Antibiotics are medications used to fight infections caused by bacteria. They’re also called antibacterials. They treat infections by killing or decreasing the growth of bacteria.
The first modern-day antibiotic was used in 1936. Before antibiotics, 30 percent of all deaths in the United States were caused by bacterial infections. Thanks to antibiotics, previously fatal infections are curable.
Today, antibiotics are still powerful, lifesaving medications for people with certain serious infections. They can also prevent less serious infections from becoming serious.
There are many classes of antibiotics. Certain types of antibiotics work best for specific types of bacterial infections.
Antibiotics come in many forms, including:
- tablets
- capsules
- liquids
- creams
- ointments
Most antibiotics are only available with a prescription from your doctor. Some antibiotic creams and ointments are available over the counter.
Antibiotics treat bacterial infections either by killing bacteria or slowing and suspending its growth. They do this by:
- attacking the wall or coating surrounding bacteria
- interfering with bacteria reproduction
- blocking protein production in bacteria
Antibiotics begin to work right after you start taking them. However, you might not feel better for 2 to 3 days.
How quickly you get better after antibiotic treatment varies. It also depends on the type of infection you’re treating.
Most antibiotics should be taken for 7 to 14 days. In some cases, shorter treatments work just as well. Your doctor will decide the best length of treatment and correct antibiotic type for you.
Even though you might feel better after a few days of treatment, it’s best to finish the entire antibiotic regimen in order to fully resolve your infection. This can also help prevent antibiotic resistance. Don’t stop your antibiotic regimen early unless your healthcare professional says you can do so.
The first beta-lactam antibiotic, penicillin, was discovered by accident. It was growing from a blob of mold on a petri dish. Scientists found that a certain type of fungus naturally produced penicillin. Eventually, penicillin was produced in large amounts in a laboratory through fermentation using the fungus.
Some other early antibiotics were produced by bacteria found in ground soil.
Today, all antibiotic medications are produced in a lab. Some are made through a series of chemical reactions that produce the substance used in the medication.
Other antibiotics are at least partly made through a natural but controlled process. This process is often enhanced with certain chemical reactions that can alter the original substance to create a different medication.
Antibiotics are powerful medications that work very well for certain types of illnesses. However, some antibiotics are now less useful than they once were due to an increase in antibiotic resistance.
Antibiotic resistance occurs when bacteria can no longer be controlled or killed by certain antibiotics. In some cases, this can mean there are no effective treatments for certain conditions.
Each year, there are more than 2.8 million cases of bacterial infections that are resistant to antibiotics, resulting in at least 35,000 deaths.
When you take an antibiotic, the sensitive bacteria are eliminated. The bacteria that survive during antibiotic treatment are often resistant to that antibiotic. These bacteria typically have unique characteristics that prevent antibiotics from working on them.
Some serious antibiotic-resistant infections include:
Clostridioides difficile difficile (C. diff)
The overgrowth of this type of bacteria causes infection in both your small and large intestines. This often occurs after someone’s treated with antibiotics for a different bacterial infection. C. diff is naturally resistant to many antibiotics.
Vancomycin-resistant enterococcus (VRE)
These bacteria often infect your bloodstream, urinary tract, or surgical wounds. This infection typically occurs in people who are hospitalized. Enterococci infections may be treated with the antibiotic vancomycin, but VRE is resistant to this treatment.
Methicillin-resistant Staphylococcus aureus (MRSA)
This type of infection is resistant to traditional staph infection antibiotics. MRSA infections typically occur on your skin. It’s most common in people in hospitals and those with weakened immune systems.
Carbapenem-resistant Enterobacteriaceae (CRE)
This class of bacteria are resistant to a lot of other antibiotics. CRE infections typically occur in people in hospitals and who are on a mechanical ventilator or have indwelling catheters.
The most important cause of antibiotic resistance is inappropriate use or overuse of antibiotics. As much as 28 percent of antibiotic use is thought to be unnecessary. This is because antibiotics are often prescribed when they aren’t needed.
Several important steps can be taken to decrease inappropriate antibiotic use:
- Take antibiotics only for bacterial infections. Don’t use antibiotics for conditions caused by viruses such as the common cold, flu, cough, or sore throat.
- Take antibiotics as directed by a healthcare professional. Using the wrong dose, skipping doses, or taking it longer or shorter than directed might contribute to bacteria resistance. Even if you feel better after a few days, talk with your healthcare professional before discontinuing an antibiotic.
- Take the right antibiotic. Using the wrong antibiotic for an infection might lead to resistance. Don’t take antibiotics prescribed for someone else. Also, don’t take antibiotics left over from a previous treatment. Your healthcare professional will be able to select the most appropriate antibiotic for your specific type of infection.
Antibiotics are used for treating infections caused by bacteria. Sometimes it’s difficult to determine if your infection is caused by bacteria or a virus because the symptoms are often very similar.
Your healthcare professional will evaluate your symptoms and conduct a physical exam to determine the cause of your infection. In some cases, they may request a blood or urine test to confirm the cause of infection.
Some common bacterial infections include:
- urinary tract infections (UTIs)
- sinus and ear infections
- strep throat
Antibiotics aren’t effective against viruses, such as the common cold or flu. They also don’t work on infections caused by fungi, such as:
- yeast infections
- athlete’s foot
- fungal toenail infections
- ringworm
These are treated with a different group of medications called antifungals.
Most antibiotics have similar side effects. Perhaps the most common side effect is gastrointestinal (GI) upset, including:
- diarrhea
- nausea
- vomiting
- cramps
In some cases, these side effects can be reduced if you take the antibiotic with food. However, some antibiotics must be taken on an empty stomach. Ask your doctor or pharmacist about the best way to take your antibiotic.
