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Taking Antibiotics Safely

Make sure to ask your medical provider or pharmacist how to take antibiotics safely, and always take them exactly as directed. Before taking an antibiotic, tell your medical provider about all medications you take and any allergies. Ask about drug side effects. Take antibiotics for the prescribed amount of time, even after you feel better.

Generic pills in RX bottle

Antibiotics are medications that treat infections caused by bacteria. Penicillin was the first antibiotic widely available in the 1940s. Since then, researchers have developed several others.

These medicines come in capsules, chewable tablets, powders for liquid suspension, intravenous formulas, creams and ointments. Most are available only by prescription, though some topical creams and ointments may be available over-the-counter.

Bacterial infections treated by antibiotics include infections of the ear, nose, throat, genitourinary tract and respiratory system. Each type of antibiotic may be more or less effective for certain strains of bacteria, so a medical provider will choose the antibiotic that will work best for the specific infection.

Common uses for antibiotics include:
  • Strep throat
  • Sinus infections
  • Ear infections
  • Urinary tract infections
  • Traveler’s diarrhea
  • Skin infections
  • Pneumonia
  • Pink eye (bacterial conjunctivitis)

Antibiotics don’t work against infections caused by fungi such as yeast infections and athlete’s foot or viruses such as the flu and the common cold.

Using antibiotics incorrectly can lead to a relapse of illness or antibiotic resistance. Certain antibiotics can’t kill bacteria with antibiotic resistance, and this can make it harder to treat serious infections.

Table that shows which conditions require antibiotics
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Source: The Centers for Disease Control and Prevention
Person holding up pill packs

How Do They Work?

Generally, antibiotics work to treat bacteria in two ways. Antibiotics called bactericidal agents cause bacterial cell death. Others called bacteriostatic agents stop bacteria growth and reproduction.

For example, bactericidal antibiotics like penicillin and amoxicillin cause breakdown in bacterial cell walls. This leads to cell death. Antibiotics like erythromycin and clarithromycin primarily prevent bacteria from synthesizing protein, stopping their growth.

Two Main Ways Antibiotics Work
Bacteriostatic antibiotics prevent bacteria cell growth, and bactericidal antibiotics kill bacteria.
Source: Clinical Infectious Diseases

Antibiotics start working right away after a person takes them. Each antibiotic may stay in the body for different lengths of time, but common antibiotics such as amoxicillin and ciprofloxacin stay in your system for about 24 hours after taking the last dose. It might take longer for people with impaired kidney function to eliminate the drug from the body.

Some antibiotics will take days to leave the body. Azithromycin stays in the body for about 15 days after the last dose.

Ask your pharmacist or medical provider for specific information on how long the antibiotic you are taking stays in the body.

Pills spill out of bottle onto surface

Common Types

There several classes of antibiotics available in the United States. These drugs are grouped together by their chemical structure. Each antibiotic class has similarities and differences in how effective they are at treating certain types of bacteria.

Common Types of Antibiotics
Class Examples How They Work
Beta-Lactams (sub classes: penicillins, carbapenems, cephalosporins, monobactams) Penicillin, Amoxil (amoxicillin), Keflex (cephalexin), Premaxin (imipenem), Omnicef (cefdinir) Kill bacteria by preventing formation of the bacterial cell wall
Fluoroquinolones, or Quinolones Cipro (ciprofloxacin), Levaquin (levofloxacin), Avelox (moxifloxacin) Kill bacteria by preventing bacteria from making DNA
Macrolides Zithromax, Z-Pak (azithromycin), Erythrocin (erythromycin) Prevent bacteria from multiplying by preventing them from making proteins
Tetracyclines Sumycin (tetracycline), Adoxa and Adoxa-Pak (doxycycline) Prevent bacteria from multiplying by preventing them from making proteins
Glycopeptides Vancocin (vancomycin), Davlvance (dalbavancin), Orbactiv (oritavancin) Kill bacteria by preventing formation of the bacterial cell wall
Polypeptides Baciim (bacitracin), polymyxin B Kill bacteria by preventing formation of the bacterial cell wall
Sulfonamides Sulfamylon (mafenide), sulfadiazine Prevent bacteria from multiplying by preventing them from making proteins
Oxazolidinones Zyvox (linezolid), Sivextro (tedizolid) Prevent bacteria from multiplying by preventing them from making proteins
Nitroimidazoles (Flagyl) metronidazole, (tindamax) tinidazole Kills bacteria by disrupting production of genetic material
Woman taking antibiotics with water

How to Take Antibiotics

Always take antibiotics for the length of time that they are prescribed, even if the symptoms have subsided. Make sure to read the drug label carefully before taking the medication and ask your medical provider or pharmacist about any side effects or precautions you should take.

