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How Long do Antibiotics Stay in Your System

Antibiotics are lifesaving and powerful medications that help in treating various bacterial infections. But they are not for every sickness. Each antibiotic has different uses based on the bacterial infection one is carrying and they can cause serious side effects. Proper knowledge about the usage of such antibiotic medications will help you to treat your infections better without causing major side effects.

Wondering which medications? Antibiotic medications are at your disposal. Take a seat back and start reading this article, because it contains every information about Antibiotics including the answer to the most common question, how long do antibiotics stay in your system?

1. But What are Antibiotic Medications?

Antibiotics are medicines that fight against all bacterial infections. They are powerful and lifesaving medications used during infections. They either kill the bacteria or stop the bacteria production by avoiding them from growing and multiplying.

Antibiotics are effective against only bacterial infections and not viral infections.

1.1 What is Bacteria?

Bacteria are small-single-celled organisms. The human body is full of Bacteria. They are Microscopic germs. Most of them are non-harmful but some cause infections. Bacteria are prokaryotic unicellular organisms1.

Harmful bacteria are known as Pathogenic Bacteria. They cause diseases such as strep throat, staph infection, cholera, tuberculosis, etc.

Good Bacteria are known as probiotics.

1.2 The Structure of Bacteria:

Well, you must have studied the structure of bacteria during your science classes back in school right? Bacteria are single-celled microbes that lack nuclei. The bacterial cell wall is made up of peptidoglycan2, a large polymer.

These single-celled microorganisms can be quite troublesome. Heard people saying they got a fever, swollen lymph nodes at their neck, headache, nausea, and vomiting?

Wanna guess what happened to them? Well, they are having Bacterial Infections. But before knowing about Bacterial Infections, let’s know about infections.

1.3 What is an Infection?

Infection is the state of the body that occurs upon the entry of any virus, bacteria, or other microbes into your body that starts to multiply.

They usually spread from one person to another person or through contaminated food or water or any other contaminated substance. Some infections are minor and some are serious but both need to be treated without fail.

1.4 What are the Stages of Infection?

There are 5 stages of an Infection. They are Incubation, Prodromal3, Illness, Stage of decline, and convalescence.4

1.5 How Can You Control Infection?

  • Sanitization.
  • Disinfection.
  • Sterilization.

1.6 Symptoms of Infections:

Symptoms of an infection depend on the organism responsible, as well as the site of the infection.

1.7 Types of Infections:

  1. Viral Infections: Viruses are tiny germs. The disease includes the Common cold, Flu, Covid-19, and HIV.
  2. Bacterial Infections: Caused due to bacterial growth. Most common infections include Tuberculosis, Strep throat, Pertussis, etc.
  3. Fungal Infections: Also known as Mycosis. The most common infections are Toenail fungus, Yeast fungus, Ringworm athlete’s foot, and jock itch.
  4. Parasitic Infections: Common infections are Malaria and amebiasis.

1.8 Prevention of Infections:

  • Wash hands often.
  • Clean surface areas.
  • Take only prescribed medications.
  • Avoid sharing your items.
  • Disinfect rooms.

1. 9 Bacterial Infections

They are diseases that can affect the skin, lungs, brain, blood, bowel, and other body parts. Septicemia is a serious blood infection.

Examples of Bacterial Infections:

  • Sepsis
  • Urinary Tract Infections
  • Meningitis.
  • Wound Infections.
  • Whooping Cough.
  • Bacterial Pneumonia.

2. What Exactly is an Antibiotic?


The term ‘antibiotic’ means “against life”. Any drug that kills germs in the body is known as an antibiotic. Antibiotics are very powerful medicines that can treat certain infections and save lives during an emergency.

Antibiotics such as Penicillin are naturally produced.

Antibiotics are available in various forms. Some of them are Tablets, Capsules, Liquids, and Chewable pills. Some come as Ointments and some as drops.

The first ever antibiotic discovered was by Alexander Fleming. He was a Scottish physician-scientist. He was recognized for his discovery of Penicillin. However, the recognition as the father of Antibiotics is with Selman Waksman.

2.1 Classification of Antibiotics:

  • Penicillin.
  • Cephalosporin.
  • Fluoroquinolone.
  • Tetracycline.
  • Macrolides.

2.2 Routes of Administration of Antibiotics:

Before the administration of Antibiotics, the Medical History of the patient has to be recorded.

Examples of some common Antibiotics:

  • Augmentin.
  • Ciprox.
  • Amoxil.
  • Keflex.
  • Zithromax.
  • Penicillin.

Antibiotics can be classified into 2 parts based on their mechanism of action.

Bactericidal Antibiotics: They kill bacteria.

Bacteriostatic Antibiotics: Inhibit growth or reproduction.

2.3 Have you Heard about Antibiotic Therapy?

Short Course Antibiotic Therapy

Antibiotic Therapy is usually based on susceptibility testing of bacteria that is isolated from urine, blood, or other infected tissues.

