Marijuana and Medication Interactions

Medically reviewed by Alexander Tabibi, MD
August 15, 2020
marijuana and medication interactions
marijuana and medication interactions

No matter for which purposes you are taking cannabis, it is always important to understand and acknowledge the possible dangers of any marijuana and medication interactions. This is true for ANY combination of products, including prescription and over-the-counter products or supplements you take.

This post is intended as information and for general knowledge only. It is not a substitute for medical advice, diagnosis, or treatment. It is recommended that you talk to a healthcare professional about this before introducing cannabinoids into your daily routine (especially if you have been diagnosed with any medical conditions or are under any medication). It is not recommended to drive or operate any machinery when using cannabis- or hemp-derived products. Use responsibly!

How Can Marijuana Affect Other Medications?

Marijuana medication interactions can be with various consequences:

  1. Cannabinoid blood levels can be increased by other drugs. Ketoconazole, verapamil, macrolides, cotrimoxazole, amiodarone, and others can augment the psychoactive properties of THC and the CBD dose-related adverse effects.
  2. Cannabinoids can affect levels of other drugs. Cannabidiol can increase levels of the active metabolite of clobazam threefold. Very high international normalized ratio levels and bleeding have been reported with the combined use of warfarin and marijuana.
  3. Additive effects can occur with other drugs. Additive effects can occur when marijuana is combined with sympathomimetics (e.g., tachycardia, hypertension), central nervous system depressants such as alcohol and opioids (e.g., drowsiness, ataxia), and anticholinergics (e.g., tachycardia, confusion).

You should review all the medications cannabinoids can affect and which you are taking with your doctor or your dispensary. Additionally, it is vital to double-check the medical instructions of any medications that you are taking in order to avoid unnecessary complications of marijuana and medication interactions.

It’s important to remember that drugs, including prescription medications, supplements, and natural remedies, including medical marijuana, CBD, or even alcohol, interact with each person and situation differently, so you need to pay close attention to your own reactions and be open and honest with your medical professional.

Cannabis is also known for certain side effects, which again vary by person. They typically include dry mouth or “cotton mouth” and dry eyes, so it’s always important to stay hydrated. These will be exacerbated if other medications or dietary supplements you take are also known to have dehydrating effects.

For some, cannabis can increase or trigger paranoid thinking or increase anxiety. This is usually related to the onset speed or uncertainty of effects as a novice user or increased intake. In some instances, and with some strains, marijuana drug interactions can be attributed to a heightened state of mind or existing mood.

What are the Potential Drug Interactions of Marijuana?

Common types of drugs that can have dangerous interactions with marijuana include:

  • Sedatives — such as Ambien, Lunesta and Benadryl. Sedatives themselves reduce one’s heart rate and blood pressure. Cannabis can worsen those effects.
  • Anti-anxiety medications — such as Xanax, Valium, and Librium. These medications can be dangerous for one’s health itself, even addictive. In combination with cannabis, they can significantly reduce heart rate and blood pressure and lead to coma or death. 
  • Antidepressants — such as Zoloft, Prozac, and Lexapro. Antidepressants and marijuana can cause heart palpitations, panic attacks, and even hallucinations when used together. Cannabis can also increase antidepressant levels preventing them from eliminating from the body.
  • Pain medications — such as codeine, Percocet, and Vicodin. Cannabis and opioid drugs both have depressant effects. Their simultaneous intake might lower blood pressure, slow brain function, and trigger extreme fatigue. Other issues may include blurred vision, chills, fatigue, hallucinations, and confusion.
  • Anticonvulsants (seizure medications) — such as Tegretol, Topamax, and Depakene. Their interaction with cannabinoids may increase sleepiness, fatigue, and possibly accidental falls and accidents when driving. This is the result of the altered concentration of substances at the blood level.
  • Anticoagulants (blood thinners) — such as Coumadin, Plavix, and heparin. Such interaction may result in increased plasma concentrations, increased international normalized ratio, and risk of bleeding.

When talking about marijuana and medication interactions, not only does the medication you are taking matter, but the delivery method is also very important. Inhaling cannabinoids get them into the blood faster, reaching their high concentration within 30 minutes, which ultimately increases the risk of acute adverse effects. It takes more time for edibles to absorb; hence their effect is usually quite gradual. Hence, they are less likely to produce high-concentration peaks. Topicals or creams will not be absorbed in quantity enough to interact with the medication.

What Interactions have Demonstrated Clinical Relevance?

The increased use of medicinal cannabis in the population allows for the development of studies providing the community with scientifically supported information that can help to make decisions. This review found and established the clinical relevance of 19 pairs of medical marijuana and medication interactions, mostly at level 3 of clinical relevance, which is medium risk, 1 interaction at level 1 (with warfarin), which is a very high risk, and 2 interactions at level 2 (with buprenorphine and tacrolimus), which is high risk. These interactions are mediated by a pharmacokinetic mechanism, and most of them are related to nervous system drugs. It is important to emphasize that the confirmation of these findings requires medical assessment and follow-up on dosage, concentration, cannabis preparation used, and route of administration. All in all, medical guidance is needed.