Cannabis & Drug Interactions

What You Should Know Before Combining Cannabis with Other Substances

Cannabis is generally considered safe on its own, but combining it with certain medications, supplements, or other substances can change how both affect the body. For some consumers, that shift is minor. For others, it can make a medication less effective, amplify side effects, or produce unexpected reactions.

Being aware of these interactions is part of being a responsible cannabis consumer. This guide covers the most commonly encountered drug interactions with cannabis, what signs to watch for, and how to approach cannabis use safely when other substances are involved. 

As always, what you find here is meant to add to, not replace, the guidance of your healthcare provider. 

Common Cannabis Drug Interactions

Cannabis interacts with over 400 known drugs. How significant any interaction is depends on the specific medication, the dose, and the individual. Here are the most commonly encountered categories that interact with cannabis:

Sedatives & Sleep Medications

Cannabis may amplify the drowsiness caused by sedatives like Ambien, Valium, and Lunesta. It can also slow the breakdown of these medications in the body, causing them to stay in your system longer than intended.

Anti-Anxiety Medications

Cannabis combined with medications like Xanax, Klonopin, or Ativan may cause excessive drowsiness and sedation. It can also interfere with how these medications are metabolized, which in some cases may increase the risk of overdose.

Antidepressants

When used alongside antidepressants like Zoloft, Lexapro, or Prozac, cannabis may increase the likelihood of dizziness, confusion, and poor coordination. In rare cases, the combination may lead to serotonin syndrome.

Pain Medications

Cannabis may affect how opioids, like morphine and oxycodone, are processed in the body. It can also interfere with how common NSAIDs, like ibuprofen, break down and leave the system.

Anti-Seizure Medications

Combining cannabis with anticonvulsants, like valproate, may raise drug levels in the bloodstream. In rare cases, this can lead to liver damage. Anyone using both should do so only under close physician guidance.

Blood Thinners

Cannabis combined with anticoagulants, like warfarin, may increase the risk of stroke and excessive blood-thinning, leading to increased bruising and slower wound healing. Always speak with your physician before using cannabis if you take any form of blood thinners.

Other Substances That May Interact with Cannabis

Interactions are not limited to prescription medications. Certain herbal supplements and over-the-counter vitamins and compounds can also interact with cannabis in ways worth knowing about.

Melatonin

Both cannabis and melatonin are commonly used to support sleep. Combining them may cause excessive drowsiness, dizziness, and nausea beyond what either produces on its own.

St. John’s Wort

St. John’s Wort is an herbal supplement often used for depression. Combining it with cannabis may increase the risk of dizziness and impairment, and may also affect how both substances are metabolized.

Valerian Root

Valerian root is commonly used for anxiety and insomnia. When combined with cannabis, it may add to sedative effects and in some cases cause confusion. Consumers using both should be mindful of increased drowsiness.

Echinacea

Echinacea is broken down by the same liver enzymes as cannabis. Consuming both together may elevate the levels of each in the body, increasing the likelihood of side effects from either substance.

Signs a Possible Interaction May Be Occurring

If you use cannabis alongside medications or supplements, knowing what to watch for helps you respond quickly if something does not feel right. Common signs that an interaction may be occurring include:

• Medication feeling more or less effective than usual
• Unusual side effects from a medication previously well-tolerated
• Excessive drowsiness, dizziness, or confusion
• Unexpected changes in mood, heart rate, or anxiety levels
• Dry mouth and dry eyes more pronounced than usual
  
  

If you experience any of these signs, it is worth discussing with your healthcare provider.

When to Seek Medical Attention

If side effects are severe, sudden, or significantly different from anything you have experienced before, seek medical attention promptly. Some interactions can escalate quickly, and waiting to see if things improve on their own is not always the right call.

How to Use Cannabis Responsibly When Taking Other Substances

If you use cannabis alongside medications or supplements, a few straightforward practices can help reduce the risk of negative interactions:

• Talk to your doctor or pharmacist first. Before combining cannabis with any medication or supplement, a conversation with your healthcare provider is the single most important step you can take.
• Be honest about your cannabis use. Your provider can only give you accurate guidance if they know the full picture, including what cannabis products you use and how often.
• Start low and go slow. Give your body time to respond before increasing the amount of either substance.
• Space out your doses. Where possible, avoid taking cannabis and other medications at the same time to minimize overlap and reduce interaction risk.
• Check for grapefruit warnings. Cannabis affects the same liver enzyme as grapefruit. If your medication label includes a grapefruit warning, cannabis may pose a similar interaction risk.
• Keep your medication list current. Make sure all healthcare providers you see have an up-to-date picture of everything you take, including cannabis.
• Never stop a prescribed medication without guidance. Do not discontinue any prescribed medication in favor of cannabis without first consulting your physician.

Cannabis & Drug Interactions: Key Takeaways

Cannabis is generally safe on its own, but it can interact with over 400 medications and a range of herbal supplements. Common interactions involve sedatives, anti-anxiety medications, antidepressants, pain medications, anti-seizure drugs, and blood thinners. Herbal supplements like melatonin, St. John’s Wort, valerian root, and echinacea can also interact with cannabis in meaningful ways.

Responsible use means staying informed. If you take medications or supplements regularly, talking to your healthcare provider before adding cannabis to your routine is the safest and most informed approach.