ETHYL alcohol (ethanol, alcohol) is a water-soluble drug that is absorbed in the stomach and small intestine, relatively slowly in the former and rapidly in the latter. It is then freely distributed throughout the body.
Since alcohol is water soluble, very little of it gets into the body fat. The concentration of alcohol is higher in the blood and tissues of women for the same volume, because women have more sub-cutaneous fat than men. Women may also have lower concentrations of an enzyme that breaks down alcohol in the stomach than men so that less alcohol is broken down before its absorption. This makes women more vulnerable to alcohol-medicine interactions than men.
When two or more drugs are taken at the same time, they may exert their effects independently of each other or they may interact. The interaction may be potentiation or antagonism of one drug by another drug or some other effect may result.
Many drug interactions are not harmful. Many of the potentially harmful interactions occur in a minority of patients. The severity of drug interactions, however, varies in different individuals.
Harmful alcohol-medicine interactions may occur even if they are not taken at the same time.
Those who are at increased risk of harmful drug interactions include the elderly, women and those whose liver or kidney function is impaired.
Harmful alcohol-medicine interactions may occur even if they are not taken at the same time. Many of the medicines that interact with alcohol can be purchased over the counter. Therein lies the potential danger for consumers.
Alcohol has a sedative effect. It can also have a mild anaesthetic effect. There are many commonly-used medicines that make a person feel sleepy. When these medicines are taken together with alcohol, there is an increase in drowsiness and dizziness. This may lead to problems of concentration or performance of tasks that require skills. The ability to drive a motor vehicle may be affected, sometimes causing danger to the driver, passengers and other road users.
Some medicines e.g. cough, cold and allergy mixtures, and painkillers (analgesics) contain ingredient(s) that can react with alcohol.
The alcohol-medicine interactions that are potentially hazardous are listed below. The combined consumption of alcohol and the medicines involved should always be avoided. Antibacterials – A disulfiram-like reaction can occur when alcohol is taken with metronidazole. The reaction includes flushing of the face, throbbing headache, palpitations, nausea, vomiting and with large dose of alcohol, irregular heart beat, decrease in blood pressure and collapse. There is an increased risk of fits when alcohol is taken with cycloserine. Anti-coagulants – Alcohol may affect anticoagulant control with the coumarins or phenindione. Occasional drinking may lead to internal bleeding. Heavier drinking may have the opposite effect leading to possible blood clots, strokes or heart attacks. Anti-depressants – Some beverages containing alcohol and some low alcohol (dealcoholized) beverages contain tyramine, which interacts with monoamine oxidase inhibitors (MAOI), to cause a dangerous increase in blood pressure that can be life threatening. A throbbing headache is an early warning symptom. If no tyramine is present, an enhanced blood pressure lowering effect may result. Alcohol increases the sedative effect when taken with tricyclics, tricyclic-related antidepressants and mirtazapine. There is increased drowsiness and dizziness with an increased risk of overdose. Paraldehyde – Alcohol increases the sedative effect when taken with paraldehyde. There is increased drowsiness and dizziness with an increased risk of overdose.
Some other alcohol-medicines interactions are listed below. Analgesics – Alcohol enhances the blood pressure lowering and sedative effects when taken with opioid analgesics. When alcohol is taken with non-opioid analgesics like aspirin, acetaminophen, celecoxib, naproxen and rofecoxib there may be stomach upsets, bleeding and ulcers, rapid heart beat and liver damage (acetaminophen). Anti-diabetics – Alcohol enhances the blood glucose lowering effect of these medicines. The risk of lactic acid acidosis is increased when alcohol is taken with metformin. Flushing may occur in susceptible patients when alcohol is taken with chlorpropamide. Anti-epileptics – Alcohol increases the sedative effect when taken with primidone. Anti-histamines – Alcohol increases the sedative effect when taken with anti-histamines. Anti-muscarinics – Alcohol increases the sedative effect when taken with hyoscine. Anti-psychotics – Alcohol increases the sedative effect when taken with anti-psychotics. Anxiolytics and hypnotics – Alcohol increases the sedative effect when taken with anxiolytics, hypnotics and barbiturates. There is increased drowsiness and dizziness with an increased risk of overdose. Blood pressure and medicines prescribed for heart conditions – Alcohol enhances the blood pressure lowering effect of adrenergic neurone blockers, alpha-adrenoreceptor blockers, angiotensin converting enzyme (ACE) inhibitors, angiotensin II receptor antagonists, beta-blockers, calcium channel blockers, clonidine, diazoxide, diuretics, methyldopa, moxonidine, nicorandil, nitrates, vasodilator antihypertensives i.e. hydralazine, minoxidil, nitroprusside. Cough, cold and allergy medicines – There may be drowsiness, dizziness and an increased risk of overdose when alcohol is taken with these medicines e.g. diphenhydramine, chlorpheniramine Cytotoxics – A disulfiram reaction can occur when alcohol is taken with procarbazine. The reaction has been described above in relation to the anti-bacterial, metronidazole. Dopaminergics – Alcohol reduces the tolerance to bromocriptine. Muscle relaxants – Alcohol increases the sedative effect when taken with baclofen, methocarbamol or tizanidine. Retinoids – Alcohol causes the formation of etretinate from acitretin.
The above lists are not comprehensive and do not contain all medicines that may interact with alcohol. More importantly, it also does not include all the ingredients in every medicine.
It is best to avoid alcohol if you are taking medicine(s) and do not know about its effects. It is advisable to consult your doctor or pharmacist to know more about the medicine(s) you are taking and whether it will interact with alcohol.
Dr Milton Lum is Chairperson of the Commonwealth Medical Trust. This article provides general information only and is not intended to replace, dictate or define evaluation and treatment by a qualified doctor. The views expressed do not represent that of any organization that he is associated with.