Mixing Alcohol and Keflex

Published On: April 19, 2023

Most people who drink alcohol will be prescribed medication at some point in their life. Whilst on medication, people tend to continue to drink alcohol, despite the effects and symptoms it may cause.

Prescription and over-the-counter medication (OTCs) will have an interaction with alcohol, sometimes with severe consequences. It is important to know how the body metabolises alcohol, in order to discuss what effects medication might have on this process.

What Happens When We Drink Alcohol?

People at a table toasting to a mix of drinks

When ingested, a small amount of alcohol is broken down and metabolised in the stomach. The rest of the alcohol is absorbed into the blood via the gastrointestinal tract (stomach and small intestine).

This is called the ‘first-pass metabolism’; the lining of the stomach produces enzymes such as alcohol dehydrogenase (ADH) that metabolise alcohol. [1]

First-pass metabolism is often detectable following low alcohol concentration (around 2 drinks per person of 70kg). Here, most alcohol may be metabolised in the stomach due to delayed gastric emptying if the alcohol level is very low.

However, as a general rule, only around 10% of alcohol is fully metabolised during the first-pass metabolism. The more alcohol that is consumed, the smaller the amount eliminated by first-pass metabolism.

Once it has been fully absorbed, the alcohol is transported through the portal vein to the liver. Some of the alcohol is metabolised during its travel to the liver; in the liver, alcohol is metabolised by ADH or by cytochrome P450. The activity of these enzymes differs according to the person, but their purpose remains the same. [2]

The remaining alcohol leaves the liver and enters circulation to be distributed throughout the body. The alcohol, if not absorbed, will eventually find its way back to the liver to finally be metabolised.

The effect of ethanol on the tissue depends on blood alcohol concentration, determined by how quickly the alcohol is absorbed, metabolised, and excreted. [3]

The alcohol that has not been metabolised during first-pass metabolism enters general circulation, dispersed throughout the water in the body as it does not absorb into fatty tissue.

Alcohol distribution tends to depend on age and gender, as women and older people tend to have less water and more body fat than men or younger people.

This difference in alcohol distribution affects the body’s alcohol concentration levels. [4] This is why women with lower water levels have a higher blood alcohol concentration than men, even when they have consumed the same amount of alcohol.

The levels are also affected by environmental factors such as: [5] [6]

  • How fast you drink (rate of alcohol consumption)
  • Whether you have eaten before or during drinking
  • Type of alcoholic drink
  • Genetics
  • Diet and age
  • Smoking
  • Time of day

Interactions Between Medication and Alcohol


Most medications prescribed, specifically, antibiotics, interact with alcohol. This alters the body’s ability to metabolise alcohol and can produce uncomfortable side effects. [7]

Research has shown two types of interactions occur between medication and alcohol:

1. Alcohol interferes with the metabolism of medication (pharmacokinetic interaction)

This interaction usually occurs in the liver, as the liver metabolises both ethanol and any medication usually by similar enzymes.

2. Alcohol enhances the effects of the medication (pharmacodynamic interaction)

This interaction enhances the effects of medication specifically in the central nervous system. For example, both alcohol and medication have sedative effects, which can both become enhanced and therefore impairing the cognitive function of the person in question.

Research has suggested that some medications may block attempts at first-pass metabolism in the stomach, causing higher blood alcohol concentration levels. [8]

A study on rats found that the rats treated with an antibiotic showed a reduced alcohol elimination rate compared to the unmedicated rats. Applied to humans, those who take antibiotics may find delayed alcohol elimination.[9]

What is Keflex?


Keflex is an antibiotic, classed as a first-generation cephalosporin.

This medication is on WHO’s (World Health Organisation) model list of essential medicines. Keflex is prescribed to treat bacterial infections such as:

  • Ear infections
  • Upper respiratory tract infections
  • Skin infections
  • Urinary tract infections and yeast infections
  • Bone infections

Cephalexin is a broad antibiotic, deemed effective at fighting a variety of different types of bacteria. Cephalexin aims to disrupt the growth of bacteria walls built by the cells, stopping them from multiplying.

Keflex may be prescribed in many forms, such as power (oral administration), tablets, or capsules.

The following are common side effects of Keflex:

  • Abdominal pain and stomach pain
  • Upset stomach
  • Skin blisters
  • Diarrhoea
  • Dark urine
  • Tiredness
  • Itchiness
  • Agitation
  • Low iron (anaemia)
  • Dizziness
  • Skin redness and flushing, hives
  • Mild hallucination
  • Hypersensitivity
  • Kidney problems and kidney function

Does Drinking Alcohol Affect Keflex?

People at a table toasting to a mix of drinks

The common notion behind antibiotics and alcohol is that the alcohol renders the medication ineffective. This is not the case for Keflex, as Keflex will continue to treat infection even if you drink alcohol.

Some antibiotics can trigger severe issues such as breathing problems and heart complications, but Keflex is not among these antibiotics.

This does not mean that mixing alcohol with Keflex is acceptable, the side effects can be extremely uncomfortable and often warrant medical attention.

