Why is it advised against drinking alcohol when taking medication?

Source: French to English Tester   Published on: 2026-04-28

Source: The Conversation – France in French (3)– By Mickael Naassila, Professor of Physiology, Director of the Alcohol & Drug Dependence Research Group GRAP – INSERM UMR 1247, University of Picardie Jules Verne (UPJV)

Anticoagulants, antihypertensives, diuretics, anxiolytics, antidepressants, antidiabetics, anticancer drugs… all these medications apparently unrelated to each other actually have one thing in common: they are sensitive to interactions with alcohol. Consuming an alcoholic beverage while undergoing treatment potentially causes various effects, some of which may be serious.

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You leave the pharmacy with in your bag a treatment for pain, anxiety, hypertension, or diabetes. Your pharmacist has very likely explained to you the medication dose to take, and over what duration. They may have lingered on the potential side effects. It is possible they also asked you if you smoked. But often, one question remains absent from this type of exchange: do you ever consume alcohol?

The association between alcohol consumption and medication is, however, one of the most common situations in everyday life. It concerns millions of people, often without them being aware of it. Yet, alcohol can modify the effectiveness of a treatment, increase its toxicity, or amplify certain side effects, sometimes with very common medications.

Behind this reality lie complex biological mechanisms, but whose consequences are very concrete: fall, fainting, bleeding, hypoglycemia, overdose, treatment inefficacy, or silent worsening of a chronic disease.

And contrary to popular belief, it is not just a problem related to sleeping pills or “heavy drinkers.”

A frequent issue

The association between alcohol and medications potentially likely to interact with this substance is far from marginal. In the United States,analysis of the national NHANES survey (1999–2010)estimated that 42.8% of adults used at least one medication likely to cause such an interaction, a proportion that exceeds 75% after age 65.In Switzerland, about one in five people aged 55 or older reported often or almost always consuming alcohol at the same time as their medications.

In older subjects who take several types of medications, the risk becomes even more marked:some studiesreport that thevast majoritypatients are exposed to at least one potential interaction. In other words, this is not a rare or exceptional situation, but a frequent everyday reality, especially among elderly people.

Alcohol and medications: a relationship that is not neutral

When we take a medication, it doesn’t just “act” in our body. It is absorbed, distributed throughout our body, transformed by the liver, then eliminated. All these stages constitute thepharmacokineticsof the drug. And alcohol can interfere with each of them.

The liver plays a central role here. Indeed, it is the one that metabolizes not only alcohol but also a large part of the medications. However, when two substances take the same biological pathways, they can interfere with each other.

Two situations must be distinguished: occasional consumption and regular consumption, as their effects on treatments are not the same.

Occasional consumption: when the medication accumulates

During an acute alcohol intake, such as an aperitif, a dinner with drinks, or an evening out, the body primarily mobilizes its ethanol degradation systems, particularly at the hepatic level. For this, the liver uses various enzymes. However, some medications are metabolized by these same enzymes. As a result: these medications are eliminated more slowly. Their concentration in the blood increases, which raises the risk of adverse effects or toxicity.

This phenomenon can be particularly problematic with so-called “narrow therapeutic index” drugs, that is, those for which a small difference in dose or concentration may be enough to cause an excessive or dangerous effect.

In other words, a glass can sometimes cause a medication to “overact”.

Regular use: when the treatment becomes less effective, or more toxic

Conversely, chronic alcohol consumption permanently alters liver function. The liver increases the production of certain biotransformation enzymes (notably cytochrome P450 2E1 or CYP2E1). This phenomenon is called “enzyme induction.” As a result, some medications are broken down more quickly than expected. They remain at effective concentrations for a shorter time, which can reduce their therapeutic effect.

Furthermore, this adaptation has a downside. It also promotes the formation of reactive metabolites, sometimes toxic. The best-known example is that ofparacetamol. After being absorbed, part of this medication is transformed into a toxic compound for the liver, N-acetyl-p-benzoquinone imine (NAPQI). Normally, this metabolite is neutralized by a compound called glutathione.

However, in chronic alcohol consumers, NAPQI production can increase because the liver produces larger amounts of the enzyme CYP2E1, which converts paracetamol into a toxic metabolite. At the same time, glutathione reserves decrease: they are used more to neutralize this toxin, and are often replenished less effectively due to alcohol, malnutrition, or liver disease. This increases the risk of liver damage, sometimes even when the medications are taken at usual doses.

