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Medical Cannabis Drug Interactions and Contraindications: Patients at Risk

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Drug administration is ever-changing to accommodate inventions in medicines and medical processes that aid wellness. The Cannabis plant, popularly known as Marijuana, is a multifunctional herb that has gained popularity in medicine over the years. With street names like weed, hashish, and hemp, cannabis contains over 400 different chemical compounds. Cannabinoids are a class of chemical compounds that interact with certain receptors in the body.

Cannabis in Medicine

Like other chemical substances, cannabinoids reportedly have physiological effects on humans. The most common of these compounds are Tetrahydrocannabinol (THC) and Cannabidiol (CBD), leading to their medicinal usage.

Cannabis is used in general for pain and symptoms management, supported by its legalization in North America, which changed the public and medical opinion on the use of cannabis. Despite their common source, cannabinoids like CBD and THC have different interactions and activities with receptors, making their medical function and physiological effects vary. CBD is most commonly used in medicine, while THC is more popular in the production of commercial things like soaps, candles, oils, and food –though there are CBD-based commercial products. CBD products are used to help with arthritis, Crohn's disease, diabetes, and multiple sclerosis, as well as anxiety, insomnia, and chronic pain. According to the National Institutes of Health, there are more than 160 active or recruiting trials involving CBD. The FDA has also approved one CBD-based drug, Epidiolex, which is for the treatment of several severe forms of rare childhood epilepsy.

Cannabis Drug Interactions

As the use of Cannabis and cannabinoids like THC and CBD becomes more popular in medicine it is important to address some areas of concern in its usage. The legalization and commercial sale of marijuana can very well lead to its wrongful medical use.

Everyone must abide by the regulations of cannabis, as it is a chemical substance like any other drug and as such must only be used or purchased based on a physician's prescription.

The interaction of cannabis with drugs can neutralize the prescribed medication or result in terrible and lasting side effects. Therefore, information about drug interactions with CBD or THC is essential.

Some Cannabis interactions with drugs include;

· Medications that are metabolized in the liver through the P450 Cytochrome system, which is responsible for the breakdown of nearly 60% of all pharmaceutical drugs. CBD (cannabidiol) may increase in serum concentrations of macrolides (azithromycin/clarithromycin commonly used antibiotics), beta-blockers, antihistamines, and statins such as atorvastatin and simvastatin (not pravastatin or rosuvastatin). THC can decrease the concentration of antidepressant and antipsychotic medications like duloxetine, haloperidol, and naproxen. If you are on acetaminophen, the metabolism can increase. And if you are on amitriptyline, the metabolism can be decreased with medical cannabis.

· Antipyrine – This is an analgesic medication that may have a moderate interaction with marijuana in the body. Some of the chemicals in cannabis may decrease how fast the body breaks down antipyrine, which may lead to an increase in the antipyrine levels and its side effects. It is advised to be cautious and talk to your primary health provider about combining cannabis and antipyrine.

· Disulfiram (Antabuse) – Combining Disulfiram and cannabis may lead to irritation, nervousness, and excitement, medically referred to as hypomania, which could be triggering for patients with anxiety disorders. The same interaction occurs with Fluoxetine (Prozac). It is advised to consult with your primary health provider about combining cannabis and Disulfiram or Fluoxetine.

· Warfarin – This is an anticoagulant used in mechanical heart valves. Warfarin's metabolism can be decreased when combined with cannabis, increasing the anticoagulation effect leading to the risk of bleeding. DOACS/anticoagulants such as apixaban and rivaroxaban are NOT metabolized by the same enzyme as cannabis but, there is a potential for interaction with CBD/THC.

· For a common antihypertensive drug, like Valsartan, the metabolism can decrease when combined with cannabis, which increases potassium levels and antihypertensive effects.

Cannabis Contraindications – Patients at Risk

The consequences and after-effects of drug interactions with cannabis are heavily dependent on factors like the dose of CBD, the dose of the medication, and any underlying health conditions. Older people are more susceptible to these interactions because they usually have multiple prescriptions as a result of age-related illnesses.

By 2034, the aging population in the United States is expected to be over 77 million, which implies that a larger number of patients will be on a long list of medications that may include CBD- or THC-based drugs, as well as the outright use of cannabis for pain management. CBD can interact with several types of products, including over-the-counter medications, herbal, and prescription medications. Some drugs should never be taken with CBD, while the use of other medications may need to be monitored to prevent risk.

Anyone using cannabis must discuss it with their doctor or pharmacist, especially if they are on any other long-term medications or have underlying medical conditions like heart issues (arrhythmia), epilepsy, immune system challenges, or problems with the kidney or lungs. Patients with severe personality or mood disorders are also advised to abstain from combining cannabis with their prescribed medication.


It is important to know your medications and the potential drug interaction with cannabis. The best way to avoid adverse effects from drug interactions is to speak with your physician or pharmacist before starting cannabis or combining it with your medication. Websites like Drug Bank (, WebMD (, and ( offer information about specific drugs interaction with cannabis so you can type in your medication to see the interaction that applies.

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