Health & Wellbeing

Antibiotic Side Effects & Resistance

Is the overuse of antibiotics contributing to the increasing risk of antibiotic resistant bacteria?


Antibiotics have saved millions of lives. Before the advent of penicillin, infections were a leading cause of death. In 1900, the leading causes of death were pneumonia, tuberculosis (TB), diarrhoea and enteritis, which along with diphtheria caused a third of all deaths. Since penicillin was introduced in the 1940s, scientists have developed more than 150 antibiotics to fight the spread of infectious diseases.

As antibiotics were seen to cure previously fatal illnesses, this led doctors and the general public to trust them as miracle drugs. In most developed countries, antibiotics are still the second most used drug after painkillers. Most people are familiar with broad-spectrum antibiotics (eradicating many different types of bacteria) and narrow-spectrum antibiotics (killing targeted bacteria).

But although antibiotics have saved millions of lives, the overuse/ misuse of antibiotics has created unforeseen problems.

Antibiotic Overuse

Antibiotics can't distinguish between the "good" and the "bad" bacteria. As is now understood, there is a delicate balance of billions of bacteria happily co-existing with us inside our digestive tract and in our bodies. These helpful bacteria “compete” and create a balance in the large intestine, the small intestine and other areas such as the genitalia to protect against fungal infections and other bacteria. They also help us utilise nutrients and bolster our immune systems. Even more recently, scientists are seeing a link between mental health and the microbiome.

When antibiotics are overused or underused, for example, a short course or failure to complete the course prescribed may only eradicate off weak bacteria, leaving stronger bacteria to emerge later. It has the potential to disrupt the normal ecology of the body and render anyone more susceptible to pathogenic (disease-causing) bacteria, yeast, viral and parasitic infections.

Overuse in farming etc. is probably the most discussed area of antibiotic use, and it creates a deficiency of beneficial bacteria and a state of dysbiosis. To leave the gut in a state of dysbiosis is to leave the body open to illnesses since it is generally accepted that a healthy gut is essential for total body health. Everything we eat passes through our intestines and is processed by the bacteria in the gut for extraction of micronutrients, energy, protein, and soluble fibre. In the event of damaged gut bacteria, we do not get the best of the food we consume and can end up run down, tired all the time and open long-term to illness. Meanwhile stronger pathogens such as Clostridium and candida may thrive unopposed.

Antibiotic Resistance

Bacterial resistance to antibiotics occurs due to changes in the bacterium's DNA, called 'Mutations'. One bacterium with a mutation can survive the antibiotic and go on to reproduce millions more with the same resistance. Not only do they survive, but having survived an antibiotic attack, their structure changes so that the same antibiotic is unlikely to eradicate them in the future.

The Soil Association state that overuse of antibiotic administration in animals is failing to keep pace with the speed at which bacteria are adapting to resist them. Inevitably leading to resistance and complicates treatment in humans since resistance to available therapies is already established.

Also, many antibiotics that are not broken down in the body remain active long after being excreted. At present, antibiotics make a considerable contribution to the growing problem of active medical substances circulating in the environment. The potential effects and risks associated with the release of antibiotics and other drugs into the environment are concerning.

Along with antibiotic over/under use, this cannot help but increase levels of multiple antibiotic resistance.

Furthermore, the discovery of new antibiotics is slow. Between 1945 and 1968, drug companies created 13 new categories of antibiotics whereas, between 1968 and today, only two new categories have emerged.

Antibiotics blister pack
Antibiotics have gradually been introduced since 1935, however the discovery of new antibiotics is slow.

Year introduced Class of drug:

  • 1935 Sulphonamides
  • 1941 Penicillins
  • 1944 Aminoglycosides
  • 1945 Cephalosporins
  • 1949 Chloramphenicol
  • 1950 Tetracyclines
  • 1952 Macrolides/lincosamides/streptogramins
  • 1956 Glycopeptides
  • 1957 Rifamycins
  • 1959 Nitroimidazoles
  • 1962 Quinolones
  • 1968 Trimethoprim
  • 2000 Oxazolidinones
  • 2003 Lipopeptides

Antibiotics known as fluoroquinolones have more recently been associated with some or all of the following adverse drug reactions:

