Like any drug, CBD is a chemical compound that has specific effects on various pathways in the body. Thus, it’s important to understand whether or not these effects may be dangerous or counterproductive when taken along with other substances.
Fortunately, it’s becoming more and more widely accepted that CBD is generally safe to use, even when taken along with other meds. An updated study published earlier this summer (2017) confirmed the “favorable safety profile” of CBD in humans, and in fact showed that it had a better side effect profile when compared to other medications with similar functions.
Likewise, the U.S. Department of Health issued a statement several years ago claiming that “serious adverse [side] effects are rare with [the use of] cannabis or its constituents.”
That being said, a few studies have shown that in significant enough doses, CBD can inhibit or deactivate a class of liver enzymes that are important for the efficient metabolization (breakdown) of prescription medications. Accumulation of unmetabolized drugs can potentially be dangerous in that it allows for the stagnant buildup of compounds in the liver, as well as a prolonged effect of the drug.
In this article, we’ll go over some common medications that have been known to be affected by continuous, high-dosage CBD use, and also talk about prescriptions for common medical conditions that may pose potentially adverse interactions with the natural cannabinoids like CBD.
First, though, it’s important to understand that this is by NO MEANS a comprehensive guide on which drugs are safe to take with CBD, and which are not. In fact, it’s believed that several of the drugs listed below may actually be enhanced when taken along with CBD. No matter the case, always make sure and speak with a physician or clinical professional before making any changes to your medications.
Interaction of CBD with Cytochrome P450 Enzymes
Cytochrome P450 (CYP) is a class of liver enzymes responsible for the metabolic breakdown of roughly 60% of clinically prescribed medications. In certain doses, several natural plant compounds (including CBD) have been known to temporarily deactivate these enzymes, which can lead to the delayed metabolization and prolonged activity of administered prescription medications (as well as some OTC medications).
While not believed to be life-threatening, prolonged metabolization of prescription medications can potentially lead to accumulation of compounds in the liver, which can present complications. Also, warfarin (a common blood thinning medication) is known to particularly be prone to the effects of deactivated CYP enzymes – individuals who take it (as well as other blood thinning drugs like heparin) are advised to speak with a doctor before administering significant doses of CBD on a regular basis.
Also, diclofenac (which is a NSAID pain reliever), is another medication that’s known to have a prolonged duration when taken simultaneously with CBD. In addition to potential liver complications, prolonged activity and delayed metabolization of these drugs (as well as others) may lead to complications involving the blood.
Since CYP activity affects roughly 60% of all marketed medications, individuals who insist on taking CBD (or other forms of cannabis, for that matter) along with other drugs are advised to monitor any changes in their respective conditions closely. While there have been no known hospitalizations as a direct result of prescription drugs interacting with CBD, there is not nearly enough pharmacologic understanding of the compounds to suggest any range of safe or unsafe doses.
For instance, while one clinical trial in 2013 reported zero CYP interaction with a CBD dose in excess of 40mg, another subsequent trial noted significant deactivation of the enzyme with a dose of 25mg. More in-depth clinical studies are certainly needed in order to better understand the full spectrum of CBD drug interactions.
Other Potential CBD Interactions with Prescription Drugs
Warfarin and diclofenac are certainly not the only medications known to be affected by the temporary deactivation of drug-metabolizing CYP enzymes. Remember, most clinical studies suggest that up to 60% of all marketed medications are broken down (at least in part) by this specific class of enzymes.
Here is a list of several of the most common prescription medications nationwide that are metabolized by Cytochrome P450 enzymes:
- Blood thinners
As we already talked about, common blood thinner medications like warfarin and heparin are subject to prolonged activity and increased effect when taken simultaneously with CBD, resulting in elevated INR (the International Normalized Ratio is a test used to monitor the effects of warfarin).
Likewise, A 2012 publication in Drug Metabolism and Pharmacokinetics verified that CBD can increase warfarin levels, which suggests that individuals with blood thinner prescriptions need to take considerable precaution if planning on taking frequent doses of CBD. Speak with a physician and monitor any changes in blood or bleeding closely.
- Medications for gastrointestinal reflux and peptic ulcers
Omeprazole, which includes the drugs Prilosec and Losec (as well as other drugs that treat gastroesophageal reflux disease) can also be affected by frequent CBD use. These drugs are targeted by the specific CYP enzyme CYP2D6, which can be effectively blocked if a significant dose of CBD is taken prior to administration.
- Antipsychotic medications for schizophrenia, bipolar, autism, etc
Risperidone is a relatively common antipsychotic medication that’s frequently prescribed to treat mild cases of schizophrenia, bipolar disorder, and ASD (autism spectrum disorder). Like omeprazole, it is also targeted for breakdown by CYP enzymes, and high doses of continuous CBD use can potentially lead to its prolonged activation. The same is true for drugs like haloperidol (Haldol), which is a similar antipsychotic medication of the same class.
