How Does Cannabis Affect Over-the-Counter Medications?

Cannabis can be an effective treatment for many health conditions, or simply a way to relax after a long day. But marijuana can interact with more than 600 different medications. This includes not only prescription drugs but also common over-the-counter (OTC) preparations.

If you’re taking cannabis along with nonprescription drugs for pain, sleep, indigestion or coughs and colds, cannabis could affect how a key set of liver enzymes processes these medications. This affects bioavailability. In other words, how available these medications are to your body to use.


How Cannabis & OTC Meds Interact Depends on Many Factors

The interactions between cannabis and common prescription medications like opioid pain relievers and benzodiazepines for mood disorders have been studied fairly extensively. But much less research has been done on how—or whether—cannabis can affect how the body responds to widely used OTC medications that anyone can buy without a doctor’s prescription.

Complicating the connection between OTC medications and marijuana are the many variables involved in consuming cannabis along with these kinds of preparations. Many different factors can play a role in how the body responds, such as:

  • The way a person consumes cannabis
  • How much marijuana someone takes
  • The kind of cannabis they ingest
  • The types of medication they’re taking
  • Whether they’re also using other medications at the same time

But because the liver metabolizes and makes all of these substances bioavailable, researchers are able to study how cannabis either inhibits or enhances the way certain liver enzymes process common OTC medications.

OTC Drugs Are Medications, Too

Although they aren’t dispensed by a doctor—and may not be as potent as their prescription counterparts are—OTC preparations are still medications that can potentially cause a wide range of reactions. These medications fall into several broad classes, which can include many different kinds of preparations.

For example, OTC pain relievers include both acetaminophen (Tylenol) and nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil) and the old standby, aspirin.

And cough and cold remedies can include medications like pseudoephedrine and dextramethorphan to treat conditions as diverse as nasal congestion, coughing and fever.

The liver breaks down, or metabolizes, all of these medications. They’re made usable to the body by a suite of liver enzymes called cytochrome P450. According to HelloMD’s Dr. Richard Kim, the CP450 family of enzymes is the body’s most important system for metabolizing drugs. It accounts for between 70–80% of the enzymes involved in breaking down drugs of all kinds. This includes not only prescription and nonprescription medications, but also things like nutritional supplements, herbal preparations— and marijuana.

The cannabis compounds tetrahydrocannabinol (THC) and cannabidiol (CBD) compete with many other drugs for receptors on enzymes in the CP450 family. When this happens, marijuana can either increase or decrease the activity of an enzyme to alter the effects of a particular drug.

Here’s a rundown of what’s known about the ways in which cannabis compounds can affect the liver’s ability to metabolize common OTC medications.


Cannabis Intensifies the Effects of OTC Pain Relievers

Cannabis, especially strains and products that are high in CBD, have been shown to be effective pain relievers. And when taken in conjunction with common OTC pain relievers like acetaminophen and ibuprofen, research suggests that cannabis can increase their effectiveness.

For example, the enzyme CYP2C9 metabolizes both ibuprofen and marijuana, and cannabis appears to inhibit the activity of the enzyme. This makes it less effective in breaking down ibuprofen, and the result is that more ibuprofen is released into the bloodstream for a more intense effect.

Cough & Cold Medications Are Varied, But Seem Generally Safe Alongside Cannabis

OTC medications for coughs, colds and flu like Sudafed and Nyquil contain a variety of active ingredients depending on the symptoms they target. But most contain substances like:

  • Pseudoephedrine to relieve nasal congestion
  • Dextromethorphan to suppress coughs
  • Guaifenesin to clear mucus

Little research has been done on the interactions between these drugs and cannabis compounds, but no major effects have been reported.

Heartburn Medications Generally Don’t Interact With Marijuana

Prilosec and similar medications for heartburn and indigestion are designed to affect the production of acids in the stomach. Although liver enzymes also metabolize these medications, and they can have their own side effects and risks, medication databases don’t list any interactions with cannabis.

Sleep Aids Can Boost Cannabis’s Sedative Effects

OTC sleep aids can include a variety of different substances to target different symptoms:

  • Dedicated sleep preparations like Unisom
  • Nighttime cold medicines such as Nyquil
  • Antihistamines such as the allergy medication Benadryl, which makes you sleepy because it reduces the production of histamines in the body

These medications have different ingredients and different ways of working in the body, but they all have sedating effects. Because marijuana can also have relaxing, calming effects, it can also boost the sedative action of these medications, so that they may work faster with a stronger sedative effect.

Interactions between cannabis and OTC medications have been studied considerably less than interactions between cannabis and well-known prescription drugs like opioid painkillers and benzodiazepines. But research on the CP450 suite of liver enzymes that metabolize drugs of all kinds suggests that cannabis could either enhance or inhibit the way your body responds to your go-to OTC medications.

Photo credit: Josué Goge

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


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