Although cannabis-based medicines like tetrahydrocannabinol (THC) and cannabidiol (CBD) are generally considered to be well-tolerated and safe, it is simply false that these compounds are entirely harmless, especially for those who take multiple other medications to manage a medical condition.

Using cannabis or CBD alongside certain prescription medications may lead to interactions. Many Americans take at least one prescription drug daily, and those who use cannabis, and especially medical marijuana patients, should be aware that interactions between cannabis, CBD, and other medications have been known to occur.

Although rare, interactions between cannabis and certain prescription drugs may result in a health emergency, and it is important to always consult a physician before starting any type of drug or supplement. In this article I will discuss how CBD or cannabis and many common prescription drugs are broken down by the body, and also list some common medications that are known to interact with cannabis. 

Cytochrome P450 Enzymes are Critical For Metabolizing THC and CBD

THC and CBD are known to interact with certain drugs by affecting the activity of the cytochrome P450 enzymes, also known as just CYP enzymes. CYP enzymes are found in cells in the liver and gastrointestinal tract, and play a role in protecting the body from ingested substances.  The CYP system is comprised of many individual enzymes that break down certain types of substances.  

Drug interactions often occur when one substance alters the rate of degradation of another substance.  If a CYP enzyme is inhibited, the body may not be able to metabolize substances effectively. For instance, drinking grapefruit juice slows down the metabolism of many prescription drugs, which may strengthen a drug’s effects and even lead to drug toxicity. 

Confusingly, the presence of one substance can induce the synthesis of more of a CYP enzyme leading to excess and increased degradation of another substance. If this is a medication that’s needed, you can suffer the consequences of not having enough.

Since some substances increase degradation and others can decrease it, it can be unpredictable how drugs will interact.  To further complicate predicting, some CYP enzymes are just “busier” than others.  

In theory, if a medication is metabolized by a CYP enzyme, there is a chance using cannabis or CBD alongside that drug may result in a negative interaction.  In reality, however, the enzymes that metabolize THC (primarily CYP3A4) are readily available, and the ones that deal with CBD (like CYP2C9 and 2C19) are already quite taxed. Most clinically relevant interactions happen with CBD not THC.

Below is a list of many familiar prescription medications that are known to interact with marijuana or CBD.

Common Drugs That Interact With Cannabis:

  • Simvastatin (Zocor)
  • Metformin (Glucophage)
  • Albuterol (Ventolin HFA)
  • Fluticasone + salmeterol (Advair Diskus)
  • Insulin glargine (Lantus Solostar)
  • Lisdexamfetamine (Vyvanse) 
  • Sitagliptin (Januvia) 
  • Aripiprazole (Abilify)

As you can see, there are many that interact.  However, in the case of THC-dominant cannabis, most of these interactions are not terribly important and/or can be monitored by your physician. 

Drugs That Interact With CBD (Cannabidiol) and CBD Oil

  • Esomeprazole (Nexium)
  • Warfarin (Coumadin)
  • Clopidogrel (Plavix)
  • Amiodarone
  • Tacrolimus, Everolimus, and others 
  • Anti-Epileptic Drugs (Phenobarbital, Dilantin, Levetiracetam)
  • Benzodiazepines (Ativan, Xanax, and others)
  • SSRIs (Prozac and others)
  • Diltiazem
  • Erythromycin

This list contains more dangerous medications that are harder to monitor and may have acutely life-threatening complications if their levels are not correct.  Hence, CBD presents greater risk of significant interaction than does cannabis or THC. 

The Following Medications Are Not Known To Interact With Cannabis:

  • Vicodin (Hydrocodone or Acetaminophen)
  • Lisinopril (Prinivil or Zestril)
  • Levothyroxine (Synthroid)
  • Azithromycin (Zithromax, Z-PAK)
  • Amlodipine (Norvasc)
  • Amoxicillin
  • Hydrochlorothiazide
  • Crestor (Rosuvastatin)
  • Lyrica (Pregabalin)
  • Spiriva Handihaler (Tiotropium)
  • Humira (Adalimumab)
  • Sovaldi (Sofosbuvir)
  • Enbrel (Etanercept)
  • Harvoni (Ledipasvir and Sofosbuvir)
  • Remicade (Infliximab)

Consult With A Qualified Cannabis Specialist In Massachusetts

Ultimately, anyone who is interested in using cannabis as medicine should first always speak with a physician who has experience treating patients with medical marijuana. A trained cannabis specialist will ensure you are a good candidate for medical marijuana and also guide you towards best practices.

In Massachusetts, you must obtain a medical marijuana card from a qualifying physician in order to enter a registered medical dispensary. If you have any questions about your eligibility for medical marijuana in Massachusetts, please do not hesitate to contact my office. As a trained physician and member of faculty at Harvard Medical School, I am passionate about helping patients find relief through medical cannabis.  For more information, or to set up a consultation with my team at InhaleMD, call us (617) 477-8886 today.

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