- Cholesterol medications
CYP3A4 is another enzyme of the Cytochrome P450 class that’s responsible for breaking down about 25% of all pharmaceutical drugs, according to the DOH (U.S. Department of Health). Frequent CBD use may increase the serum concentration of several popular cholesterol-lowering drugs, including atorvastatin and simvastatin. As of now, however, similarly-functioning statins like pravastatin and rosuvastatin are not believed to be affected by the temporary deactivation of CYP3A4.
- Blood pressure medications
While CBD by itself is not particularly known to increase blood pressure, the combination of THC and CBD have been known to initiate cardiac stress responses and reduce arterial blood flow. Patients who take medication for blood pressure need to be cognizant of the possibility that marijuana use may enhance the effect of their medication, which can cause serious complications.
- Epilepsy and seizure medications
While CBD for epilepsy and seizures is generally regarded as an incredibly safe and effective treatment option, a 2015 publication in Epilepsia showed that frequent CBD use can potentially increase levels of the drug Clobazam in children.
Other medications affected by the inhibition of Cytochrome P450 enzymes
The following list of general medications have been acknowledged by the U.S. Department of Health to potentially increase in concentration as a result of CBD-induced inhibition of metabolic liver enzymes:
Drugs metabolized by CYP3A4 enzymes:
- Macrolides (these include antiobiotics such as Zithromax, Klacid and the erythromycins Erymax, Erythrocin, and Erythroped)
- Calcium channel blockers (including Norvasc, Cardizem and Tiazac)
- Benzodiazepines (common anti-anxiety medications including Xanax, Klonopin, and Valium)
- Cyclosporine (Neoral) (this is an immunosuppressant medication used primarily after organ transplants to lower the risk of organ rejection)
- Sildenafil (including Viagra and other PDE5 inhibitors like Cialis and Levitra)
- Antihistamines (these include common OTC medications for allergic reactions: Zyrtec, Benadryl, Allegra, and Claritin)
- Antiretroviral (ARV) drugs including commonly prescribed HIV/AIDS medications
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Drugs metabolized by CYP2D6 enzymes:
- Tricyclic antidepressants (TCAs including amitriptyline, amoxapine, desipramine (Norpramin), doxepin, imipramine (Tofranil), nortriptyline (Pamelor), protriptyline (Vivactil) and trimipramine (Surmontil)
- Beta blockers and opioid pain medications (including codeine and oxycodone)
It’s important to note, however, that a drug mentioned on the above list does not necessarily mean it shouldn’t be taken simultaneously with CBD. Many people use CBD every day along with some combination of the above medications, without any adverse side effects.
In fact, it’s believed that some medications actually work favorably when taken along with cannabis. The bottom line is that additional clinical study is needed if we’re to determine the complete spectrum of CBD drug interactions.
What About CBD and Alcohol?
In terms of potentially harmful or fatal side effects, combining CBD with alcohol is generally regarded as being safe. However, that’s certainly not to say that it’s recommended; excessive alcohol use (like any excessive drug use) is dangerous, and certainly not advised.
That being said, using CBD (or other forms of cannabis) while drinking alcoholic beverages is not life-threatening or catastrophically harmful in the same way that drinking and taking sleep meds, benzodiazepines, or other depressants is.
The general takeaway message from all of this should be that CBD is regarded as an incredibly safe and therapeutic medication, with virtually no side effects or risk for addiction/withdrawal. While much more research is needed to fully understand the interactions it may have with other medications, it’s generally accepted that, due to its wide range of use, CBD has the potential to actually eliminate the need to take multiple medications. Or at the very least, reduce one’s current prescription drug use.
Many thousands of people, in fact, have used CBD-based products simultaneously while weaning off other, more dangerous medications such as prescription opiates and antidepressants. (Check out an in-depth article on CBD oil for chronic pain relief here).
Thus, compiling any one complete list of CBD drug interactions is virtually impossible, given the fact that the human body is an INCREDIBLY complex network of interdependent chemical reactions. The pharmacology and physiologic pathways of even the most common and well-studied drugs is not even fully understood.
At this point at least, anecdotal evidence is far more dominant in the cannabis world than is clinical research, and nearly all of that evidence points to CBD as an extremely safe, natural remedy with minimal contraindications.
As we’ve mentioned several times, though, it’s always important to speak with a physician or health professional before implementing any kind of change to your medication. Even though it’s a 100% natural therapeutic compound, at the end of the day CBD is a chemical with a specific physiological pathway, and like all chemicals it presents the opportunity to interact adversely with any number of other drug compounds.