Cannabis is the most frequently used psychotropic drug in the United States. Marijuana use is widespread among young adults. Mature men and women also report recreational or regular use of cannabis. As legislation becomes more accepting of cannabis, we witness the increased presence of various products containing cannabinoids.

Cannabinoids are active compounds in cannabis plants. The two most popular cannabinoids are CBD and THC. The latter is responsible for the “high effect” linked with marijuana. On the other hand, CBD is popular for its supposed health benefits. Products containing these compounds have become easily accessible both online and in physical stores.

As much as they’re easy to use, these products could harm you, especially if you’re taking medications. Evidence shows cannabinoids may impair the effectiveness of certain pharmaceuticals. You’ll learn more about this in our article below.

New Research: Cannabinoids and Medications

Since more and more people use marijuana and products with cannabinoids, it’s perfectly understandable why new studies emerge all the time. Most studies revolve around the potential beneficial effects of cannabinoids in the treatment of certain health conditions, but they only inspect short-term effects. The latest piece of research on cannabinoids reveals their negative impact on some medications.

This particular study was carried out by researchers at Penn State College of Medicine. The main objective of the study was to provide a detailed and comprehensive drug-drug interaction list aligned with the cannabinoid manufacturer. They composed a list of 57 medications that may not function properly when used in combination with medical cannabinoids, CBD oil or hemp oil, and medical or recreational marijuana. The journal Medical Cannabis and Cannabinoids published the results of this important research.

Keep in mind this is not a random list.

Scientists evaluated the prescribing information for four prescription cannabinoid medications and compared it with info from common medications used for the management of different health problems. Information about prescription cannabinoid drugs includes a list of enzymes that break down these compounds, including CBD and THC.

Researchers explain that unregulated cannabinoid products usually contain the same active ingredients as items with medical cannabinoids. That’s exactly why these products are so problematic. The reality is that CBD manufacturers are not systematically regulated. As a result, labeled formulations of CBD products may not accurately reflect the stated concentration or actual composition. The purposeful presentation of inaccurate concentration makes a person take more of CBD and other cannabinoids without even realizing it.

The significance of this study is in the fact it offers healthcare professionals more knowledge when considering the potential impact of over the counter (OTC) or illicit cannabinoid products. At the same time, patients need to be honest with their doctors about the products they use. This is particularly important because many patients fail to report the use of cannabis-related products, which can, in turn, lead to impaired efficacy of their medications.

What Drugs May Have Impaired Effectiveness Due to Cannabinoids? 

The list of medications whose functions can decrease due to cannabinoids is truly extensive. Different classes of drugs may interact with cannabinoids, including heart medications, antifungal drugs, and even antibiotics. For example, one of those medications is warfarin (Coumadin), an anticoagulant used to treat blood clots and prevent stroke in people with atrial fibrillation, valvular heart disease, and artificial heart valves.

Factors That Affect Drug-Drug Interaction

According to this study, drug-drug interaction and the impact of cannabinoids on medications you’re taking depends on numerous factors. These include:

  • Frequency of use of cannabinoids
  • Route of administration
  • Gastrointestinal absorption
  • Hepatic (liver) metabolism
  • Renal (kidney) excretion
  • A patient’s genomic profile

When Do Drug-Drug Interactions Occur?

The scientists found that clinically relevant drug-drug interventions i.e., the negative impact of cannabinoids on other pharmaceuticals, generally arise under certain scenarios. These include the cases when a cannabinoid inhibits, induces, or serves as a competing substrate for a metabolic enzyme of an herbal, prescription, or OTC medication.

These interactions can be complicated when they involve a number of medications. In other words, cannabinoids can interact with different medications (both prescription and OTC) and may decrease their effectiveness.

If you (or someone you know) have problems with marijuana use, then you may want to consider an inpatient cannabis addiction treatment center in North Texas, like Stonegate Center. The treatment is necessary for a clean life and improved management of health problems for which you’re taking medications. Since cannabis isn’t in your system anymore, the effectiveness of those medications can improve significantly.