Distribution, dehydration, elimination: less visible but important effects

Alcohol does not only disrupt metabolism.

The dehydration it promotes can reduce the volume of distribution of certain water-soluble drugs (water-soluble, editor’s note) and increase their concentration in the blood plasma.

The changes in body composition observed in some chronic alcohol consumers, notably a relative increase in fat mass, can also promote the accumulation of lipophilic molecules (which have an “affinity” for fatty tissues) and prolong their duration of action.

Finally, when prolonged consumption has damaged the liver or kidneys, elimination capacities decrease. The medications then accumulate more easily, exposing to an increased risk of overdose or prolonged adverse effects.

Often invisible to the patient, these mechanisms profoundly alter the balance between the benefit and risk of the treatment.

It should be noted that during drug development, certain pharmacokinetic interactions can be studied, especially if a risk is suspected. However, clinical trials often include few heavy drinkers. Furthermore, they exclude frail patients and poorly assess actual alcohol consumption (occasional, chronic, or variable).

After marketing, pharmacovigilance can detect warning signals, but alcohol is frequently underreported or not investigated. Result: many interactions with alcohol are probably underestimated and therefore go unnoticed.

When effects add up: pharmacodynamic interactions

Alcohol can also interact directlywith the effects of drugs on the body. This is then called ‘“pharmacodynamic interactions”.

In this case, alcohol does not necessarily change the concentration or distribution of the medication, but thethe way the body responds to it.

Alcohol mainly acts as a depressant of the central nervous system (brain and spinal cord). It enhances its main inhibitory system (GABAergic transmission), while inhibiting the function of molecular structures involved in neuronal excitation (NMDA glutamatergic receptors).

This double effect causes sedation, psychomotor slowing, vigilance disorders, impaired reflexes, and decreased cognitive performance. In other words, alcohol slows down the general activity of the brain as well as the functioning of the body and lowers the level of alertness.

When medications acting on these same pathways are combined with alcohol, their effects do not simply add up: they potentiate each other. This is notably the case:

• benzodiazepines (for example, alprazolam – trade name Xanax – or bromazepam – trade name Lexomil);

• hypnotics (for example, zolpidem – brand name Stilnox – or zopiclone – brand name Imovane);

• opioids (for example, morphine, which is notably found in the medication marketed under the name Tramadol);

• of certain sedative antihistamines (for example, hydroxyzine – brand name Atarax or dexchlorpheniramine – brand name Polaramine);

• of several psychotropic drugs (for example, Tercian for cyamemazine, Largactil for chlorpromazine).

Clinically, this can manifest as severe drowsiness, confusion, coordination disorders, falls, household or road accidents.

In the most severe cases, particularly with opioids or certain anxiolytics, central nervous system depression can reach the respiratory centers and become potentially fatal, as patients are no longer able to breathe.

A sometimes brutal reaction: the “antabuse” effect

Some interactions are even more spectacular. Normally, alcohol is transformed into acetaldehyde, then quickly converted into acetate thanks to an enzyme called aldehyde dehydrogenase (ALDH).

But some medications block this second step. Acetaldehyde then accumulates in the body, causing a reaction known as type“antabuse”.

Symptoms can appear quickly: facial redness, headaches, nausea, vomiting, tachycardia, hypotension, intense discomfort.

This mechanism is deliberately used with thedisulfiramin the management of alcohol dependence. The principle is not to “cure” the addiction directly, but to create a strong deterrent: if the person drinks, they risk a rapid and unpleasant reaction.

If disulfiram is indeed a medication (in medicine, a treatment can act either by correcting a biological mechanism, or by modifying behavior or preventing relapse), its use nevertheless raises ethical questions: it is only acceptable if the patient is clearly informed, voluntary, and medically supported. Today, it is used less than in the past, but can still be useful in certain well-controlled situations.

Similar reactions can also occur with other medications, including certain antibiotics, such as metronidazole, or certain antifungals.

It must be kept in mind that sometimes small amounts of alcohol are enough, including those contained in syrups, mouthwashes, or certain food preparations…

Frequent interactions with very common treatments

The subject of interactions with alcohol goes far beyond medications with an “obvious risk.” Some commonly used medicationsare also affected by this issue.

