How Does Cannabis Interact With Other Drugs?

June 20, 2017

Just about every drug — including “natural” over-the-counter herbal remedies and even fruits (like grapefruit) — can potentially interact with other drugs. In fact, caffeine has more than 80 identified drug interactions — including 25 that are considered “moderately severe” to “severe.”

In this regard, cannabis — while generally less likely to produce interactions than many drugs — is no exception.

But, not all interactions are necessarily adverse. Some drugs can work together synergistically. For example, research suggests cannabis improves the effectiveness of opioids, allowing chronic pain patients to significantly decrease their dosage.

The following is a list of some of the most commonly prescribed medications and their known drug interactions with cannabis. (Note: this isn’t an exhaustive list, and some interactions may not have been identified yet.)

Cannabis Drug Interactions


Alcohol is one of the most common substances that people use with cannabis. Mixing alcohol with most substances is generally not a good idea. The evidence on how drinking may interact with cannabis suggests that alcohol increases the level of THC in a user’s bloodstream. However, there’s also evidence suggesting that people consume less alcohol if they consume cannabis first.

Possibly the greatest risk is that because cannabis inhibits nausea and vomiting, if you drink too much, your body may not expel the toxins.


The most commonly prescribed — newer classes of antidepressants — like SSRIs (e.g. Prozac, Paxil, Zoloft),  SNRIs (e.g. Cymbalta), NDRIs (e.g. Wellbutrin) carry a relatively low risk of producing adverse reactions with cannabis. However, MAOIs (like Marplan) and tricyclics (such as Tofranil) carry higher risks for adverse reactions. In fact, both of those classes of antidepressants have fallen out of favor over the years, because they can produce adverse reactions with many different drugs and substances.

Blood Pressure Medications

There are two receptors in the brain —  CB1 and CB2 — that work together like a lock and key when activated by cannabinoids such as THC. Activating these receptors can induce a cardiovascular stress response which may reduce blood flow in coronary arteries while elevating oxygen consumption. Few adverse events have been reported from patients using cannabis and blood pressure medications, however, exercising caution and monitoring blood pressure is critical.

Drugs That Affect Blood Sugar Levels

Some evidence suggests cannabis may improve the metabolic process and blood sugar control while decreasing insulin resistance. However, most of these studies are large studies examining general patterns across populations. In other words, most are not clinical studies that look specifically at how the drugs could potentially interact. While some evidence seems to suggest cannabis may work synergistically with these types of drugs, it may lower blood glucose levels too dramatically, so close monitoring is important.

Drugs That Increase Risk of Bleeding

Both THC and CBD may enhance the effect of medications used for blood thinning (e.g. warfarin or heparin), or drugs known to carry their own risk of blood thinning (e.g. ibuprofen, naproxen, etc.). How? By possibly slowing down the metabolism of these drugs. To a lesser extent, THC may displace warfarin from protein binding sites.


Based on existing research, there seems to be a bidirectional modulatory relationship with two key physiological systems that influence pain sensation: the body’s natural cannabinoid system — the endocannabinoid system — and the body’s natural opioid system — the opioidergic system.

Many researchers and studies have found that cannabis can work with opioids synergistically, and can enable patients to decrease (or eliminate) their reliance on prescription opioids. Definitely a good thing as we continue to battle the worst opioid epidemic in our nation’s history.

Dr. Donald Abrams, an oncologist, and professor at UC, San Francisco, conducted a small study in 2011. His team found that patients who used cannabis in combination with opioids experienced a 27% reduction in pain while allowing them to decrease their intake of opioids. Moreover, they found that cannabis produced no significant change in blood level concentrations after adding cannabis.

Abrams believes patients can safely use cannabis as an adjunct to pain treatment, allowing patients to reduce opioid intake while experiencing fewer side effects.

CBD and Cytochrome P450

You’re probably familiar with CBD, the most prominent (largely) non-psychoactive cannabinoid in cannabis. But, what is Cytochrome P450? It’s a class of essential enzymes, that can cause interactions not just with cannabis — but numerous drugs. The effects can be beneficial or adverse, so patients should be aware of the potential effects.

The most common cannabis drug interactions are seen in epilepsy and anti-seizure medications. In 2015, researchers published a study finding CBD can increase blood concentrations of the anticonvulsant, clobazam, particularly in kids. Likewise, it may also increase norclobazam, an active metabolite of clobazam. Fortunately, the remedy seems to be relatively simple: by reducing the dose of clobazam, patients can minimize unwanted side effects.

Again, overall cannabis is generally well-tolerated, and most patients don’t experience adverse cannabis drug interactions. And, in fact, many patients can reduce their reliance on other drugs with higher interaction risks. Nonetheless, it’s important for patients to consult with their medical professional to minimize potential risks.

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