It’s important to make sure you take your antibiotics at regularly scheduled doses — for example, every 8 hours or every 12 hours. This is so the medicine’s effect spreads out evenly over the course of a day. Make sure to ask your medical provider if you should take your medication with food or on an empty stomach.

If you miss a dose, take it as soon as you remember to. But if it’s closer to your next scheduled dose, skip it and take your next dose at the regular scheduled time. Never take two doses at once to make up for a skipped dose.

The CDC recommends:
  • Talk to your medical provider if you have questions about your medicine.
  • Don’t share your antibiotics with others.
  • Don‘t save extra antibiotics for later. Take your medication for the length of time prescribed by your medical provider.
  • Never flush expired antibiotics and ask your pharmacist for the best way to dispose of old medicines.
  • Don’t take someone else’s antibiotics because you feel sick. This could make you sicker or cause side effects.

Can you drink alcohol while taking antibiotics?

In general, it’s safe to drink alcohol in moderation with most antibiotics. But three antibiotics — metronidazole, tinidazole and trimethoprim-sulfamethoxazole — can lead to serious reactions with alcohol, according to the UK’s National Health Service and the University of Pittsburgh Medical Center.

Potential reactions with these two medications include:
  • Nausea
  • Headache
  • Dizziness
  • Irregular or fast heartbeat
  • Flushing
  • Abdominal and chest discomfort
  • Vomiting

Can you eat dairy while taking antibiotics?

Eating dairy products such as butter, cheese, milk and yogurt can interfere with how some antibiotics work. You may have to wait up to three hours after taking an antibiotic to consume dairy products.

Do antibiotics affect birth control?

Some antibiotics may increase the breakdown of estrogen, decreasing the effectiveness of birth control. But according to Planned Parenthood, the only antibiotic that could make birth control less effective is rifampin, known under brand names Rifadin and Rimactane.

Medicine bottles stored on shelf

Storing Medicine Properly

In general, you should store antibiotics in a cool, dry place. But it’s important to follow instructions on the drug label and any instructions given by a medical provider or pharmacist regarding your specific antibiotic. For example, some medicines may need to be refrigerated.

Is It Safe to Take Expired Antibiotics?
Don’t take expired antibiotics. Expired antibiotics may fail to properly treat infections and lead to antibiotic resistance.
Source: U.S. Food and Drug Administration

Each package of medicine will have an expiration date printed on it. Don’t take antibiotics past the expiration date. Expired antibiotics may fail to properly treat infections and lead to antibiotic resistance, according to the FDA.

Tests on drug stability from the mid-1980s to early 1990s found that liquid antibiotics showed signs of physical decay after expiration, according to an article published by Harvard.

Man hesitant to take his medicine

Side Effects of Antibiotics

Antibiotics save lives, but nearly one out of five ER visits each year is linked to antibiotic side effects. These side effects are also the most common cause of ER visits for children younger than 18 years of age, according to Cleveland Clinic.

Because these are powerful drugs, people should be mindful of misusing them. Most common side effects are mild. If they get worse or don’t go away, talk to your medical provider.

Common antibiotic side effects include:
  • Diarrhea
  • Stomachache
  • Nausea
  • Yeast infections
  • Headache

Some side effects can be serious. These include allergic reactions and an infection caused by Clostridium difficile.

Allergic Reactions

Before you take antibiotics, tell your medical provider if you’ve had a history of allergic reactions to penicillin or other antibiotics.

