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Amoxicillin

Amoxicillin is a penicillin-class antibiotic in the beta-lactam class approved to treat bacterial infections, including infections of the nose, ears, throat, skin and urinary tract. Medical providers may also prescribe it with other drugs to treat stomach ulcers caused by H. pylori bacteria.

Amoxicillin Pill
Amoxicillin Facts
  1. Used to Treat Bacterial infections of the nose, ears, throat, skin, urinary tract; bronchitis; pneumonia
  2. Initial FDA Approval 1974
  3. Manufacturer Teva Pharmaceuticals, Sandoz and other generic manufacturers

Amoxicillin is one of the most commonly prescribed antibiotics. It’s similar to penicillin and can kill a wide variety of bacteria including Streptococcus species, Listeria monocytegenes, Enterococcus, Haemophilus influenzae, some E. coli, Actinomyces, Clostridial species, Shigella, Salmonella, and Corynebacteria.

This antibiotic belongs to a specific class of drugs called beta-lactam antibiotics. Beta-lactam antibiotics such as amoxicillin work by binding proteins and inhibiting certain processes in bacterial cells. This causes the cell walls to break down and destroys the bacteria, a process called bactericidal killing.

Fact
Amoxicillin doesn’t work against the flu, colds or other viral infections, and taking amoxicillin and other antibiotics for these illnesses increases the risk of developing antibiotic-resistant infections.
Source: U.S. National Library of Medicine

Amoxicillin begins to work quickly after a patient takes it, and it reaches peak blood concentrations in about one or two hours, according to the drug’s label. People should see their symptoms improve within 72 hours, or about three days, and as early as 24 hours, according to licensed pharmacist Brian Staiger.

If patients don’t see an improvement in three days, they should speak to their medical provider about other treatment options.

How to Take Amoxicillin

Instructions for how to take amoxicillin are different depending on the condition being treated. Amoxicillin is typically prescribed in its generic form, but it’s available in the following brand names in the United States: Amoxil, Larotid and Moxatag.

This medicine is an oral antibiotic, which means it has to be taken by mouth. It comes in immediate-release and extended-release capsules, chewable tablets or a suspension that can be mixed into cold drinks.

People can take this drug with or without food.

Amoxicillin comes in the following strengths:
  • Chewable tablets: 125 mg, 250 mg
  • Capsules: 250 mg, 500 mg
  • Powder for oral suspension: 125 mg/5 mL, 250 mg/5 mL

Recommended Dosages

In general, patients should continue taking amoxicillin for at least 48 to 72 hours after their symptoms go away, according to the drug label.

Make sure to follow your medical provider’s instructions on how to take the medicine, and try to take it at the same time each day. Take any missed doses as soon as you remember to. But if it’s almost time for the next dose, skip the missed dose and take your next scheduled dose. Don’t try to make up for a missed dose by taking two doses at the same time.

Recommendations for Adults and Children
Infection Adults and Children Weighing More Than 40 kg Children Older Than 3 Months Weighing Less Than 40 kg
Mild, moderate or severe lower respiratory tract 875 mg every 12 hours

or

500 mg every 8 hours
45 mg/kg/day in divided doses every 12 hours

or

40 mg/kg/day in divided doses every 8 hours
Mild or moderate ear, nose, throat skin, skin structure and genitourinary tract 500 mg every 12 hours

or

250 mg every 8 hours
25 mg/kg/day in divided doses every 12 hours

or

20 mg/kg/day in divided doses every 8 hours
Severe ear, nose, throat, skin, skin structure and genitourinary tract 875 mg every 12 hours

or

500 mg every 8 hours
45 mg/kg/day in divided doses every 12 hours

or

40 mg/kg/day in divided doses every 8 hours
Source: U.S. National Library of Medicine

Dosages for Impaired Kidney Function

Medical providers will adjust the dosage for people with severe kidney impairment.

Because children younger than three months of age have incomplete kidney development, medical providers should adjust the dosage to 30 mg/kg/day divided every 12 hours.

Dosage for H. Pylori Infection

Medical providers combine amoxicillin with clarithromycin and lansoprazole — known by the brand name Prevacid — to treat H. pylori infections.

