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Antibiotic Interactions

The most common side effects of antibiotics are diarrhea, feeling sick and vomiting. Some antibiotics are Teratogens (that can affect the fetus causing birth defects). Some families of antibiotics may have adverse effects on some region : Tetracycline affects bone growth and discolors the teeth. Antibiotics can also induce Dysbiosis (Dysbacteriosis or the condition where the natural flora of the gut are in a state of imbalance).

Some cases of Antibiotics associated enterocolitis can occur after a prolonged treatment with many antibiotics - especially from Clindamycin, Ampicillin, Amoxicillin or any in the Cephalosporin class. The Colitis triggered by the Antibiotics is an inflammation of the intestines caused by the toxins released due to the proliferation of the normally harmless bacterium Clostridium Difficile. In half the cases of antibiotics associated Colitis, it can take the form of a severe Colitis known as Pseudomembranous Enterocolitis where Pseudo membranes (membrane like collections of WBC, mucus and protein) are excreted. Initial symptoms include lower abdominal cramps and diarrhea which can progress to nausea, vomiting, general fatigue, Abdominal pain and very high fever. In severe form, it can cause dehydration, mineral imbalance, low blood pressure, edema in deep skin, toxic megacolon (enlargement of the large intestine) or perforation of the large intestine. This is the reason why additional antibiotics like Vancomycin or Metronidazole are prescribed to control the bacteria - Clostridium Difficile. Additional supplements containing Lactobacillus Acidophilus - the good bacteria that help to reestablish themselves in the intestines - can help.


Antibiotics Toxicity: Some persons develop an allergic reaction to antibiotics such as penicillin and cephalosporin. Others feel sick and experience loss of appetite and bloating and indigestion. Swelling of face and tongue, breathing difficulty and rashes cam become quite serious leading to a life-threatening allergic reaction known as anaphylaxis. Typical side effects of some drugs are listed below:


Penicillin: Penicillins are drugs of choice for many aerobic gram positive infections. Some varieties of penicillin such as ampicillin have effect on gram negative organisms as well. Amino penicillins are administered often as they are broad spectrum antibiotics. Penicillin are often associated with side effects such as allergy, rash, neuro toxicity which includes gangrene and necrosis.

Cephalosporins: Some of the second and third generation cephalosporins are used as broad spectrum antibiotics for the treatment of gram positive and gram negative infections. The drugs administered are cefuroxime, cefotaxime, ceftriaxone, ceftazidime and cefpirome. In many cases cephalosporins induce fever along with thrombocytopenia. Some cephalosporins are not recommended as they are nephrotoxic and have low renal clearance rates.

Aminoglycosides: Aminoglycosides are widely recommended for gram positive and gram-negative infections of the respiratory and urinary tract. Aminoglycosides are administered in many post-operative infections and hospital acquired infections. These drugs are contraindicated during pregnancy as they induce ototoxicity and nephro toxicity. Co-administration of other drugs like diuretics, muscle relaxants, cyclosporin or antifungals can exacerbate toxicities.

Macrolides: Macrolides are a group of broad spectrum antibiotics administered for various infective conditions pertaining to upper respiratory tract and also urinary tract. The drug Azithromycin is safe and widely recommended in pregnancy associated urinary infections. Neuromuscular blockage and rashes have been reported in some cases as side effects of macrolides. The antibiotic Azithromycin from the class of antibiotics - macrolids can cause potentially fatal irregular heart rhythm for some patients as per the recent FDA warning. The risk factor is for those with low levels of Potassium/ Magnesium or those with slower than normal heart rate or it can interfere with some medications to control cardiac arrhythmia or those suffering from the condition - Torsades de pointes , a rare form of Arrhythmia or Cardiac Dysrhythmia (refers to an abnormal rhythm in the heart which results in irregular contraction). However FDA noted that other than Macrolides class of antibiotics, flouroquinolones can also cause QT prolongation for some susceptible patients.

Fluoroquinolones: Fluoroquinolones can induce side effects other than the common ones. These include headache, confusion, dizziness and photo toxicity. Convulsions are noticed in a few cases.


Rifampin which also comes under the name of Rifampicin (Rifadin) is a powerful antibacterial drug prescribed for leprosy, meningitis and tuberculosis. In many cases, this drug is prescribed over a long period and can cause hepatotoxicity if not adequately monitored. This class of drugs imparts red/orange tinge to body fluids. It may potentiate or antagonize the actions of some drugs - thus requiring extreme caution in prescribing other drugs. Even some oral contraceptives may be rendered ineffective when combined with Rifamycin class of antibiotics.


Antibiotic Side Effects

Drug interactions are also not uncommon. Antibiotics can react with herbal or alternate remedies. Some drug combinations are contraindicated, like in the case of penicillin and birth control pills. Penicillin and methotrexate, used in the treatment of cancer and autoimmune diseases is another combination that can produce serious side effects. Cephalosporins are contraindicated with blood thinners. Tetracyclines are contraindicated with retinoids (Vitamin A belongs to this group), blood thinning medications, diuretics, antacids, sucralfate, colestyramine, ergotamine, methysergide and insulin.