Earlier Research

The latest study included a list of many medications whose effectiveness may be lowered due to cannabinoids. But it’s not the only study of this kind.

The well-known CMAJ published an interesting paper in March 2020 regarding this subject. The main subject of this feature was to discuss drug interactions with cannabinoids. Probably the most interesting part of this paper was that other medications could increase the levels of cannabinoids in the body.


Both THC and CBD are metabolized by cytochrome P40. Liver enzyme CYP2C9 metabolizes THC as well. Ketoconazole (Nizoral), an antifungal medication, acts as a CYP3A4 inhibitor, and it may nearly double THC and CBD concentrations. Similar interactions could occur with other CYP3A4 inhibitor drugs such as macrolides (class of antibiotics) and verapamil (used for the treatment of high blood pressure and to control angina).

In other words, some medications may augment the psychoactive effects of THC and intensify CBD presence. While this may seem like a good thing, actually, it’s not. A higher concentration of THC and CBD caused by these drugs also elevates the risk of dangers they carry and side effects they cause. That’s why it’s incredibly important for patients to be honest with their healthcare providers about marijuana use.

Just like some drugs may elevate the concentration of cannabinoids, vice versa can be true as well. The same study found that CBD inhibits enzyme CYP2C19, thus increasing levels of the active metabolite of clobazam by three times. Interactions with drugs metabolized by CYP2C19 should be anticipated.

This enzyme is responsible for the metabolism of drugs such as antimalarial (proguanil), oral anticoagulants (R-warfarin), chemotherapeutic agents (cyclophosphamide), anti-epileptics (diazepam, phenobarbitone), among others. By acting on an enzyme that metabolizes certain drugs, cannabinoids such as CBD can impair the effectiveness of those medications.

Although more research is necessary, the study also found that marijuana could have serious interactions with other drugs, including:

  • Warfarin – increased international normalized ratio and risk of bleeding
  • Clobazam – higher risk of benzodiazepine toxicity
  • Central nervous system depressants and sympathomimetics – addictive effects occur when marijuana is combined with alcohol, opioids, anticholinergics, and sympathomimetics
  • Theophylline (used for respiratory diseases), clozapine (an antipsychotic medication), and olanzapine (used for the treatment of bipolar disorder and schizophrenia) – reduced effectiveness

Other studies that focused on cannabinoids and drug interactions are discussed below.

The March 2019 issue of the journal Medicines published a study that showed that cannabinoids might act on P450 isoenzymes to affect the metabolism of various drugs. The P450 isoenzymes catalyze oxidative reactions in the liver, intestine, kidney, brain, and lung. They metabolize several cannabinoids, including THC, CBD, and CBN (cannabinol). The cannabinoids may inhibit or induce CYP (cytochrome P40), a hemoprotein that participates in the metabolism of drugs, may affect the metabolism of many drugs metabolized by these CYPs.

The Journal of Clinical Medicine published a study in July 2019 which found that CBD exhibits both pharmacodynamic and pharmacokinetic properties that could lead to adverse drug events and drug-drug interactions. The study debunked a common belief wherein CBD was regarded as a completely safe and biologically inert compound. Instead, its profile is complicated, and it has the potential to interact with other medications and medical conditions.

In September 2017, the journal Epilepsia published a study that found that the concomitant administration of CBD significantly changed serum levels of rufinamide, topiramate, clobazam, zonisamide, and eslicarbazepine in patients with epilepsy. In subjects who took concomitant valproate, abnormal liver function was recorded. This discovery is huge because many people with epilepsy (or those whose loved one has this condition) rely on CBD to feel better. However, CBD may actually interfere with medications they’re supposed to take.

Cannabinoids May Increase Opioid Use

Cannabinoid advocates suggest that marijuana and products containing cannabinoids may prevent many problems, including opioid use. That’s not entirely correct, however. Research from 2011 found that cannabinoids may augment the analgesic effects of opioids. This would mean that lower doses of opioids would be necessary to treat chronic pain and other problems. As a result, the overuse of opioids would reduce. The reality is entirely different, however.