If you experience any of the following allergic reactions, seek medical help immediately:
  • Swollen face, lips, mouth or tongue
  • Difficulty breathing
  • Skin rash or hives
  • Difficulty swallowing or breathing
  • Itching
  • Skin peeling or blisters
  • Wheezing

Clostridium Difficile

Antibiotics alter the helpful bacteria in your gut and can lead to an overgrowth of a bacterium called Clostridium difficile, or C. diff, which can cause severe diarrhea and potentially fatal colitis. Tell a medical provider if you develop severe diarrhea, fever, cramping, stomach pain or bloody stool after using antibiotics.

Taking Probiotics with Antibiotics May Help with Side Effects

In the case of diarrhea, abdominal cramping or gas, some research suggests taking a probiotic with your antibiotic may help lessen side effects, according to Cleveland Clinic. Probiotics also include fermented foods like sauerkraut or yogurt.

Probiotics can also help with diarrhea from C. diff. In fact, one study published in the Journal of Family Medicine by Drs. Blake Rodgers, Kate Kirley and Anne Mounsey found “a reduction of 66% in C difficile-associated diarrhea in patients taking probiotics with their antibiotics.”

The most commonly used probiotics for antibiotic-associated diarrhea are Lactobacillus rhamnosus-based and Saccharomyces boulardii-based probiotics. Before taking any probiotics, make sure you ask your medical provider or pharmacist if they are safe for you.

Scientist testing bacteria in petri dish

Antibiotic Resistance

Antibiotic resistance occurs when bacteria develop protections against antibiotics.

“If you keep using the same antibiotics routinely, the bugs basically mutate, and they can live through antibiotic treatment,” immunologist and thoracic surgeon Dr. Hooman Noorchashm told Drugwatch.

This means fewer drugs can kill them, and these infections may become more dangerous. Antibiotic-resistant bacteria cause more than 2.8 million infections annually, and more than 35,000 Americans die each year because of them, according to the Centers for Disease Control and Prevention.

Common antibiotics and resistant infections include:
Penicillin, released in 1941
Staphylococcus aureus (staph infection), Streptococcus pneumoniae (pneumonia, ear infections, sinus infections and meningitis), Neisseria gonorrhoeae (gonorrhea)
Vancomycin, released in 1958
Enterococcus faecium (endocarditis, prostatitis, urinary tract infections, intra-abdominal infection, wound infection and cellulitis)
Ciprofloxacin, released in 1987
Neisseria gonorrhoeae (gonorrhea)
Ceftazidime-avibactam, released in 2015
Ceftazidime-avibactam-resistant KPC-producing Klebsiella pneumoniae (pneumonia, wound or surgical site infections, bloodstream infections and meningitis)
Graphic showing how antibiotic resistant bacteria work
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Anytime antibiotics are used, they may cause resistance. But misusing antibiotics can make bacteria resistant faster.

Antibiotic resistance can occur anytime antibiotics are used. That’s why it’s important not to use antibiotics if you don’t need them and to make sure you take antibiotics as directed for the full length of treatment to kill all organisms.

Pharmacist advises customer on prescription

Takeaways for Using Antibiotics Safely

Dr. Hooman Noorchashm prescribed antibiotics to his patients for years. These are some quick, basic tips that he gave his patients for taking antibiotics safely.

Get a Specific Diagnosis
“You want to make sure that there’s a specific bug that you are afflicted by and have a diagnosis for, like strep throat for example,” Noorchasm said. “You don’t want to take antibiotics just because you feel sick.”
Don’t Take Antibiotics to Prevent Sickness
“You don’t want to take antibiotics prophylactically (to prevent illness) unless your medical provider has given you a clear indication,” said Noorchashm. “For example, some patients with heart valves who are going to have a dental procedure have to take antibiotics to prevent infections.”
Communicate Allergies
“Tell your medical provider about any known allergies to penicillin (or other antibiotics) to make sure they don’t give you that class of antibiotics,” said Noorchashm.
Ask About Side Effects
“All of these drugs at a certain rate will cause adverse events, anywhere from colitis from C. diff to nerve damage and hearing loss,” Noorchashm said. “This is why you don’t want to use them unless you are treating a real bacterial infection.”

Please seek the advice of a medical professional before making health care decisions.