– Anticoagulants and antithrombotics:Chronic alcohol consumption can increase the hemorrhagic risk. It promotes digestive lesions (gastritis, ulcers, esophageal varices), disrupts platelet aggregation, and can alter coagulation.viahepatic involvement;

– Antihypertensives:Acute consumption can cause vasodilation (dilation of blood vessels), a drop in blood pressure, dizziness, or fainting. Conversely, chronic consumption promotes hypertension and can complicate treatment control;

– Diuretics and beta blockers:The combination can increase hypotension. In some cases, alcohol can also worsen bradycardia or discomfort;

– Psychotropics, anxiolytics, hypnotics, antidepressants, antipsychotics:Alcohol often increases sedation, confusion, memory disorders, and the risk of falling;

– Antidiabetics:Alcohol inhibits glucose production (neoglucogenesis) in the liver, which can promote sometimes severe hypoglycemia, particularly in patients treated with insulin or certain hypoglycemic medications;

– Anti-cancer treatments:Alcohol can increase liver toxicity, worsen fatigue, digestive disorders or skin conditions, and sometimes interfere with the metabolism of certain molecules.

A risk that is exploding among elderly people

Elderly people probably constitute themost exposed populationon interactions between alcohol and medications.

Indeed, with age, polypharmacy becomes common. A significant portion of those over 75 take multiple medications simultaneously, sometimes up to five or even more. However, the more treatments increase, the greater the risk of interactions.

Added to this situation are physiological changes related to aging, such as a decrease in body water mass (the amount of water contained in the body), which promotes an increase in blood alcohol concentration. The relative increase in fat mass extends the action of certain lipophilic drugs, while the decline in renal and hepatic functions slows the elimination of drugs as well as, sometimes, their active or toxic metabolites, favoring their accumulation and increasing the risk of adverse effects. Finally, with age, the brain becomes more sensitive to sedative substances.

Interactions between medications and alcohol often result in elderly people experiencing falls, fractures, acute confusion, and medication-related accidents leading to hospitalizations and loss of autonomy.

It should be noted that, in this context, even an alcohol consumption considered “moderate” can produce disproportionate effects.

Why is there so little talk about this problem?

Several reasons can explain why the issue of interactions between medications and alcohol is so rarely addressed: because alcohol is culturally trivialized; because mentioning its consumption can seem intrusive; because time is often lacking at the counter or during consultation; because these interactions seem less concerning than those that can occur with other medications, etc.

But ignoring the issue does not make it disappear. Alcohol is a biologically active substance, capable of interacting with many treatments. As such, it should be part of the therapeutic dialogue, in the same way that allergies, tobacco, or other medications taken concurrently are. Today, asking a patient if they smoke has become a preventive reflex. Asking if they drink alcohol should be just as much.

So, the next time your doctor writes your prescription, or when you go to pick up your medication at the pharmacy, just ask: “Is there a possible interaction with alcohol consumption, even occasional?”

This question, if it were asked more often on both sides of the counter, could prevent many silent accidents…

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For further information

– TheFrench Society of Alcoholism and Addictology (SF2A)is currently carrying out aguide for healthcare professionals on alcohol and medication interactions ;

– On the SF2A website, the pageAlcoholConsoScience provides health professionals with scientifically validated information on the impact of alcohol consumption on health.

Mickael Naassila is a senior member of the Institut Universitaire de France (IUF). He is President of the French Society of Alcoholism and Addictology (SF2A) and of the European Society for Biomedical Research on Alcoholism (ESBRA); Vice-President of the French Federation of Addictology (FFA) and Senior Vice-President of the International Society for Biomedical Research on Alcohol and Addictions (ISBRA). He is a member of the Institute of Psychiatry, co-head of the GDR Psychiatry-Addictions, and head of the National Alcohol Research Network REUNIRA and the project AlcoolConsoScience. He has received funding from the ANR, from IReSP/INCa Addiction Control Fund.

Camille André and Naouras Bouajila do not work for, advise, hold shares in, or receive funds from any organization that could benefit from this article, and have declared no affiliations other than their university positions.

–ref. Why is it advised against drinking alcohol when taking medications?https://theconversation.com/why-is-it-advisable-not-to-drink-alcohol-when-taking-medication-281078