What you should know about cannabis and drug interactions

You have probably read or heard something along the lines ‘consult your physician before taking cannabis if you are on any prescription pills.’ That statement consists of wise words that you should adhere to at all times.

Prescription pills can interact with cannabis, foods, beverages, supplements, and even with each other, leading to mild or severe side effects. Consequently, without sounding redundant, always consult your doctor to avoid such incidents.

What is a drug-drug interaction?

A drug or medication interaction occurs when a person takes a combination of drugs (2 or more) that are incompatible with each other. In such cases, one of the drugs interferes with the other(s) by countering or accelerating their effects. This may lead to drug inefficiency, severe side effects, and sometimes the loss of life.

How does cannabis interact with other drugs?

P450 enzymes metabolize all drugs before they are available in the consumer’s system. The Cytochromes P450 are a group of enzymes responsible for metabolizing many compounds. These enzymes are primarily located in the liver but can also be found in cells throughout the body in small quantities.

There are more than 50 enzymes under the P450 class, but only six are responsible for metabolizing 90% of prescription drugs. These enzymes include CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4. Cannabinoids, THC and CBD, in particular, inhibit or induce the function of these Cytochrome P450 (CYP450) enzymes.

This interferes with enzymatic function, which affects the concentration of certain drugs. Cannabinoids play three prominent roles in drug interactions.

1. Victims: cannabinoid levels are affected by the presence of another drug.
2. Perpetrators: the cannabinoids affect the levels of other drugs
3. Overlapping other drug’s effects: cannabis and other drugs have similar effects on a consumer.

Cannabinoids as drug interaction victims

Ketoconazole, a potent antifungal agent, is a CYP3A4 inhibitor. This enzyme metabolises THC and CBD. Elevated levels of these cannabinoids lead to an increase in the psychoactive effects of THC and adverse side effects of CBD, such as drowsiness and elevated levels of liver enzymes like transaminase. The same results may be experienced with CYP3A4 inhibitors like Verapamil and Macrolides.

CYP2C9 is a P450 enzyme that metabolizes THC and not CBD. Cotrimoxazole, amiodarone, and fluoxetine are classes of drugs that, when consumed, are likely to inhibit the metabolism of THC, leading to increased psychoactive effects. Below is a breakdown of the different classifications of prescription drugs and how cannabis interacts with each of them.

Cannabis interactions with different classes of drugs

Blood thinners

Blood thinners or anticoagulants like warfarin work by preventing blood clots in the body. Combining this class of drugs and cannabis is not advised. THC and CBD can increase warfarin levels in the body by inhibiting the CYP2C9 enzyme. A high warfarin content in the body leads to excessive bleeding that can be fatal.

Benzodiazepines 

Cannabis can interact with benzodiazepines, including Clobazam. The drug is used to treat seizures in Lennox Gastaut syndrome patients. CBD increases the levels of Clobazam by three times through the inhibition of the CYP2C19 enzyme.

Bronchodilators

Bronchodilators are used in opening up airways of patients with lung-related conditions, such as asthma and chronic bronchitis. The drugs become less effective when taken in tandem with cannabis (smoking). This is because cannabis speeds up the metabolism of bronchodilators by 40%.

Psychiatric drugs

Mental health and pain are the leading causes of the sudden rise in medical cannabis consumption. The prevalence of these two conditions is alarming as they are among the top contributors to the global burden of health.

Medical cannabis interacts with psychiatric medications, specifically tricyclic antidepressants like dothiepin and imipramine. The combination may lead to increased heart rate and elevated blood pressure. It may lead to confusion, hallucination, and aggressiveness in severe cases.

Immunosuppressants

Studies suggest that CBD is a potential therapeutic option for kidney transplant patients. The cannabinoid is a natural immunosuppressant and immunomodulator. There are limited documented interactions between medical cannabis and immunosuppressants; however, consult a physician before self-medicating cannabis while taking this classification of drugs.

OTC painkillers

The majority of Over-the-counter pain medications have minimal interaction with cannabis. Drugs containing acetaminophen/paracetamol pose a slight risk of causing liver damage when used with cannabis. Cannabis is a potent analgesic compound that can be utilized to replace OTC drugs. It offers a better, natural alternative with minimal side effects.

Opioids

Medical cannabis has numerous therapeutic and medicinal applications that can benefit millions of patients. One significant contribution that the plant can offer is helping in the fight against the abuse of opioids. Replacing opiates with cannabis reduces the number of fatalities attached to the overdose of opiates.

CBD, in particular, inhibits the function of the CYP2B6, CYP3A4, and other cytochrome P450 enzymes to increase the levels of morphine, oxycodone, and methadone in the body.

While this may be beneficial when opiates are taken in low doses, high doses may lead to excess opiates in the system, leading to an overdose. Additionally, both opioids and cannabis have depressant effects and may significantly compromise the central nervous system when combined.

Antibiotics

There are no recorded interactions between cannabis and antibiotics. Studies available indicate that combining the two may enhance the effectiveness of the antibiotics. Before combining the two, seek advice from a physician.

Take away

Cannabis can interact with different drugs, from opioids to sedatives. Cannabinoids can be the victims of the interactions, whereby their levels of availability in the system are affected by other drugs, such as Ketoconazole.

As perpetrators, cannabinoids inhibit or induce the functioning of P450 enzymes, resulting in the acceleration or delay of the metabolism of drugs. In other instances, cannabis has similar effects as prescription drugs, so the effects overlap.

Medical cannabis is legal in most parts of the world. The plant is easily accessible and is marketed as a potential therapeutic agent for a myriad of conditions. Yes, studies have proven that it does help with pain, mental health issues, mood regulations, inflammation, appetite, and many more diseases. What is usually left out is that cannabis can and does interact with prescription pills.

Before self-medicating with cannabis, always consult a qualified physician, preferably one with medical cannabis expertise. The doctors are best placed to advise on whether you should include cannabis into your treatment regime or not.