Antibiotic Resistance

Micro organisms evolve resistance to Antibiotics over a period of time resulting in drug resistance. This may occur due to abuse of Antibiotics by the patients or unwarranted prescription of broad spectrum antibiotics or the permeation of antibiotics through consumption of livestock fed with antibiotics for growth promotion or other non therapeutic reasons.


Drug resistance has started soon after the discovery of Penicillin by Sir. Alexander Fleming in 1929. Certain strains of staphylococci developed resistance to Penicillin after some time. Comparatively newer antibiotics introduced in the middle of 20th century barely managed to keep the race against bacteria under control. As the development of antibiotics is becoming more expensive and not remunerative enough for the drug companies, the pace of development of new antibiotics has drastically come down in the recent times.


Usage of Antibiotics should be restricted to therapeutic use alone. Indiscriminate usage of antibiotics can only enhance the drug resistant strains of bacteria which will affect the choice of treatment. It has been noted that about 70 % of bacterial infections in hospitals are resistant to at least one of the antibiotics commonly used to treat such infections.


Resistance to the treatment of life threatening infections caused by a common intestinal bacteria, Klebsiella Pneumoniae, Carbapenem antibiotics has spread to all parts of the world. Klebsiella pneumoniae is a major cause of hospital acquired infections such as pneumonia, bloodstream infections, wound or surgical site infections and meningitis. In many countries, because of drug resistance, Carbapenem antibiotics would not work in more than half of patients treated.

Staphylococcus aureus or commonly called as Staph aureus or MRSA is one of the pathogens which can infect skin,lungs or blood and is one the major drug resistant bacteria. Methicillin Resistant Staphylococcus Aureus - MRSA is a strain of staphylococcal bacteria resistant to the antibiotic Methicillin and other antibiotics that normally control staph infections. Now there are 2 variations of MRSA: Hospital Acquired MRSA - HA-MRSA and Community Acquired MRSA - CA-MRSA.

The drug Methicillin was the drug of choice for some time against this pathogen. When Methicillin resistant Staphylococcus Aureus emerged in the hospitals, it was found that many of the infections are resistant to other drugs like - methicillin, tetracycline and erythromycin as well. According to WHO, patients with MRSA are estimated to be 64% more likely to die than people with a non-resistant form of the infection.

Finally the only drug left to control MRSA infection was vancomycin until in 2002, another vancomycin resistant strain (VRSA) appeared. The struggle against such infections continue with newer antibiotics like Daptomycin and Linezolid though some hospitals have reported resistance to these antibiotics too.


Antibiotics interactions with Alcohol :

Many non-prescription medications such as cough syrup, tonics may contain alcohol in their formulation which can result in drug interactions. Alcohol may cause severe reaction when combined with some anti-microbial.

Perhaps the most important alcohol-antibiotic interactions are with the anti protozoal agent belonging to the Nitroimidazole group – Metronidazole or Tinidazole which is used for a variety of infections, including gastrointestinal (like Giardiasis and Amebiasis) and respiratory / Urinary Tract Infections (UTI).

Anti protozoal drugs result in reactions when combined with alcohol. Even the new Nitazoxanide which is relatively free from the bitter metallic taste of the Metronidazole and Tinidazole still can react with alcohol in a reaction called 'disulfiram' which may cause nausea, vomiting, flushing of skin, stomach cramps, headaches, rapid heart rate and difficulty in breathing. A similar reaction can occur with other antibiotics as well.

Alcohol is a depressant of the central nervous system and when combined with antibiotics it can lead to drowsiness, confusion and dizziness. The effects can get serious while driving and in the elderly if the patient is consuming CNS depressant medications such as opioid pain relievers. Alcohol can potentiate the actions of some drugs while limiting the actions of other drugs.

Avoid drinking alcohol completely when the following drugs are taken:( We have even included many older drugs which may no longer be prescribed here)

  • Metronidazole: Used to clear infections - dental, UTI or leg ulcers and pressure sores.
  • Tinidazole: To treat infections and clear bacteria called Helicobacter pylori (H pylori) from the gut.

Be wary of drinking alcohol while taking the following drugs:

  • Co-trimoxazole: Consuming alcohol while taking this drug can sometimes cause a similar reaction to that of Metronidazole or Tinidazole, although this is very rare.
  • Linezolid: It can interact with alcoholic drinks - even if the alcohol content is low enough - such as wine, beer, sherry and lager.
  • Doxycycline: Known to interact with alcohol and in people with a history of chronic alcohol consumption, the effectiveness of Doxycycline may be reduced.
  • Erythromycin: There is a minor interaction with alcohol that may slightly reduce or delay the effect of this drug

Antibiotic Side Effects | Antibiotic Interactions | Antibiotics with Alcohol

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Collection of Pages - Last revised Date: October 18, 2017