2.4. Examples of Antibiotic Therapy:

  • Glycopeptides.
  • Aminoglycosides.
  • Fluoroquinolones.

A duration of 3-7 days of antibiotic drugs is recommended in adults. Your healthcare provider will prescribe the drugs and the duration of antibiotics.

Which are the emergency medical care antibiotic drugs used in a hospital?

Since Bacterial Infections are very common in the emergency department, they are compulsorily supplied to the emergency department. Healthcare providers are often tasked with providing antibiotics for outpatient management in hospitals. The most common Life-saving antibiotic5 used commonly is Penicillin.

There are specific antibiotics that perform specific tasks. So, there are some specific antibiotics such as Penicillin(naturally produced) that kill bacteria by destroying the bacterial cell wall.

Many Antibiotics are produced in Nature by soil bacteria and fungi. These antibiotics are known as Natural Antibiotics. They are:

1. Ginger

2. Honey

3. Clove

4. Oregano

The most potent Strong Antibiotic created is Vancomycin 3.0.

Some antibiotics when mixed with alcohol may lead to certain side effects like Nausea, Vomiting, Stomach ache, flushing, and liver damage. So drinking alcohol is prohibited when on antibiotics.

According to the Clinical Data, certain antibiotics are yet to be clinically developed.

2.5 How Fast Does the Antibiotic React?

Antibiotics start their work right after they are consumed. However, some Antibiotics take a few hours to react.

Overweight patients or people with high body mass may require higher doses of antibiotics for the medications to be effective.

The most commonly used Antibiotic these days is Amoxicillin. According to the National Library of Medicine, Therapeutic Drug Monitoring6, certain antibiotics present in blood can be measured.

2.6 How Long Do Antibiotics Stay in Your System?

There is no specific period for any antibiotic to survive in your system. It differs from person to person. In general, antibiotics may stay in your system from a few hours to a few days.

But most of the common antibiotics may stay up to 24 hours in your system after taking the last dose. Specific Antibiotics continue their antibacterial effects after the last dose. So, antibiotics stay in your system for 24 hours minimum.

2.7 What Are the Different Classes of Antibiotics?

  • Aminoglycosides.
  • Carbapenems.
  • Fluoroquinolones.
  • Glycopeptides and Lipoglycopeptides.
  • Macrolides.
  • Monobactams.
  • Oxazolidinones.
  • Penicillins.
  • Polypeptides.
  • Ribamycins.
  • Sulfonamides.
  • Streptogramins.
  • Tetracyclines.

We know all medications have Side effects. Ever wondered what might be the adverse reactions of antibiotics?

2.8 The Side Effects of Antibiotics include:

Side Effects of Antibiotics, Adverse Effects of Antibiotics, Pharmacology Made Easy

  • Mild Skin rash or Skin Infection.
  • Short term Diarrhea
  • Nausea
  • Fungal Infections.
  • Severe Allergic reactions.
  • Stomach cramps.
  • Watery or bloody Diarrhea.

In case the side effects persist, you must contact your doctor. He/She may adjust the dose or prescribe another new antibiotic.

2.9 Which Are the Safest Antibiotics for Older Age?

Temafloxacin is considered the safest drug for the elderly, patients with comorbidities, and other reasons.

2.10 Which Drug Has to be Avoided for Old Age People?

But heard from doctors that the older age group should avoid certain antibiotics? Doctors recommend old people avoid the use of Cipro and fluoroquinolones.

Why? Because they have prompted warnings from the Food and Drug Administration about their risks of various serious side effects.

2.11 Can We Get Antibiotics Over the Counter?

Antibiotics are very clearly defined as Prescription drugs by a registered medicinal practitioner. So, without a prescription, you can not get antibiotics. They are available over the counter.

If a Pharmacist gives antibiotics to anyone without a prescription, then it is considered an Illegal practice. It is generally termed as OTC sale of antibiotics.7

Antibiotic Allergies or Hypersensitivity can lead to an emergency. Always inform the Medicine practitioner about the previous Antibiotics consumed.

Severe allergy reactions called anaphylactic reactions is a life-threatening medical emergency that requires immediate medical care.

Some resistant genes are carried on plasmids. So they can be transferred to bacteria of other species.

3. What Happens When You Take Antibiotics?

Whenever you consume a prescribed antibiotic, all the microbes that are present in the body are exposed to the drug.

Several medical conditions make people particularly vulnerable to infection. So this makes Antibiotic Prophylaxis8 necessary.

Heard of the spleen, right? It filters out the bacteria which is harmful to the blood. If the spleen doesn’t work, it means only antibiotics can prevent the infection.