For triple therapy, the recommended dose for adults is 500 mg clarithromycin, one gram amoxicillin and 30 mg lansoprazole. All of these medications are given twice daily (every 12 hours) for 14 days.

For dual therapy, the recommended dose for adults is 30 mg lansoprazole and one gram amoxicillin each given three times daily (every 8 hours) for 14 days.

Overdose

In general, people who mildly overdose on amoxicillin don’t suffer serious problems, according to the drug’s label. In a study of 51 children at a poison control center, research suggests that an overdose of less than 250 mg/kg body weight doesn’t cause serious issues.

But kidney disorders resulting in organ failure after overdose have been reported in a small number of patients.

Help for an Overdose
In case of overdose, contact your local poison control center, call 1-800-222-1222 or visit PoisonHelp.org.

What Is It Used to Treat?

The FDA approved amoxicillin to treat several types of bacterial infections. The agency also approved it to treat and prevent H. pylori infections in combination with clarithromycin and lansoprazole.

The Centers for Disease Control and Prevention recommend that people exposed to anthrax take amoxicillin to prevent getting sick, according to an article by Drs. Bobak J. Akhavan and Praveen Vijhani published in the U.S. Library of Medicine.

Approved uses of amoxicillin include:
  • Genitourinary tract infections
  • Ear infections
  • Nose infections
  • Throat infections
  • Lower respiratory tract infections
  • Bacterial pharyngitis
  • Bronchitis
  • Tonsillitis
  • Skin and skin stricture infections
  • Bacterial rhinosinusitis
  • Pneumonia

In addition to FDA-approved uses, some medical providers prescribe it for off-label uses, such as erysipeloid (a bacterial infection of the skin among people who handle fish and meat) and for prevention of infectious endocarditis.

People with hip replacements, knee replacements or other prosthetic joints may take it to prevent infection during dental procedures. Medical providers may prescribe it with metronidazole to treat periodontitis.

Amoxicillin may also treat Lyme disease, according to the CDC.

Common Side Effects

The most common amoxicillin side effects reported in clinical trials occurred in more than one percent of trial participants. Clinical trials also reported common side effects in patients who used amoxicillin in combination with clarithromycin and lansoprazole (triple therapy) and with lansoprazole (dual therapy).

This isn’t a complete list of potential side effects. Contact your medical provider if you experience any side effects that won’t go away or interfere with your daily activities.

Amoxicillin common side effects (more than one percent) include:
  • Diarrhea
  • Rash
  • Vomiting
  • Nausea
Common triple therapy side effects include:
  • Diarrhea (7 percent)
  • Headache (6 percent)
  • Taste perversion (5 percent)
Common dual therapy side effects include:
  • Diarrhea (8 percent)
  • Headache (7 percent)

Serious Side Effects

Amoxicillin may cause rare, serious side effects related to hypersensitivity reactions and Clostridium Difficile-associated diarrhea (CDAD). If you experience any of these side effects, the National Institutes of Health and U.S. Library of Medicine recommend stopping the medication and seeking emergency medical help.

  • Difficulty swallowing or breathing
  • Hives
  • Itching
  • Rash
  • Severe diarrhea
  • Skin peeling or blisters
  • Swelling of the throat, face, tongue, eyes and lips
  • Watery or bloody stools with or without fever and stomach cramps
  • Wheezing

Allergic Reactions

Some people who take amoxicillin have had serious and occasionally fatal allergic reactions. This is more common in people with a history of allergic reactions to penicillin. Discontinue the drug immediately and seek treatment for allergic reactions (rash, swelling of the throat, face, tongue, eyes and lips).

Clostridium Difficile-Associated Diarrhea (CDAD)

Treatment with amoxicillin affects the normal bacteria in the colon and may lead to overgrowth of toxin-producing bacteria called C. difficile. These toxins cause diarrhea that can occur over two months after taking antibiotics.

It can range from mild diarrhea to fatal colitis. Some patients may require colectomy, a surgery to remove part of the colon.

Medical providers will likely stop therapy and treat symptoms with hydration and nutrition and evaluate the need for surgery.

