In some circles, cannabidiol is almost always advertised as an all-natural, all-safe medicine that anybody can take any time, but is this true? While its good side-effect profile is well established, often less attention is given to CBD oil interactions with many pharmaceutical drugs. So, let's explore what you need to know about CBD drug interactions before you jump on the hemp oil bandwagon.
Based on the growing body of research, it’s true that CBD oil is safe to use in most circumstances. It's also true that there are no known reports of CBD overdoses or deadly complications.
But the possible risk of interaction with other pharmaceuticals can indeed pose a danger, yet this is rarely discussed in the popular literature. Longtime CBD advocates might be surprised to learn about the hepatic drug interactions linked to CBD consumption. 
Before getting into the nitty-gritty of CBD drug interactions, it’s necessary to understand how the human body processes CBD and most medicines in the first place.
Many of the potential health benefits of cannabinoids like CBD are, in part, thanks to the way they are broken down for absorption into the rest of the body. This is done through a process called "metabolization," which takes place in the liver.
When you take CBD orally, it processes in the same way as many other drugs. Cannabidiol enters into the digestive tract and is slowly absorbed through the stomach lining into the hepatic portal system. This term may sound like something straight out of Star Trek. However, it's a system of veins connecting the stomach to the liver that also acts as one of the body’s filters.
Most drugs have relatively low bioavailability, so only a small percentage passes through this portal into the liver. Anything that ends up there is metabolized and turned into a host of other substances with different molecular structures, called metabolites.
Depending on the drug, the metabolite equivalents might serve to boost or reduce the drug's effectiveness. For example, codeine is transformed into morphine through metabolization, making it much more potent.
Regarding CBD, there is evidence suggesting that some of its metabolites may be extremely beneficial. The findings are preliminary, though, and more in vivo studies are necessary. 
Roughly 60 percent of today’s prescribed pharmaceuticals are processed through the liver by what is called the P450 family of enzymes. Cytochrome P450-complex enzymes are also responsible for metabolizing CBD.
In fact, CBD is a real liver enzyme monopolizer. Once CBD enters the liver, the cannabinoid takes up nearly all of its P450 enzyme-processing capability, so to speak. In this way, it keeps the liver from breaking down any other hepatically-metabolized drugs.
This can affect how these medicines work—read on for more about that.
The duration of CBD's effect in the liver is pretty unpredictable, at least based on the current body of research. It seems that many external influencers can ultimately lead to a shorter or longer monopolization of the P450 enzymes.
The size of the dose apparently also plays a role in the duration of influence, but so too does a patient's unique metabolism. It may come down to the delivery method of CBD and whether it was taken as a full-spectrum or an isolate. 
Interestingly, something as benign as grapefruit comes with a similar warning about possible drug interaction. Although CBD is thought to be a much stronger inhibitor of the P450 enzyme, physicians have long advised their patients to steer clear of grapefruit when taking certain medications.
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As mentioned, because of CBD's P450-hogging effect, other drugs don’t metabolize as expected. According to the preliminary studies done so far, CBD may increase the blood levels of certain medications and decrease the levels of others. Increased blood levels essentially make the drug stronger than it’s supposed to be, while decreased levels would affect its efficacy. 
As you can imagine, there may be both positive and negative effects to increased and decreased drug potency, depending on circumstance, medical condition, and medicine.
Although there is still limited research on the subject, it’s possible that too much CBD could trigger toxic levels of certain drugs in the bloodstream. Certain anticoagulant drugs also use the P450 metabolic pathway, and when taken with CBD, increased serum levels could prove fatal. In fact, increased anticoagulant blood levels due to cannabidiol consumption have been proven by research. 
There may also be a benefit to CBD hemp oil interaction with the P450 enzyme. Because, increased drugs in the bloodstream, ergo increased potency, could mean that patients would be able to reduce their dose of such medication.
In a study from 2015, children with seizure disorders were given CBD as a co-therapy to clobazam, an anti-seizure drug. The result was that the doctors were able to reduce the clobazam dosage, because CBD elevated the pharmaceutical’s plasma levels. On average, participants were able to reduce their clobazam intake with 1 mg/kg daily, and this helped alleviate the drug's side effects. 
Considering that 60 percent of clinically prescribed medication is metabolized in the liver via the P450 enzyme, it's not feasible to list them all here.
Some of the most common types of medications that may trigger CBD hemp oil interactions include:
Before adjusting any current prescriptions or deciding to use CBD in conjunction with other drugs, always speak to a qualified medical professional. All drugs mainly metabolized by the liver pose a risk, however small, for adverse CBD drug interaction.
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Despite the possibility of drug interaction, there is no need to panic about CBD oil. Cannabidiol continues to be one of the safest alternative therapies on the market.
In a review published in 2017, entitled An Update on Safety and Side Effects of Cannabidiol: A Review of Clinical Data and Relevant Animal Studies, the authors asserted: "In general, the often described favorable safety profile of CBD in humans was confirmed and extended by the reviewed research.”
In fact, the most commonly reported side effects, as described in this review, were relatively rare and mild. Some of those listed included feeling tired, bouts of diarrhea, and changes in appetite. These are usually self-correcting and easy to manage. Said the authors, "In comparison with other drugs, used for the treatment of [the same] medical conditions, CBD has a better side effect profile."
The authors also asserted that "some knowledge gaps ... should be closed by additional clinical trials to have a completely well-tested pharmaceutical compound." 
According to the Department of Health, Columbia, absolute contraindications for CBD and cannabis include acute psychosis and other unstable psychiatric conditions. Relative contraindications include severe cardiovascular, immunological, liver, or kidney disease, especially in acute illness. 
Again—if you do wish to pursue CBD as a co-therapy to other drugs, always seek medical advice, and adjust dosages of any medications only on the recommendation of a doctor. Yet CBD oil interactions need not put you off, as it can even complement the medicine you are taking.