  • Tendonitis, Tendon Rupture, Tendon, Ligament, Joint and Muscle Damage
  • Vision Damage, Hearing Loss, Taste Perversion
  • Peripheral Neuropathy (Tingling, burning sensation)
  • Insomnia, Nightmares, Anxiety Attacks, Depersonalization, Cognitive Disorders
  • Brain, Heart, Liver, Kidney, Pancreas, Blood and Endocrine Disorders
  • Severe Psychotic Reactions, Suicidal Thoughts or Actions
  • Gastrointestinal Damage

Antibiotics & Cystitis

Most people, when they suffer their first few episodes of cystitis, go to the doctors and are prescribed antibiotics. Initially, the antibiotics are effective, especially if you have never had cystitis before. However, with every additional infection, that particular antibiotic is likely to become less effective, as the bacterium builds up resistance.

Therefore, every time you have another episode of cystitis, you have a real dilemma. Doctors, who are naturally and correctly wary of over-prescribing antibiotics, are unlikely to want to give you increasingly powerful antibiotics. Meanwhile, your episodes of cystitis may last longer and longer, and you run the risk of kidney infections and chronic pain.

Antibiotic side-effects

The side effects of broad-spectrum antibiotics, and in particular Fluoroquinolone-based antibiotics such as Ciprofloxacin, can include, the following (these reported effects are freely available online):


Heart attack, heart murmur, palpitations, angina, cerebral thrombosis, sudden death on the first dose.

Nervous System

Convulsive seizures, psychosis, depression, hallucinations, paranoia, insomnia, nightmares, dizziness.


Liver failure, jaundice, gastrointestinal bleeding, diarrhoea, ulcerative colitis, burst intestine, vomiting, constipation.

Muscles and Bones

Tendon seizure, tendon bursting and ripping, jaw, arm or back pain, joint stiffness, neck and chest pain, aching all over, gout.

Kidneys and Urinary tract

Kidney failure, calcification in kidneys, urethral bleeding, severe thrush, vaginitis.


Respiratory arrest, blood clotting in lungs, shortness of breath, pulmonary oedema, hiccough.


Anaphylactic shock, skin sloughing (falling off), dermatitis, skin death, vasculitis, angioedema, swelling of the lips, eyes, or face, fever, chills, going purple.

Sensory disturbances

Blurred vision, eye pain, disturbed vision, hearing loss, dizziness, tinnitus, involuntary eye movements, and altered sense of taste.

On serious adverse events were seen in 7.5% (25/335) of ciprofloxacin-treated patients compared to 5.7% (20/349) of control patients.

In this trial, the overall incidence rates of adverse events regardless of relationship to study drug and within six weeks of treatment initiation were 41% (138/335) in the ciprofloxacin group versus 31% (109/349) in the comparator group.

The most frequent events were gastrointestinal: 15% (50/335) of ciprofloxacin patients compared to 9% (31/349) of comparator patients. Serious adverse events were seen in 7.5% (25/335) of ciprofloxacin-treated patients compared to 5.7% (20/349) of control patients.

Discontinuation of drug due to an adverse event was observed in 3% (10/335) of ciprofloxacin-treated patients versus 1.4% (5/349) of comparator patients.

Other adverse events that occurred in at least 1% of ciprofloxacin patients were diarrhoea 4.8%, vomiting 4.8%, abdominal pain 3.3%, accidental injury 3.0%, rhinitis 3.0%, dyspepsia 2.7%, nausea 2.7%, fever 2.1%, asthma 1.8% and rash 1.8%.

Immune system effects

When you take antibiotics, as we must sometimes, your immune system can become weakened, meaning that you are more prone to infection than before you took the antibiotics. So one infection may be killed, but you may get re-infected more easily later. If this re-infection is with a more resistant strain of the bacteria that caused the original infection, it poses many problems to us all.

Thrush - Candida Albicans

It is well-known that taking antibiotics increases your chances of developing thrush. As a general rule, the stronger the antibiotic, the worse the episode of thrush you get afterwards. Eventually, the thrush can become as persistent because the fungus builds up resistance to the treatments you use against it.


Vasculitis of varying levels of severity is one of the listed side effects of some broad-spectrum antibiotics commonly used. It is caused by an immune reaction that can disrupt DNA and RNA, making white blood cells on the attack against your own body. Lupus-like effects are common.

