What Happens When You Mix Cannabis With Prescription Drugs?

Cannabis has a long list of healing properties. That’s why many people report reducing their use of some prescription medications while consuming marijuana. But if you’re taking cannabis alongside standard pharmaceuticals, it’s important to remember that cannabis can interact with more than 600 prescription drugs. This happens because of marijuana’s effects on a key set of liver enzymes that break down medications to make them available to the body and brain.


Why Is Cannabis Such Effective Medicine?

Research has revealed—and many consumers confirm—that cannabis can affect all kinds of processes in the body from relieving pain to fighting inflammation. This is because cannabinoids in the cannabis plant interact with the receptors in the body’s endocannabinoid system (ECS). These ECS receptors are found in our organs, tissues, brain and central nervous system. Cannabis triggers their activity in the same way as the natural cannabinoids produced by the body do.

In conventional medicine, health conditions are typically treated by an array of very different drugs, each targeted to a specific process and a certain set of symptoms. For example, a person might take one medication for depression, another to relieve arthritis pain and a third for migraines.

But cannabis can relieve symptoms of all of these conditions. Because ECS receptors are in so many different parts of the body, marijuana can mimic results similar to a variety of prescription medications. People are starting to see that cannabis has similar effects to that of opioid painkillers, antidepressants, sleep aids and anti-anxiety drugs—but without many of the harmful side effects that these pharmaceuticals can produce.


How Marijuana Affects the Breakdown of Chemicals in the Liver

To understand how medications and cannabis interact, we have to look to the liver. Medications and other kinds of chemicals including alcohol, herbs and supplements are metabolized, or broken down, through the liver.

One aspect of this breakdown involves oxidation by liver enzymes. This is a process that makes these substances more water-soluble, so that the kidneys can filter them out more quickly. Marijuana can affect the behavior of these liver enzymes, which work hard to make medications bioavailable in the right amount and at the right time.

Although it’s a complex process, one set of liver enzymes, collectively called Cytochrome P450, is mainly responsible for the oxidation of medications and other chemicals. And at least four of the enzymes in the CYP450 family are known to be affected by cannabis. The complex relationship between cannabis and the human body plays out in the ways cannabis either reduces or increases the activity of each of these liver enzymes.

When cannabis inhibits the activity of a liver enzyme, it reduces the enzyme’s ability to oxidize certain chemicals. This means that higher levels of these chemicals enter the bloodstream and cause more intense effects. But when cannabis increases an enzyme’s activity, it boosts the enzyme’s ability to oxidize a chemical. In so doing, more of the chemical is processed out and less is released into the bloodstream, thereby weakening its effects.

To add to the complexity, not only do the enzymes in this group react to various chemicals differently in the presence of cannabis, they’re also responsible for metabolizing cannabis itself. This means that the various enzymes in this group act differently on cannabis compounds like tetrahydrocannabinol (THC) and cannabidiol (CBD), too.

THC, CBD, Liver Enzymes & How They all Work Together

The CYP450 enzymes that interact with cannabis include:

  • CYP1A2: Smoking cannabis increases the activity of the CYPIA2 enzyme, which lowers the amount of medications, including lidocaine and melatonin, released into the bloodstream.

  • CYP3A4: This enzyme is one of two known to affect the metabolism of THC and CBD. In the presence of several drugs including ketoconazole, an antifungal agent, CYP3A4 reduces the expression of THC, so that less of the cannabinoid is released into the bloodstream. But when a person takes medications such as the antibiotic rifampin along with cannabis, this enzyme increases the levels of THC in the blood.

  • CYP2C9 & CYP2C19: CYP2C9 metabolizes THC, while CYP2C19 breaks down CBD. In the presence of cannabis, these enzymes boost the activity of numerous drugs including rifampin, the antipsychotic carbamazepine as well as the class of sedative drugs called barbiturates. That said, these enzymes inhibit the effect of many medications including the antifungal fluconazole and a variety of antibiotics and anti-inflammatories when taken with cannabis in your system.

It’s clear that all of these substances influence each other in unique and delicate ways. Compounding all of this is the fact that cannabis’s effects can vary tremendously depending on consumption method, a user’s weight and health, and even the unique makeup of each individual’s ECS.

The list of medications that interact with cannabis is a long one, and cannabis can replace or reduce the need for more than a few. But the nature of those interactions can sometimes be hard to predict. If you’re at all concerned with how one of your medications interacts with cannabis, be sure to consult with your doctor.

Photo credit: Joshua Coleman

If you’re new to cannabis and want to learn more, take a look at our Cannabis 101 post. HelloMD can help you get your medical marijuana recommendation; it’s easy, private and 100% online.

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