You see, a study from the January 2018 issue of the American Journal of Psychiatry found that cannabinoids could lead to increased use of opioids. Even after adjusting other factors, cannabinoid use was still significantly associated with developing non-medical prescription opioid use and opioid use disorder.

While this is technically not about interactions per se, it paints a picture of how cannabinoids can be harmful to our health and wellbeing. Let’s not forget that opioid misuse has become a major problem in the United States, and cannabinoids could contribute to it. That’s yet another reason why a 90-day residential drug rehab center for marijuana abuse is necessary for people who use cannabis. It could help prevent a patient from using other, more dangerous substances.

Side Effects of CBD

If you ask anyone about CBD, they will tell you it’s safe and powerful. We are swamped with posts of that kind online, and people can’t stop talking about CBD. Nothing is as it seems! While CBD is considered safe and effective, it may not be the case for some users. Consumption of CBD may induce various side effects, including:

  • Dry mouth
  • Diarrhea
  • Reduced appetite
  • Drowsiness
  • Fatigue
  • Nausea
  • Irritability

As seen above, CBD may interact with different medications, including blood thinners. A major source for concern here is the lack of regulation of this market. As a result, people have easy access to products that lack both quality and purity. Plus, dosages can be unreliable, too.

When we’re talking about CBD interactions, it’s important to mention medications and supplements containing “grapefruit warning” on the label. You see, both CBD and grapefruit interfere with cytochromes P40. Above in the post, we elaborated that cytochrome 450 is a group of enzymes important for drug metabolism.

Grapefruit contains a class of chemicals called furanocoumarins, which disrupt the normal function of CYPs. By slowing down the way in which CYPs usually break down medications in the gut and liver, grapefruit can increase the side effects of these drugs. So, when you combine CBD and grapefruit, you get the major risk of decreased effectiveness of certain drugs and more intense side effects.

Evidence shows that the consumption of CBD may lead to liver toxicity.

Can You Get Addicted to Marijuana?

How many times have you heard from someone they opted for marijuana because it’s impossible to get addicted? Somehow the use of cannabis (and thereby other cannabinoid products) is associated with good health. A common misconception is that cannabis can help people relax, but without addiction.

Actually, you can get addicted to marijuana, and it’s a common problem. A marijuana addiction rehab center for women near Dallas-Fort Worth, Texas witnessed the rise of patients who need help and guidance to overcome cannabis use and achieve a successful recovery.

Not only is cannabis addiction possible, but it’s also fairly common. According to the National Institute on Drug Abuse, about 30% of people who use marijuana may have some degree of marijuana use disorder. People who start using marijuana before the age of 18 are four to seven times more likely to develop an addiction to this substance. In 2015, about four million people in the United States met the diagnostic criteria for marijuana use disorder. Only 138,000 people voluntarily sought treatment for cannabis use.

A major factor in the development of cannabis addiction is genetics, but environmental factors and mental health problems also play a role.

Marijuana dependence occurs when the brain adapts to large amounts of the drug by decreasing the production of endocannabinoid neurotransmitters and reducing sensitivity to them. Some men and women believe they need cannabis to deal with their problems, and not a day goes by without them using this substance. That’s a clear indication of cannabis addiction, and proper treatment is necessary.


While cannabinoids are usually praised for their supposed health effects, the latest study confirms that CBD, THC, and other cannabinoids may impair the function of other drugs. The list of drugs whose effectiveness is affected by cannabinoids is truly extensive. Addiction to cannabis is entirely possible. Problems with cannabis use require proper approach and treatment, just like alcohol dependence, opioids addiction, and other similar problems.


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Stonegate Center
Address: 7510 FM 1886, Azle, TX 76020
Phone: (817) 993-9733
Fax: (817) 704-4576
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Stonegate Center is a private faith-based and gender-separate rehab center located in Azle, Texas. We offer long-term residential addiction treatment for men and women struggling with drug & alcohol addiction. Our rehab center serves the communities of Fort Worth, Dallas, and as far as Oklahoma & New Mexico.

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