GI upset usually goes away after you stop treatment. If it doesn’t, you should call your doctor. Also call your doctor if you develop:
- severe diarrhea
- stomach pain and cramping
- blood in your stool
- fever
Antibiotics are most effective when used appropriately. This starts with ensuring that you really need the antibiotic. Only use antibiotics prescribed by your doctor for a bacterial infection.
Talk with your doctor or pharmacist about the best way to take your antibiotic. Some should be taken with food to reduce side effects, but others need to be taken on an empty stomach.
Antibiotics should also be taken in the prescribed amount and for the directed length of treatment. You might feel better within a few days after starting the antibiotic, but you should talk with your healthcare professional before stopping your treatment early.
Your doctor prescribed you a 10-day course of antibiotics for that nasty case of bronchitis, but you’re feeling better after five days. Do you still have to keep taking your prescription? Isn’t it better to not take medication you don’t really need?
Well, yes…and no! Antibiotics are powerful drugs designed to kill bacteria—think strep throat, ear infections, and urinary tract infections, among others—but they’re no good in the fight against viral illnesses. Taking an antibiotic when you have a virus like the common cold or flu won’t help you and, worse, it can actually do some harm.
“Taking antibiotics for a cold [is one of the things] that causes antibiotic resistance,” says Natalie Long, MD, a University of Missouri Health Care family practitioner. “When you do that, all the non-harmful bacteria in your body are exposed to the antibiotic and can adapt or evolve, making it harder for them to be killed by that antibiotic in the future.”
That said, if you’ve got a bacterial infection, you probably need an antibiotic to get rid of it—and yes, you need to take every single pill, regardless of how quickly you start feeling better. Here’s why.
How do antibiotics work?
According to Gwen Egloff-Du, Pharm.D., at Summit Medical Group in New Jersey, there are two types of antibiotics: bacteriostatic and bactericidal. Bacteriostatic antibiotics, like azithromycin and doxycycline, stop bacterial growth. Bactericidal antibiotics, like amoxicillin and cephalexin, kill the bacteria itself.
When you show up sick at your healthcare provider’s office, your healthcare provider assesses your symptom history to determine if your illness is viral or bacterial. If you have a bacterial infection requiring antibiotic therapy, says Long, he or she will consider the organ system affected. Different parts of the body harbor different types of bacteria common to that location, so healthcare providers prescribe antibiotics that have a good chance of being effective there (i.e., ear infections are caused by different bacteria than UTIs, and will likely require a different kind of antibiotic).
How does your healthcare provider determine duration of antibiotics?
Sometimes you take an antibiotic for five days, but sometimes it’s 14. What gives?
Long says that treatments vary based on a number of factors, and the duration of antibiotic treatment is something that’s continually revisited by physicians and researchers.
“Some infections are clear cut, like ear infections, and the duration is pretty standardized,” she explains. “Others, like UTIs, have a range of anywhere from three to 14 days based on how sick you are, whether you need to be admitted to the hospital, and how quickly you respond to the drug.” Another important determining factor is what other chronic conditions you may have chronically, such as asthma, diabetes, or heart disease.
But I’m feeling better…what happens if you don’t finish antibiotics?
Dr. Egloff-Du says there are two reasons why you need to take the full prescribed treatment of antibiotics. The first is obvious: Your healthcare provider selected the therapy for a reason, and that’s to get you healthy again. The second reason? The dreaded antibiotic resistance we mentioned earlier.
“By completing your course of treatment, you increase the odds of killing all the bacteria responsible for causing your current illness,” she says. “When you halt treatment early, you allow a small portion of bacteria to remain in your body and that bacteria has the potential to strengthen, change, and develop resistance.”
So even if you’re feeling better after a few days, that doesn’t mean all of the bacteria which made you sick is actually gone yet. Per the Centers for Disease Control (CDC), antibiotic resistance is a major public health threat that affects upward of 2 million people every year.
Look, we’ve all been there—when you’re supposed to do something twice a day for two weeks, it’s not hard to forget about it at least once. In fact, it’s so common that Dr. Long says she actually considers this when she prescribes common antibiotics to patients (because it’s easier to remember one pill a day versus four!).
So what should you do if you miss a dose of antibiotics? That depends on how long it takes you to realize your mistake.
“If you are a few hours late in taking your antibiotic, take it as soon as you remember,” advises Dr. Egloff-Du. “But if your next dose is due soon, do not double up.”
The general rule is if you are more than 50% of the way toward your next dose, you should skip. So for example, if you are supposed to take your antibiotic every 12 hours, you could take it if it’s less than six hours away from your next scheduled dose. If it’s beyond six hours, simply take the next dose when it’s due, understanding that your therapy will need to be extended to incorporate the dose you missed. (If you’re not sure what to do, remember that you can always ask your healthcare provider or pharmacist for assistance.) For people who struggle to remember their medication, Dr. Egloff-Du offers a few helpful tips.
“Many patients find pill boxes helpful and others set alarms on their cell phone,” she says. “Combining [your dose] with one of your daily routines, like taking it when you eat breakfast at 8 a.m. every morning, can also be helpful.”
RELATED: The best pill reminder smartphone apps
If you miss several doses or days of therapy for any reason, Dr. Egloff-Du adds, it’s important to talk to your healthcare provider; likewise, if unpleasant side effects of antibiotics are deterring you from taking your prescription, you should also pick up the phone—your healthcare provider may be able to suggest an alternative therapy.