People more vulnerable to infection include those:

1. Who has just had their spleen removed

2. Take Chemotherapy for Cancer.

3. Have Blood Disorders like Sickle Cell Anaemia.

Antibiotic Prophylaxis may also be recommended for recurring infections, like:

1. Cellulitis

2. Urinary Tract Infection.

3. Genital Herpes.

4. Rheumatic Fever.

3.1 What is the Last Line of Antibiotics?

But what exactly is the last line of antibiotics? It treats multiple drug-resisting infectious agents. Vancomycin is the drug of choice.

3.2 How Do You Recover From Overuse of Antibiotics?

Include probiotic supplements in your daily diet if you are facing antibiotic overuse. It will prevent the most common side effect: antibiotic-associated Diarrhea.

3.2.1. The most overused Antibiotics are:

1. Azithromycin.

2. Amoxicillin

3. Cephalexin.

4. Ciproflaxin.

A point to be noted here is, that antibiotics can do more harm than good.

3.2 When Should We Stop Taking Antibiotics?

10/10 doctors always recommend completing the full course of antibiotics, even if the patient recovers earlier or feels better. This is to prevent any relapse of the infection.

3.3 How Do You Rebuild Your Immune System After Antibiotics?

Taking a full course of antibiotics can weaken your immune system during the time of treatment, which is why rebuilding your strength is of utmost importance. One can include the following in their diet:

  • Some foods rich in fiber include Nuts, Seeds, Whole Grains, Broccoli, Berries, Peas, bananas, etc.
  • Some Antibiotics are considered to be the safest antibiotics. They are Penicillin and Cephalosporin.
  • Certain Antibiotics should be avoided during Pregnancy. They are Tetracyclines and Fluoroquinolones.

Ever heard about the myth “Probiotics should be taken after taking Antibiotics?”

Well, there is a shred of scant solid evidence suggesting probiotics work if taken this way. Researchers have found out that taking probiotics after antibiotics delays gut health recovery.

3.4 Which Antibiotics Cause Skin Rashes?

Most Antibiotics cause Skin rashes. Amoxicillin causes skin rash as a side effect.  In most cases, rashes go away within a week by stopping amoxicillin.

3.5 How is an Allergic Reaction to an Antibiotic-Treated?

They can be treated by:

  • Antihistamines: To treat Itching or Rash.
  • Epinephrine: To treat Anaphylaxis.
  • Steroids: Reduces Inflammation.
  • Desensitization.

3.6 What to Avoid While Taking Antibiotics?

Taking Antibiotics with Fruit Juice or Milk is strictly prohibited. These products interact with antibiotics and affect how the body absorbs them. Wait at least 3 hours after taking antibiotics before consuming dairy products.

Bacteria are small-single-celled organisms. If left untreated, Bacterial infections may cause serious health issues. Antibiotics start their work right after they are consumed.

Taking Antibiotics with Fruit Juice or Milk is strictly prohibited. Antibiotics are administered Intravenously or by intramuscular injections if in a hospital. Antibiotics fight only Bacterial Infections and not viral infections. Antibiotic Allergies or Hypersensitivity can lead to an emergency.


Well, to conclude this article, we can say that, the duration of antibiotics staying in your body depends on the duration of your treatment and also your overall health status.

Depending on the severity of the infection caused, the duration of treatment can be as long as over six weeks, or as short as three to seven days.

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  1. Halberg, F., et al. “Prokaryotic and eukaryotic unicellular chronomics.” Biomedicine & pharmacotherapy 59 (2005): S192-S202. ↩︎
  2. Vollmer, Waldemar, Didier Blanot, and Miguel A. De Pedro. “Peptidoglycan structure and architecture.” FEMS microbiology reviews 32.2 (2008): 149-167. ↩︎
  3. Yung, Alison R., and Patrick D. McGorry. “The prodromal phase of first-episode psychosis: past and current conceptualizations.” Schizophrenia bulletin 22.2 (1996): 353-370. ↩︎
  4. Huang, Yiying, et al. “Impact of coronavirus disease 2019 on pulmonary function in early convalescence phase.” Respiratory research 21 (2020): 1-10. ↩︎
  5. McKenna, Maryn. “The antibiotic paradox: why companies can’t afford to create life-saving drugs.” Nature 584.7821 (2020): 338-342. ↩︎
  6. Kang, Ju-Seop, and Min-Ho Lee. “Overview of therapeutic drug monitoring.” The Korean journal of internal medicine 24.1 (2009): 1. ↩︎
  7. Jacobs, Tom G., et al. “Assessing the impact of law enforcement to reduce over-the-counter (OTC) sales of antibiotics in low-and middle-income countries; a systematic literature review.” BMC health services research 19.1 (2019): 1-15. ↩︎
  8. Smaill, Fiona M., and Rosalie M. Grivell. “Antibiotic prophylaxis versus no prophylaxis for preventing infection after cesarean section.” Cochrane database of systematic reviews 10 (2014). ↩︎



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