Buzz Kill: Cannabis Drug Interactions

With the passing of medical and/or recreational cannabis in 34 states plus the District of Columbia, more Americans than ever will have ready access to state-sanctioned cannabis. Many baby boomers, exposed to cannabis use in the 1960s, are taking prescription drugs for chronic diseases. However, now they are increasingly adding cannabis to treat diseases or chronic pain, or recreationally to relax and wind down. But before you take your next puff or consume your next edible, let’s take a moment to see which prescription medications could really kill your buzz if you take them with cannabis.
Both cannabis and prescription drugs, as well as foods and alcohol, are metabolized in the body by certain enzymes that make it easier to eliminate from the body. The exact combination of enzymes used to metabolize a drug or food is specific to each substance. And these substances can also keep other enzymes from working temporarily, or can temporarily speed up the activity of enzymes. When two medications, or a medication and a food, use the same enzymes to get out of the body, one or both of the substances will stay in the body longer and can have increased effects (including side effects). When one substance temporarily stops the activity of an enzyme, the other substance will take longer to get out of the body, which may lead to increased effects (either wanted or unwanted). And when one substance speeds up the effects of the enzyme, it will lead to decreased amounts and effects of the other substance. Let’s look at specific examples of drug interactions with cannabis
Cannabis interactions with prescription medications include:

• Anti-seizure medications: increased effectiveness of these medications; lower doses of the anti-seizure medication may be required.
• Opiate pain medications (such as hydrocodone): lower doses of the pain medication may be needed.
• Blood pressure medications: possible increased dizziness due to additive effects.
• Certain antibiotics and antifungals: may decrease THC and CBD elimination and increase their effects.Rifampin (another antibiotic): may speed up the elimination of THC and CBD, decreasing their effects.
• Cimetidine (an over-the-counter antacid): may decrease THC elimination and increase THC effects.
• Warfarin (a blood-thinner): increased effects of warfarin and increased risk of bleeding.
• Psychiatric medications (such as risperidone and haloperidol): THC may decrease levels of some antipsychotic medications, possibly requiring a decrease in dose. CBD may increase the effects of antidepressants, so lower doses of the antidepressant may be needed.
• Medications that cause dizziness or drowsiness: THC and CBD may increase these effects.

So, if cannabis can possibly interact with all of these medications, what should you do? Here are a few tips:

• Tell your healthcare professionals that you also use cannabis. Medical professionals do not report your use to any authorities unless required by law (ie laws are broken associated with cannabis use). Trust me, they don’t want to have to do all that paperwork. But they can watch out for drug interactions and side effects, and can adjust your medications as needed, or even choose an alternative medication that won’t interact with your cannabis. And, ask your doctor or pharmacist whether a drug will interact with your cannabis before starting any new medication, including over-the-counter medicines or herbs.
• Take your first dose (of the new drug or cannabis) at home, where you can monitor for adverse effects and possible reactions to your current medications. Nobody wants to get sick or feel bad when they are not at home. Record any unusual symptoms that you notice, including times and any contributing factors, such as tiredness or irritability, and report them to your doctor.
• DON’T stop any medication without first letting your doctor know. He or she may be able to help find a solution to any issue you may have (by changing doses, drugs, or even just the timing of your meds). If your doctor doesn’t know you’ve stopped a medication, they may increase the dose, then wonder why it’s still not working. Also, certain medications need to be weaned off to avoid withdrawal symptoms.
• Seek additional care (doctor’s visit, quick care, or emergency room) if you are having trouble breathing, are still having symptoms after attempts to treat yourself, or if symptoms are severe or life-threatening. However, if symptoms are generally mild, you can attempt to self treat or allow the symptoms to wear off at home as appropriate.

Cannabis is generally well-tolerated by most people, but can interact with a few prescription drugs. Knowing which medicines might interact with your cannabis, partnering with your healthcare professionals to ask how cannabis may affect your prescription medicines, and being aware of what effects to expect and how to treat them, will allow you to get the most out of your cannabis therapies. Doing a little work and asking a few questions will help to avoid killing your buzz.

Dr. Kit, Pharm. D, RPh is a licensed pharmacist and co-owner of Medigrow, a Nevada grow school.