Alcohol and medication: a dangerous cocktail!

To better understand the risks of drinking alcohol while taking medication, we first need to know what happens to medication once it is in our system. With the exception of digestive system treatments, most medications we swallow are absorbed through our stomach and intestinal walls. They then enter the bloodstream to reach our heart, brain, muscles, and other tissues, where they take effect. However, before arriving at their destination, medications – like alcohol – must first pass through the liver, our body’s sorting centre. Its role? To protect us by detecting and transforming foreign substances, also known as xenobiotics. With the help of specialized proteins, the liver modifies these substances to deactivate them, enabling their elimination, often through urine. However, it is not always that simple: some medications need this transformation to be active and work effectively in our body.

The same applies to alcohol. Once swallowed, it begins to be absorbed into the bloodstream from the stomach, then the intestines, before also passing through the liver. Unlike some medications, alcohol does not need to be activated to take effect: instead, the liver eliminates it by transforming it into another substance, called acetaldehyde. This task is not accomplished by the same proteins that process medications. Alcohol is mainly eliminated by a specific enzyme, alcohol dehydrogenase, whereas most medications are broken down by a group of proteins known as cytochromes P450.

There is a close link between the two mechanisms, however: alcohol can affect the levels of certain cytochromes in different ways, depending on the amount and frequency of alcohol consumption. Take warfarin for example, sold under the name Coumadin and various generic brands. This anticoagulant is used to prevent the formation of blood clots. Drinking alcohol occasionally, can slow down the elimination of warfarin, making the blood thinner than expected – which in turn increases the risk of bleeding. Conversely, regular consumption stimulates cytochrome activity, which may result in warfarin being eliminated too quickly…reducing its efficacy and increasing the risk of clots [3].

The same applies to many other medications: for identical doses, consuming alcohol will increase the effects of the medication for some people, while for others the effects will decrease! It’s not easy to figure out… and sometimes even risky, especially if side effects occur when a medication becomes too powerful. This is the case, for example, with many medications that affect alertness such as for anxiety, pain and depression. Mixed with alcohol, their sedative effect can be amplified, increasing the risk of drowsiness, loss of balance and slowed reflexes. Another combination to be wary of is alcohol with certain oral diabetes medications. Together, they can cause severe hypoglycemic episodes.

You also have to be careful if alcohol decreases the effectiveness of a medication to the point that it can no longer fulfill its role. When a medication no longer protects against the complications of a high-risk condition – such as heart and blood pressure medications and certain cancer drugs – the consequences can be serious.

Even without medication, alcohol is a toxic substance for the liver. It is the main cause of liver damage such as fatty liver or drug-induced hepatitis, which, in the long term can evolve into cirrhosis.

The liver doesn’t only transform medications: it also has to manage the residues, known as metabolites, produced by this transformation. Some of these metabolites may be toxic for the liver. One of the most concerning is acetaminophen (Tylenol and its generic equivalents). Even without consuming alcohol, this medication can produce a harmful metabolite, capable of destroying liver cells. With alcohol, the risk increases significantly, placing considerable strain on the liver.

The alcohol-medication combination can also have an effect on how alcohol is absorbed by our body. Some medications slow down gastric emptying, i.e. the passing of food and liquids from the stomach to the intestine. As a result, alcohol may be absorbed faster than normal. Even with moderate consumption, the effects of inebriation can be faster and more intense than expected.

The well-known “morning-after” effects – headache, dizziness, sweating, nausea, vomiting, etc. – are largely caused by an accumulation of acetaldehyde, a substance produced when the liver transforms alcohol. Some medications increase this accumulation, which intensifies the side effects. This is the principle behind disulfiram, better known as Antabuse, used to help people going through alcohol withdrawal: it acts as a powerful deterrent by making alcohol consumption extremely unpleasant.

This type of reaction is not limited to Antabuse. Other medications such as some antibiotics, antifungals and oral hypoglycemics can also cause an Antabuse effect if taken at the same time as alcohol.

The list of medications to avoid or use with caution with alcohol is long… and hard to memorize. It includes not only prescription medications, but also many over-the-counter products, such as acetaminophen, antihistamines, anti-inflammatories, and anti-nausea drugs. These medications are often available under different brand names, sometimes as a secondary ingredient in combination products. Even if the name stays the same, the dose may vary from one product to another.

Although we can’t memorize all the names of the medications to avoid, we can – and should – make a habit of reading drug warnings. In Canada, every drug sold in pharmacies, whether prescription or over-the-counter, must include clear instructions on what precautions to take, especially with respect to alcohol. In riskier cases, the pharmacist will often take the time to inform you directly at the time of purchase – even for over-the-counter medication. A good reflex to adopt: if in doubt, ask.

However, information doesn’t always flow both ways: there are no mandatory warnings on alcohol products, not even a simple general warning about health risks or possible drug interactions. Thankfully, things are evolving. We now have a wide variety of alcohol-free products such as beers, mocktails and sparkling wine, so we can share a toast without affecting our ongoing treatment. An excellent way to take care of ourselves…without compromising on pleasure!