The side effects caused by Keflex and alcohol are similar:

  • Facial flushing (chest, neck, and face)
  • Nausea
  • Vomiting
  • Headaches

By combining the two, you are doubling your chances of experiencing the negative side effects, risking how intense they will be and how long they may last. Drinking whilst taking Keflex will also increase the likelihood that it will take you longer to recover from your illness.

Alcohol impacts the nervous system and the immune system. Alcohol has been shown to disrupt the immune pathways, affecting the body’s ability to fight against infection and therefore lengthen the time of recovery.

Both Szabo and Saha researched the effects of alcohol, finding that it dramatically weakens host defences, leaving heavy drinkers at risk of health complications, viral infections, and systematic inflammation. [11]

The stomach and intestines (gastrointestinal system) are alcohol’s first contact point because it is absorbed into the bloodstream.

Alcohol affects the number of microbes in the gut and disrupts gut function. These organisms affect how the immune system functions, disrupting the communication between organisms and the immune system.

Alcohol disrupts:

  • The ciliary function of upper airways
  • The function of immune cells
  • The function of the epithelia in lower airways

Alcohol has been linked to pneumonia and a variety of pulmonary diseases such as tuberculosis. Consumption does not have to be classed as chronic to lead to health complications and unpleasant side effects.

Your energy levels will be low, and you will be exposing yourself to a variety of infections, and adverse effects.

Our bodies and minds need essential rest when in recovery. Alcohol disrupts sleep patterns and energy levels, elongating the body’s response to medication and illness.

Try to avoid alcohol and too much caffeine when in recovery and taking antibiotics; give your body the best chance at fighting infection.

Mixing alcohol with antibiotics can lead to decreased functioning of the immune system, meaning it will take longer for you to feel better. Seek medical advice and medical attention if you are suffering from negative drug interactions from alcohol consumption.

Ask your doctor about alcohol consumption before you are prescribed medication for an illness or condition.

Keflex Abuse


Cephalexin is not considered to be addictive. However, Keflex may be abused by individuals who frequently engage in drug use through IV and injections, so it has the potential for abuse. This may appear as a misuse of antibiotics, defined as either not taking them as directed, or taking them too much for the wrong reasons.

This can lead to creating drug-resistant infections, with severe consequences for the patient and the rest of society. This can leave the patient susceptible to other bacterial infections, becoming difficult to treat due to overdosing or misusing Keflex.

Whilst alcohol might not affect the effectiveness of Keflex, misusing this antibiotic will. The properties that fight bacteria will disappear following prolonged periods of treatment or overdosing; this can lead to a developed allergic reaction and painful gastrointestinal issues.

It is best not to mix this medication with alcohol, as the interaction with alcohol only leads to a longer recovery and increased vulnerability to infection.

Aim to abstain from alcohol during treatment, as excessive alcohol consumption and chronic alcohol exposure can lead to more severe issues than a damaged immune system.


[1] Lim RT, Jr, Gentry RT, Ito D, Yokoyama H, Baraona E, Lieber CS. First-pass metabolism of ethanol is predominantly gastric. Alcoholism: Clinical and Experimental Research. 1993;17:1337–1344.

[2] Martin NG, Perl J, Oakeshott JG, Gibson JB, Starmer GA, Wilks AV. A twin study of ethanol metabolism. Behavior Genetics. 1985;15:93–109.

[3] Zakhari S. Overview: how is alcohol metabolized by the body? Alcohol Res Health. 2006;29(4):245-54. PMID: 17718403; PMCID: PMC6527027.

[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6527027/#b8-245-255

[5] Bennion LJ, Li T-K. Alcohol metabolism in American Indians and whites: Lack of racial differences in metabolic rate and liver alcohol dehydrogenase. New England Journal of Medicine. 1976;294:9–13.

[6] Kopun M, Propping P. The kinetics of ethanol absorption and elimination in twins and supplementary repetitive experiments in singleton subjects. European Journal of Clinical Pharmacology. 1977;11:337–344

[7] Thomasson HR. Gender differences in alcohol metabolism. Physiological responses to ethanol. Recent Developments in Alcoholism. 1995;12:163–179.

[8] Weathermon R, Crabb DW. Alcohol and medication interactions. Alcohol Res Health. 1999;23(1):40-54. PMID: 10890797; PMCID: PMC6761694.

[9] Caballeria J, Baraona E, Deulofeu R, Hernandez-Munoz R, Rodes J, Lieber CS. Effects of H-2 receptor antagonists on gastric alcohol dehydrogenase activity. Digestive Disease Sciences. 1991;36:1673–1679.

[10] Nosova T, Jokelainen K, Kaihovaara P, Vakevainen S, Rautio M, Jousimies-Somer H, Salaspuro M. Ciprofloxacin administration decreases enhanced ethanol elimination in ethanol-fed rats. Alcohol and Alcoholism. 1999;34:48–54

[11] Sarkar D, Jung MK, Wang HJ. Alcohol and the Immune System. Alcohol Res. 2015;37(2):153–5. PMCID: PMC4590612.


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