Interactions

Amoxicillin’s drug label provides a list of drugs that may interact with the antibiotic. Tell your doctor about any vitamins, supplements and medications you take before taking amoxicillin.

Probenecid
Using amoxicillin and probenecid together may increase blood levels of amoxicillin.
Oral Anticoagulants
There have been reports that taking amoxicillin with oral anticoagulants (blood thinners) such as warfarin may increase blood-thinning effects. Medical providers may need to adjust blood thinner doses and test blood levels for proper anticoagulation levels.
Allopurinol
Taking allopurinol with amoxicillin increases the incidence of rashes compared to receiving amoxicillin alone.
Oral Birth Control
Because amoxicillin affects gut flora it may reduce the effectiveness of combined oral estrogen/progesterone contraceptives.
Other Antibacterials
Other antibacterial drugs such as macrolides, chloramphenicol, tetracyclines and sulfonamides may interfere with penicillin’s bacterial-killing effects. Researchers have seen the effect in test tubes and petri dishes (in vitro), but they aren’t sure how or if the effect works in the human body.
Amoxicillin and Laboratory Tests
Using amoxicillin may cause false-positive reactions when testing blood glucose using urine tests such as Clintest, Benedict’s Solution, or Fehling’s Solution. People with diabetes should use Clinistix, TesTape or other glucose tests based on enzymatic glucose oxidase reactions instead. Pregnant women taking amoxicillin had a transient decrease in blood levels of total conjugated estriol, estradiol, estriol-glucuronide and conjugated estrone.

Before Taking Amoxicillin

Amoxicillin might not be safe or effective for everyone. Before taking this medicine, make sure to tell your doctor or pharmacist about any medications you are taking, if you are allergic to penicillin and about any health conditions you have.

Tell your medical provider or pharmacist:
  • If you are allergic to amoxicillin, penicillin antibiotics, cephalosporin antibiotics or any of the ingredients in amoxicillin tablets, capsules or suspension. Make sure to get a list of ingredients from your pharmacist.
  • About other prescription medications, nutritional supplements, vitamins, herbal products and nonprescription medicines you are taking or plan to take, especially allopurinol, other antibiotics, blood thinners, birth control pills, and probenecid.
  • If you have a virus called mono (mononucleosis).
  • If you have or have ever had kidney disease or allergic reactions such as rashes or hives.
  • If you are breastfeeding, are pregnant or plan to get pregnant.
  • If you have phenylketonuria, also known as PKU. Some amoxicillin chewable tablets contain aspartame, an artificial sweetener that forms phenylalanine.

Non-Penicillin Antibiotic Alternatives

People who are allergic to penicillin or amoxicillin have a few alternative antibiotic choices. The alternative you take may depend on the condition you are treating.

Make sure to ask a medical provider about your options. The following are some of the most common alternatives.

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

6 Cited Research Articles

  1. Akhavan, B.J. and Vijhani, P. (2019, October 21). Amoxicillin. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK482250/
  2. American Academy of Allergy, Asthma & Immunology. (n.d.). Penicillin Allergy PAQ. Retrieved from https://www.aaaai.org/conditions-and-treatments/library/allergy-library/penicillin-allergy-faq
  3. Centers for Disease Control and Prevention. (n.d.). Lyme Disease Treatment. Retrieved from https://www.cdc.gov/lyme/treatment/index.html
  4. Staiger, B. (2019, October 28). How Long Does It Take For Amoxicillin To Work? Retrieved from https://www.pharmacistanswers.com/questions/how-long-does-it-take-for-amoxicillin-to-work
  5. U.S. National Library of Medicine. (2018, August 1). LABEL: AMOXICILLIN capsule, AMOXICILLIN powder, for suspension, AMOXICILLIN tablet, chewable. Retrieved from https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=4c0f348a-a65d-409c-8668-207c82a5e3cb#LINK_42803a7b-6eaa-4048-b348-588800206185
  6. U.S. National Library of Medicine. (n.d.). Amoxicillin. Retrieved from https://medlineplus.gov/druginfo/meds/a685001.html
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