Symptoms can include, but are not limited to:


Red or purple dots, usually most numerous on the legs. When the spots are larger, about the size of the end of a finger, they are called purpura. Some look like large bruises. These are the most common vasculitis skin lesions, but hives, itchy lumpy rash, and painful or tender lumps can occur. Areas of dead skin can appear as ulcers, small black spots appear at the ends of the finger or around the fingernails and toes, or you may get gangrene of fingers or toes.


Aching in joints, arthritis with pain, swelling and heat in joints. Deformities resulting from this arthritis are rare.


Vasculitis in the brain can cause many problems, from mild to severe. They include headaches, behavioural disturbances, confusion, seizures, and strokes. May be fatal.

Peripheral Nerves

Peripheral nerve symptoms may include numbness and tingling (usually in an arm or a leg, or in areas which would be covered by gloves or socks), loss of sensation or loss of strength, particularly in the feet or hands.


Vasculitis can cause inadequate blood flow in the intestines, resulting in crampy abdominal pain and bloating. If areas in the wall of the intestine develop gangrene, blood will appear in the stool. If the intestinal wall develops a perforation, surgery may be required.


Vasculitis may affect the coronary arteries. If it occurs, it can cause a feeling of heaviness in the chest during exertion (angina), which is relieved by rest. Heart attacks rarely occur as a direct result of vasculitis.


Vasculitis in lung tissue can cause pneumonia-like attacks with chest x-ray changes that look like pneumonia, and symptoms of fever and cough. Occasionally, inflammation can lead to scarring of lung tissue with chronic shortness of breath.


Vasculitis can involve the small blood vessels of the retina. Sometimes, vasculitis of the eyes causes no symptoms. Usually, however, there is visual blurring which comes on suddenly and stays, or a person may even lose a portion of their vision. In temporal arteritis, there is a sudden loss of part or all of the vision in one eye, usually accompanied by a severe headache.

Distribution in the body

After oral administration, ciprofloxacin is widely distributed throughout the body. Tissue concentrations often exceed serum concentrations in both men and women, particularly in genital tissue including the prostate. Ciprofloxacin is present in active form in the saliva, nasal and bronchial secretions, mucosa of the sinuses, sputum, skin blister fluid, lymph, peritoneal fluid, bile, and prostatic secretions. Ciprofloxacin has also been detected in lung, skin, fat, muscle, cartilage, and bone. The drug diffuses into the cerebrospinal fluid (CSF); however, CSF concentrations are less than 10% of peak serum concentrations. Low levels of the drug have been detected in the aqueous and vitreous humors of the eye.

Source - From a Ciprofloxacin Product Label


Antibiotics have a major role to play in human health, but the conclusion must surely be reached that they should be used conservatively, avoiding potential and universal hazards. Hazards that go far beyond the individual instance of use to turn up in food, water and increased bacterial resistance such as is seen with MRSA and EBSL (ESBL refers to an antibiotic-resistance enabling enzyme that the bacteria are producing, as a means of protecting themselves against attack.)

Evidence, Research & Further Reading

Ciprofloxacin product label: PDF

Ciprofloxacin side effects:

Fuchs, S., Simon, Z., Brezis, M. (1994) ‘Fatal hepatic failure associated with ciprofloxacin’, The Lancet, vol. 242, pp.738-739.

Hooper, D.C. (2001) ‘Emerging Mechanisms of Fluoroquinolone Resistance’, Emerg Infect Dis, vol. 7, no. 2, pp.337-41.

Hooton, T.M., Winter, C., Tiu, F., & Stamm, W.E. (1995) ‘Randomized comparative trial and cost analysis of 3-day antimicrobial regimens for treatment of acute cystitis in women’, Journal of the American Medical Association, vol 273, pp.41-5.

Howard, S.J., Catchpole, M., Watson, J. & Davies, S. (2013) ‘Antibiotic Resistance: global response needed’, The Lancet Infectious Diseases, vol 13, no. 12, pp.1001 - 1003.

Osborn, H.M.I. & Gridley, J.J. (2000) ‘Recent advances in the construction of beta-D-mannose and beta-D-mannosamine linkages’, J. Chem. Soc., Perkin Trans, Vol 1, pp.1471-1491.

Sweet RL, Gibbs RS (1995) ‘Urinary tract infection’, in Infectious Disease of the Female Genital Tract. 3rd ed., pp.429-64, Baltimore: Lippincott Williams & Wilkins.