Michelle Llamas, Senior Content Writer
Written By Michelle Llamas Senior Writer

Michelle Llamas has been writing articles and producing podcasts about drugs, medical devices and the FDA for seven years. She specializes in fluoroquinolone antibiotics and products that affect women’s health such as Essure birth control, transvaginal mesh and talcum powder. Michelle collaborates with experts, including board-certified doctors, patients and advocates, to provide trusted health information to the public. Some of her qualifications include:

  • American Medical Writers Association (AMWA) Engage Committee and Membership Committee member
  • Centers for Disease Control and Prevention (CDC) Health Literacy certificates
  • Original works published or cited in The Lancet, British Journal of Clinical Pharmacology and the Journal for Palliative Medicine
Edited By

18 Cited Research Articles

  1. American Chemical Society. (n.d.). Discovery and Development of Penicillin. Retrieved from https://www.acs.org/content/acs/en/education/whatischemistry/landmarks/flemingpenicillin.html
  2. Centers for Disease Control and Prevention. (n.d.). About Antibiotic Resistance. Retrieved from https://www.cdc.gov/drugresistance/about.html
  3. Centers for Disease Control and Prevention. (n.d.). Antibiotic Do’s and Don’ts. Retrieved from https://www.cdc.gov/antibiotic-use/community/about/can-do.html
  4. Centers for Disease Control and Prevention. (n.d.). Antibiotic Resistance Patient Safety Atlas. Retrieved from https://gis.cdc.gov/grasp/PSA/Downloads/OAU-Antibiotic-Class-Definitions.pdf
  5. Centers for Disease Control and Prevention. (n.d.). Be Aware Partner Toolkit. Retrieved from https://www.cdc.gov/antibiotic-use/week/toolkit.html#anchor_smv
  6. Cleveland Clinic. (2020, January 24). How to Prevent Diarrhea While You Take Antibiotics. Retrieved from https://health.clevelandclinic.org/how-to-prevent-diarrhea-while-you-take-antibiotics/
  7. Cleveland Clinic. (n.d.). Antibiotic Safety and Side Effects. Retrieved from https://my.clevelandclinic.org/health/drugs/16386-antibiotic-safety-and-side-effects
  8. InformedHealth.org. (2013, December 18). Using medication: Using antibiotics correctly and avoiding resistance. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK361005/
  9. Merck Manuals. (2018). Overview of Antibiotics. Retrieved from https://www.merckmanuals.com/home/infections/antibiotics/overview-of-antibiotics
  10. Mergenhagen, K.A. et al. (2020). Fact versus Fiction: a Review of the Evidence behind Alcohol and Antibiotic Interactions. Retrieved from https://aac.asm.org/content/64/3/e02167-19
  11. National Health Service. (n.d.). Can I drink alcohol while taking antibiotics. Retrieved from https://www.nhs.uk/common-health-questions/medicines/can-i-drink-alcohol-while-taking-antibiotics/
  12. Pankey, G.A. & Sabath, L.D. (2004, March 15). Clinical Relevance of Bacteriostatic versus Bactericidal Mechanisms of Action in the Treatment of Gram-Positive Bacterial Infections. Retrieved from https://academic.oup.com/cid/article/38/6/864/320723
  13. Planned Parenthood. (2019, September 12). Can antibiotics affect my birth control? Retrieved from https://www.plannedparenthood.org/learn/teens/ask-experts/can-antibiotics-affect-my-birth-control
  14. Rodgers, B., Kirley, K. & Mounsey, A. (2013). Prescribing an antibiotic? Pair it with probiotics. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3601687/
  15. Shmerling, R.H. (2020, February 6). Q: Is it ok to use medications past their expiration dates? Retrieved from https://www.health.harvard.edu/staying-healthy/is-it-ok-to-use-medications-past-their-expiration-dates
  16. Staiger, B. (2019, October 28). How Long Does Amoxicillin Last In Your Body? Retrieved from https://www.pharmacistanswers.com/questions/how-long-does-amoxicillin-stay-in-your-system
  17. U.S. Food and Drug Adminsitration. (2016, March 1). Don’t Be Tempted to Use Expired Medicines. Retrieved from https://www.fda.gov/drugs/special-features/dont-be-tempted-use-expired-medicines
  18. University of Pittsburgh Schools of Health Sciences. (2016, January 8). How to Reduce the Side Effects of Antibiotics. Retrieved from https://share.upmc.com/2016/01/how-to-reduce-side-effects-of-antibiotics/
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