Antibiotics 101

Medical Author: Melissa Conrad Stoppler, MD
Medical Editor: William C. Shiel, Jr, MD, FACP, FACR

Mary thinks she may have a bladder infection. She makes the call to her doctor and is able get an appointment to come in and give a urine sample. Sure enough, bladder infection. Her doctor prescribes an antibiotic for the infection. Mary goes to the pharmacy, fills the prescription and as she is driving home, begins to think of questions that she should have asked her doctor about the antibiotic.

This scenario has run through many patients' minds. What are the side effects of the antibiotic? How soon should I begin to feel better? What if I don't feel better after 4 or 5 days? When should I call my doctor? Should I be concerned about a rash or other side effects that develop while taking the antibiotic?

Antibiotics 101

Antibiotics are a class of drugs that treat bacterial infections by stopping growth of bacteria or killing the bacteria directly. It's important to remember that antibiotics are ineffective in treating infections causes by viruses, which include the majority of colds, sore throats (with the exception of streptococcus-induced, or so-called "strep throat"), coughs, and flu-like illnesses.

In fact, taking antibiotics when they are not really necessary will not speed your recovery and can even contribute to a problem known as antibiotic resistance. Antibiotic resistance refers to the capacity of many bacteria to become resistant to a particular antibiotic so that it is no longer effective against these bacteria. It is known that the increasing use of antibiotics when they really aren't needed has contributed to this problem and has led to the evolution of many bacterial strains that no longer respond to treatment with common antibiotics; a phenomenon known as antibiotic resistance.

The evolution of antibiotic-resistant strains of Staphylococcus aureus [methicillin-resistant Staph aureus or MRSA, and vancomycin-resistant enterococci (VRE)] has received much attention in recent years, and a new strain of the bacterium Clostridium difficile, which can cause intestinal illness in people taking antibiotics for other conditions, has arisen which is much more difficult to treat and is associated with a higher death rate.

The following points are critical to remember when taking any antibiotic:

1. Take all the medication that your doctor has prescribed for the recommended length of time. Because antibiotics tend to work fairly rapidly, you may feel much better after taking only a few days' worth of a prescribed seven-day course of antibiotics. Never stop taking the medication because you feel better. Taking the full prescribed course of antibiotics ensures that the infection is eradicated and won't recur.

2. Because your doctor chooses antibiotics based upon your individual medical history along with the type of bacteria likely to be causing your infection, never assume that an antibiotic prescribed for someone else will be effective for you - never "borrow" antibiotics. Sharing any prescription medications is a dangerous practice and can even be deadly. Likewise, never "save up" antibiotics for your own later use.

3. Antibiotics generally work rapidly. Be sure to ask your doctor when to expect results and find out what you should do if you experience no improvement after a couple of days.

4. Antibiotics can cause a number of side effects. Nausea, diarrhea, and allergic reactions are some known side effects of antibiotics. Antibiotics also may kill naturally-occurring bacteria that protect the body from yeast infection, so yeast infections may occur while you are taking antibiotics. Be sure to ask your doctor what kind of side effects you may experience with a particular antibiotic. Always call your doctor if the side effects are severe or worrisome.

5. If your doctor directs you to stop taking an antibiotic or switch to a different antibiotic, properly dispose of all unused medication. Ask your pharmacist about take-back programs and places where you can return unused or expired medications for safe disposal. A person needing an antibiotic should be evaluated by a physician each time an antibiotic is needed - don't save old antibiotics to treat future infections.

6. Ask your doctor or pharmacist whether or not you should take the medication with food and if you should change your habits during the course of treatment (for example, avoiding direct sunlight, not drinking alcohol or eating certain foods).

7. Be certain that you have a clear idea of the directions for taking an antibiotic. If you have questions, ask. For example, does "four times a day" mean every six hours even in the night, or just at meals and at bedtime?