Antibiotics are defined as any substance that kills bacteria or inhibits their growth.

The development and use of antibiotics has been instrumental in modern medicine.

Proper use of these drugs allows us to cure many diseases that used to be very serious, even fatal.

As a pharmacy employee, it's important to understand the different types of antibiotics and how they work.

It's important to understand that antibiotics only work on bacteria and the various illnesses that are caused by bacteria. They have no effect on viral infections such as colds or the flu.

Bacteria are living organisms, much like any other. Despite their small size, they share the same goals as every other living thing: eat, find shelter, and reproduce.

The basic functions of antibiotics can be divided into several classes. The first class is bactericidal antibiotics. These function by directly killing the bacteria. Think of these as a poison.

The other way to kill off bacterial infections is with bacteriostatic antibiotics.

These prevent the bacteria from reproducing, either by attacking their ability to divide into new cells or by blocking essential proteins from being manufactured.

As bacteria have very short lifespans, blocking reproduction is a very effective way to control a bacterial infection.

Here are some of the most common families of antibiotics, along with side effects common to the drugs in each family.


These are used to treat infections caused by Gram-negative bacteria, such as E. Coli. They function by preventing growth and reproduction by blocking the creation of an essential protein. Common side effects include hearing loss, vertigo and kidney damage.


These are considered a broad spectrum antibiotic, as they attack a wide range of types of bacteria. They function by attacking reproduction, specifically the ability to synthesize cell walls. Common side effects include nausea, diarrhea and upset stomach, as well as headaches.


There are several generations of cephalosporins. They all function in the same way, preventing the synthesis of the cell walls of bacteria. This prevents reproduction. They also all share common side effects: upset stomach, diarrhea, nausea, and allergic reaction.


The most famous antibiotic, the discovery of penicillin was a crucial discovery for modern medicine. These antibiotics are used to treat a wide range of illnesses, including strep throat and syphilis. Common side effects are upset stomach and diarrhea. It's also fairly common to find patients who are allergic to penicillin.


Sulfanomides are frequently used to treat urinary tract infections. Allergy, crystals in urine, and kidney failure are common side effects. They prevent reproduction by blocking the production of folate. Folate is required for the bacterial cells to divide.


Tetracyclines are commonly used to fight chlamydia and syphilis.

They function by blocking the binding of an amino acid to the ribosome.

Common side effects include sensitivity to sunlight, upset stomach, staining of the teeth and possible bone growth depression.

All modern antibiotics are what is called semisynthetic. That is, they are derived from a naturally occurring substance and then enhanced and altered synthetically.

The days of harvesting penicillin from a moldy pie pan are long behind us.

Most of the side effects from using antibiotics stem from the disruption of normal bacteria within the body.

Our digestive systems rely on helpful bacteria to function, which is why upset stomach and diarrhea are such common side effects from most antibiotics.

This can be partially alleviated by ingesting probiotics, but this won't always be effective.

Probiotics are simply beneficial bacteria that are re-introduced into the body, either in certain foods (yogurt) or in capsule form as a supplement.

The other common fear with antibiotics is that we are creating drug-resistant strains of various diseases.

And while there is some truth to this, careful and correct diagnosis and prescription of antibiotics will help keep this to a minimum. It's natural for all creatures to evolve, so certain strains that can survive doses of antibiotics is entirely normal and is to be expected.

The problem stems from frequent overuse and misuse of antibiotics.

Doctors have prescribed antibiotics to people with viral infections(no affect at all) simply to make the patient feel like something is being done.

This rampant overuse has created drug-resistant strains at a much faster rate than would typically be seen in nature. This is why proper usage of antibiotics is so important.

By understanding exactly how each type of antibiotic works and which bacteria it works on, it's possible to provide safe and effective cures for patients without the risk of overuse.

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